Physiological and morphological observations on Thiovulum sp

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Abstract
Cell suspensions of Thiovulum sp., collected from enrichment cultures, were grown, maintained, and harvested for periods up to 7 mo. In open-flow cultures run with aerated seawater, a continuous supply of H2S was provided by difffusion through a semipermeable membrane from either a live culture of Desulfovibrio aestuarii, neutralized NaS, or a N2-H2S gas mixture. Attempts to grow Thiovulum in pure culture failed despite variation in concentrations of dissolved O2 and H2S in stratified as well as in completely mixed systems. Uptake of 14CO2 and some organic compounds by purified cell suspensions was measured, and values were corrected for the activity of heterotrophic and autotrophic contaminants as determined in control experiments. Cell populations exhibited maximum uptake activities during formation of the characteristic veils. Substantial uptake of CO2 in air-saturated seawater was coincident with an optimal concentration of H2S of about 1 mM. Glutamate and a selection of vitamins (B12, biotin and thiamine) did not significantly affect the uptake of CO2. No substantial uptake of C from acetate, glutamate, mannitol and Casamino acids was found. Within the range of error indicated, the data are consistent with acceptance of a chemolithotrophic nature for Thiovulum.