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
