Chemoautotrophic sulfur bacteria in the marine environment. I. Isolation, cultivation, and distribution

Abstract

Chemoautotrophic sulfur bacteria were isolated in pure form from estuarine, neritic, and oceanic environments by the use of small-volume enrichment cultures. Thiosulfate was the only energy source added to the medium. Bicarbonate and carbon dioxide were the carbon sources.The bacteria were found in seawater samples collected at the surface and at a depth of 30 meters. Clay and mud sediments contained chemoautotrophs and heterotrophic pseudomonads with the capacity to oxidize thiosulfate.The isolated microorganisms differed greatly in their morphologies. Cells ranged in shape from vibrios to several varieties of rods which occurred alone, in pairs, in long chains, and in clusters. All of the bacteria were aerobic, Gram-negative, and non-sporulating.Growth characteristics with respect to the formation of elemental sulfur, production of tetrathionate, and final pH varied markedly. Colonies on thiosulfate – mineral salts agar were all 1 mm or less in diameter. A test, of two of the chemoautotrophs indicated a need for seawater in the growth medium.Out of a total of six different chemoautotrophic bacteria, one was identified as a strain of Thiobacillus thioparus. Another was facultatively autotrophic. The other four types were not compatible with the descriptions of any of the known thiobacilli.