Microbiology Workshop
MICROBIAL ENERGY SOURCES
Microbes need energy for
- maintenance
- growth
- reproduction
A. OBTAINING ENERGY (NUTRITION)
Energy may be obtained by
- Autotrophy (Autotrophs)- using existing sources of free energy
- Heterotrophy (Heterotrophs)- using energy rich compounds formed by other organisms
- use energy from independent source
- make energy rich carbon compounds (organic molecules) from inorganic molecules using carbon dioxide as carbon source
- PHOTOAUTOTROPHS
- use photosynthesis to convert light energy to chemical energy to produce organic molecules.
- some bacteria, all algae, some protists - CHEMOAUTOTROPHS
- use chemosynthesis to convert chemical energy into organic compounds
- important in nutrient recycling
- only found in bacteria.
- use organic compounds, previously formed by either living or dead organisms, to provide energy
- organic compounds digested and energy made available to organism
- EXTRACELLULAR DIGESTION
- food detected
- enzymes released
- organic molecules digested
- breakdown products absorbed
- waste products left behind
- used by all fungi, some bacteria, some protists - PHAGOCYTOSIS
- food particles enclosed in food vacuole
- enzymes released
- organic molecules digested
- breakdown products absorbed
- waste products eliminated
- used by protists only.
B. USING ENERGY (RESPIRATION)
- energy obtained by nutrition is used in cellular respiration to provide energy for microbial activity
- microbes can be classified according to whether or not they use oxygen for cellular respiration as
- AEROBES
- use oxygen during respiration
- have enzymes to prevent oxygen doing damage to the cell- ANAEROBES
- are able to respire in the absence of oxygen
- obligate anaerobes - lack the enzymes preventing oxygen damage, stop functioning in the presence of oxygen; may even be killed
- facultative anaerobes - can use oxygen when it is available, can function in the absence of oxygen - fermentation