Microbio 303 FInal Exam

what are methanogens

they are obligate anaerobes that produce methane, there are many diverse species

what are the 5 habitats of methanogens?

1. anoxic sediments, such as swamps and moist landfills

2. animal digestive tracts

3. geothermal sources of H2 and CO2

4. artificial biodegradation facilities such as sewage sludge digesters

5. endosymbionts of anaerobic protozoa

Where on the human body might you find methanogens, besides in the large intestine

in the mouth

what is methanogenesis ( and then what is the electron donor and electron carrier

• a type of aerobic respiration.

• hydrogen is usually the electron donor

• the electron acceptor (co2, formate, alcohols, methanol, acetate, or methyl amines) is reduced to methane.

• has a unique set of c1 carriers and electron carriers (f420)

• electron transfer generates PMF or NAMF, used to make ATP via ATP synthase.

What electron donors cannot pair with carbon dioxide as a terminal electron acceptor

what is the MP proton gradient

it is a unique way of living. H is used to reduce co2 to methane using one carbon carriers to create methane, making proton motive force in the process.

what are acetogens

• anaerobic bacteria, mainly are the species firmicutes

• use co2 as electrons captor and reduce to acetate

• multiple donors are possible, but hydrogen common

• pathway is acetyl-coA pathway

how do the acetogens use the acetyl coa pathway

basically builds acid part and methanol part and stick them together. to make methyl groups that get combined with acetyl coa to make acetate. use energy of acetyl coa bond to make ATP

how do methanogens and aceogens compete with each other?

They compete for CO2 and H2. methanogens win when CO2 or cobalt low→ cobalt because it is part of B12 and if you don’t have a lot of cobalt round you can’t make vitamins you need that hampers acetogens.

acetogens present in higher nutrient solutions where cobalt is around

sometimes producer consumer relationships may be mandatory for producer. What is this called and what happens?

syntrophy, when a metabolic process in which two different organisms cooperate ot degrade a substrate. Often the producer organisms can’t degrade substrate without the participation of the consumer organism.

syntrophy=mandatory

Syntrophomonas oxidizes butyrate to acetate to make ATP. How is this an example of syntroph relationship?

butyrate is electron donor and protons are electron acceptor, generating a hydrogen as a product. but it is unfavorable unless hydrogen is removed. if hydrogen is taken away by methanogens, make methane and then methane floats away and reaction is favorable. needs methanogens present or no metabolism.

how is interspecies hydrogen transfer used in syntrophic relationships?

the producer needs consumer to remove products for metabolism to occur, it hands off the hydrogen to the methanogen.

microbial communities are common for aerobic and anaerobic degredation? How does each type work?

Aerobic:

• aerobic respiration predominates

• oxidized products such as CO2, nitrate, sulfate get produced.

• oxygen is quickly consumed

Anaerobic":

• nitrate and sulfate respiration when possible

• fermentation

  • fermenters produce partially oxidized products that can be used by acetogens, methanogens, and syntrophs

when sulfate is available in the environment, what outcompetes methanogens and acetogens?

SRB

if something happened in the butyrate community so that methanogen only removed half the hydrogen, the rate of butyrate degradation would do what?

decrease bc methanogen needs to remove H to allow respiration. so if rate of removing H slows then the rate decreases.

which type of hydrogen utilizer is present in the human colon?

acetogens and methanogens