microbe host

Define and contrast: symbiosis, mutualism, parasitism, commensalism.

symbiosis means living together. mutualism, parasitism and commensalism are all types of symbiosis. mutualism is when both partners are benefitting. commensalism is when one partner is benefitting and the other is unaffected. parasitism is when one partner is benefitting at the expense of the other.

Could a single organism be a commensal sometimes and a parasite at other times? Explain.

yes this is called an opportunistic pathogen. opportunistic pathogens normally live in the host harmlessly but can cause disease if the host is compromised.

Why are mutualisms common in nature?

because together the symbiotic partners have new abilities that they do not have alone which allows them to fill new environmental niches

What is an endosymbiosis?

endosymbiosis is when the symbiont lives inside host’s cells

Between which types of organisms are endosymbioses commonly observed?

they are most commonly observed in bacteria invertebrate symbioses

Give three examples of an endosymbiont and its host and describe what each partner gains from the endosymbiosis.

1. aphids and buchnera - buchnera is providing aphids with 10 essential amino acids

2. bacteria and tube worms - tube worms are dependent on chemosynthetic bacteria by using inorganic carbon as its carbon source and H2S as its energy source

3. nitrogen-fixing bacteria and legumes - rhizobia reduces N2 into ammonia (NH3) as a usable nitrogen source. the bacteria receives dicarboxylic acids from the plant (mutualism)

What is the microbiota? Specifically, where is the microbiota commonly found?

microbiota is all genes and microbes; commonly found on the gut, skin, and mouth

What are some examples of how the human microbiome affects human health?

immune system training, metabolism, and modifying drug effectiveness

Describe how the human microbiome can influence drug effectiveness.

an example the when the liver inactivates SN-38 by adding G to it. the SN38G moves to the intestine where it is activated again in the wrong spot by the cleavage of the G. this causes side effects.

How did research by Wallace et al. seek to alleviate side effects of the colon cancer drug CPT-11 (irinotecan)?

the wallace paper was looking for inhibitors for the bacterial enzyme B-glucs that reactivates the SN38. inhibitor + anti cancer drug (CPT-11) had the best tissue outcomes

What is an opportunistic pathogen?

an opportunistic pathogen is a pathogen that can cause disease when presented the opportunity

Under what conditions would an opportunistic pathogen be able to cause disease?

immunocompromised host, entry into unusual body site, disturbance of normal microbiota

what is microbiota antagonism?

normal microbiota competes with pathogens for space and nutrients

Define: virulence factor. Give examples of the various roles virulence factors may play.

a virulence factors are structures or proteins produced by pathogens that help them to cause disease; they help pathogens adhere, invade, evade defenses, and damage host

What is/are the virulence factor(s) of C. tetani, the bacteria that causes tetanus?

exotoxin that blocks inhibitory neurotransmitters which causes spastic paralysis

How do those virulence factor(s) help C. tetani cause disease?

helps cause the disease because it is a strict anaerobe so when entered through wounds will produce toxin

What is/are the virulence factor(s) of e. coli o157:h7, the bacteria that causes tetanus? How do those virulence factor(s) help e. coli o157:h7 cause disease?

e. coli o157:h7 uses adhesins to attach to the intestinal epithelium to produce shiga-like toxins which damage kidneys causing HUS

What is/are the virulence factor(s) of b. anthracis, the bacteria that causes tetanus? How do those virulence factor(s) help b. anthracis cause disease?

the virulence factors for B. anthracis are antiphagocytic capsules (inhibits phagocytosis of actively growing bacteria), virulence plasmid (carries toxin genes), and anthrax toxin (kill macrophages and causes internal bleeding, septic shock, and death)

Unnecessary antibiotic use can lead to infection by which types of pathogens? Why?

by opportunistic and antibiotic resistant pathogens because it disrupts the normal microbiota and allows pathogens like c. diff to overgrow and cause disease.

Would you consider a ribosomal protein (one of the proteins that makes a functional ribosome) to be a virulence factor? Why or why not?

no because the ribosomal protein doesn’t help the pathogen cause disease

True or false: Most bacteria associated with the human body are endosymbionts.

true

True or false: Opportunistic pathogens usually synthesize exotoxins. Explain.

false because opportunistic pathogens don’t typically produce exotoxins. they only cause disease when the host is immunocompromised

Do you think DNA polymerase would be considered a virulence factor? Why or why not?

no because it doesn’t help the pathogen cause disease