The process of oxidation of elemental sulfur by Thiobacillus thiooxidans involves at least two steps; an instant adhesion of bacterial cell to solid sulfur particles, and subsequent steady state sulfur oxidation by the cells attached to sulfur granules. Some properties of the first step, namely, sulfur-cell adhesion process, were elucidated as follows:
1) The process exhibited pH dependency which was identical to that in sulfur oxidation and an optimum pH was at 2-5.
2) Treatment of the cells with SH-binding reagents brought complete loss of adhesion ability and this blocking of adhesion was released by the addition of SH-donor. Consequently the thiol groups, which may exist in the cell envelope, must be essential for the adhesion process.
3) Both the adhesion ability and oxygen uptake activity were significantly affected in the presence of 2, 4-DNP, HOQNO, and some heavy metal chelators, and anoxia also had a fairly potent inhibitory action on the attachment of bacteria to solid sulfur particles. Therefore, the adhesion process must be energy-dependent.