Identification and phylogenetic analysis of an okenone-containing halophilic purple sulfur bacterium

Abstract:

[Objective] To exploit resources of purple sulfur bacteria and their photosynthetic genes. [Methods] A purple sulfur bacterium strain 283-1 of okenone-containing, halophilic, high sulfide tolerance was isolated by agar dilution method in Pfennig medium from photolithoautotrophic enrichments of Dongfeng saltern, Qingdao, China. [Results] Cells of strain 283-1 were Gram–negative, halophile, straight or slightly curved rods, motile by monopolar single flagella, no gas vacuoles, carotenoid of okenone series and bacteriochlorophylla as photosynthetic pigment, purple red. It could photolithoautotrophically grow under anoxic condition in the light with sulfide as electron donor, sulfur globules accu-mulate as intermediate oxidation product and stored in the form of highly refractile globules inside the cells. The strain 283-1 belonged to Gammaproteobacteria, Chromatiales, Chroamtiaceae, genus of Marichromatium. Phylogenetic analysis based on 16S rRNA gene sequence also confirmed that strain 283-1 belonged to Marichromatium genus. However, the physiological characteristics of strain 283-1 were significantly different from four species of the genus Marichromatium. NaCl requirement range from 1% to 15%, good growth was observed at 7.5mmol· L-1NaS·9H2O, 45℃, 5000lux and pH9.0, a number of organic substances of C3 and C4 of TCA cycles and gluconate could be photoassililated in the presence of sulfide, no growth factors were required. [Conclusion] On the basis of 16S rRNA gene sequence analysis and its mor-phological and physiological characteristics, strain 283-1 is a new isolate of Marichromatium genus, named as Marichromatium sp. 283-1.

Key words:purple sulfur bacterium; okenone; halophile; sulfide tolerance; phylogenetic analysis