Unit 2 - Lecture 4 Flashcards
Metabolic Diversity of Microorganism
what are chemolithotrops?
- organisms that can use inoragnic compounds to obtain energy for their metabolic processes
- energy source: inoragnic compounds
- may be the first form of energy conservation taht evolved on Earth- widespread among lineages
- can also be autotrophs (CO2 as carbon source)
- are very diverse because the energy sources are highly present in the environment
what are the energy sources used by chemolithotrophs?
- H2S, S0, H2, FE2+, NH4+
- carbon source - CO2
- use of inorganic compounds create ATP and reducing power through oxidation of the energy sources
Hyrdogen (H2) Oxidation
what are the electron acceptors coupled with the oxidation of H2?
- H2 is a great electron donor, (highly reduced)
- NO3-,SO4’2-, Fe3+, CO2
- Aerobic H2 oxidizing bacteria use O2 as an terminal e- acceptor; oxidize H2 as e- donor and reduce O2 to form water
Hydrogen H2 Oxidation
what is the enzyme and its function developed by chemolithotrops that use H2?
2 distinct hydrogenases, specific organism name
- enzyme called hydrogenase
- two hydrogenase - evolutionary advantageous
1. cytoplasmic hydrogenase - soluble enzyme = autotrophy
2. membrane-intergrated = energy conservation - Most have one - membrane integrated enzyme = both energy conservation and autotrophy
- RALSTONIA EUTROPHA - model for studying aerobic H2 oxidation by species that make two hydrogenases
Hydrogen H2 Oxidation
Explain how Hz-oxidozing bacteria can grow as chemoorganotrophs
- 2 choices: glucose (organic source) and H2 (inorganic source)
- will chose glucose rather than H2
- if glucose is present = no hydrogenase will be synthetized (energy conservation)
- they are facultative chemolithotrophs (mixed nature)
Hydrogen H2 Oxidation
what is the ecological significance of having a mixed metabolism in H2-oxidizing bacteria?
- in oxic areas H2 production is low
- from either: no fermentation or rapid consumption by anaerobes
- they MUST have this alternative metabolism to survive
- shift between chemooragnotopgic and chemolithotropic lifestyles
- bacteria thtat uses O2 are a special group - advantageous and dominant
Oxidation of reduced sulfur compounds
What is the bacteria that uses reduced sulfur and what compounds can they use?
- colourless sulfur bacteria
- use reduced sulfur as electron donors
- DIFFERENT than pruple and green sulfur bacteria (which performs anoxygenic photosynthesis)
- uses: H2S (hydrogen sulfide), S0 (elemental sulfur)
Oxidation of reduced sulfur compounds
what are the two modes of using reduced sulfur compounds
- oxidation of H2S/H0 to SO$z- through intermediary
- oxidation of H2S/S0 to SO42- without intermeddlers (through Sox system of genes)
Iron (Fe2+) Oxidation
explain acificiation
- must complete the oxidation of large amounts of iron to produce small amounts of cell material
1. Ferric iron (Fe3+) produce spontaneously forms insouble ferric hydroxide
2. precipitates formed in aquatic environment
3. this reaction drives pH down - this reaction is the reason for iron bacteria evolving to be acidophilic
Iron (Fe2+) Oxidation
what are the 2 bacteria and 1 archaea known
- acidithiobacillus ferroxidans
- leptospirillum ferrooxidans
- common in acid polluted environments such as coal-mining runoff waters
- feeroplasma is arhaea - extremely acidophilic that can group at pH below 0
Iron (Fe2+) Oxidation
explain the problem that microorganisms face with using Fe2+ as an energy source
- energy source used ONLY in form of Fe2+ ion
- at neutral pH Fe2+ SPONTANEOUSLY becomes Fe3+ ( when i comes in contact with air)
- must develop a system that rapidly uses Fe2+
Nitrification and Anammox
define nitrification and anammox
- reduced inorganic compounds: ammonia (NH3) and nitrite (NO2-)
- nitrification = oxidized aerobically by chemolithotrophic nitrifying bacteria
- anammox = anoxic conditions, ammonia can be oxidized by a special group of bacteria
- widely distributed in souls, water, wastewaters and the oceans
Nitrification and Anammox
describe the process of oxidizing ammonia(NH3) to nitrite (NO2-)
- in aerobic conditions
- Ammonia Oxidizing Bacteria (AOB) and Ammonia Oxidizing Archaea (AOA)
- Nitrite Oxidizing Bacteria (NOB): oxidize nitrite to nitrate (NO3-)
Nitrification and Anammox
explain the carbon metabolism of nitrifying bacteria
generation of NADG, alternative metabolism in comparison to AOB
- nitrifying bacteria use Calvin cycle to fix CO2
- energetically expensive - high energy requirements
- run reverse electron flow to generate NADH
- can grow on glucose organic substrates = chemooragnotrophy; AOB doe not have this option, they are obligated chemolithotrophs
Nitrification and Anammox
how does nitrying prokaryotes play an ecological role?
- nitrate is a key plant nutrient
- nitrigers are important in sewage and wastewater treatment; removing of toxi amines and ammonia and release less toxic nitrogen compounds
- ammonia is prduced by decomposition of organic matter in sediments; converting to nitrate where algae and cyanobacteria use to grow
