The Roll-Tube Method for Cultivation of Strict Anaerobes

Habitats devoid of oxygen include the interior of the alimentary tracts of most mammals, the lower portions of many oligotrophic lakes, the sediment underlying bodies of water, and water logged soils. Water, the continuous phase in all these habitats, is chiefly responsible for the lack of O2. One ml of water equilibrated with air contains only about 8 /il of O2, compared to 210 ?l 02/ml of air. This oxygen is soon used by aerobic microbes if other suitable foods are available. Oxygen is re moved by metabolism as rapidly as it enters anaerobic habitats. Both euryoxic and anaerobic bacteria have evolved in these habitats. In most continuously anaerobic habitats obligate anaerobes are more a bundant than euryoxic types, possibly because the latter bear a burden of aerobic metabolic capacities unused in the anaerobic environment. Usual aerobic petri plates or similar containers are suitable to culture the euryoxic microbes, but most anaerobes fail to grow in the presence of air. The anaerobes can be classed as oxyduric, i.e. surviving exposure to O2 but not growing in its presence, and oxylabile Species, killed by exposure to O2. Many oxyduric anaerobes can be handled in much the same fashion as aerobes, except that after plates are streaked they must be incubated