ANAEROBIC ALKALITHERMOPHILES, A NOVEL GROUP OF EXTREMOPHILES

Although some anaerobic and aerobic mesophiles have long been known to grow at alkaline pH (above 9.5), little was known until recently abou t thermophilic alkaliphiles, termed now alkalithermophiles. This minir eview describes presently known and recently validly described anaerob ic alkalithermophilic bacteria (pH(opt)(55C) > 8.5; T-opt > 55 degrees C) and alkalitolerant thermophiles (pH(opt)(55C) < 8.5 but pH(max)(55 C) above 9.0). Some of these are widely distributed, but others have b een isolated (thus far) only from one specific location. This novel gr oup of anaerobic bacteria is comprised of physiologically different ge nera and species which, so far, all belong to the Gram-type positive B acillus-Clostridium phylogenetic subbranch. An interesting feature of these anaerobic alkalithermophiles is that most of the isolates have s hort doubling times. The fastest growing among them are strains of The rmobrachium celere, with doubling times as short as 10 min while growi ng above pH 9.0 and above 55 degrees C.