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MICR 221 TESTED QUESTIONS WITH ALL REVISED ANSWERS – UPDATED!!
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MICR 221 TESTED QUESTIONS WITH ALL REVISED ANSWERS – UPDATED!! What is commensalism - Answer-a symbiotic relationship in which one organism benefits and the other is neither helped nor harmed What is mutualism - Answer-a symbiotic relationship in which both organisms benefit What is pathog...

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  • August 29, 2024
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  • 2024/2025
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  • what is commensalism
  • micr 221 tested questions with all revised answers

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MICR 221 TESTED QUESTIONS WITH
ALL REVISED ANSWERS –
UPDATED!!
What is commensalism - Answer-a symbiotic relationship in which one organism
benefits and the other is neither helped nor harmed

What is mutualism - Answer-a symbiotic relationship in which both organisms benefit

What is pathogenesis - Answer-a symbiotic relationship in which one organism is
harmed (the pathogen may or may not grow outside of the host)

What is parasitism - Answer-a symbiotic relationship in which one organism is harmed
(the parasite cannot grow outside of the host)

Bovine Rumen - Answer-organ that harbours bacteria that digest cellulose and other
polysaccharides

bacteria allow cow to obtain nutrients from grass/grain diets. Cow provides habitat for
bacterial growth and a continual food supply

Non pathogenic E.coli - Answer-consumes the remaining oxygen present in the
intestine, thereby allowing the growth of obligate anaerobes like Bacteriodes (E.coli
derives no obvious benefit from co existence with anaerobes)

Why care about commensalism or mutualism - Answer-bacteria comprise a large part of
us
bacteria help create us

What can colonize on skin - Answer-staphylococcus and streptococcus spp.

What can colonize on the oral cavity - Answer-streptococcus, fusobacterium,
actinomyces spp.

What can colonize in the nasopharynx - Answer-strep, staph, neisseiria meningitidis.

What can colonize the stomach - Answer-helicobacteri phylon

What can colonize the GI tract - Answer-lactobacillus, bacteriodes, bifidobacterium,
clostridium, escherichia, eterococcus

,What is plaque - Answer-when bacteria grow on the surface of teeth in the hum
crevices, the resulting film is called plaque

What are plaques comprised of - Answer-several species of bacteria are early
colonizers on the teeth and later aid later colonization (fusobacteria)

Colonization of Teeth - Answer-adhesion of early colonizers

recruitment of late colonizers

Adaptation of oral bacteria to challenging micro environments - Answer-early colonizers
are exposed to a pH of 3-4

late in colonization, bacteria are present in an anoxic environment

What are some examples of mutualistic bacteria by transforming the hosts physiology
and (in some cases) anatomy - Answer-Bacteria can stimulate development of the
intestine and the development of the immune system

evidence for the above two concepts were obtained from studies with germ free
(gnotobiotic) mice

What are gnobiotic mice - Answer-there are animals that are simplified that have known
microbes

by c-section then put into a sterile box and are given microbe free food

What is special about gnotobiotic animals - Answer-they have defects in development of
the intestinal epithelium and in the immune system. They can therefore beused to study
the impact of particular mutualistic bacteria on intestinal or immunological development

What type of neonates are in the human intestine - Answer-they are colonized primarily
with facultative anaerobes

What do obligate anaerobes emerge as during weaning - Answer-they emerge as key
colonizers. then by adulthood, obligate anaerobes (mainly bacteriodes) predominate

What does the intestinal epithelium develop during weaning - Answer-it develops a
capillary network, ensuring abundant blood supply. Colonization with bacteriodes
correlates with intestinal blood vessel development)

How does bacteria stimulate the development of the intestine - Answer-due to vascular
formation. the intestinal epithelium needs to be highly vascularized to have proper villi

Why aren't animals hard-wired to produce a functional intestine in the absence of
bacteria - Answer-the co-evolution of humans and bacteria for intestines to develop

, properly. They may have not been important during weaning (but requires protection
after weaning)

What are the immune system defects exhibited by gnotobiotic mice - Answer-- higher
susceptibility to infections
- diminished by cytokine levels
- reduced levels of innate immune cells (eg neutrophils)
- reduced serum immunoglobin levels
- reduced levels of CD4 T cells

What does the colonization of gnotobiotic mice with Bacteriodes restore - Answer-they
restore normal levels of CD4 T cells

What is the expansion of splenic CD4 T cells caused by - Answer-a bacterial capsular
polysaccharide antigen termed 'PSA'

What are some evidences in support of microbial contribution to obesity (HUMAN) -
Answer-in humans
: compared to lean individuals, obese individuals have a lower proportion of
Bacteriodetes and a higher proportion of Firmicutes in their intestine

: when obese individuals lost weight, due to caloric restriction, their proportion of
bacteriodetes increase, and proportion of Firmicutes decreased.

What is microbial growth? - Answer-it is the increase of the population of cells and not
about its development

How do bacteria duplicate? - Answer-through a process called binary fission

Cell Numbers increase .......... - Answer-exponentially

What is the mean generation time - Answer-The time that it takes for one cell (and
therefore a whole population) to divide

What is the Mean Generation Time for E. Coli - Answer-20 minutes

What is the Mean Generation Time for M. Tuberculosis - Answer-12 Hours

What scale is used to measure microbial growth? And why - Answer-The logarithmic
scale is used to be able to clearly see the numbers and that it does not clash lines with
the arithmetic scale

What component is important for cell arrangement - Answer-the plane of division

What happens when there's only one plane of division - Answer-It becomes a
diploccocus

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