They cause such diseases as syphilis, yaws, and Lyme disease. One usually harmless ubiquitous sp. Many are ecologically important chemoheterotrophs capable of metabolizing usual organic materials plus some which can't be used by other heterotrophs. Medically important ones are Mycobacterium leprae and M. tuberculosis . Streptomycin and other important antibiotics are obtained from this group.
Some species are nitrogen fixers.
Metabolic Diversity Among Bacteria Bacteria play a significant role in ecosystems . Saprobes derive their nourishment from dead organic material. Autotrophic bacteria derive energy from light or oxidation of inorganic molecules. Photoautotrophic bacteria use light as a source of energy and CO 2 as a source of carbon. Cyanobacteria use chlorophyll a and produce oxygen as a byproduct of noncyclic photophosphorylation.