Microbiology Week 14

Assalamualaikum and Good morning.... How r you everyone? I hope everyone will be fine as well. 😊😊😊 This is fourteenth week of my microbiology class. In microbiology, we study about the nutritional types of microorganisms.

2 major nutritional concern:
a.Source of energy
b.Source of carbon

Energy sources
• phototrophs: light as primary energy source
• chemotrophs: inorganic and organic compunds as primary energy source (from redox reactions)

Carbon sources
• Autotrophs (self feeders): CO2 – lithotrophs
• heterotrophs (feeders on others): organic carbon – organotrophs

Combine the energy and carbon sources:
• Photoautotrophs
• Photoheterotrophs
• Chemoautotrophs
• Chemoheterotrophs

Photolithoautotrophy
- Photolithotrophic autotrophs or photoautotrophs
- Source of energy: Light Source of C: CO2 Source of e-: reduced inorganic molecules e.g. Algae and cyanobacteria: H2O Purple and green sulfur bacteria: H2, H2S and elemental S

Photoorganoheterotrophy
- Photoorganotrophic heterotrophs
- Source of energy: Light Source of C: Organic C molecules Source of e-: Organic molecules
- Common inhabitants of polluted lakes/streams

Chemolithoautotrophy
- Chemolithotrophic autotrophs
- Source of energy: Oxidation of organic/inorganic compounds Source of C: CO2 Source of e-: Reduced inorganic molecules (iron, N, S)
- Contribute to chemical transformations of elements in the ecosystem

Chemoorganoheterotrophy
- Chemoorganotrophic heterotrophs or chemoheterotrophs
- Source of energy: Oxidation of organic/inorganic compounds Source of C: Organic C molecules Source of e-: Organic molecules
- Same organic nutrient à satisfy all requirements
- Most pathogenic m/os

Mixotrophic
- Alter metabolic patterns in response to environmental changes
- E.g. Purple nonsulfur bacteria Photoorganoheterotroph
    – absence of O2 Chemoorganoheterotrophs
    – presence of O2 The term mixotroph can describe organisms (usually algae or bacteria) capable           of  deriving metabolic energy both from photosynthesis and from external energy sources. These         organisms may use light as an energy source, or may take up organic or inorganic compounds.

Photoautotroph
• Photosynthetic bacteria, algae, cyanobacteria and green plants.
• obtain energy from photophosphorylation and fix carbon from CO2 via the Calvin-Benson cycle to synthesize organic compounds.
• photosynthetic bacteria:
– oxygenic phototrophs, produces O2 : cyanobacteria.
– anoxygenic phototrophs, do not produce O2, anaerobic condition: green sulfur bacteria (eg. Chlorobium) and purple sulfur bacteria (Chromatium)
• Green sulfur bacteria
– Chlorobium
– Use sulfur (S), sulfur compounds (H2S) or hydrogen gas (H2) to reduce CO2 and form organic compounds.
• Purple sulfur bacteria
– Chromatium
– Also use sulfur, sulfur compounds or H2 to reduce CO2.
– They are distinguished from the green sulfur bacteria by the location of their bacteriochlorophyls, location of stored sulfur and ribosomal RNA

Photoheterotrophs
• use light as an energy source and an organic compound for their carbon source or electron donor
• They are anoxygenic
• purple nonsulfur bacteria (Chloroflexus)
• green non sulfur bacteria (Rhodopseudomonas)

Chemoautotrophs
• use inorganic compounds as their energy source and CO2 as their carbon source
• Inorganic sources of energy:
– H2S : Beggiatoa
– S : Thiobacillus thioxidans
– NH3 : Nitrosomonas
– NO2 - : Nitrobacter
– H2 : Hydrogenomonas
– Fe2+ : Thiobacillus ferrooxidans
• energy stored in ATP - produced by oxidative phosphorylation

Chemoheterotrophs
• use complex organic molecules as their carbon and energy sources
• The energy source and carbon source are usually the same organic compound (glucose)
• most bacteria and all fungi, protozoa and animals
– saprophytes: live on dead organic matter
– parasites: derive nutrients from living host