LEC. 4 - Metabolic Diversity of Microorganisms Flashcards
What are chemolithotrophs?
use inorganic compounds to get energy for their metabolic processes
Which type of metabolism is considered to be the first form of energy conservation evolving on Earth?
chemolithotrophy
How do we know that chemolithotrophy was the first form of energy conservation evolving on Earth?
found on base of Bacteria and Archaea phylogenetic tree
Chemolithotrophs have the ability to act as autotrophs and can use CO2 as their carbon source. However, what are the 2 main components that they require in order for this to work?
- reducing power
- ATP
How do chemolithotrophs create ATP and reducing power?
by oxidizing the following:
1. H2S
2. S0
3. H2
4. Fe2+
What are the 4 energy sources for chemolithotrophs?
- H2S
- S0
- H2
- Fe2+
What is an indicator that chemolithotrophy is one of the oldest metabolic processes?
- energy source
- the fact that it uses a carbon source (CO2)
Along with H2 and H2S, list 2 other potential energy sources for chemolithotrophs.
- Fe2+
- NH4+
What are hydrogen bacteria?
use hydrogen as an electron donor
Bacteria and Archaea are awesome at multi-tasking. What is the other thing that they can couple the action of oxidizing H2 with?
reducing other electron acceptors like:
1. NO3-
2. SO42-
3. Fe3+
4. CO2
What is aerobic H2 oxidizing bacteria?
uses O2 as terminal electron acceptor
What do aerobic H2 oxidizing bacteria oxidize as the electron donor?
H2
What do aerobic H2 oxidizing bacteria reduce?
O2 to form water
For chemolithotrophs that use H2, what is the name of the enzyme that they developed?
hydrogenase
What are the 2 different types of hydrogenases that chemolithotrophs evolved?
- Cytoplasmic hydrogenase
- Membrane-integrated hydrogenase
How could one describe cytoplasmic hydrogenase?
as a soluble enzyme
What is the name of the hydrogenase that most H2-oxidizing have?
membrane integrated enzyme
There are some pretty unique organisms out there that use 2 hydrogeneses. What is an example of such an organism?
Ralstonia eutropha
What is the main goal of the membrane enzyme for H2-oxidizing chemolithotrophs?
energy conservation
What is the main goal of soluble enzyme for H2-oxidizing chemolithotrophs?
autotrophy
If an organism has only 1 type of enzyme present, what are the 2 functions that they are now responsible for carrying out?
energy conservation and autotrophy
H2 - oxidizing bacteria has the ability to act as autotrophs with the use of the Calvin cycle and can also grow as what other type of -troph?
chemoorganotrophs
If chemoorganotrophs are given the decision to choose between glucose (organic source) or H2 (inorganic source), which one would they choose and why?
glucose because it gives them more energy
For chemoorganotrophs, if there is glucose present will they synthesize hydrogenase and why?
no, energy conservation
H2 bacteria are known to have a mixed nature. What term classifies this?
facultative chemolithotrophs
In an oxic area, would H2 production be low or high?
low
Why would H2 production be low in an oxic area?
- no fermentation
- rapic consumption by anaerobes
What is the backup plan for H2 oxidizing bacteria?
they shift between chemoorgaotrophic and chemolithotrophic lifestyles based on the nutrients that are available to them in environment
What do colourless sulfur bacteria use as electron donors?
reduced sulfur compounds
In comparison to colorless sulfur bacteria, what type of photosynthesis do purple and green sulfur bacteria perform?
anoxygenic photosynthesis
What are the 2 reduced sulfur compounds that chemolithotrophs can use?
- hydrogen sulfide
- elemental sulfur
What is the first mode of biochemistry that chemolithotrophs who use reduced sulfur compounds as energy source have?
oxidation of hydrogen sulfide and/or S0 to sulfate (SO42-) through intermediary
What is the second mode of biochemistry that chemolithotrophs who use reduced sulfur compounds as energy source have?
oxidation of hydrogen sulfide and/or S0 to sulfate (SO42-) without intermeddlers (Sox system of genes)
Why does iron bacteria have to complete the oxidation of large amounts of iron?
because they’re only able to produce small amounts in an acidic environment
What are the 3 steps of acidification, the very process that is happening because of iron oxidation?
- spontaneously produced ferric iron forms insoluble ferric OH-
- precipitates are formed in an aquatic environment
- reaction lowers pH
Why did iron bacteria evolve to be acidophillic?
bc of reaction of acidification bc of iron oxidation
What are 2 of the best known iron bacteria?
- Acidithiobacillus ferrooxidans
- Leptospirillum ferrooxidans
What is the electron donor for Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans?
Fe2+
Why type of an environment are Acidithiobacillus ferrooxidans
and Leptospirillum ferrooxidans most common in?
acid polluted
What is ferroplasma?
- archaea
- acidophillic iron oxidizer
What is the only form of iron that microorganisms can use as an energy source?
Fe2+ ion
At a neutral pH, Fe2+ will spontaneously become?
Fe3+
Why must iron bacteria develop an oxidation system that is fast?
bc it can change to Fe3+ if it comes into contact with air, and thus, not usable
What are 3 examples of bacteria that are able to oxidize Fe3+ rapidly before it gets exposed to oxygen?
- Gallionella ferruginea
- Sphaerotilus natans
- Leptothrix discophora
What is nitrification?
chemolithotrophic nitrifying bacteria aerobically oxidizes NH3 and NO2-
If ammonia were to be present in an anoxic environment, which type of bacteria would be able to oxidize ammonia?
anammox
How could one describe the areas that nitrifying and anammox bacteria are widely distributed in?
wet and moist
Which 2 organisms are responsible for oxidizing ammonia to nitrite in aerobic conditions?
AOB (ammonia oxidizing bacteria) and AOA (ammonia oxidizing archaea)
Which group of bacteria is responsible for completing the full process of nitrification?
NOB (nitrite oxidizing bacteria)
What does NOB (nitrite oxidizing bacteria) do?
oxidize nitrite to nitrate (NO3-)
Which cycle do both NOB and AOB use to fix CO2?
calvin
Why do NOB and AOB run reverse electron flow to generate NADH?
high energy requirements
How does NOB use chemoorganotrophy?
growth on glucose or organic substrates
Does AOB have alternate metabolism plan?
no, they are chemolithotrophs
What is the name of the key plant nutrient that NOB and AOB are responsible for producing through a convertion process?
nitrate
Why are nitrifiers (NOB and AOB) important for sewage and wastewater treatments?
- remove toxic amines and ammonia
- release less toxic nitrogen compounds
How are nitrifiers significant to lakes?
- decomposing organic matter in sediments produces ammonia
- nitrifiers oxidize ammonia to generate nitrite
- NOB convert nitrite to nitrate
- algae and cyanobacteria need nitrate to grow
What is anammox (anaerobic ammonia oxidation)?
ammonia oxidation in anoxic environment
What performs anaerobic ammonia oxidation?
anaerobic bacteri
in an anammox reaction, what is the electron donor and what is the electron acceptor and what is produced?
donor: ammonia
acceptor: nitrite
produces N2 gas
What is a major anammox organism?
Brocadia anammoxidans
Describe Brocadia anammoxidans.
- lack peptidoglycan
- cytoplasm has membrane-enclosed compartments
In Brocadia anammoxidans, what are the membrane enclosed compartments called?
anammoxosome
How are the lipids that build anammoxosome different and not typical bacterial lipids?
have glycerol and cyclobutene (C4) ring attached to glycerol with ester and ether bonds
What are the dense lipids present inside anammoxosome called?
ladderane lipids
Significance of Anammox:
What is the source of nitrite for anammox?
aerobic AOA and AOB
How is anammox crucial for wastewater treatment?
it removes ammonia and nitrite to produce N2 and H2O
What is fermentation?
microbes degrading organic compounds in metabolic process bc no other stuff is available
If fermentative organisms do not run the electron transport chain, then what do they do?
create ATP and NADH through Substrate Level Phosphorylation
Briefly, how does fermentation work?
- substrate is electron donor and acceptor
- SLP makes ATP
microbes fermenting sugars to make acids/alcohols as primary products
primary fermenters
microbes using products from primary fermenters to make gasses for other microbes (methanogens, sulfidogens, acetogens)
secondary fermenters
What is the number one product that is excreted from fermentation?
H2
What are some other end products of fermentation?
alcohols and acids
What are fermentations classified by?
- substrate fermented
- products formed
What are some of the broad categories of fermentation?
- alcoholic fermentation
- lactic acid fermentation
- mixid acid fermentation
- butyric acid
- acetogenic fermentation
In homolactic fermentation, what is the product?
lactate
In homolactic fermentation, some organisms have ethanol dehydrogenase and they reduce pyruvate to…
ethanol
Because there is no aldolase that is present in heterofermentative, how will the process change?
going from 6C to 5C
Which type of bacteria is responsible for eating and transforming lactose, fat and protein in milk?
lactic acid
What is the importance of homofermentation to cheese?
mild flavour + acidity of cheddar
What is the importance of heterofermentation to cheese?
complex “fruity” flavour and holes of swiss
What performs butyric acid fermentation?
clostridum
What is the gram + organism content in butyric acid fermentation leading it be what?
low and aerotolerant
What are the early fermentation products in butyric acid fermentation and how do they affect the pH?
- acetate and butyrate
- lowers pH
What is the name of the process that has no cytochromes?
butyric acid fermentation
How does low pH in butyric acid fermentation affect the genes that are produced?
- different sets of genes will redirect process
- microbe consumes butyrate and acetate to make butanol and acetone
In the stickland reaction fermentation, what is the electron donor and acceptor?
alanine - donor
acceptor - glycine
What are the substrates in the stickland reaction fermentation?
- 2 amino acids
- ADP
- Pi
What are the products in the stickland reaction fermentation?
- acetate
- ammonium
- CO2
- 3 ATP
Why is the strickland reaction important for our bodies?
prevents cavities
How does strickland reaction work in our mouths?
- comes between free roaming proline and amino acids (made by plaque)
- product: δ-NH2 valeric acid
- degrades to ammonia
- ammonia removes H+, lowers acidity
What part of our mouth is proline found in?
saliva
What is the name of a common plaque bacteria?
Peptostreptococci
What does Peptostreptococci do in our mouth?
complete glucose fermentation, producing free amino acids