1 Flashcards
(47 cards)
bacteria vs archaea
- bac: cell walls made of the polysaccharide peptidoglycan; some dont have cell walls
- arch: cell walls r other chemicals; none known to cause disease
molds
- microscopic
- multicellular organisms that grow as long filaments
that intertwine to make up the body of the mold. Molds reproduce
by sexual and asexual spores, which are cells that produce
a new individual without fusing with another cell. The cottony growths on cheese, bread, and jams are molds.
yeasts
Yeasts are unicellular and typically oval to round. They reproduce
asexually by budding, a process in which a daughter cell grows off the mother cell. Some yeasts also produce sexual
spores. An example of a useful yeast is Saccharomyces cerevisiae, which causes bread to
rise and produces alcohol from sugar
protozoa
Protozoa are single-celled eukaryotes that are similar to animals
in their nutritional needs and cellular structure. Most protozoa
are capable of locomotion, and one way scientists categorize
protozoa is according to their locomotive structures: pseudopods,
cilia,
or flagella.
- Some protozoa, such as the malariacausing
Plasmodium, are nonmotile in their
mature forms.
- Protozoa typically live freely in water, but some live inside
animal hosts, where they can cause disease. Most protozoa reproduce
asexually, though some are sexual as well.
pseudopods
extensions of a cell that
flow in the direction of travel
cilia
numerous,
short protrusions of a cell that beat rhythmically to propel the
protozoan through its environment
flagella
also extensions of a cell but are fewer, longer, and more whiplike
than cilia
algae
unicellular or multicellular photosynthetic eukaryotes;
that is, like plants, they make their own food from carbon
dioxide and water using energy from sunlight. They differ from
plants in the relative simplicity of their reproductive structures.
Algae are categorized on the basis of their pigmentation and the
composition of their cell walls.
large algae
Large algae, commonly called seaweeds and kelps, are common
in the world’s oceans. Chemicals from their gelatinous cell
walls are used as thickeners and emulsifiers in many food and
cosmetic products as well as in a hardening agent called agar in
microbiological laboratory media.
unicellular algae
common in freshwater
ponds, streams, and lakes and in the oceans as well. They are
the major food of small aquatic and marine animals and provide
most of the world’s oxygen as a by-product of photosynthesis.
The glasslike cell walls of diatoms provide grit for many
polishing compounds.
parasitic worms
range in size
from microscopic forms to adult tapeworms over
7 meters (approximately 23 feet) in length. Even though most of
these worms are not microscopic as adults, many of them cause
diseases that were studied by early microbiologists. Further,
laboratory technicians diagnose infections of parasitic worms
by finding microscopic eggs and immature stages in blood,
fecal, urine, and lymph specimens.
redi
When the flask remained unsealed,
maggots covered the meat within a few days. When the flask
was sealed, flies were kept away, and no maggots appeared on the
meat. When the flask opening was covered with gauze, flies were kept
away, and no maggots appeared on the meat, although a few maggots
appeared on top of the gauze.
- began to doubt aristotle’s theory of spontaneous generation
needham
He boiled beef gravy and infusions of plant material
in vials, which he then tightly sealed with corks. Some
days later, Needham observed that the vials were cloudy, and
examination revealed an abundance of “microscopical animals
of most dimensions.” As he explained it, there must be a “life
force” that causes inanimate matter to spontaneously come to
life because he had heated the vials sufficiently to kill everything.
spallanzani
Spallanzani boiled infusions for almost an
hour and sealed the vials by melting their slender necks closed.
His infusions remained clear unless he broke the seal and exposed
the infusion to air, after which they became cloudy with
microorganisms. He concluded three things:
• Needham either had failed to heat his vials sufficiently
to kill all microbes or had not sealed them tightly
enough.
• Microorganisms exist in air, can contaminate
experiments.
• Spontaneous generation doesnt occur
pasteur’s experiments
- swan necked flasks
- Pasteur followed this experiment with demonstrations
that microbes in the air were the “parents” of Needham’s microorganisms.
He broke the necks off some flasks, exposing the
liquid in them directly to the air, and he carefully tilted others
so that the liquid touched the dust that had accumulated in
their necks. The next day, all of these flasks were cloudy with
microbes. He concluded that the microbes in the liquid were
the progeny of microbes that had been on the dust particles in
the air.
pasteur fermentation conclusions
- yeast cells arise only frm other yeast cells
- yeasts r facultative anaerobes
- (anaerobic) bacteria ferment grape juice to produce acids; yeast cells ferment to produce alcohol
pasteur 4 hypothesis
- spontaneous fermentation occurs (rj)
- air ferments grape juice (swan flask; rj)
- bacteria ferment grape juice into alcohol (juice inoculated w/ bacteria n sealed; rj, acids)
- yeasts ferment gj into alcohol
germ theory of disease
Pasteur’s discovery that bacteria are responsible for spoiling
wine led naturally to his hypothesis in 1857 that microorganisms
are also responsible for diseases. This idea came to be known as
the germ theory of disease. Because a particular disease is typically
accompanied by the same symptoms in all affected individuals,
early investigators suspected that diseases such as cholera,
tuberculosis, and anthrax are each caused by a specific germ,
called a pathogen.14 Today we know that some diseases are genetic
and that allergic reactions and environmental toxins cause
others, so the germ theory applies only to infectious diseases.
buchner
Studies on fermentation began with the idea that fermentation
reactions were strictly chemical and did not involve living organisms.
This idea was supplanted by Pasteur’s work showing
that fermentation proceeded only when living cells were present
and that different types of microorganisms growing under
varied conditions produced different end products.
In 1897, the German scientist Eduard Buchner (1860–1917)
resurrected the chemical explanation by showing that fermentation
does not require living cells. Buchner’s experiments demonstrated
the presence of enzymes, which are cell-produced
proteins that promote chemical reactions. Buchner’s work
began the field of biochemistry and the study of metabolism.
etiology
study of causation of disease
anthrax
potentially fatal disease, primarily of animals, in which toxins
produce ulceration of the skin. Anthrax, which can spread to
humans, caused untold financial losses to farmers and ranchers
in the 1800s.
koch and anthrax
Koch carefully examined the blood of infected animals,
and in every case he identified a rod-shaped bacterium that
formed chains. He observed the formation of resting stages (endospores)
within the bacterial cells and showed that the endospores
always produced anthrax when they were injected into
mice. This was the first time that a bacterium was proven to
cause a disease. He had been fortunate when he chose anthrax
for his initial investigations, because anthrax bacteria are quite
large and easily identified with the microscopes of that time.
how did koch solve his problem
However, most bacteria are very small, and different types exhibit
few or no visible differences. Koch puzzled how he was to
distinguish among these bacteria.
He solved the problem by taking specimens (e.g., blood,
pus, or sputum) from disease victims and then smearing the
specimens onto a solid surface such as a slice of potato or a
gelatin medium. He then waited for bacteria and fungi present
in the specimen to multiply and form distinct colonies. Koch hypothesized that each colony consisted
of the progeny of a single cell. He then inoculated samples
from each colony into laboratory animals to see which caused
disease.
koch’s postulates
series
of steps that must be taken to prove the cause of any infectious
disease.
1. The suspected causative agent must be found in every case
of the disease and be absent from healthy hosts.
2. The agent must be isolated and grown outside the host.
3. When the agent is introduced to a healthy, susceptible host,
the host must get the disease.
4. The same agent must be found in the diseased experimental
host.
