Tn5-induced mutations affecting sulfur-oxidizing ability (Sox) of Thiosphaera pantotropha

Mutants of Thiosphaera pantotropha defective in chemolithoautotrophic growth were obtained by transpositional mutagenesis with Tn5 coding for kanamycin resistance. The suicide vehicle for introducing Tn5 to T. pantotropha was pSUP5011 harbored by Escherichia coli. Kanamycin-resistant isolates were screened for the inability to grow with reduced sulfur compounds (Sox-). Four classes of Sox- mutants were obtained. Three were of different pleiotropic phenotypes: (i) unable to grow with formate, nitrate, and xanthine; (this class strongly suggested the involvement of a molybdenum cofactor in inorganic sulfur-oxidizing ability); (ii) no growth with hydrogen; (iii) slight growth with hydrogen and formate. Two plasmids, pHG41 (about 450 kilobase pairs) and pHG42 (110 kilobases), were identified in lysates of T. pantotropha. In one Sox- mutant pHG41 could not be detected. Revertant analysis suggested that pHG41 and pHG42 were not involved in the Sox character.