BIOLOGY, ECOLOGY, AND BIOTECHNOLOGICAL APPLICATIONS OF ANAEROBIC-BACTERIA ADAPTED TO ENVIRONMENTAL STRESSES IN TEMPERATURE, PH, SALINITY, OR SUBSTRATES

Anaerobic bacteria include diverse species that can grow at environmen tal extremes of temperature, pH, salinity, substrate toxicity, or avai lable free energy. The first evolved archaebacterial and eubacterial s pecies appear to have been anaerobes adapted to high temperatures. The rmoanaerobes and their stable enzymes have served as model systems for basic and applied studies of microbial cellulose and starch degradati on, methanogenesis, ethanologenesis, acetogenesis, autotrophic CO2 fix ation, saccharidases, hydrogenases, and alcohol dehydrogenases. Anaero bes, unlike aerobes, appear to have evolved more energy-conserving mec hanisms for physiological adaption to environmental stresses such as n ovel enzyme activities and stabilities and novel membrane lipid compos itions and functions. Anaerobic syntrophs do not have similar aerobic bacterial counterparts. The metabolic end products of syntrophs are po tent thermodynamic inhibitors of energy conservation mechanisms, and t hey require coordinated consumption by a second partner organism for s pecies growth. Anaerobes adapted to environmental stresses and their e nzymes have biotechnological applications in organic waste treatment s ystems and chemical and fuel production systems based on biomass-deriv ed substrates or syngas. These kinds of anaerobes have only recently b een examined by biologists, and considerably more study is required be fore they are fully appreciable by sciences and technology.