Competition for dimethyl sulfide and hydrogen sulfide by Methylophaga sulfidovorans and Thiobacillus thioparus T5 in continuous cultures

Pure and mixed cultures of Methylophaga sulfidovorans and Thiobacillus thioparus T5 were grown in continuous cultures on either dimethyl sulfide, dimethyl sulfide and H2S, or H2S and methanol, In pure cultures, M. sulfidovorans showed a lower affinity for sulfide than T.thioparus T5. Mixed cultures, grown on dimethyl sulfide, showed coexistence of both species, M. sulfidovorans fully converted dimethyl sulfide to thiosulfate, which was subsequently further oxidized to sulfate by T.thioparus T5. Mixed cultures supplied with sulfide and methanol showed that nearly all the sulfide was used by T.thioparus T5, as expected an the basis of the affinities for sulfide, The sulfide in mixed cultures supplied with dimethyl sulfide and H2S, however, was used by both bacteria. This result may be explained by the fact that the H2S-oxidizing capacity of M. sulfidovorans remains fully induced by intracellular H2S originating from dimethyl sulfide metabolism.