Understanding:
• Microorganisms are metabolically diverse
Microorganisms may be differentiated according to their diverse morphological and metabolic characteristics:
- Microorganisms may differ in their cellular organisation – e.g. prokaryotes versus eukaryotes
- Microorganisms may exhibit different nutritional requirements – e.g. autotrophic versus heterotrophic
- Their method of respiration may vary according to type – e.g. aerobic versus anaerobic respiration
- They may have different structural characteristics – e.g. shape or cell wall composition
Modes of Nutrition
Microorganisms can be categorised according to their mode of nutrition:
- Photoautotrophs use light energy to synthesise organic molecules (e.g. cyanobacteria)
- Chemoautrophs use energy from chemical oxidation to synthesise organic molecules (e.g. nitrogen-fixating bacteria)
- Heterotrophs obtain organic nutrients via feeding (e.g. amoeba)
- Saprotrophs release digestive enzymes onto non-living organic matter and absorb the products (e.g. fungi)
Nutritional Patterns in Microorganisms
Methods of Respiration
Microorganisms can also be categorised according to their mechanism of respiration:
- Obligate anaerobes respire anaerobically and can only grow in the absence of oxygen
- Aerotolerant anaerobes respire anaerobically but can grow in the presence of oxygen
- Facultative anaerobes can respire anaerobically or aerobically depending on oxygen availability
- Obligate aerobes only respire aerobically and cannot survive in the absence of oxygen
Respiration Patterns in Microorganisms
