Phylogenetic relationship of phototrophic purple sulfur bacteria according to pufL and pufM genes

The phylogenetic relationship of purple sulfur bacteria (PSB), of the order Chromatiales (class Gammaproteobacteria), was analyzed based on photosynthetic gene sequences of the pufL and pufM genes, and the results compared to phylogenetic trees and groupings of the 16S rRNA gene. Primers for pufL and pufM genes were constructed and successfully used to amplify the pufLM genes of members of 16 genera of Chromatiales. In total, pufLM and 16S rRNA gene sequences of 66 PSB strains were analyzed, including 29 type strains and 28 new isolates. The inferred phylogenetic trees of the pufLM and 16S rRNA genes reflected a largely similar phylogenetic development suggesting coevolution of these essential genes within the PSB. It is concluded that horizontal gene transfer of pufLM genes within the PSB is highly unlikely, in contrast to the situation in other groups of anoxygenic phototrophic bacteria belonging to Alpha- and Betaproteobacteria. The phylogeny of pufLM is therefore in good agreement with the current taxonomic classification of PSB. A phylogenetic classification of PSB to the genus level is possible based on their pufL or pufM sequences, and in many cases even to the species level. In addition, our data support a correlation between Puf protein structure and the type of internal photosynthetic membranes (vesicular, lamellar, or tubular) (AU)

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Selection of sulfur oxidizing bacterium for sulfide removal in sulfate rich wastewater to enhance biogas production

Sulfur oxidizing bacteria (SOB) were isolated and tested in order to remove sulfide from high sulfate wastewater to reduce the amount of hydrogen sulfide (H2S) in the produced biogas. A promising SOB isolate, designated as isolate T307, was selected due to its best sulfide removal (86.7 percent) in the effluent of a sulfate reduction reactor (SRR) over a 24 hrs incubation. The bacterium was able to grow better as a mixotroph (yeast extract as a carbon source) than as a chemolithoautotroph. In addition, as a heterotroph, the bacterium grew well with yeast extract and peptone. Based on partial 16S rRNA gene sequence, the isolated T307 was an Alcaligenes sp. and was able to convert most of sulfide species (total sulfide: TS; dissolved sulfide: DS and H2S) into elemental sulfur or sulfate over a 20 hrs period of cultivation by controlling the speed of shaking. In a biogas reactor set, after pre-treating a sulfide medium with Alcaligenes sp. T307 there was a much higher specific yield of CH4 (238 ml CH4 g-1COD removed) and more biogas (154 ml L-1 d-1) was produced with the biogas containing more methane (48.1 percent CH4, 51.5 percent CO2 and 0.41 percent H2S) in comparison to a control with a specific yield of CH4, (72 ml CH4 g-1COD removed) 86 ml L-1 d-1 biogas produced with a composition of 35.5 percent CH4, 63.7 percent CO2 and 0.86 percent H2S.