Microbial Roles in the Environment

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
                              and fungi.

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
                               organisms.

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.