ASSIMILATION OF MINERAL SULFUR AND NITROGEN BY XANTHOMONAS-MALTOPHILIA

Manifestation of the auxotrophic requirement of Xanthomonas maltophili a strains for sulfur-containing amino acids was shown to depend on the availability of oxidized or reduced sulfur compounds in the medium. W hen grown in a synthetic medium supplied with sulfate or sulfite, 100 X. maltophilia strains out of the 101 studied were unable to assimilat e mineral nitrogen and showed auxotrophic requirements for methionine or cysteine. Upon addition of 1 - 5 g/l of thiosulfate instead of the salts mentioned, 94% strains did not show amino acid auxotrophy and re adily assimilated ammonium nitrogen; they utilized the same range of c arbon compounds as in the medium with methionine. Tetrathionate and el emental sulfur were less efficient than thiosulfate: bacteria develope d less actively and utilized fewer carbon substrates. In the presence of sulfide, only several X. maltophilia strains assimilated ammonium s alt, using only a few organic acids and proline as carbon sources. Thi osulfate was shown to maintain the development of cysteine-dependent P seudopnonas diminuta strains in synthetic media lacking this amino aci d but supplied with necessary vitamins.