1. Decomposers -
Many microbes help decompose or break down dead material
and release organic nutrients into the surrounding environment.
These agents of decay are called saprobes and include bacteria
2. Producers - some
microbes, such as the cyanobacteria and algae serve not only
as sources of food, but also contribute up to 50% of gaseous oxygen
production in the atmosphere.
3. Soil formation
- some members of the Archea actively demineralize rock and
begin the process of building soil usable by plants and other
4. Symbiotic relationships
- many microbes form lifelong associations with other
organisms. These relationships may be purely
commensualistic, doing no harm or good to the host,
while others are mutualistic with both colonist and
host organisms benefiting.
5. Agents of disease
- some symbiotic relationships are parasitic, meaning that the
organism does the host harm through the association. Only
about 2000 of the known bacterial species are pathogens
(agents of disease), but the harm they cause is medically,
socially and economically substantial.