Lecture 3 - Bacterial Nutrition Flashcards
What do Bacteria require in terms of nutrition?
Bacteria Require
* Carbon
* Hydrogen
* Nitrogen
* Phosphorus
* Oxygen
* Sulphur
These elements make up 96% of dry weight for a prokaryotic cell
4% = Na, K, Cl, Mg, Fe and trace elements
What are the two methods in which bacteria aquire of carbon.
Autotroph
* Fixation of inorganic carbon (CO2) used to make simple sugars
Cyanobacteria, green and purple sulphur bacteria
Heterotroph
* Assimilation of organic carbon - Can’t make own sugars
Simple sugars (most bacteria)
Complex sugars (actinomycetes and the gliding bacteria)
How do bacteria aquire nitrogen and phosphorus.
Assimilation
* NH4, NO3, organic N (e.g. amino acids)
Nitrogen Fixation
* N2 (gaseous nitrogen)
Some cyanobacteria and actinomycetes
Acquisition of Phosphorus
Assimilation of PO4 - all bacteria always in phosphate form.
What other resorces do bacteria require for growth?
- H, O, S, Na, K, Cl, Mg, Fe
- Trace elements e.g. Cu, Mn, Zn
- Appropriate temp, pH, salinity etc.
- Electron Donor
- Energy Source
How are bacteria catagorised by thier growth requriements?
Source of Energy
- Phototroph (light)
- Chemotroph (chemical reactions)
Source of Electrons
- Organotroph (organic matter)
- Lithotroph (inorganic compounds)
Source of Carbon
- Autotroph (inorganic C)
- Heterotroph (organic C)
What is a functional guild in regards to bacteria?
A guild is a group of species that exploit the same class of environmental resources in a similar way - regardless of taxonomic position. Each guild is represented by a core genus that has the most information about it and is able to be cultured.
What are the bacterial guilds?
Bacterial guilds
Aerobic habitat
- Guild A: Aerobic Decomposers (DOC)
- Guild B: Gliding Bacteria (POC)
Border of aerobic/anaerobic habitat
- Guild C: Nitrifying Bacteria (CO2)
- Guild D: Colourless Sulphur Bacteria (CO2)
Anaerobic habitat
- Guild E: Sulphate Reducing Bacteria (DOC)
- Guild F: Green and Purple Sulphur Bacteria (CO2)
- Guild G: Methanogenic bacteria (CO2)
What are the features of guild A?
Guild A - Aerobic Decomposers
* Utilise DOC for energy, carbon and source of electrons
* Biggest group of bacteria (aerobic)
* Core genus: Pseudomonas
* Flavobacterium, Vibrio, Alteromonas, Legionella, Rhizobium, Agrobacterium, Azotobacter, Azomonas
* “Decomposer” term is misleading (generally scavenging smaller molecules)
* Mineralisers – organic carbon to inorganic carbon
* Bacteria most closely associated with eukaryotes
* Disease causing species
Can be tested by growth on lactose - Production of acid (pH changes)/production of gas
Breakdown simple sugars
Describe the features of Guild B
Guild B - Gliding Bacteria
· Utilise POC for energy, carbon and source of electrons
* True decomposers – POC to DOC
* Mineralisers – DOC – CO2
* Cellulose, chitin, pectin, keratin. Some degrade agar
* Core genus: Cytophaga
* Sporocytophaga, Flexibacter, Myxococcus
No flagella - glide on surfaces
Describe the features of Guild E.
Guild E - Sulphate reducing bacteria
* High level of DOC in anaerobic environments
* SO4 –most abundant electron acceptor in anaerobic environments
* Anaerobic respiration
* Dissimilatory sulphate reduction (Sulphate respiration)
* Second largest bacterial guild
* SO4 - Desulfovibrio, Desulfotomaculum; S0 - Desulfuromonas
* H2S is the end product
Hydrogen sulphide (H2S) production
formation of ferrous sulphide (insoluble)
Describe the features of Guild F.
Guild F - Green and Purple Sulphur Bacteria
chromatium
* Photolithoautotrophs – but anaerobic
* Anoxygenic photosynthesis
* Bacteriochlorophyll – Bchl a & b (purple), Bchl c, d & e (green)
* Sulphide as electron source
* Use infra-red light energy to fix CO2
* Sulphur granules: in cells (Purple), outside cell (Green)
* Purple: Chromatium, Thiospirillum
* Green: Prosthecochloris, Pelodictyon
Up to 10μm long
There are NON-Sulphur Bacteria
* Anaerobic
* Photolithoautotrophic AND chemolithoautotrophic
* Highly complicated
* Chloroflexus (green), Rhodospirillum (purple)
* Generally Thermophilic so not discussed here.
There are also Colourless Sulphur Bacteria.
Describe the features of Guild D
Guild D - Colourless Sulphur Bacteria
Thiliobacillus
* Chemolithoautotrophs – aerobic
* Electron donor abundant in anaerobic environment
* Guild sits on border of aerobic and anaerobic
* Thiobacillus, Thiospira, Thiomicrospira
* Acid tolerant – extreme environments
Oxidises iron, leach metals
Describe the sulfer cycle
The Sulfur Cycle
S04 is converted to H2S via bacteria in Guild E
H2S is converted to SO4 via bacteria in Guild D (aerobic) and F (anaerobic) - which guild depends on whether the conditions are aerobic or anaerobic.
Describe the features of nitrifying bacteria.
Guild C - Nitrifying bacteria
Bacteria can carry out all possible transformations of N
* Nitrification
* Denitrification
* Nitrogen Fixation
Guild C – Nitrification
NH4+ + (O) = NO2- + H20 Nitrosomonas, Nitrosococcus
NO2- + (O) = NO3- Nitrobacter, Nitrococcus
What bacteria are responsible for denitrification?
NO3 -> NO2 -> N2 (reduction)
There is no specific guild that carry out denitrification instead the bacteria that carry out this process are found throughout the Guilds.
* Dissimilatory nitrogenous oxide reduction
* Microaerophilic species
* Bacillus licheniformis (A), Pseudomonas stutzeri (A), Thiobacillus denitrificans (D)
* End-product - gaseous N (N2, N2O)
can be used by some bacteria in nitrogen fixation
What bacteria carry out nitrogen fixation.
Nitrogen fixation so most of the bacteria involved are anaerobic bacteria. Like in denitrification there is no specific guild that carries out this process.
* Gaseous N ‘fixed’ by “Diazotrophs”
* Some cyanobacteria, some members of Azotobacteriaceae, Methylococcaceae, Rhizobiaceae, Rhodospirillales. Some species of Bacillus and Clostridium
* N2 reduced to NH4 - catalysed by nitrogenase
* Very O2 sensitive - anaerobic process
* Anaerobic fixation - Clostridium
Aerobic fixation requires specific adaptations - filamentous, one cell becomes anaerobic.
Describe the nitrogen cycle
- NH4 is converted to NO2 by bacteria in guild C specifically Nitrosomonas
- NO2 is converted to NO3 by bacteria in Guild C specifically Nitrobacter
- NO3 is converted to N2 through denitrification - no particular guild
- N2 is converted to NH4 through nitrogen fixation - no particular guild
NO3 can be converted directly to NH4 via organic-N (assimilatory nitrate reduction)
Describe the features of guild G
Guild G - Methanogenic Bacteria
* Within the domain Archaea (or Archaebacteria)
* A bacterium which carries out “methanogenesis”
* The formation of methane (CH4)
* CO2 + 4H2 = CH4 + 2H2O
* Acetate, methanol, methylamines (slower)
* CH3COOH = CH4 + CO2
* Chemolithoautotrophic (like Guilds C & D)
* Obligate anaerobes
* Methanobacterium, Methanoplanus, Methanospirillum, Methanococcus
Methanotrophs: utilise the methane
Methanotrophs
* Methylococcus, Methylomonas
Methanotrophy – use of CH4 as sole C source
CH4 – Methanol – Formaldehyde – Formate – CO2
* Formate – accumulated in biomass * Aerobic/Microaerobic – O2 is the electron acceptor CO2 is the electron acceptor for methanogens
