Microbial Nutrition

Question	Answer
What is the difference between anaerobic respiration and fermentation?	Anaerobic respiration consists of both substrate-level phosphorylation (glycolysis and the Krebs cycle) and the electron transport chain and yields a great deal of energy by uses NO3 or SO4 as a terminal electronc acceptor - whereas fermentation also occurs in the absence of oxygen by only substrate-level phosphorylation and yields a lot less energy.
What is a facultative anaerobe?	An organism that can grow in aerobic and anaerobic conditions.
What is an obligate aerobe?	An organism that needs an O2 environment in order to grow.
What is an obligate anaerobe?	An organism that finds an O2 environment toxic e.g. Pseudomonas aeruginosa, or some enteric bacteria.
What is a lithotroph?	An organism that uses reduced inorganic substances as its electron source.
What is an organotroph?	An organism that extracts electrons or hydrogen from organic compounds.
What is a mixotroph?	An organism which relies on inorganic ENERGY sources and organic CARBON sources.
What is a photolithotrophic autotroph?	An organism that uses light energy and CO2 as a carbon source.
What is a chemoorganotrophic heterotroph?	An organism that uses organic compounds as sources of energy, hydrogen, electrons and carbon for biosynthesis. This is typically the same nutrient for all 4 and includes almost all pathogenic microbial species.
What is a photoorganotrophic heterotroph?	A photosynthetic organism that uses light energy and organic matter as both their electron donor and carbon source.
What is a chemolithotrophic autotroph?	An organism that oxidises reduced inorganic compounds (e.g. Fe, N, S) to derive both energy and electrons for biosynthesis; CO2 is the carbon source.
What is a chemolithotrophic heterotroph?	An organism that oxidises reduced inorganic compounds to derive both energy and electrons from photosynthesis and derives its carbon from organic sources.
Can microorganisms belong to more than one nutritional type?	Most species tend to only belong to one nutritional class but some show great metabolic flexibility in response to environmental changes, such as purple non-sulphur bacteria acting as photoorganotrophic heterotrophs in anaerobic conditions and oxidising organic molecules and functioning chemotrophically at normal O2 levels.
What are the two processes by which bacteria can obtain energy?	Respiration and fermentation.
Which elements do microbial cells predominately consist of?	H, O, C, N, P and S.
Which bacteria can use N2 as a nitrogen source?	Nitrogen fixing bacteria such as Rhizobium species.
Which microorganisms can assimilate organic compounds (such as amino acids, sugars, nitrogen bases, aromatic compounds etc) and use them to make new cell material?	Bacteria.
Name two organic forms of nitrogen.	NH3, NO3-.
What is phosphorus required for?	Synthesis of nucleic acids and phospholipids.
What is sulphur required for and which inorganic forms is it found it?	Sulphur is required for the disulphide bonds in the amino acids methionine and cysteine and in vitamins such as thiamin and biotin. It is generally found as SO4- or HS-.
Microorganisms in which habitat are more likely to require sodium for growth?	Marine microorganisms.
What is a siderophore?	A molecule, which may be a peptide, or phenolic or an ester, among many other forms, which is a strong chelate of ferric (Fe3+) or ferrous (Fe2+) iron and binds to it and transports it into the cell.
How is a siderophore used?	It is excreted into the environment and then transported back into the cell once it has bound to iron. It is reduced inside the cell if Fe3+ has been bound and the siderophore is recycled back out into the environment.
Name a species that requires a large amount of iron and suggest where it might find it in the human body.	Haemophylis influenzae requires a lot of Fe2+ and can sequester it from the haem groups of haemoglobin in erythrocytes.
Name a species that can live in taps with only water, calcium and magnesium and requires very little iron.	Pseudomonas aeruginosa.
Name a species that uses no detectable iron and seems to use Mn2+ in place of it.	Borrelia burgdorferii.
What might iron be used for in a microbe cell?	In cytochromes and Fe-S compounds in the electron transport chain.
What do 'growth factors' consist of in microbial nutrition?	Vitamins, amino acids, purines and pyrimidines.
Name some genii of lactic acid bacteria which are renowned for their vitamin requirements exceeding that of humans.	Lactobacillus, Leuconostoc and Streptococcus.
What is an autotroph? Give examples of autotrophic microorganisms.	An organism that can fix CO2, by reducing it and incorporating it into organic molecules. Cyanobacteria and algae can do this.
What is a heterotroph? Give examples of heterotrophic organisms.	Heterotrophs are organisms that cannot expend the energy to reduce CO2 and so rely on the presence of reduced, complex, pre-formed molecules for a supply of carbon. These usually come from other organisms and tend to be a source of both carbon and energy. Methylotrophic bacteria and actinomycetes are heterotrophs.
What is a prototroph?	An organism requiring the same nutrients as more of the naturally occurring members of its species.
What is an auxotroph?	An organise that has mutated so that it cannot synthesis a molecule essential for growth and reproduction that must then obtain it or a precursor of it, and that differs from most naturally occurring members of its species.
What is a phototroph?	An organism that uses light as its energy source.
What is a chemotroph?	An organism that obtains energy from the oxidation of organic or inorganic chemical compounds.

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	Created by sophietevans over 11 years ago