Pandiyan Indiragandhi

Pandoraea thiooxydans sp. nov., a facultatively chemolithotrophic, thiosulfate-oxidizing bacterium isolated from rhizosphere soils of sesame (Sesamum indicum L.)

A facultatively chemolithoautotrophic, thiosulfate-oxidizing, Gram-negative, aerobic, motile, rod-shaped bacterial strain, designated ATSB16(T), was isolated from rhizosphere soils of sesame (Sesamum indicum L.). 16S rRNA gene sequence analysis demonstrated that this strain was closely related to Pandoraea pnomenusa LMG 18087(T) (96.7 % similarity), P. pulmonicola LMG 18016(T) (96.5 %), P. apista LMG 16407(T) (96.2 %), P. norimbergensis LMG 18379(T) (96.1 %) and P. sputorum LMG 18819(T) (96.0 %). Strain ATSB16(T) shared 96.0-96.4 % sequence similarity with four unnamed genomospecies of Pandoraea. The major cellular fatty acids of the strain ATSB16(T) were C(17 : 0) cyclo (33.0 %) and C(16 : 0) (30.6 %). Q-8 was the predominant respiratory quinone. The major polar lipids were phosphatidylmethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine and two unidentified aminophospholipids. Hydroxyputrescine and putrescine were the predominant polyamines. The genomic DNA G+C content of the strain was 64.0 mol%. On the basis of the results obtained from this study, strain ATSB16(T) represents a novel species of the genus Pandoraea, for which the name Pandoraea thiooxydans sp. nov. is proposed. The type strain is ATSB16(T) (=KACC 12757(T) =LMG 24779(T)).

Thiosulfate oxidation and mixotrophic growth of Methylobacterium oryzae

Thiosulfate oxidation and mixotrophic growth with succinate or methanol plus thiosulfate was examined in nutrient-limited mixotrophic condition for Methylobacterium oryzae CBMB20, which was recently characterized and reported as a novel species isolated from rice. Methylobacterium oryzae was able to utilize thiosulfate in the presence of sulfate. Thiosulfate oxidation increased the protein yield by 25% in mixotrophic medium containing 18.5 mmol.L-1 of sodium succinate and 20 mmol.L-1 of sodium thiosulfate on day 5. The respirometric study revealed that thiosulfate was the most preferable reduced inorganic sulfur source, followed by sulfur and sulfite. Thiosulfate was predominantly oxidized to sulfate and intermediate products of thiosulfate oxidation, such as tetrathionate, trithionate, polythionate, and sulfur, were not detected in spent medium. It indicated that bacterium use the non-S4 intermediate sulfur oxidation pathway for thiosulfate oxidation. Thiosulfate oxidation enzymes, such as rhodanese and sulfite oxidase activities appeared to be constitutively expressed, but activity increased during growth on thiosulfate. No thiosulfate oxidase (tetrathionate synthase) activity was detected.