ABSTRACT
With increasing temperature the diversity of organisms decreases, but in spite of that the diversity of thermophilic bacteria, in general, is quite large. The presently known aerobic heterotrophic thermophilic bacteria are, however, confined to only a few genera. Five of the main genera discussed in this chapter have been isolated only on one occasion and only from one location. Thermomicrobium was isolated from a continental hot spring; Rhodothermus, from a submarine hot spring; Saccharococcus, from a sugar beet factory; Acidothermus, from an acidic hot spring; and Scotothermus, from a hot water pipeline. Thermomicrobium apparently has a special place in bacterial evolution as indicated by its special cell wall and unique membrane structures. The genus Rhodothermus was first isolated from marine, shallow water alkaline hot springs in the northwest part of Iceland, but recently it also has been found in marine hot springs in Portugal.
