Microbio 303 Exam test quiz and
answers graded A+
Methanogens - ANS✅✅- Archaea, many diverse species
- obligate anaerobes
- produce methane
Methanogen Habitats - ANS✅✅1. Anoxic sediments: marsh, swamp and lake sediments, paddy
fields, moist landfills
2. Animal digestive tracts: ruminant of cows, sheep, cecum of horses and rabbits, large intestines of
humans, handgun of termites
Methanogenesis - ANS✅✅- a type of anaerobic respiration
- various electron donors are possible (hydrogen is common)
- electron acceptor (carbon dioxide, formate, alcohols, methylamines, methanol, acetate) is reduced
to methane
- unique set of C1 carriers and electron carriers (e.g. F420 --> makes it easy to identify in culture, will
absorb light and shine green)
- electron transfer generates PMF or NaMF, used to make ATP via ATP synthase
- use ETC:
MF = methanofuran
MP = methanopterin
Fd = ferredoxin
F420 = coenzyme F420
CoM = coenzyme M
CoB = coenzyme B
****draw on paper
1. reduction of CO2 to formyl
2. reduction of formyl to methylene and then methyl
3. reduction of methyl group to methane
,Acetogens - ANS✅✅- anaerobic bacteria, most are Firmicutes
- use carbon dioxide as electron acceptor, reduce to acetate
(produce an est. 10 trillion kg of acetate per year)
- multiple donors are possible, but hydrogen is common
- pathway is called the acetyl-CoA pathway
Acetyl-CoA Pathway - ANS✅✅- looks like carbon fixation
- creates NaMF
- 2 places ATP is generated:
1. NaMF
2. Substrate level phosphorylation
Net: 4H2 + 2HCO3- + H+ --> acetate- + 4 H2O
1. reduction of CO2 to methyl group in one spot and then reduction of CO2 to carbonyl group in
another (2 ways for CO2 to come in)
2. combine to form acetate
Methanogens vs. Acetogens - ANS✅✅- methaogens and acetogens compete for CO2 and H2
- normally, methogens would outcompete acetogens (more negative delta G)
- can change based on environment
Microbial Metabolic Partnerships - ANS✅✅- organisms cooperate with each other (producers and
consumers) --> contrasts survival of the fittest ideals
- more cooperation than competition for microorganisms
Producer-consumer Relationships may be mandatory for producer: syntrophy - ANS✅✅- a
metabolic process in which two different organisms cooperate to degrade a substrate
- often producer organism can't degrade substrate without the participation of the consumer
organism
Example of Syntrophy in Syntrophomonas - ANS✅✅- syntrophomonas oxidizes butyrate to acetate
to make ATP
- butyrate is electron donor, protons are electron acceptor, generating hydrogen as product
,- unfavorable unless hydrogen is removed
- syntrophs remove H2 to make it more favorable
Microbial communities are common for aerobic and anaerobic degradation - ANS✅✅Aerobic
degradation
- aerobic respiration predominates
- oxidized products that are produced: carbon dioxide, nitrate, sulfate
-oxygen is quickly consumed (rate is driving by amount of reduced substrates)
Anaerobic degradation
-nitrate and sulfate respiration where possible
-fermentation: fermenters produce partially oxidized products; these can be used by acetogens,
methanogens and syntrophs (and then broke down into H2, CO2, H2O, H2S)
- when sulfate is available, sulfate reducing bacteria outcomplete methanogens and acetogens (have
higher energy yield)
Symbiosis - ANS✅✅Intimate association between two different types of organisms
-does NOT need to be beneficial
Mutualism - ANS✅✅Both benefit
Commensalism - ANS✅✅One benefits, the other is neither harmed nor benefitted
Amensalism - ANS✅✅One benefits while the other is harmed (e.g. pathogenesis)
Microbial partnerships are ubiquitous in nature - ANS✅✅- almost all plants and animals have
permanent, resident, microbial partners (they are called "normal microbiota" - also "commensal
microbiota" but not all organisms benefit)
- often community of microbes on: mucosal surface, in body cavity, in specific organ
, - sometimes are intracellular symbionts (can become part of organism → mitochondria)
Many organisms are "Metaorganisms" - ANS✅✅- holobiont= bost plus its microbiota
- hologenome = host genome plus microbiome (microbiota genome)
- Also called "superorganisms"
How do we study symbiotic microbes? - ANS✅✅Manipulate host animals
- germ-free animals (axenic)
- gnotobiotic animals (take axenic animal and add back what you want; know everything in it)
Animal model systems
- drosophila and C. elegans
- mice and zebrafish
Microbiome analysis
- sequence and analysis all genomes of all members of the microbiota - look for important gene
functions
Functions of symbiotic microbes - ANS✅✅- assimilation of major nutrients for host (carbon,
nitrogen, phosphorous)
- provision of minor but essential nutrients (amino acids and vitamins)
- protection from predators or parasites or environmental stresses (ex. quorum sensing in squid)
- role in reproduction (give different phenotype)
- role in normal physiology (neurological, digestive, etc.)
- Role in development (especially development of the immune system)
answers graded A+
Methanogens - ANS✅✅- Archaea, many diverse species
- obligate anaerobes
- produce methane
Methanogen Habitats - ANS✅✅1. Anoxic sediments: marsh, swamp and lake sediments, paddy
fields, moist landfills
2. Animal digestive tracts: ruminant of cows, sheep, cecum of horses and rabbits, large intestines of
humans, handgun of termites
Methanogenesis - ANS✅✅- a type of anaerobic respiration
- various electron donors are possible (hydrogen is common)
- electron acceptor (carbon dioxide, formate, alcohols, methylamines, methanol, acetate) is reduced
to methane
- unique set of C1 carriers and electron carriers (e.g. F420 --> makes it easy to identify in culture, will
absorb light and shine green)
- electron transfer generates PMF or NaMF, used to make ATP via ATP synthase
- use ETC:
MF = methanofuran
MP = methanopterin
Fd = ferredoxin
F420 = coenzyme F420
CoM = coenzyme M
CoB = coenzyme B
****draw on paper
1. reduction of CO2 to formyl
2. reduction of formyl to methylene and then methyl
3. reduction of methyl group to methane
,Acetogens - ANS✅✅- anaerobic bacteria, most are Firmicutes
- use carbon dioxide as electron acceptor, reduce to acetate
(produce an est. 10 trillion kg of acetate per year)
- multiple donors are possible, but hydrogen is common
- pathway is called the acetyl-CoA pathway
Acetyl-CoA Pathway - ANS✅✅- looks like carbon fixation
- creates NaMF
- 2 places ATP is generated:
1. NaMF
2. Substrate level phosphorylation
Net: 4H2 + 2HCO3- + H+ --> acetate- + 4 H2O
1. reduction of CO2 to methyl group in one spot and then reduction of CO2 to carbonyl group in
another (2 ways for CO2 to come in)
2. combine to form acetate
Methanogens vs. Acetogens - ANS✅✅- methaogens and acetogens compete for CO2 and H2
- normally, methogens would outcompete acetogens (more negative delta G)
- can change based on environment
Microbial Metabolic Partnerships - ANS✅✅- organisms cooperate with each other (producers and
consumers) --> contrasts survival of the fittest ideals
- more cooperation than competition for microorganisms
Producer-consumer Relationships may be mandatory for producer: syntrophy - ANS✅✅- a
metabolic process in which two different organisms cooperate to degrade a substrate
- often producer organism can't degrade substrate without the participation of the consumer
organism
Example of Syntrophy in Syntrophomonas - ANS✅✅- syntrophomonas oxidizes butyrate to acetate
to make ATP
- butyrate is electron donor, protons are electron acceptor, generating hydrogen as product
,- unfavorable unless hydrogen is removed
- syntrophs remove H2 to make it more favorable
Microbial communities are common for aerobic and anaerobic degradation - ANS✅✅Aerobic
degradation
- aerobic respiration predominates
- oxidized products that are produced: carbon dioxide, nitrate, sulfate
-oxygen is quickly consumed (rate is driving by amount of reduced substrates)
Anaerobic degradation
-nitrate and sulfate respiration where possible
-fermentation: fermenters produce partially oxidized products; these can be used by acetogens,
methanogens and syntrophs (and then broke down into H2, CO2, H2O, H2S)
- when sulfate is available, sulfate reducing bacteria outcomplete methanogens and acetogens (have
higher energy yield)
Symbiosis - ANS✅✅Intimate association between two different types of organisms
-does NOT need to be beneficial
Mutualism - ANS✅✅Both benefit
Commensalism - ANS✅✅One benefits, the other is neither harmed nor benefitted
Amensalism - ANS✅✅One benefits while the other is harmed (e.g. pathogenesis)
Microbial partnerships are ubiquitous in nature - ANS✅✅- almost all plants and animals have
permanent, resident, microbial partners (they are called "normal microbiota" - also "commensal
microbiota" but not all organisms benefit)
- often community of microbes on: mucosal surface, in body cavity, in specific organ
, - sometimes are intracellular symbionts (can become part of organism → mitochondria)
Many organisms are "Metaorganisms" - ANS✅✅- holobiont= bost plus its microbiota
- hologenome = host genome plus microbiome (microbiota genome)
- Also called "superorganisms"
How do we study symbiotic microbes? - ANS✅✅Manipulate host animals
- germ-free animals (axenic)
- gnotobiotic animals (take axenic animal and add back what you want; know everything in it)
Animal model systems
- drosophila and C. elegans
- mice and zebrafish
Microbiome analysis
- sequence and analysis all genomes of all members of the microbiota - look for important gene
functions
Functions of symbiotic microbes - ANS✅✅- assimilation of major nutrients for host (carbon,
nitrogen, phosphorous)
- provision of minor but essential nutrients (amino acids and vitamins)
- protection from predators or parasites or environmental stresses (ex. quorum sensing in squid)
- role in reproduction (give different phenotype)
- role in normal physiology (neurological, digestive, etc.)
- Role in development (especially development of the immune system)
