Massive Natural Occurrence of Unusually Large Bacteria (Beggiatoa Sp.) at a Hydrothermal Deep-Sea Vent Site.

摘要

WHITE web-like 'mats' of the filamentous sulphur-oxidizing bacterium Beggiatoa are commonly observed on the surface of anoxic sediments. As a typical interface organism Beggiatoa requires a source of inorganic reduced sulphur and dissolved free oxygen. The first pure cultures of marines strains of Beggiatoa were recently obtained by artificially reconstructing an O2-H2S interface in a semi-solid medium that supports the gliding mobility of the filaments. The maximal thickness of these Beggiatoa mats in culture was 1.0 mm. We now report the discovery of dense layers of filamentous sulphur-oxidizing bacteria up to 3 cm thick on the sediment surface, and up to 30 cm thick between stands of vestimentiferan tube worms at the Guaymas Basin hydrothermal vent site in the Gulf of California at a depth of 2,010 m. The mats are essentially monocultures of Beggiatoa-type organisms containing filaments of three width classes, the largest filaments being 116-122 micron in diameter. Freshly collected filaments showed chemoautotrophic metabolism and active gliding motility. The phenomenon of a natural mass growth of a bacterium is of great physiological and ecological interest, and could also be of biotechnical importance considering the difficulties of mass cultivation of interface organisms such as Beggiatoa and the other 'large' sulphur-oxidizing bacteria such as Thiovulum and Thioploca. Keywords: Aquatic bacteria; Reprints. (kt)