121 Flashcards
(289 cards)
1
Q
pros of microbes on food
A
food materials may require microbiologival activity such as yogurt
2
Q
cons of microbes in food
A
food spoilage
food borne disease
3
Q
why dont we know the true diversity of sample by culture
A
as we cannot culture all bacteria from a sample
4
Q
3 domains of life
A
euksryotes
archea
bacteria
4
Q
eukaryote
A
include fungi,animals,plants
an organism that consists of one or more cells each of which has a nucleus and other well developed compartments
5
Q
bacteria
A
constitute a large domain of prokarytotic microorganisms
range from spheres to rods and sprirals
6
Q
archaea
A
similar to bacteria in size
intermediate between bacteria and eukaryotes
7
Q
archea characteristics
A
presence of tRNA and ribosomal RNAs
peptidoglycan cell walls
linked lipids built from phytanyl chains
occur in unusual habitats
8
Q
virus size
A
0.01-0.2 um
9
Q
bacteria size
A
0.2-5 um
10
Q
eukaryotes size
A
5-100um
11
Q
yeast size
A
5-10um
12
Q
protists size
A
50-1000um
13
Q
algae size
A
10-100um
14
Q
cell volume importance
A
high SA:V of smaller cells leads to fast nutrient exchange
smaller cells = faster growth
lots of cells=mutation risk
15
Q
barrier function
A
separation of cell from its environment
16
Q
selectively permeable barrier
A
controls movements of molecules in or out a cells (transport proteins)
17
Q
functions of bacterial cell membrane
A
barrier function
selectively permable membrane
site of respiration/photosynthesis
energy conservation(proton motive force)
18
Q
diplococci
A
2 cells in line
19
Q
streptococci
A
chain of cells
20
Q
clump of cocci
A
clumps of cells
21
Q
gram stain
A
stain with crystal violet
add iodine forms a complex
wash with ethanol
counterstain with safranin
22
Q
why does lysozyme lyse and penicillin kill archaea
A
lack peptidoglycan , have variety of cell walls including ppseudo-peptidoglycan
23
Q
gram + cell wall
A
almost 90% peptidoglycan - thick layer- with a cytoplasmic membrane layer as well on the inside. many have teichoic acids embedded. negatively charged so surface is negative so can bind to divalanet cations like mg and ca
24
gram- cell wall
thin layer of peptidoglycan surrounded by an outer membrane composed of lipids, proteins and lipopolysaccharides and porins . only 10% peptidoglycan
25
peptidoglycan structure
only found in bacteria
rigid layer glycan strands linked by glycosidic bonds. crosslinked strands by peptides.
lysozymes break G-M bonds bursting the cell
26
fimbriae
short, thin, hair like, proteinaceous appendages ( up to 1000/cell)
recognition and attachment to surfacs
27
pili
similar to fimbriae except onger thicker and less numerous (1/10), required for mating
28
polar flagellum
flagellum at end of cell
29
monotricheous
1 flagellum
30
amphitrichous
1 flagellum at each on of cell
31
lophotrichous
cluster of flagella at 1 or both ends
32
peritrichous
flagellum spread over entire surface of cell x
33
bacterial cytoplasm
contains ribosomes and nucleoid, cellular inclusions sometimes, macromolecules( rna, proteins), organic materials eg carbs + lipids
inorganic ions
34
the nucleoid in bacteria
irregularly shaped region, is location of singular chromosome or sometimes 2
35
plasmids
usually small closed circular dna molecules
exist and replicate independently of chromosome
not required for growth and reproduction
may carry genes that confer selective advantage eg drug resistance
36
cellular inclusions
granules of organic or inorganic material that are reserved for future use
may contain:
glycogen
poly-b-hydroxybutyrate (PHB)
polyphosphate granules
sulpher granules
37
cellular inclusions magnetism
specialist bacteria with magnetosomes
contain iron in form of magnetite
use is to orient cells in magnetic fields
38
gas vesicles- cellular inclusions
used for buoyancy in some aquatic bacteria
39
advantages of endospores
survive 100-1000 years- produced under unfavourable conditions
highly resistible to heat, drying. radiation and chemicals very low water content
contain calcium dipicolinate
special proteins protect dna
40
calcium dipicolinate
binds free water and helps dehydrate cell
41
halophillic bacteria
250 million year old crystal salt
42
culture media definition
nutrient solution that provide all the elements required for growth
43
chemically defined media
the exact chemical composition is known
44
complex media
exact chemical composition not known made of digests fo complex material such as milk protein beef yeast etc
45
binary fission
how bacterial cell divides into 2
dna replication
cell elongation
septum formation
46
doubling time/generation time
time needed for a population to double
exponential growth
47
batch culture
culture that is grown in a closed system, no additional nutrients are added and no waste products removed during culture period
48
lag phase in bacterial population
time interval between inoculation and maximal division rate ( cells adjusting to new environment )
49
log phase in bacterial growth
bacteria growing exponentially , constant doubling, maximum growth rate
50
stationary phase in bacteria growth curve
bacteria no longer reproduces but are still alive , no nutrients left...
51
viable but nonculturable bacteria
bacteria in a very low metabolic activity state where they dont divide but are alive and have the ability to become culturable once resuscitated
(or they just cant grow on conventionalble media )
52
total count
non specific dye that stains all bacteria , in most cases dead cells too
53
viable count
uses fluorescent activity dyes which counts all cells with activity
54
culturable count
count cells that can form colonies on solid media or increase turbidity in liquid media
55
advantages of total cell count
easy and fast
56
disadvantages of total cell count
uses special microscope counting slide
does not differentiate between live and dead bacteria
57
heterotrophs
require organic molecules made by other organisms
58
autotrophs
co2 is principal carbon source
59
phototrophs
use light as energy sourve to produce atp
60
chemotrophs
oxidise organic or inorganic compounds
61
where do obligate aerobes grow
need o2 for growth so grow close to top of test tube
62
abligate anaerobes
cannot grow in presence of o2 so grow at bottom of a test tueb
63
facultative anaerobes
can grow with and without o2
64
aerotolerant anaerobes
do not need o2 but can tolerate it
65
microaerophillic
need o2 but tolerate it at a low concentration
66
mesophile
grow best between 20-40 degrees
most bacteria in our body are these
67
thermophiles
grow bet between 45-80 degrees
live in hot springs compost heaps etc
68
hyperthermophiles
grow best above 80 degrees
live in hot springs
69
facultative aerobe
not required but grows better with oxygen
70
a useful enzyme produced by thermophilic bacteria
taq polymerase from thermus aquaticus used for pcr
71
histology
study of animal and plant tissues
72
cytology
study of cells under microscope
73
light microscope mag res ect
x1000 magnification
200 nm resolution
brightfield
phase-contrast
fluorescent
74
electron microscope
1 x 10^6
resolution down to 0.2nm
scanning EM
transmission EM
75
resolution
separation distance at which 2 objects in an image can be apart and still distinguished as separate
76
whats a host
organisms that supports growth of viruses, bacteria and parasites
77
pathogen
organism that causes disease, by impairing or interfering with the normal physiological activities of the host
78
pathogenicity
the ability to cause disease
79
virulence
the degree or intensity of pathogenicity (determined by toxicity and invasiveness)
80
infection
bacteria persist in host without necassarily causing tissue damage
81
disease
overt damage to the host, parts of body cannot fulfill their normal function
82
why did miasma theory sometime works
it was based on theory of bad smells causing disease so lots of cleaning and diverting of sewage was done and it prevented cholera. Dr. William Farr was convinced by this theory and that cholera was transmitted by air
83
robert koch
1843-1910
established germ theory
tried to prove specific microorganisms caused disease (kochs postulates)
developed simple methods for obtaining disease in pure culture
84
kochs postulates
infecting mice or collecting microorganisms from dead animals
led to discovery of causes for anthrax, TB and cholera
85
opportunistic pathogens
only cause serious disease when host defences are impaired
e.g. pseudomonas aeruginosa
often exist in envrionment
86
primary pathogens (obligate)
capable of causign diseae in absence of immune defects
e.g. syphilis- treponema pallidum
need to cause disease to survive
human-human and animal-human transmission
87
reservoirs
bacterial pathogens need at least 1 reservoir
such as other humans, animals and environment
88
reservoir examples for anthrax
agent= bacillus anthracis
reservoir in livestock and soil
89
reservoirs examples for legionnaires disease
agent= legionella pneumophila
reservoir in high moisture environments like air con
90
direct host-host transmission
airborne= aerosols like coughing
body contact like kissing and touching
91
indirect host-host transmission
vector-borne- living organisms like arthropods(insects,tics), vertebrates (rats,dogs)
non living- food, water, soil, fork, bedding, surgery instruments
92
colonisation
establishment of a stable population of bacteria in the host
body naturaly has this- microflora
pathogen must be able to compete for nutrients/surface attachment sites
93
why do bacteria adhere to tings
to overcome flushing mechanisms
e.g. streptococci to tooth surface and staphylococci to plastic catheters
94
how do bacteria adhere to things
association- involves non-specific forces like charges/ hydrophobicity
then adhesion- specfic host receptors. can form biofilm from aggregation which can disperse and spread
95
adhesions
fimbriae and pili
capsules and slime layer
flagella
(lipo) teichoic acids (gram+)
96
host receptors for adhesion include
blood group antigens
extracellular matric proteins e.g. fibronectin, collagen
97
invasion of bacteria
some bacteria penetrate through/between cells
some invade epithelial and some invade phagocytic cells
98
invasion of bacteria using lytic compounds
often accomplished by lytic compounds that attack the host tissue
e.g. collagenase
also determined by evasion of host defences
99
invasins
virulence factors
100
resisting phagocytosis
bacteri produce structures preventing effective contact. capsules, special surface proteins
101
bacteria surviving inside phagocytic cells
often very pathogenic bacteria
102
antibody avoidence
capsules
antigenic variation- switch between different types of surface structure
sometime degradation of antibodies
103
avoidance of complement
capsules can prevent complement activation
lipopolysaccharides (gram - ) sometimes hinder pore formation
104
how does tissue damage occur
irone acquisition
direct effect of bacterial toxins
indirect effects of bacterial toxins
induction of autoimmune response
105
nutrient acquisition- iron uptake
essential element for bacteria growth
bacteria express high affinity iron uptake systems to get the iron as iron levels too low in tissues
siderophores- bind iron with high affinity
direct binding of iron transport proteins like transferrin
106
exotoxin
act on specific targets e.g. protein synthesis
made by gram + and -
protein
secreted by living bacteria
heat labile
highly immunogenic
potential lethal
107
endotoxins
(LPS) bound to cell
action is indirect- activates many host systems that cause damage
made by gram-
lipopolysaccharide
part of cell membrane
heat stable
weakly immunogenic
lethal at high concs
108
human exposure to exotoxins
ingestion of preformed exotosin e.g. food poisoning
colonisation of mucosal surface or tissue like cholera
colonisation of wound- e.g. clostridium perfringens grows in wounds or abscess causing tissue degradation
109
whys is called endotoxin
as they are bound to cells and released when bacterium lyses or during cell growth
activates host systems leading to fever, shock, blood coagulation, inflammation
110
prokaryotes in summary
circular chromosome with plasmids
fimbria adhesion
capsule adhesion/evasion
no nucleus
no membrane enclosed organelles
rapid reproduction
binary fission
benefit or harm- mutualist, commensal, pathogen
111
3 domains of protists
prokaryotes- bacteria and archaea
eukaryotes- eukarya
112
4 eukaryote supergroups
excavata
SAR
archaeplastida
unikonta
113
ER simple
protein glycosylation
membrane factory
lipid synthesis
114
photoautotrophic
'plastids'
green plastid= chloroplast
photosynthesis
algae- some have a cell wall
115
heterotrophic protists
feed on bacteria, fungi, and other protists
termed protozoa- non have cell wall
116
mixotrophic
do both photoautotrophic and heterotrophic
non have a cell wall
117
direct microscopic count- viewing protist cells
easy and fast
however uses special microscope counting slide
and does not differentiate between live and dead
known as total cell count
need to fix motile cells beforehand
118
protists divide by what
mitosis
119
doubling time for protists
hours/days at 37 degree
120
protist daughter cells
genetically identical but may vary in other components
121
lag time - protist
time interval between inoculation and maximal division rate- cells adjust to new environment
122
log phase- protists
constant doubling time
growth rate is maximal
123
stationary phase- protists
can no longer reproduce but are still alive
124
death phase- protist
death or cyst formation
125
advantages of cyst
-Produced under unfavourable conditions
-Highly resistant to heat, drying & radiation
-Very low water content
-Can survive for 20 years in the environment
-Good resistance to antibiotics/disinfectants
-Effective dispersal mechanism
Can be transmitted to others via faeces
126
where are cell walls always present in protists
non- motile photosynthetic protists
cysts
127
cell walls are not present in what protists
motile photosynthetic protists
heterotrophic protists
mixotrophic protists
need to overcome osmosis
128
obligate aerobes- o2
need o2 for growth
so top of tube
129
obligate anaerobes - o2
cannot grow in presence of o2
so bottom of tube
130
faculatative anaerobes - o2
can grow with and without o2
so spread out tube but collected at top slighlty
131
aerotolerant anaerobes- o2
do not need o2 but tolerate it
spread evenly through tube
132
microaerophilic - o2
need o2 but tolerate is only at low concentration
collected just under top of surface of tube
133
endosymbiont theory
-For mitochondria and plastids
-Bacteria originally living as endosymbiont in cells
-Dependency then became permanent
-Alpha-proteobacterium became a mitochondrion
Hydrogenosome evolved from a mitochondrion
-Cyanobacterium became a chloroplast
134
evidence for endosymbiont theory
- size of organelle= size of bacterium
- phylogeny analysis relates their DNA to their bacterial origin
- have own circular DNA and replicate by binary fission
- contain same ribosomes as bacteria
- have double membrane- engulfing mechanism
135
organellar mixotrophy
- selective digestion
-eat algal cells
- doesnt digest plastids (kleptoplastids)
-plastids fix co2
-plastids do not encode for polymerases
-die and need replenishing so eats more
protists can live without the plastids
136
cellular mixotrophy
- no digestion
- eats algal cells
- no digestion of algae
-algae fix co2
-algae divide in cell
- endosymbiosis
- protists can live without the algae
137
constitutive mixotrophs
- algae evolve into organelles
- over time
- through complicated genetic transfer events
- endosymbiotic algae become true organelles
-protists cannot live without them
- only seen in flagellates
138
organellar mixotrophy seen in
ciliates and amoebae
139
cellular mixotrophy seen in
ciliates and amoebae
140
constitutive mixotrophy seen in
flagellates
141
mixotrophy feeding vs photosynthesis
high light- photosynthesis> feeding
low light- feeding > photosynthesis
142
whats the most developed protozoan
ciliates
143
ciliates mouth and anus
cytostome- mouth
cytoproct- anus
144
2 types of nucleus and ciliate
macronucleus and micronuclei
145
cilia
microtubule-based hair-like organelles
free swimming
usually attached (sessile)
146
motile cilia
9+2 dynein motor protein
ciliates
human- bronchia; and oviduct epithelium
147
non-motile cilium
9+0 no dynein motor protein
primary cilium on all human cells
148
what do some cilia fuse to form
cirri
149
what are cilia used for
movement
feeding- direct prey to mouth
sieve
filter feeding
cytostome contains stiffer cilia
150
vorticella
prey drawn towards cell
vortex at cell mouth
very large feeding currents
no swimming so use cilia only for feeding
looks like a moon cup
151
suctorian ciliates
exception to rule
numerous microtubule tentacles
each tentacle ends with a cytostome
extrusomes- secrete toxins
dissolve prey contents and suck out
raptorial feeding
can look like dandelions
152
mixotrophic ciliates
do not contain their own plastids
acquire photoautotrophic ability 2 ways:
- organellar mixotrophy
- cellular mixotrophy
153
do ciliates reproduce asexually or sexually?
both
asexual- transverse binary fission, involves mitosis
sexual- conjugation, involves mitosis an meiosis, micronuclei swap, allows for genetic variation
154
are flagellum in flagellates forwards and backwards
no
they are propeller like motion (9+2)
155
where are flagellates found in humans
sperm
156
do flagellates possess macronucleus
yes this only
157
how do flagellates divide
longitudinal binary fission
158
flagellates are mainly anaerobic true or false
false they are mainly aerobic
159
how do flagellates feed
heterotrophy
photoautotrophy
mixotrophy
160
heterotrophic flagellates
mostly aerobic
consume pre-formed organic carbon
organic carbon (sugar) to inorganic carbon (co2)
use flagella for movement
raptorial feed and filter feeding
161
hispid flagellum
hair = hispid
swim backwards kinda
162
raptorial feeding with hispid flagellum
create feeding current when moving flagellar
prey is drawn to base of flagellum
ingested via cytoplasmic extensions (pseudopodia)
163
raptorial feeding with naked flagellum
created currents due to flagellar movement
less contact with the base of the flagellum
less efficient capture pray cause they are swimming headfirst into prey not tail first
164
increasing prey capture with naked flagellum
filter feeding
collar of tentacles (microvilli)
contain actin- contractile
165
choanoflagellates
only group with a collar of tentacles
all have single naked flagellum
attach to surface by stalk
more closely related to animals than other protists
166
photoautotrophic flagellates
- also called phytoflagellate
own plastids- green/golden
photosynthesise
inorganic carbon (co2) to organic carbon (glucose)
all are aerobic
use flagella for movement towards light and nutrients
167
euglena - photoreception
eyespot/stigmas- organelle containing carotenoid lipid globules. shading device for photoreceptors to detect light direction
168
mixotrophic flagellates
phytoflagellates that eat
constitutive mixotrophy- have own plastids
all aerobic
can ingest prey - raptorial
use flagella for movement and prey capture
one type of feeding is normally over-riding
depends on the genus and light climate
169
mixotrophic flagellates as solitary cells
ochromonas
few plastids
prefers to feed on prey
170
mixotrophic flagellates and colonys
some form colonys
dinobryon
plastids dominate cell
prefer to photosynthesise
171
amoebae nucleus
one macronucleus
172
are amoebae anaerobic or aerobic
aerobic
173
most amoebae or mixotrophic t/f
false - most are heterotrophic and some are mixotrophic
174
amoebae reproduce asexually t/f
true
175
whats the most publicised protozoan
amoebae
176
all amoebae are stationary t/f
false
some move but some are stationary
177
naked amoebae- how they move and what do they produce
amoebae proteus
move by cytoplasmic streaming
produce pseudopodia on surfaces
178
how do naked amoebae feed
feed by direct interception of prey
raptorial feeding
no specific location for ingestion- can be anywhere
179
3 cell forms of naked amoebae
trophozoites- feeding form
cysts- produce resting phase
floating form- stiffened pseudopodia for dispersal
180
shelled amoebae
enclosed in shell
can be made of anything- the shell
intrashellular cytoplasm within shell
project extrashellular cytoplasm to move/ feed
raptorial or diffusion feeding
can produce cysts
181
testate amoebae
freshwater, marine and terrestrial
rapotiral
182
foraminiferans
marine only
CaCO3 tests
diffusion feeding
183
diffusion feeding
stationary predator captures prey with sticky extrashellular cytoplasm (axopodia)
184
radiolarians
marine only
silica tests
diffusion feeding
185
heliozoans
freshwater
silica tests
diffusion
186
good ecological impacts of protists
- all of the protists
microbes- base of every food chain
keep bacterial populations healthy
important in nutirent cycling
187
bad ecological impact of protists
mainly amoebae
allow evolution of new bacterial pathogens
act as a reservoir for them too
188
what does predation stop bacteria from reaching
the stationary phase
keeping bacteria in log phase
189
what ratio to protists have to keep their cellular C:N:P
50:10:
co2, nh4, po4
190
what % of human cells are bacterial
90%
191
what protist is naturally present in humans
amoebae- entamoeba coli
exists in gut- not pathogenic
192
gut infections caused by what protists examples
amoebae- entamoeba histolytica
one ciliate- balantidium coli
flagellates- giardia lamblia
cause dysentery and produce cysts
reservoir- water and animals/humans
transport- water, faecal-oral
treatable- takes months due to cysts
193
eye infection caused by protists
amoebae- genus acanthamoeba
causes keratitis
reservoir- water
transport- dirty contact lenses
treatable but can lead to glaucoma
194
brain infection caused by protists
amoeba- naegleria fowleri
primary amoebic meningoencephalitis (PAM)
reservoir- warm water
unusual flagellate stage
transmission- up nose
fatal within 2 weeks
195
STDs caused by protists
trichomonas vaginalis
anaerobic, no cysts
infects urethra, vagina, prostate
reservoir- humans
males asymptomatic
transmission- sexual intercourse
treatable
196
blood/tissue infections caused by protists
flagellates e.g leishmania mexicana
aerobic, no cysts
reservoir- dogs
transmission- sand fly
attacks tissues e.g. liver
cutaneous- infects macrophages
treatable
197
whats a virus
simple
miniscule infectious
obligate
intracellular
parasite comprising of genetic material surrounded by protein coat or envelope derived from host cell membrane
198
average size of viruses
20-300nm
can be seen with an electron microscope
199
giant viruses- mimiviruses
750nm
bigger than bacteria
seen under light microscope
200
pandoravirus
>1000nm in length
biggest known virus
2.9megabyte genome
enclosed 2556 genes
only infect amoeba
201
2 phases of a virus
extracellular virion (outside host cell)- for transmission
intracellular virus (after infecting host cell)- for replication
202
whats viral replication
the formation of biological viruses during the infection process in the target host cell
203
what is bacterial multiplication
the asexual reproduction or cell division of a bacterium into 2 daughter cells by binary fission
204
virion
virus particle
205
virus nucleocapsid
capsid- protein coat, made up of many proteins, subunits= capsomers
nucleic acid (DNA or RNA)
206
helical capsomers
bond together in a spiral fashion
207
polyhedral capsomers
capsi is roughly spherical. icosahedran symmetric carry 20 faces and 12 corners
208
binal (complex) capsomer
neither helical or polyhedral. have irregular shapes or have complex structures. may have both helical and isometric symmetries
209
function of capsid
- protects the nucleic acid from enzyme digestion
- special sites that allow virion to attach to host cell
- proteins that enable virion to penetrate the host cell membrane
210
groups of organisms that can be infected by viruses
bacteria
protozoa
algae
fungi
plants
animals
viruses- virophages
211
whats a bacteriophage
viruses of bacteria
a particle weights a femtogram (10^-15)
10^30 bacteriophage particles in worlds water
biomass of bacteriophages outweighs elephants by 1000fold
212
bacteriophage genome
only a few with envelopes
most have dsDNA
many are complex
213
replication steps of lytic bacteriophage T4 (6 steps)
adhesion
penetration
replication
maturation
release
reinfection`
214
Bacteriophage T4 is virulent and kills the host: it is a lytic phage. t/f
true
215
Many bacteriophages have an alternative life cycle where they don’t kill the host: temperate phages or lysogenic phages. t/f
true
216
prophage- bacteriophages
genome of temperaete phage integrates into host chromosome and becomes prophage.
produces a repressor protein which blocks lytic genes
also replicates with host chromosome- lysogeny or lysogenic cycle
immune against infection of same phage because of repressor
217
Stresses (UV light, toxin) initiate induction to resume lytic cycle
t/f
true
218
use of phages in biomedicine
EBI- listeria bacteriophage - on unprocessed foods like cheese, meats and fish
a bacteriophage enzyme detects and kills bacillus anthracis spores
biomarkers for disease
as delivery vectors
disease therapy
219
what are some viruses named after
- host organism
-location
- scientists
- site in body
- how contracted
- cytopathology
- a combination
causes a lot of issues when classifying
220
internal committee on the taxonomy of viruses (ICTV)
established by federation of European microbiology societies (FEMS) virology division
1 of the main methods for taxonomy of viruses
221
Baltimore system of virus classification
system developed by David Baltimore
1 of the main methods for taxonomy of viruses
222
phenotypic criteria for ICTV taxonomy
- molecular composition of genome
- virion/capsid structure
- presence of an envelope
-host range
- pathogenicity
223
genotypic criteria for ICTV for taxonomy of viruses
- sequence similarity
-gene contents
- gene synteny
- gene expression system
- phylogenetic relationships
224
ICTV- highest and lowest levels of classification
species- 9110 -lowest
genus - 2224 genera
family- 189
order- 59
class- 39
phylum- 17
kingdom- 10
realm- 6- highest level
225
Baltimore system of virus classification
viral genome must make mRNA that can be read by host ribosomes
all viruses follow this rule to date
all viruses make mRNA
- dsDNA
- gapped dsDNA
- ssDNA
- dsRNA
-+ssRNA
- -ssRNA
- +ssRNA with DNA intermediate
226
possible ways viruses can infect cells
transformation into tumour cell
lysis- death then release
persistent infection
latent infection- virus present but no harm till later
227
virus lifecycle 3 steps
entry- attachment and uncoating
replication- replication, biosynthesis
exit- assembly, budding
228
attachment stage of virus lifecycle
different viruses can attach to same receptors
but some viruses of same family may bind to different ones
one virus can bind to multiple receptors
229
entry stage of virus lifecycle
3 possible mechanisms
1. injection of nucleic acid
2. fusion of envelope with host membrane
3. endocytosis
230
replication of viruses purposes
1. viral proteins - synthesis of mRNA (unanimous)
2. viral genome- generation of viral genetic material (virus-dependent)
viral proteins + genome = assembled virus
231
true pathogens
healthy host
adapted to high temp and low o2 tension
restricted to geographic location
display thermal dimorphism
usually asymptomatic
not obligate parasites
232
true pathogens dont display thermal dimorphism t/f
false- they do
233
true pathogens are normally asymptomatic in healthy host t/f
true
234
true pathogens are obligate parasites t/f
false they arent
235
thermal dimorphism- true pathogens
if you increase temp- animal habitat- yeast form, reproduction via budding or endospores, parasitic
decrease in temp- natural habitat, hyphal form, reproduction via spores saprophytic
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histoplasmosis
true pathogen
histoplasma capsulatum
most common
500 000 cases/yr in USA
<50 deaths
leads to pneumonia and sometimes spreads to internal organs
237
coccidiodomycosis
true pathogen
coccidiodes immitis
most common in alkaline desert soils in US
60% no symptoms
40% fever
0.5% growth in lungs
mild lung infections which can spread to meningitis and skin rashes
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opportunistic
immunocompromised host
distributed worldwide
lots of species always increasing
no specific adaptation to host environment
superficial/benign to chronic systemic infections
prognosis- poor
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candidiosis- candida albicans
20% of us are inhabited
immunocompetent- non invasive local infection
immunocompromised- systemic causing organ failure
most common fungal pathogen causing death
4th biggest killer in tertiary car hospitals
invades wounds/burns
dimorphic yeast- hyphal form is aggressive
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dermatophytes
superficial infections on healthy host
worldwide
most common = ringworm, atheltes foot
not life-threatening just discomfort and unsightly
241
why are human mycoses a rising clinical problem
more immunocompromised hospital patients
a poor understanding of fungal biology and limited antifungal treatments
242
how do we control myocoses of humans
azoles- ketoconazole, fluconazole
polyenes- nystatin, amphotericin B
243
what does 5 fluorocytosine do
inhibits RNA synthesis fungistatic
244
pathogens of immature tissue
broad host range
soil-borne attack roots
water-logged soils
245
pathogens of mature tissue
usually high degree of host specificity.
necrotrophic pathogens
biotrophic pathogens
246
whats an example of a necrotrophic pathogen
armillaria mellea
major root rot pathogen of broad-leaved trees
excrete ligninases, cellulose and pectinases
247
necrotrophic pathogens
- excrete toxins and cell wall digesting enzymes
- host cell death
- tissue invasion
- evoke host resistance mechanism
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biotrophic pathogens
maintain host viability
limited tissue invasion
do not evoke resistance mechanisms
life cycle depend on living host
arrive as spores on leaves
249
haustorial biotrophs
biotropic pathogens
puccinia graminis- via stomatal openeing, infect mesophyll cells
erysiphe graminis- infect directly through cuticle epidermal layer
250
fungi to control insect pests
>1billion dollars spent in USA to control insect pests
over 400 species of fungi attack insect and mites
251
verticillium lecanii
produces spores in liquid fermentors
fresh pores are sticky so attach insects which become contagious
spores do not need to be ingesed
germination needs rh>95% at 15-18c for 12h
252
mechanisms to control phytopathogenic fungi
parasitism of the pathogen by the BCA
production of antibodies, BCA poisons the pathogen
competition for nutrients water and space
253
parasitism
fungi that parasitize other fungi - mycoparasites
254
trichoderma - trichodermin gliotoxin
produce antibiotics
trianum- sold for control of fungal diseases
255
yeast in food and drink
baking and brewing
saccharomyces cerevisiae
C6H12O6--> 2C2H5OH + 2CO2
S. cerevisiae yeast extract paste marmite
256
soya bean products- food and drink
has positive and negatives
fermentation of beans with aspergillus oryzae
beans soaked for 16hrs
aerobic fermentation 3d-3m
20% salt
anaerobic fermentation with zygosaccharomyces 3m-3yr
drained and pasteurised
257
quorn- food and drink yeast
developed after concerns in protein content in food
grows on glucose syrup
ammonia- nitrogen source
filaments spun and flavoured to resemble meat
258
enzymes produced commercially by aspergillus niger
glucoamylases- liquid starch to high glucose syrup
pectinases- breakdown pectins in plant cell wall for juices
glucose oxidase- food preservation and diagnostic tests
phytases- improvement of animal feed
259
problems with fungal cell factories
starch-based food cooked at high temp recently discovered to have high levels of acrylamide a carcinogen
260
fungal cell factories- antibiotics
penicillin
alexander flemming 1928
used at end of WW11
improved yields from 2mg to 30gl-1
chemically altered semi-synthetic penicillins
261
statins
fungal metabolites that inhibit the biosynthesis of cholesterol and are used to reduce plasma cholesterol levels
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examples of old disease
polio
hepatitis
smallpox
influenza
warts
rabies
measles
rubella
leukemia
263
examples of re-emerging diseases
west nile fever, dengue fever, ebola, aids, monkeypox, sars-cov-2
264
what does rhabdovirus cause disease in
animals humans and plants
265
what shape is rabies virion
bullet shape
170nm long
266
replication of rabies virus
1. RNA-polymerase
2. translation into protein by host
3. transcription of viral RNA
4. assembly
267
what group is the rabies virus
group V virus (-ssRNA)
268
how many deaths does rabies causes worldwide /yr
30 000
269
where does rabies virus enter
peripheral nervous system and then migrates to the central nervous sytem to the brain
270
how does rabies kill person
causes swelling of the brain (encephalitis)
271
furious rabies
80-90% of cases
change in behaviour and voice
paralytic stage
death
272
dumb rabies
10-20% of cases
predominantly paralytic
lapse into stage of sleepiness
death within 3 days
273
where is monkeypox endemic
central and west africa
274
monkey pox group classification
group 1 virus, dsDNA
275
how many cases of monkeypox in 29 EU countries
20455
and 73604 total cases
276
how is monkey pox transmitted
animal-animal- bites/scratches
human-human- direct skin contact with lesions on skin or indirect with contaminated domites such as bedding/clothing
277
ACAM2000- live vaccinia virus - smallpox(mokeypox) vaccine
single dose
not recommended for immunocompromised/pregnant as can replicate
lesion at innoculation site
278
modified ankara (MVA) smallpox vaccine
2 doses 4 weeks apart
no lesion at site
does not replicate
279
LC16m8 licensed in japan smallpox vaccine
single does
less replication than other viruses and so safer
280
viroids
infectious agent that resemble viruses
small circular ssRNA
naked
no capsid
resistant to proteases and nucleases
only infects plants
doesn't encode proteins
replicate autonomously
281
whats a prion
small proteinaceous infectious particles which resist inactivation and contain no genetic material
often called spongiform encephalopathies
282
cellular prions
localise on the neurons synapses between neurons or facilitate the uptake of copper into the cell
caused by the accumulation of the misfolded protein scrapie prion protein
283
do we know how prions cause disease
no
most likely infection with prion protein (=PrP^sc) produces more copies of PrP^sc, leading to disease
284
scrapie - sheep
a degenerative fatal disease of the CNS of sheep and goats
symptoms of ataxia and recumbency
no treatment
selective breeding for genetic resistance, surveillance and depopulation
285
BSE (bovine spongiform encephalopathy)- cattle
mad cow disease- erratic behaviour
4 million cows killed during eradication programme in uk
3 different presentations- classical BSE, H-type atypical BSE and L-type atypical BSE
classical BSE is the only form that can be transmitted to humans through consumption of meat causing creutzfeldt-jakob disease
286
kuru- human
means trembling
caused by prions
reported in fore tribe of papau new guinea via funerary cannibalism
287
CJD (creutzfeld-jacob disease)
lose ability to think and move properly and suffer from memory loss
always fatal usually within 1yr
lots of types like sporadic which is most common
familial CJD- rare genetic condition
varient CJD- consuming meat
latrogenic CJD- when infection is accidentally spread from someone with CJD through medical or surgical treatment
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