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Purple non-sulfur bacteria (PNSB) are a diverse group of bacteria studied for various possible applications. They are commonly surveyed in bioenergy research as they produce biohydrogen, a candidate for clean alternative energy. This study aimed to assess the biohydrogen production ability and genetically characterize a high biohydrogen-producing PNSB (MAY2) isolated from Los Baños, Laguna, Philippines via whole genome sequencing (WGS). MAY2, when grown in mixed volatile fatty acids, produced biogas with 38% hydrogen. WGS results revealed that the isolate is positively classified under the genus Rhodobacter johrii. Also, 82 genetic hallmarks for biohydrogen production were found in the isolated genome which are involved in the production of key enzymes and proteins relevant to the photofermentative and hydrogen regulation pathways. Its nitrogenase gene cluster is stringently regulated by two genes, nifA and rofN, whose function and expression are easily affected by several environmental factors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Two Gram-stain-negative, aerobic, ovoid to short rod-shaped bacterial strains, designated as WL0062 T and WL0115, were isolated from coastal zone of the Yellow Sea, Jiangsu Province, PR China, respectively. Strain WL0062 T grew optimally at 28 °C, pH 7.0-8.0 and with 1.0-3.0% (w/v) NaCl. Strain WL0115 grew optimally at 28 °C, pH 6.0-7.0 and with 1.0-3.0% (w/v) NaCl. In the bac120 tree, strains WL0062 T and WL0115 clustered together with Sedimentimonas flavescens B57 T . The respiratory quinone of both strains was ubiquinone-10. The major polar lipids of both strains were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, glycolipid, phosphatidylmonomethylethanolamine, and one unidentified polar lipid. The major fatty acids of strain WL0062 T were summed features 8 (C 18 : 1  ω 6 c and/or C 18 : 1  ω 7 c ). The major fatty acids of strain WL0115 were summed features 8 (C 18 : 1  ω 6 c and/or C 18 : 1  ω 7 c ), C 18 : 0 , iso-C 17 : 1  ω 5 c and C 20 : 4  ω 6/9/12/15 c (arachidonic acid). The G+C content of genomic DNA of strains WL0062 T and WL0115 was 64.0 mol% in both of them. Combined with the analysis of average nucleotide identity, average amino acid identity, and digital DNA-DNA hybridization, strain WL0062 T represents a novel species of the genus Rhodobacter , for which the name Rhodobacter flavimaris sp. nov is proposed. The type strain is WL0062 T (=MCCC 1K06014 T =JCM 34676 T =GDMCC 1.2427 T ). Strain WL0115 (=MCCC 1K07531=JCM 35568=GDMCC 1.3088) should belong to the same species as Sedimentimonas flavescens B57 T . In addition, on the basis of phylogenomic relationship and phenotypical characteristics, the genera Paenirhodobacter , Sedimentimonas , and Sinirhodobacter are proposed as synonyms of Rhodobacter .

Microbially mediated arsenic redox transformations are key for arsenic speciation and mobility in rice paddies. Whereas anaerobic anoxygenic photosynthesis coupled to arsenite (As(III)) oxidation has been widely examined in arsenic-replete ecosystems, it remains unknown whether this light-dependent process exists in paddy soils. Here, we isolated a phototrophic purple bacteria, Rhodobacter strain CZR27, from an arsenic-contaminated paddy soil and demonstrated its capacity to oxidize As(III) to arsenate (As(V)) using malate as a carbon source photosynthetically. Genome sequencing revealed an As(III)-oxidizing gene cluster (aioXSRBA) encoding an As(III) oxidase. Functional analyses showed that As(III) oxidation under anoxic phototrophic conditions correlated with transcription of the large subunit of the As(III) oxidase aioA gene. Furthermore, the non-As(III) oxidizer Rhodobacter capsulatus SB1003 heterologously expressing aioBA from strain CZR27 was able to oxidize As(III), indicating that aioBA was responsible for the observed As(III) oxidation in strain CZR27. Our study provides evidence for the presence of anaerobic photosynthesis-coupled As(III) oxidation in paddy soils, highlighting the importance of light-dependent, microbe-mediated arsenic redox changes in paddy arsenic biogeochemistry., (© 2023 Applied Microbiology International and John Wiley & Sons Ltd.)

Strain HX-7-19 T was isolated from the activated sludge collected from an abandoned herbicide manufacturing plant in Kunshan, China. Cells were Gram-reaction-negative, rod-shaped, and non-motile. The phylogenetic analysis based on 16S rRNA gene indicated that strain HX-7-19 T formed a clade with Rhodobacter blasticus CGMCC 1.3365 T (96.3% sequence similarity). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain HX-7-19 T and R. blasticus CGMCC 1.3365 T were 76.2% and 20.3%, respectively. The genomic DNA G + C content of strain HX-7-19 T was 65.9%. The major fatty acids (> 10% of the total fatty acids) were C 18:1 ω7c and C 18:1 ω7c 11-methyl. The major respiratory quinone was quinone Q-10. The major polar lipid profile consists of phosphatidylglycerol (PG), diphosphatidyl-glycerol (DPG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC). Photosynthesis pigments bacteriochlorophyll a and carotenoids were formed and photosynthesis genes pufL and pufM were detected. On the basis of phenotypic and phylogenetic evidences, strain HX-7-19 T is considered as a novel species in the genus Rhodobacter, for which the name Rhodobacter kunshanensis sp. nov. is proposed. The type strain is HX-7-19 T (= KCTC 72471 T  = CCTCC AB 2020148 T )., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)