ch23 Flashcards
(210 cards)
1
Q
definitive n intermediate hosts
A
Parasitic infections often involve several hosts—a definitive
host in which mature (often sexual) forms of the parasite are
present and usually reproducing and, with many parasites, one
or more intermediate hosts in which immature parasites undergo
various stages of maturation.
2
Q
In general, parasites infect
human hosts in one of three major ways
A
by being ingested, through vector-borne transmission, or via direct contact and
penetration of the skin or mucous membranes
3
Q
protozoa
A
unicellular eukaryota diverse
group defined by three characteristics: They are eukaryotic, are
unicellular, and lack a cell wall.
4
Q
Among the many protozoa that enter the body via __,
most have two morphological forms:
A
ingestion; A feeding and reproducing
stage called a trophozoite, which lives within the host,
and a dormant cyst stage, which can survive in the environment
and is infective to new hosts.
5
Q
excystment
A
Once ingested by a host,
cysts undergo excystment and develop into new trophozoites, which resume feeding and reproducing.
6
Q
encystment
A
In most cases, trophozoites
undergo encystment before leaving the host in the feces,
becoming available to infect other hosts.
7
Q
parasitic diseases
A
Many protozoan and helminthic parasites exist
worldwide, especially in the tropics and subtropics, and particularly
among people living in rural, undeveloped, or overcrowded
places. Parasitic diseases are also emerging as serious
threats among developed nations in nontropical regions.
8
Q
ciliates
A
Ciliates (sil´e@ats) are protozoa that in their trophozoite stages
use cilia for locomotion, for acquiring food, or both. Balantidium
coli is the only
ciliate known to cause disease in humans.
9
Q
B coli detection
A
Paradoxically, cysts are few and usually cannot be recovered
from stool (fecal) samples, although they are the infective
stage. Noninfective trophozoites, by contrast, can be detected,
and their presence is diagnostic for the disease. Fresh stool
samples must be used for diagnostic purposes because the
trophozoites do not survive long outside the intestinal tract.
10
Q
balantidiasis
A
In healthy adults, B. coli infection is generally asymptomatic.
For those in poor health, however, balantidiasis
occurs. Persistent diarrhea, abdominal pain,
and weight loss characterize the disease. Severe infections produce
dysentery (frequent and painful diarrhea, often containing
blood and mucus) and possibly ulceration and bleeding
11
Q
b coli cycl
A
Following ingestion, excystment occurs in the small intestine,
releasing trophozoites that use their cilia to attach to (and then
burrow through) the mucosal epithelium lining the intestine.
Eventually, some trophozoites undergo encystment, and both
cysts and trophozoites are shed in feces. Trophozoites die
outside the body, but cysts are hardy and infective.
12
Q
b coli host
A
Pigs are its most common
host, but it is also found in rodents and nonhuman primates
13
Q
b coli trasmission
A
Humans become infected by consuming food or water
contaminated with feces containing cysts.
14
Q
balantidiasis
A
Prevention of balantidiasis relies on good personal hygiene,
especially for those who live around or work with pigs. Additionally,
efficient water sanitation is necessary to kill cysts or remove
them from drinking water.
15
Q
amoebae
A
protozoa
that have no truly defined shape and that move and acquire food
through the use of pseudopods. Although amoebae are abundant
throughout the world in freshwater, seawater, and moist
soil, few cause disease. The most important amoebic pathogen
is Entamoeba.
16
Q
types of amebiasis
A
Depending on the health of the host and the virulence
of the particular infecting strain, three types of amebiasis can result
1. luminal
2 amebic
3. invasive extraintestinal
17
Q
emtamoeba transmission
A
Infection occurs most commonly through the drinking of
water contaminated with feces that contain cysts. The parasite
can also be ingested following fecal contamination of hands or
food or during oral-anal intercourse.
18
Q
entameboa cycle
A
Excystment in the small intestine releases trophozoites that
migrate to the large intestine and multiply. The organism uses
pseudopods to attach to the intestinal mucosa, where it feeds
and reproduces via binary fission. Both trophozoites and cysts
are shed into the environment in feces, but the trophozoites die
quickly, leaving infective cysts.
19
Q
lumial amebiasis
A
The least severe form, luminal amebiasis,
occurs in otherwise healthy individuals. Infections are asymptomatic;
trophozoites remain in the lumen of the intestine,
where they do little tissue damage.
20
Q
amebic dysentery
A
Invasive amebic dysentery
is a more serious and more common form of infection characterized
by severe diarrhea, colitis (inflammation of the colon),
appendicitis, and ulceration of the intestinal mucosa. Bloody,
mucus-containing stools and pain are characteristic of amebic
dysentery, which affects about 500 million people worldwide.
21
Q
invasive extraintestinal amebiasis
A
In the most serious disease, invasive extraintestinal amebiasis,
trophozoites invade the peritoneal cavity and the bloodstream,
which carries them throughout the body. Lesions of dead cells
formed by the trophozoites occur most commonly in the liver
but can also be found in the lungs, spleen, kidneys, and brain.
Amebic dysentery and invasive extraintestinal amebiasis can be
fatal, especially without adequate treatment.
22
Q
emtamoeba prevntion
A
Several preventive measures interrupt the transmission
of Entamoeba. Discontinuing the use of human wastes as fertilizer
reduces the transmission of amebiasis. Normal methods
of treating wastewater and drinking water are helpful
but not completely effective because the infectious cysts are
hardy. Effective processing of water requires extra chemical
treatment, filtration, or extensive boiling to eliminate all
cysts. Good personal hygiene can eliminate transmission via
intimate contact.
23
Q
emtamoeba prevntion
A
Several preventive measures interrupt the transmission
of Entamoeba. Discontinuing the use of human wastes as fertilizer
reduces the transmission of amebiasis. Normal methods
of treating wastewater and drinking water are helpful
but not completely effective because the infectious cysts are
hardy. Effective processing of water requires extra chemical
treatment, filtration, or extensive boiling to eliminate all
cysts. Good personal hygiene can eliminate transmission via
intimate contact.
24
Q
2 other amoebae
A
Acanthamoeba and Naegleria cause rare and usually fatal infections
of the brain
25
2 other amoeba env
Acanthamoeba and Naegleria are common free-living inhabitants
of warm lakes, ponds, puddles, ditches, mud, and moist
soil. They are also found in artificial water systems such as
swimming pools, air-conditioning units, humidifiers, and dialysis
units. Contact lens wearers who use tap water (as opposed
to sterile saline solution) to wash and store their lenses
create an additional focal point for infection.
26
acanthamoeba transmission
Acanthamoeba usually enters a host through cuts or scrapes
on the skin, through the conjunctiva via abrasions from contact
lenses or trauma, or through inhalation of contaminated water
while swimming.
27
keratitis
Acanthamoeba trophozoites when inoculated into the eye can invade and perforate the eye, resulting in keratitis.
Damage can be extensive enough to require corneal replacement.
28
2 other amoeba diseases
Acanthamoeba - keratitis, amebic encephalitis
Naegleria - amebic meningoencephalitis
29
amebic encephalitis symptoms
The more common disease caused by infection with Acanthamoeba
is amebic encephalitis (inflammation of the brain), characterized
by headache, altered mental state, and neurological deficit.
Symptoms progressively worsen over a period of weeks until the
patient dies
30
naegleria transmission
Infection with Naegleria occurs when swimmers inhale
water contaminated with trophozoites, which then invade
the nasal mucosa and replicate. the tropozoites migrate to the brain
31
amebic meningoencephalitis symptoms
(inflammation of the brain and its membranes). Severe headache,
fever, vomiting, and neurological tissue destruction lead
to hemorrhage, coma, and usually death within three to seven
days after the onset of symptoms.
32
2 other amoeba prevention
acanthamoeba, naeglria are environmentally hardy, control
and prevention of infection can be difficult. Swimmers and bathers
should avoid waterways in which the organisms are known
to be endemic. Nonsterile solutions should never be used to
clean or store contact lenses. Swimming pools should be properly
chlorinated and tested periodically to ensure their safety.
Air-conditioning systems, dialysis units, and other devices that
routinely use water should also be cleaned thoroughly and regularly
to prevent amoebae from becoming resident.
33
flagellates
protozoa that possess at least
one long flagellum, which is used for movement. The number
and arrangement of the flagella are important features for
determining the species of flagellate present within a host.
34
flagellates types
- trypanosoma, leishmania: kinetoplastids
- giardia: diplomonad
- tricomonas: parabasalid
35
interphase
during which the cells grow
and eventually replicate their DNA, and a stage during which
the cell’s nucleus divides.
36
prophase
- cell condenses its DNA molecules into
visible threads called chromatids
- a set of microtubules is
constructed in the cytosol to form a spindle
- In most cells,
the nuclear envelope disintegrates during prophase so
that mitosis occurs freely in the cytosol
37
chromosome
2 identical chromatids jointed together at centromere
38
metaphase
chromosomes line up on a plane in the
middle of the cell and attach near their centromeres to
microtubules of the spindle.
39
anaphase
Sister chromatids separate and crawl along the
microtubules toward opposite poles of the spindle. Each
chromatid is now called a chromosome.
40
telophase
The cell restores its chromosomes to their less
compact, nonmitotic state, and nuclear envelopes form
around the daughter nuclei.
41
meiosis early prophase I
homologous chromosomes line up side by side. An aligned pair of homologous chromosomes is
known as a tetrad.
42
meiosis late prophase I
Once tetrads have formed, the homologous
chromosomes exchange sections of DNA in a random
fashion via a process called crossing over. This results in
recombinations of their DNA. It is because of meiotic
crossing over that the offspring produced by sexual
reproduction have different genetic makeups from their
siblings. Prophase I can last for days or longer.
43
meiosis metaphase I
Tetrads align on a plane in the center of the
cell and attach to spindle microtubules. Metaphase I differs
from metaphase of mitosis in that homologous chromosomes
remain as tetrads.
44
meiosis anaphase I
Chromosomes of the tetrads move apart from
one another; however, in contrast to mitotic anaphase, sister
chromatids remain attached to one another.
45
telophase I meiosis
The first stage of meiosis is completed as the
spindle disintegrates. Typically, the cell divides at this
phase to form two cells. Nuclear envelopes may form.
Each daughter nucleus is haploid, though each haploid
chromosome consists of two chromatids.
46
meiosis 2
6 Prophase II. Nuclear envelopes disintegrate, and new
spindles form.
7 Metaphase II. The chromosomes align in the middle of
each cell and attach to microtubules of the spindles.
8 Anaphase II. Sister chromatids separate as in mitosis.
9 Telophase II. Daughter nuclei form. The cells divide,
yielding four haploid cells.
47
meiosis 2
6 Prophase II. Nuclear envelopes disintegrate, and new
spindles form.
7 Metaphase II. The chromosomes align in the middle of
each cell and attach to microtubules of the spindles.
8 Anaphase II. Sister chromatids separate as in mitosis.
9 Telophase II. Daughter nuclei form. The cells divide,
yielding four haploid cells.
48
cytokinesis
typically occurs simultaneously with telophase of mitosis,
though in some algae and fungi it may be postponed or may
not occur at all. In these cases, mitosis produces multinucleate
cells called coenocytes
49
cell plate
In plant and algal cells, cytokinesis occurs as vesicles deposit
wall material at the equatorial plane between nuclei to
form a cell plate, which eventually becomes a transverse wall
between daughter cells
50
cytokinesis of protozoa and some fungal cells
Cytokinesis of protozoa
and some fungal cells occurs when an equatorial ring of actin
microfilaments contracts just below the cytoplasmic membrane,
pinching the cell in two
51
yeasts cytokinesis
Single-celled fungi called
yeasts form a bud, which receives one of the daughter nuclei
and pinches off from the parent cell
52
scizogony
In schizogony, multiple mitoses
form a multinucleate schizont (skiz´ont); only then does cytokinesis
occur, simultaneously releasing numerous uninucleate
daughter cells called merozoites
53
schizogony in plasmodium
Some protozoa, such as Plasmodium—the
cause of malaria—reproduce asexually within red blood cells
and liver cells via a special type of reproduction called schizogony. The body of an
infected host responds to the release of huge numbers of merozoites
with the cyclic fever and chills characteristic of malaria.
54
the organisms we
| commonly refer to as protozoa are classified in six kingdoms:
Parabasala, Diplomonadida, Euglenozoa, Alveolata, Rhizaria,
and Amoebozoa.
formed largely according to similarities
in nucleotide sequences and ultrastructure.
55
algae are
| distributed among the kingdoms
Stramenopila, Rhodophyta,
| and Plantae
56
water molds and slime modls kingdom
water molds are in the kingdom Stramenopila;
| and slime molds are in the kingdom Amoebozoa
57
most species of protozoa
Protozoa require moist environments; most species live worldwide
in ponds, streams, lakes, and oceans, where they are critical
members of the plankton—free-living, drifting organisms
that form the basis of aquatic food chains. Other protozoa live
in moist soil, beach sand, and decaying organic matter, and a
very few are pathogens—that is, disease-causing microbes—of
animals and humans.
58
most species of protozoa
Protozoa require moist environments; most species live worldwide
in ponds, streams, lakes, and oceans, where they are critical
members of the plankton—free-living, drifting organisms
that form the basis of aquatic food chains. Other protozoa live
in moist soil, beach sand, and decaying organic matter, and a
very few are pathogens—that is, disease-causing microbes—of
animals and humans.
59
some ciliates
Some ciliates have two nuclei: a larger macronucleus,
which contains many copies of the genome (often more than
50n) and controls metabolism, growth, and sexual reproduction,
and a smaller micronucleus, which is involved in genetic recombination, sexual reproduction, and regeneration
of macronuclei.
60
protozoa: Several groups lack mitochondria,
| whereas all the others have mitochondria with
discoid or tubular
cristae rather than the platelike cristae seen in animals,
plants, fungi, and many algae.
61
contractile vacuoles
some protozoa
have contractile vacuoles that actively pump water from the cells,
protecting them from osmotic lysis
62
all __ protozoa
All free-living aquatic and pathogenic protozoa exist as a motile
feeding stage called a trophozoite (trof@o@zo´ıt), and many
have a hardy resting stage called a cyst
63
cyst
hardy resting stage of protozoa. characterized
by a thick capsule and a low metabolic rate. Cysts of protozoa
are not reproductive structures because one trophozoite forms
one cyst, which later becomes one trophozoite. Such cysts allow
intestinal protozoa to pass from one host to another and to survive
harsh environmental conditions such as desiccation, nutrient
deficiency, extremes of pH and temperature, and lack of oxygen.
64
most protozoa are __trophic
Most protozoa are chemoheterotrophic; that is, they obtain nutrients
by phagocytizing bacteria, decayed organic matter, other
protozoa, or the tissues of a host
65
protoz and botanists
Because the protozoa called
dinoflagellates and euglenids (discussed shortly) are photoautotrophic,
botanists historically classified them as algal plants
rather than as protozoa.
66
protozoa reproduction
Most protozoa reproduce asexually only, by binary fission or
schizogony; a few protozoa also have sexual reproduction in
which two individuals exchange genetic material. Some sexually
reproducing protozoa become gametocytes (gametes)
that fuse with one another to form a diploid zygote.
67
(specific protoz agroup) reproduction
Ciliates,
such as Paramecium, reproduce sexually via
a complex process called conjugation
68
parabasala
Parabasalids lack mitochondria, but each has a single nucleus
and a parabasal body, which is a Golgi body–like structure.
69
trichomonas
parabasalid. lives in the human vagina
(see Figure 23.9). When the normally acidic pH of the vagina is
raised, Trichomonas proliferates and causes severe inflammation
that can lead to sterility. It is spread by sexual intercourse and is
usually asymptomatic in males.
70
giardia
diplomonad. a diarrheacausing
pathogen of animals and humans that is spread to new
hosts when they ingest resistant Giardia cysts.
71
diplomonadida
- lack mitochondria,
Golgi bodies, and peroxisomes
- have rudimentary mitosomes in the cytoplasm and mitochondrial
genes in the nuclear chromosomes, a finding that suggests that
diplomonads might be descended from typical eukaryotes that
somehow lost their organelles
72
euglenozoa
- euglenids and some flagellated protozoa called kinetoplastids
- eukaryotic microbes that share certain characteristics of
both plants and animals.
- have a crystalline rod of unknown
function in the flagella, and mitochondria with
disk-shaped cristae
73
knetoplastids
- trypanosoma, leishmania
- have a single large mitochondrion that contains a
unique region of mitochondrial DNA called a kinetoplast. As
in all mitochondria, this DNA codes for some mitochondrial
polypeptides.
- live iside aimals, some r pathognic
74
euglenids
photoautotrophic,
unicellular microbes with chloroplasts containing
light-absorbing pigments—chlorophylls a and b and carotene.
For this reason, botanists historically classified euglenids in the
kingdom Plantae.
75
y euglenids not i plantae
euglenids store food as a unique polysaccharide
| called paramylon instead of as starch.
76
Euglenids are
| similar to animals in that
they lack cell walls, have flagella, are chemoheterotrophic phagocytes (in the dark), and move
77
euglenoid movemnt
move by using
their flagella as well as by flowing, contracting, and expanding
their cytoplasm. Such a squirming movement, which is similar to
amoeboid movement but does not involve pseudopods, is called
euglenoid movement.
78
pellicle
A euglenid has a flexible, proteinaceous, helical pellicle that
underlies its cytoplasmic membrane and helps maintain its shape.
79
eyespot
Typically each euglenid also has a red “eyespot,” which plays a
role in positive phototaxis by casting a shadow on a photoreceptor
at the flagellar base, triggering movement in that direction.
80
alveolates
protozoa with small membranebound
cavities called alveoli16 (al@ve´o@lı) beneath their cell
surfaces.
Alveolates share at least one other characteristic—tubular
mitochondrial cristae. This group is further divided into three
subgroups: ciliates, apicomplexans, and dinoflagellates.
81
ciliates
alveolates. All ciliates are
chemoheterotrophs and have two nuclei—one macronucleus
and one micronucleus
82
apicomplexans
alveolates. all chemoheterotrophic pathogens of animals.
infective forms are characterized by an ornate complex of
organelles at their apical ends, that enables them to penetrate host cells.
- plasmodium, toxoplasma, cryptosporidium cyclospora
- major feature: schizogony
- all have complicated life cycles
involving at least two types of hosts
83
dinoflagellates
alveolates. unicellular microbes that have photosynthetic pigments,
such as carotene and chlorophylls a, c1, and c2. make up a large proportion of freshwater and marine plankton.
- botanists have historically classified
the dinoflagellates as algae because dinoflagellates are photoautotrophic
- manny r bioluminescent
- some produce neurotoxins
84
red tide
Other dinoflagellates produce a red pigment, and their abundance
in marine water is one cause of a phenomenon called a
red tide.
85
amoeba
Unicellular eukaryotes called amoebae are protozoa that move
and feed by means of pseudopods (see Figure 3.29). Beyond this
common feature and the fact that they all reproduce via binary
fission, amoebae exhibit little uniformity
- 2 kingdoms: rhizaria, amoebozoa
86
rhizaria
Rhizaria is a group of amoebae with threadlike pseudopods.
| - foraminifera, radiolaria
87
foraminifera
rhizaria. A major taxon is composed of armored marine amoebae known
as foraminifera. A foraminiferan has a porous shell composed of
calcium carbonate arranged on an organic matrix in a snail-like
manner. most r fossil species
88
radiolaria
rhizaria. ornate shells composed of silica (SiO2)
89
amoebozoa
Amoebozoa constitute a second kingdom of amoebae distinguished
from rhizaria by having lobe-shaped pseudopods
and no shells.
- naegleria, acathamoeba, entamoeba
90
smile molds
Taxonomists formerly considered another group of amoebozoa—slime
molds—to be fungi, but the lobe-shaped pseudopods
by which they feed and move as well as their nucleotide sequences
show that they are amoebozoa. Scientists have identified two
types of slime molds: plasmodial molds and cellular slime molds.
91
slime molds vs fungi
• They lack cell walls, more closely resembling the amoebae
in this regard.
• They are phagocytic rather than absorptive in their nutrition.
92
plasmodial molds
aka acellular slime molds
- exist as streaming, coenocytic, colorful filaments of cytoplasm
that creep as amoebae through forest litter, feeding by phagocytizing
organic debris and bacteria. The body, called a plasmodium,
may contain millions of diploid nuclei and cover many
square centimeters.
93
celllar slime molds
exist as individual haploid myxamoebae
that phagocytize bacteria, yeasts, dung, and decaying
vegetation. life cycle all haploid
94
fngi v protozoa
like most protozoa in that they are
chemoheterotrophic; however, unlike protozoa, they have cell
walls, which typically are composed of a strong, flexible, nitrogenous
polysaccharide called chitin.
95
mycorrhiza e
the roots of about 90% of vascular
plants form mycorrhizae,20 which are beneficial associations between
roots and fungi that assist the plants to absorb water and
dissolved minerals.
96
thallus
```
The vegetative (nonreproductive) body of a fungus is called
its thallus
```
97
hyphae
The thalli of molds are large and composed of long,
branched, tubular filaments called hyphae.
Hyphae are either
septate (divided into cells by cross walls called septa) or aseptate (not divided by septa)
Aseptate hyphae are coenocytic (multinucleate)
98
thalli of yeasts
The thalli of
yeasts are typically small, globular, and composed of a single
cell, which may have buds
99
thalli of yeasts
The thalli of
yeasts are typically small, globular, and composed of a single
cell, which may have buds
100
dimorphic
In response to environmental conditions such as temperature
or carbon dioxide concentration, some fungi produce both
yeastlike thalli and moldlike thalli (Figure 12.15d); fungi that
produce two types of thalli are said to be dimorphic (which
means “two-shaped”).
101
mycelium
The thallus of a mold is composed of hyphae intertwined
to form a tangled mass called a mycelium (plural: mycelia;
Figure 12.16). Mycelia are typically subterranean and thus
usually escape our notice, though they can be very large.
102
fruiting bodies
sch as puffballs n mushrooms, are the reproductive structures of molds and are
only small visible extensions of vast underground mycelia.
103
Fungi acquire nutrients by
absorption; that is, they secrete catabolic
enzymes outside their thalli to break large organic molecules
into smaller molecules, which they then transport into their
thalli.
104
saprobes
most fungi r. they absorb nutrients
| from the remnants of dead organisms
105
haustoria
Fungi that derive their nutrients from living plantsand animals usually have modified hyphae called haustoria, which penetrate the tissue of the host to withdraw
nutrients.
106
most fngi r
aerobic. though many yeasts (e.g., Saccharomyces)
| are facultative anaerobes that obtain energy from fermentation
107
budding
Yeasts typically bud in a manner similar to prokaryotic budding.
Following mitosis, one daughter nucleus is sequestered
in a small bleb (a blisterlike outgrowth) of cytoplasm that is
isolated from the parent cell by the formation of a new wall
108
pseudohypha
In some species, especially Candida albicans
(kan´did@aI al´bi@kanz), which causes human oral thrush
and vaginal yeast infections, a series of buds remain attached
to one another and to the parent cell, forming a long filament
called a pseudohypha. Candida invades human tissues by
means of such pseudohyphae, which can penetrate intercellular
cracks.
109
filamentous fungi reproduction
Filamentous fungi reproduce asexually by producing lightweight
spores, which enable the fungi to disperse vast distances
on the wind.
110
sporangiospores
Sporangiospores form inside a sac called a sporangium,26
which is often borne on a spore-bearing stalk, called a
sporangiophore,27 at either the tips or sides of hyphae
111
chlamydospores
form with a thickened cell wall inside
| hyphae
112
conidiospores / coidia
are produced at the tips
or sides of hyphae but not within a sac. There are many
types of conidia, some of which develop in chains on stalks
called conidiophores
113
The process of sexual reproduction
| in fungi
1 Haploid (n) cells from a + thallus and a - thallus fuse to
form a dikaryon, a cell containing both + and -nuclei. The
dikaryotic stage is neither diploid nor haploid but instead
is designated (n + n).
2 After a period of time that typically ranges from hours
to years but can be centuries, a pair of nuclei within
a dikaryon fuse to form one diploid (2n) nucleus.
3 Meiosis of the diploid nucleus restores the haploid state.
4 The haploid nuclei are partitioned into + and - spores,
which reestablish + and - thalli by mitoses and cell
divisions.
114
four major subgroups
into which taxonomists traditionally divided the kingdom
Fungi.
diviosns = phyla
- 3 are based on the type of sexual spore produced (divisions Zygomycota,
Ascomycota, and Basidiomycota)
- the 4th (the deuteromycetes)
was a repository of fungi for which no sexual stage is
known.
115
four major subgroups
into which taxonomists traditionally divided the kingdom
Fungi.
diviosns = phyla
- 3 are based on the type of sexual spore produced (divisions Zygomycota,
Ascomycota, and Basidiomycota)
- the 4th (the deuteromycetes)
was a repository of fungi for which no sexual stage is
known.
116
Division Zygomycota
Fungi in the division Zygomycota are coenocytic molds called
zygomycetes. most are saprobes; the rest are obligate parasites of insects
and other fungi.
- reproduce asexually via sporangiospores
117
zygosporangia
the distinctive feature of most zygomycetes is the formation
of sexual structures called zygosporangia (sometimes incorrectly
termed zygospores). Zygosporangia of R. nigricans are black,
rough-walled structures that develop from the fusion of sexually
compatible hyphal tips 5 to 8 . Like fungal spores, zygosporangia
can withstand desiccation and other harsh environmental
conditions.
118
microsporidia
small organisms that are difficult
to classify. mor similar 2 zygomycetes than 2 protozoa. obligatory intracellular parasites; that is, organisms
that must live within their hosts’ cells. Microsporidia
spread from host to host as small, resistant spores.
119
microsporidia
small organisms that are difficult
to classify. mor similar 2 zygomycetes than 2 protozoa. obligatory intracellular parasites; that is, organisms
that must live within their hosts’ cells. Microsporidia
spread from host to host as small, resistant spores.
120
Division Ascomycota
- molds and yeasts
- characterized by the formation
of haploid ascospores within sacs called asci.29 Asci occur in
fruiting bodies called ascocarps
121
Division Ascomycota
- molds and yeasts
- characterized by the formation
of haploid ascospores within sacs called asci. Asci occur in
fruiting bodies called ascocarps
- also reproduce asexually by conidiospores
- most of the fungi that spoil food
are ascomycetes
- penicillium
122
Division Basidiomycota
- visible fruiting bodies
- Mushrooms and other fruiting bodies of basidiomycetes are called basidiocarps (Figure 12.23). The
entire structure of a basidiocarp consists of tightly woven hyphae
that extend into multiple, often club-shaped projections
called basidia, the ends of which produce sexual basidiospores.
123
Deuteromycetes
created the division
Deuteromycota (also called imperfect fungi) to contain the fungi
whose sexual stages are unknown—either because they do not
produce sexual spores or because their sexual spores have not been
observed. More recently, however, the analysis of rRNA sequences
has revealed that most deuteromycetes in fact belong in the division
Ascomycota, and thus modern taxonomists have abandoned
Deuteromycota as a formal taxon. Nevertheless, many medical laboratory
technologists, health care practitioners, and scientists continue
to refer to “deuteromycetes” because it is a traditional name
124
lichens
partnerships between fungi and photosynthetic
microbes—commonly cyanobacteria or, less frequently,
green algae. In a lichen, the hyphae of the fungus, which is
usually an ascomycete, surround the photosynthetic cells
(Figure 12.25) and provide them nutrients, water, and protection
from desiccation and harsh light. In return, each alga or
cyanobacterium provides the fungus with products of photosynthesis—carbohydrates
and oxygen.
125
chagas disease
- trypanosoma cruzi
- endemic throughout Central and South America.
- Trypansoma-induced heart disease is one of the leading causes of
death in Latin America.
126
chagas disease stages
Chagas’ disease progresses over the course of several
months through the following four stages:
1. An acute stage characterized by chagomas, which are swellings
at the sites of the bites
2. A generalized stage characterized by fever, swollen lymph
nodes, myocarditis (inflammation of the heart muscle), and
enlargement of the spleen, esophagus, and colon
3. A chronic stage, which is asymptomatic and can last for years
4. A symptomatic stage characterized primarily by congestive
heart failure following the formation of pseudocysts, which
are clusters of amastigotes in heart muscle tissue
127
chagas disease transmission
Transmission occurs through the bite of true bugs—a
type of insect—in the genus Triatoma (trı@aI@to´maI). These bloodsucking
bugs feed preferentially from blood vessels in the lips,
which gives the bugs their common name—kissing bugs
128
chagas siease reservoirs
Opossums and armadillos are the primary reservoirs for T. cruzi,
but most mammals, including humans, can harbor the organism.
129
african sleeping sickness
Untreated African sleeping sickness progresses through
three clinical stages. First, the wound created at the site of each
fly bite becomes a lesion containing dead tissue and rapidly
dividing parasites. Next, the presence of parasites in the blood
triggers fever, swelling of lymph nodes, and headaches. Finally, invasion of the central nervous system results in meningoencephalitis,
characterized by headache, extreme drowsiness, abnormal
neurological function, and coma. The patient will die
perhaps within six months of onset of disease.
130
All T. brucei infections are characterized by
cyclical waves
of parasitemia (parasites in the blood) that occur roughly every
7 to 10 days. Although the presence of parasites in the blood is
in itself serious, these cycles are particularly dangerous because
with each wave of replication, T. brucei changes its surface glycoproteins
and thus its surface antigens. The result is that by the
time the host’s immune system has produced antibodies against
a given set of glycoproteins, the parasite has already produced
a new set, continually leaving the host’s immune system one
step behind the parasite. Once infected, a patient is incapable of
clearing the infection and never becomes immune.
131
african sleeping sickness trasmission
Although humans usually
become infected when bitten by tsetse flies previously infected
while feeding on infected animals.
132
af sleeping sickness prevention
Clearing of tsetse fly habitats and broad application of insecticides
have reduced the occurrence of African sleeping
sickness in some localities
133
zoonosis
a disease of animals trasmitted to humans. leishmaniasis
134
leishmania endemic
Leishmania is endemic in parts of the tropics and subtropics,
135
leishmania reservoir
is a genus of kinetoplastid protozoa
commonly hosted by wild and domestic dogs and small
rodents.
136
Leishmania has two developmental stages:
amastigotes,
which lack flagella and multiply within a mammalian host’s
macrophages and monocytes (types of white blood cells), and
promastigotes, each of which has a single anterior flagellum and
develops extracellularly within a vector’s gut.
137
leishmania transmission
Transmission of the parasites occurs through the bite of infected female blood-sucking
sand flies
138
Three clinical forms of leishmaniasis are commonly observed.
cutaneous, mucotaneous, visceral
139
cutaneous leishmaniasis
Cutaneous leishmaniasis involves large painless skin
ulcers that form around the bite wounds. Such lesions often
become secondarily infected with bacteria. Scars remain when
the lesions heal
140
mucocutaneous leishmaniasis
results when skin
lesions enlarge to encompass the mucous membranes of the
mouth, nose, or soft palate. Damage is severe and permanently
disfiguring (Figure 23.7). Neither of these forms of leishmaniasis
is fatal
141
visceral leishmaniasis
aka kala-azar.
- fatal in 95% of untreated cases. In this disease, macrophages
spread the parasite to the liver, spleen, bone marrow, and lymph
nodes. Inflammation, fever, weight loss, and anemia increase in
severity as the disease progresses. Visceral leishmaniasis is becoming
increasingly problematic as an opportunistic infection
among AIDS patients.
142
leishmaniasis prevention
Prevention is essentially limited to reducing exposure by
| controlling reservoir host and sand fly populations.
143
giardiasis organism
giardia intestinalis
144
giardiasis organism env
Giardia lives in the intestinal tracts of animals and
humans worldwide. The organism is very hardy and can also be
found in water, in soil, on food, and on surfaces that have been
contaminated with feces. The organism can survive for months in
the environment because of the protective outer shell of its cyst.
145
giardiasis
one
of the more common waterborne gastrointestinal diseases in the
United States
146
giardiasis transmission
Infection usually results from the ingestion of cysts in
contaminated drinking water or accidental ingestion during
swimming. Hikers, campers, and their pets are at particular
risk because infected wild animals shed Giardia into mountain
streams.
147
giardiasis symptoms
Giardiasis can range from an asymptomatic infection to
significant gastrointestinal disease. Signs and symptoms, when
they occur, include severe watery diarrhea, abdominal pain,
bloating, nausea, vomiting, ineffective absorption of nutrients,
and low-grade fever. Stools are foul smelling, usually with
the “rotten-egg” smell of hydrogen sulfide. Incubation lasts
roughly one to two weeks, and symptoms resolve after one to
four weeks in normal, healthy adults. In extreme cases, the attachment
of parasites to the intestinal mucosa causes superficial
tissue damage, and fluid loss becomes life threatening. Chronic
giardiasis can occur, often among animals.
148
giardiasis prevention
To prevent infection in regions where Giardia is endemic,
filtering water is necessary. When hiking, neither humans nor
their pets should drink unfiltered stream or river water.
149
trichomonas vaginalis
VAGINOSIS globally distributed
and is the most common protozoan causing disease
in people of industrialized nations
150
t vaginalis env
lives on the vulvas and in the vaginas of women and in the urethras and
prostates of men
151
T. vaginalis occurs most frequently
| in people
with a preexisting sexually transmitted disease,
such as chlamydial infection, and in people with multiple sex
partners.
152
T. vaginalis occurs most frequently
| in people
with a preexisting sexually transmitted disease,
such as chlamydial infection, and in people with multiple sex
partners.
153
vaginosis
In women, infection results in vaginosis (vaj@i@no´sis),
which is accompanied by a purulent (pus-filled) odorous discharge,
vaginal and cervical lesions, abdominal pain, painful
urination, and painful intercourse. Since inflammation is
not typically involved, it is “vaginosis” rather than “vaginitis.”
Trophozoites feed on vaginal tissue, leading to erosion of
the epithelium. T. vaginalis infection may cause inflammation
of the urethra or bladder of men, but more typically men are
asymptomatic
154
Four species of Plasmodium 1plaz@mo´de@uIm2 typically cause
| malaria in humans:
P. falciparum, P. vivax, P. ovale, and P. malariae
155
malaria endemic
throughout the tropics and subtropics
156
malaria transmission
Females of 60 different species of the
| mosquito genus Anopheles r plasmodim vectors
157
People living in endemic areas and their descendants
throughout the world have evolved to have one or more of the
following genetic traits that increase their resistance to malaria:
• Hemoglobin C. Humans with two genes for hemoglobin C
are invulnerable to malaria. The mechanism by which this
mutation provides protection is unknown.
• Genetic deficiency for the enzyme glucose-6-phosphate
dehydrogenase. Trophozoites must acquire this enzyme from
a human host before the trophozoite can synthesize DNA;
thus, humans without the enzyme are spared malaria.
• Lack of so-called Duffy
antigens on erythrocytes. Because
P. vivax requires Duffy antigens in order to attach to and
infect erythrocytes, Duffy-negative individuals are resistant
to this species
158
jaundice
The inability
of the liver to process the inordinate amount of hemoglobin
released from dying erythrocytes results in jaundice.
159
malaria fever correlates w/
erythrocyte
lysis and most likely results from efforts of the immune
system to remove cellular debris, toxins, and merozoites.
160
malaria fever correlates w/
erythrocyte
lysis and most likely results from efforts of the immune
system to remove cellular debris, toxins, and merozoites.
161
blackwater fever
P. falciparum causes a form of malaria called blackwater fever,
which is characterized by extreme fever, large-scale erythrocyte
lysis, renal failure, and dark urine discolored by excreted hemoglobin.
Protozoan proteins inserted on the surfaces of infected
erythrocytes cause erythrocytes to become rigid and inelastic
such that they cannot squeeze through capillaries, blocking
blood flow and causing small hemorrhages in various tissues
(and ultimately tissue death).
162
cerebral malaria
Cerebral malaria results when tissue
death occurs in the brain. Falciparum malaria can be fatal
within 24 hours of the onset of symptoms.
163
malaria prevention
Control of malaria involves limiting contact with mosquitoes
carrying Plasmodium. Widespread use of insecticides,
drainage of wetlands, and removal of standing water can
reduce mosquito breeding rates.
164
toxoplasma gondii organism
Wild and domestic mammals and
birds are major reservoirs for Toxoplasma, and cats are the definitive
host, in which the protozoan reproduces sexually
165
t gondii transmission
Humans typically become infected by ingesting undercooked
meat containing the parasite. Ingestion or inhalation with contaminated soil can also
be a source of infection. The protozoan can also cross a placenta
to infect the fetus.
166
t gondii disease
Although the majority of people infected with T. gondii
have no symptoms, a small percentage develop toxoplasmosis, a fever-producing illness with headache,
muscle pain, sore throat, and enlarged lymph nodes in the head
and neck. Toxoplasmosis generally results in no permanent
damage and is self-limiting, resolving spontaneously within a
few months to a year. However, toxoplasmosis is more severe in
two populations: AIDS patients and fetuses
167
t gondii prevennetion
The best prevention is to thoroughly cook or deepfreeze
| meats and to avoid contact with contaminated soil.
168
cryptosporidiosis
- zoonosis
| - aka cryptosporidium enteritis
169
cryptosporidiosis symptoms
Signs and symptoms of Cryptosporidium enteritis include
severe diarrhea that lasts from one to two weeks accompanied
by headache, muscular pain, cramping, and severe fluid and wight loss
170
cryptosporidiosis oranism
Cryptosporidium parvum 1par@vuIm2, an apicomplexan,
causes the disease. Once thought to infect only livestock and
poultry, Cryptosporidium is carried asymptomatically by about
30% of people living in developing nations.
171
cryptosporidiosis oranism env
It is estimated that
most natural waterways in the United States are contaminated
with the oocysts of Cryptosporidium from livestock wastes
172
cryptosporidiosis transmission
Infection most commonly results from drinking water contaminated
with oocysts, but direct fecal-oral transmission resulting
from poor hygienic practices also occurs, particularly in
day care facilities.
173
cryptosporidiosis prevention
Drinking from rivers
and streams should be avoided in areas where Cryptosporidium
is found; filtration is required to remove oocysts from drinking
water because they cannot be killed by chlorination. Good personal
hygiene can eliminate fecal-oral transmission of the parasite.
174
cyclosporiasis organism
Cyclospora cayetanensis, a waterorne apicomplexan
175
cyclosporiasis transmission
The disease is not transmitted between
individuals; rather, it is acquired by eating or drinking
oocysts in contaminated food or water
176
cyclosporiasis prevention
The only reliable methods for reducing risk
of infection in the United States are thoroughly washing fruits
and vegetables prior to eating them raw. Cooking or freezing
also kills many oocysts.
177
cyclosporiasis symptoms
Once Cyclospora enters the intestine, it invades the mucosal
layer, causing symptoms, which develop after about a week.
Manifestations include cramps, watery diarrhea, myalgia (muscle
pain), and fever. Symptoms are more severe in AIDS patients,
leading to severe dehydration and weight loss. The disease usually
resolves in days or weeks in immunocompetent patients.
178
helminths
Helminths are macroscopic, multicellular, eukaryotic worms
found throughout the natural world, some in parasitic associations
with other animals. They are not microorganisms, though
microbiologists generally study them in part because the diagnostic
signs of infestation—eggs or larvae—are microscopic.
179
3 groups of helminths
cestodes (tapeworms), trematodes (flukes), nematodes (roundworms)
180
monoecious
each worm has bot sex organs
181
cestodes
All cestodes, commonly called tapeworms, are flat, segmented,
intestinal parasites that completely lack digestive systems.
Though they differ in size when mature, all possess the same
general body plan
182
scolex
a small
attachment organ that possesses suckers and/or hooks used to
attach the worm to host tissues (see the photo at the beginning
of the chapter). Anchorage is the only role of a scolex; there is
no mouth. Cestodes acquire nutrients by absorption through the
worm’s cuticle
183
proglotids
Behind the scolex is the neck region. Body segments, called
proglottids 1pro@glot´idz2, grow from the neck continuously
as long as the worm remains attached to its host. New proglottids
displace older ones, moving the older ones farther from the
neck. Proglottids mature, producing both male and female reproductive
organs.
184
strobila
a chain of proglottids, called a strobila
reflects a sequence of development:
proglottids near the neck are immature, those in the
middle are mature, and those near the end are gravid
—full of
fertilized eggs.
185
taenia
saginata - beef tapeworm
| solium - pork tapeworm
186
echinococcs granulosus
an
unusual tapeworm of canines in that its body consists of only
three proglottids—one immature, one sexually mature, and one
gravid.
187
echinococcs granulosus transmission human
Humans become accidental intermediate hosts by consuming
food or water contaminated with Echinococcus eggs shed in
dogs’ feces. The eggs release larvae into the intestine; the larvae
invade the circulatory system and are carried throughout the body, where they form hydatid cysts and cause
hydatid disease. Hydatid cysts form in any organ but occur primarily
in the liver
188
echinococcs granulosus transmission animal
Canines are infected by eating cysticerci
in various herbivorous hosts, such as cattle, sheep, and
deer
189
trematodes
e flat, leafshaped
worms (Figure 23.19). A fluke has no anus and so has an
incomplete digestive tract. A ventral sucker enables a parasite
to attach to host tissues and obtain nutrients
- Grouped according to the site in the body they parasitize
190
fasciola disease
Acute disease characterized by tissue death, abdominal
pain, fever, nausea, vomiting, and diarrhea accompanies the
migration of the parasite from the intestine to the liver; chronic
infection begins when flukes take up residence in the bile ducts.
191
fasciola organism
Two species of liver fluke—Fasciola hepatica and F gigantica infect sheet n cattle worldwide
192
fasciola transmission
Fasciola also can infect humans, who become accidental
definitive hosts when they ingest metacercariae encysted
on aquatic vegetation such as watercress.
193
schistosomiasis
"snail fever"
194
schistosomiasis organism
Blood flukes in the genus Schistosoma, dioecious.
| - humans r pricipal definitive ost
195
schistosomiasis ransmission
Cercariae burrow through the skin of humans who
contact contaminated water while washing clothes and utensils,
bathing, or swimming.
196
nematodes
Nematodes, or roundworms, are long, cylindrical worms that
taper at each end, possess complete digestive tracts, and have a
protective outer layer called a cuticle.
197
ascariasis organism
ascaris lmbricoides. nematode
198
ascariasis ndemic
tropical n subtropical regions
199
ascariasis symptoms
Most infections are asymptomatic, though if the worm burden
(number of worms) is high, intestinal symptoms and signs
can include abdominal pain, nausea, vomiting, and complete
intestinal obstruction, which may be fatal. Transitory fever and
pulmonary symptoms, including dry cough, difficulty in breathing,
and bloody sputum, may occur during larval migration
200
ascariasis prevention
Proper sanitation
and hygiene, including treatment of sewage and drinking
water, are important for prevention. Good personal hygiene
and cooking practices are also important methods of preventing
infection in endemic areas.
201
enterobius
- pinworm
- most common parasitic worm found
in the United States
- particularly in temperate
climates, in school-age children, and in conditions of overcrowding
202
enterobius organism
nematode enterobius vermicularis
203
symptoms enerobius
One-third of all Enterobius infections are asymptomatic.
When symptoms do occur, intense perianal itching is the chief
complaint. Scratching can lead to secondary bacterial infections.
204
enterobisu prevention
Prevention of reinfection and
spread to family members requires thorough laundering of all
clothes and bedding of infected individuals. Further, infected
individuals should not handle food to be consumed by others.
205
filarial nematode
—a type of nematode that infects not the intestinal
tract of vertebrate hosts but rather the lymphatic system, causing
filariasis
206
filariasis orgaism
wucereria bancrofti, a filarial nematode
207
filariasis symptoms
Filariasis remains asymptomatic for years. As the disease
progresses, lymphatic damage occurs—subcutaneous tissues
swell grotesquely because blocked lymphatic vessels cannot
drain properly. The end result is elephantiasis
208
elephantiasis
generally in the lower extremities, in which tissues enlarge and
harden in areas where lymph has accumulated (Figure 23.26).
Elephantiasis can be further associated with secondary bacterial
infections in affected portions of the body
209
wuchereria prevention
Prevention relies on using insect repellents or mosquito
netting; wearing loose, long, light-colored clothing; or remaining
indoors when mosquitoes are most active.
210
wuchereria transmissionn
Mosquitoes ingest circulating larvae called microfilariae while feeding on humans
