Roseomonas fluvialis sp. nov., an aerobic bacteriochlorophyll a-containing freshwater bacterium isolated from river epilithic biofilm.

A strictly aerobic bacteriochlorophyll a-containing alphaproteobacterium, designated strain S08T, was isolated from a biofilm sampled at Tama River in Japan. The non-motile and rod-shaped cells formed pink-beige pigmented colonies on agar plates containing organic compounds and showed in vivo absorption maxima at 798 and 866 nm in the near-infrared region, typical for the presence of bacteriochlorophyll a. The new bacterial isolate is Gram-negative, oxidase-negative and catalase-positive. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain S08T was closely related to species in the genus Roseomonas. The closest phylogenetic relative of strain S08T was Roseomonas lacus TH-G33T (98.2 % sequence similarity). The major cellular fatty acids were C16 : 0, C18 : 1 2-OH and summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c). The predominant respiratory quinone was ubiquinone-9. The major polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an aminolipid. The G+C content of the genomic DNA was 70.6 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between strain S08T and the related Roseomonas type strains were all far lower than the cut-off value for the delineation of species. The results of polyphasic comparisons showed that strain S08T was clearly distinguishable from other members of the genus Roseomonas. Therefore, we propose a new species in the genus Roseomonas, namely, Roseomonas fluvialis sp. nov. The type strain is S08T (=DSM 111902T=NBRC 112025T).

Neotabrizicola shimadae gen. nov., sp. nov., an aerobic anoxygenic phototrophic bacterium harbouring photosynthetic genes in the family Rhodobacteraceae, isolated from a terrestrial hot spring.

A bacteriochlorophyll-containing bacterium, designated as strain N10T, was isolated from a terrestrial hot spring in Nagano Prefecture, Japan. Gram-stain-negative, oxidase- and catalase-positive and ovoid to rod-shaped cells showed the features of aerobic anoxygenic phototrophic bacteria, i.e., strain N10T synthesised bacteriochlorophylls under aerobic conditions and could not grow anaerobically even under illumination. Genome analysis found genes for bacteriochlorophyll and carotenoid biosynthesis, light-harvesting complexes and type-2 photosynthetic reaction centre in the chromosome. Phylogenetic analyses based on the 16S rRNA gene sequence and 92 core proteins revealed that strain N10T was located in a distinct lineage near the type species of the genera Tabrizicola and Xinfangfangia and some species in the genus Rhodobacter (e.g., Rhodobacter blasticus). Strain N10T shared < 97.1% 16S rRNA gene sequence identity with those species in the family Rhodobacteraceae. The digital DNA-DNA hybridisation, average nucleotide identity and average amino acid identity values with the relatives, Tabrizicola aquatica RCRI19T (an aerobic anoxygenic phototrophic bacterium), Xinfangfangia soli ZQBWT and R. blasticus ATCC 33485T were 19.9-20.7%, 78.2-79.1% and 69.1-70.1%, respectively. Based on the phenotypic features, major fatty acid and polar lipid compositions, genome sequence and phylogenetic position, a novel genus and species are proposed for strain N10T, to be named Neotabrizicola shimadae (= JCM 34381T = DSM 112087T). Strain N10T which is phylogenetically located among aerobic anoxygenic phototrophic bacteria (Tabrizicola), bacteriochlorophyll-deficient bacteria (Xinfangfangia) and anaerobic anoxygenic phototrophic bacteria (Rhodobacter) has great potential to promote studies on the evolution of photosynthesis in Rhodobacteraceae.

Roseobacter cerasinus sp. nov., isolated from a fish farm.

An obligate aerobic and bacteriochlorophyll a-containing bacterium, designated strain AI77T, was isolated from a fish farm in Uwa Sea, Japan. Cells were Gram-stain-negative, coccoid- to oval-shaped, and showed no motility. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain AI77T is a member of the genus Roseobacter and closely related to Roseobacter ponti MM-7T (97.8 %), Roseobacter denitrificans OCh 114T (97.3 %) and Roseobacter litoralis OCh 149T (97.3 %). The G+C content of strain AI77T was 61.0 mol%. The average amino acid identity values of the genome in strain AI77T with those in R. denitrificans OCh 114T and R. litoralis OCh 149T were 73.26 % (SD 16.46) and 72.63 % (SD 16.76), respectively. The digital DNA-DNA hybridization values of strain AI77T with the type strains R. denitrificans OCh 114T and R. litoralis OCh 149T were 18.70 and 18.50 %, respectively. The dominant fatty acids (>10 % of total fatty acids) of AI77T were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and saturated fatty acid C16 : 0. The sole respiratory quinone was ubiquinone-10. The predominant polar lipids were phosphatidylcholine, phosphatidylglycerol and diphosphatidylglycerol. Based on the genetic and phenotypic data obtained herein, we conclude that strain AI77T represents a new species of the genus Roseobacter, for which we propose the name Roseobacter cerasinus sp. nov.; the type strain is AI77T (=DSM 110091T=NBRC 114115T).

Aquabacterium pictum sp. nov., the first aerobic bacteriochlorophyll a-containing fresh water bacterium in the genus Aquabacterium of the class Betaproteobacteria.

A strictly aerobic, bacteriochlorophyll a-containing betaproteobacterium, designated strain W35T, was isolated from a biofilm sampled at Tama River in Japan. The non-motile and rod-shaped cells formed pink-beige pigmented colonies on agar plates containing organic compounds, and showed an in vivo absorption maximum at 871 nm in the near-infrared region, typical for the presence of bacteriochlorophyll a. The new bacterial strain is Gram-negative, and oxidase- and catalase-positive. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain W35T was closely related to species in the genus Aquabacterium. The closest phylogenetic relatives of strain W35T were Aquabacterium commune B8T (97.9 % sequence similarity), Aquabacterium citratiphilum B4T (97.2 %) and Aquabacterium limnoticum ABP-4T (97.0 %). The major cellular fatty acids were C16  :  1ω7c (50.4 %), C16  :  0 (22.7 %), summed feature 8 (C18  :  1ω7c/C18  :  1ω6c; 9.7 %), C18  :  3ω6c (5.5 %), C12  :  0 (5.3 %) and C10  :  0 3OH (2.7 %). The respiratory quinone was ubiquinone-8. Predominant polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The G+C content of the genomic DNA was 70.4 mol% (genome data) and 71.4 mol% (HPLC). The genome size of strain W35T is 6.1 Mbp and average nucleotide identity analysis indicated genome similarities of strain W35T and related Aquabacterium type strains to be 78-79 %. The results of polyphasic comparisons showed that strain W35T was clearly distinguishable from other members of the genus Aquabacterium. Therefore, we propose a new species in the genus Aquabacterium, namely, Aquabacterium pictum sp. nov. The type strain is W35T (=DSM 106757T=NBRC 111963T). The description of the genus Aquabacterium is also emended.

Emended description of the genus Tabrizicola and the species Tabrizicola aquatica as aerobic anoxygenic phototrophic bacteria.

The genus Tabrizicola with its type species and strain Tabrizicola aquatica RCRI19T was previously described as a purely chemotrophic genus of Gram-negative, aerobic, non-motile and rod-shaped bacteria. With the present study, we expand the description of the metabolic capabilities of this genus and the T. aquatica type strain to include chlorophyll-dependent phototrophy. Our results confirmed that T. aquatica, does not grow under anaerobic photoautotrophic or photoheterotrophic conditions. However, the presence of the photosynthesis-related genes pufL and pufM could be demonstrated in the genomes of several Tabrizicola strains. Additionally, photosynthetic pigments (bacteriochlorophyll a) were formed under aerobic, heterotrophic and low light conditions in T. aquatica strain RCRI19T. Furthermore, all the genes necessary for a fully operational photosynthetic apparatus and bacteriochlorophyll a are present in the T. aquatica type strain genome. Therefore, we suggest categorising T. aquatica RCRI19T, isolated from freshwater environment of Qurugöl Lake, as an aerobic anoxygenic phototrophic (AAP) bacterium.

Litoreibacter roseus sp. nov., a novel bacteriochlorophyll a-containing bacterium.

A strictly aerobic, bacteriochlorophyll (BChl) a-containing alphaproteobacterium, designated strain K6T, was isolated from seawater around an aquaculture site in the Uwa Sea in Japan. The novel strain grew optimally at 30 °C at pH 7.0-7.5 and in the presence of 2.0 % (w/v) NaCl. The nonmotile and coccoid or rod-shaped cells formed pink-pigmented colonies on agar plates containing organic compounds. Cells showed an in vivo absorption maximum at 870 nm in the near-infrared region, indicating the presence of BChl a in the light-harvesting 1 complex. The new bacterial strain was Gram-stain-negative and oxidase- and catalase-positive. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain K6T was closely related to species in the genus Litoreibacter. The closest phylogenetic relatives of strain K6T were Litoreibacter ponti GJSW-31T (98.56 % sequence similarity), Litoreibacter janthinus KMM 3842T (97.63 %) and Litoreibacter albidus KMM 3851T (96.88 %). The G+C content of the genomic DNA was 58.26 mol%. The average nucleotide identity value of strain K6T with the type strain of L. ponti was 77.16 % (SD 4.79 %). The digital DNA-DNA hybridization value of strain K6T with the type strain of L. ponti was 19.40 %. The respiratory quinone was ubiquinone-10. The major cellular fatty acids were C18 : 1 ω7c, C16 : 0 and 11-methyl C18 : 1 ω7c. The dominant polar lipids were phosphatidylcholine and phosphatidylglycerol. On the basis of the genetic and phenotypic data obtained in the present study, we propose a new species in the genus Litoreibacter: Litoreibacter roseus sp. nov., whose type strain is K6T (=DSM 110109T=NBRC 114114T). Strain K6T represents the first confirmed species that produces BChl a within the genus Litoreibacter.

Phylogenetically Diverse Aerobic Anoxygenic Phototrophic Bacteria Isolated from Epilithic Biofilms in Tama River, Japan.

The diversity of aerobic anoxygenic phototrophic (AAP) bacteria in freshwater environments, particularly in rivers, has not been examined in as much detail as in ocean environments. In the present study, we investigated the phylogenetic and physiological diversities of AAP bacteria in biofilms that developed on submerged stones in a freshwater river using culture methods. The biofilms collected were homogenized and inoculated on solid media and incubated aerobically in the dark. Sixty-eight red-, pink-, yellow-, orange-, or brown-colored colonies were isolated, and, of these, 28 isolates contained the photosynthetic pigment, bacteriochlorophyll (BChl) a. Phylogenetic analyses based on 16S rRNA gene sequences showed that the isolates were classified into 14 groups in 8 operational taxonomic units (OTUs) and distributed in the orders Rhodospirillales, Rhodobacterales, and Sphingomonadales of Alphaproteobacteria and in Betaproteobacteria. Physiological analyses confirmed that none of the representative isolates from any of the groups grew under anaerobic phototrophic conditions. Seven isolates in 4 OTUs showed a 16S rRNA gene sequence identity of 98.0% or less with any established species, suggesting the presence of previously undescribed species of AAP bacteria. Six isolates in 2 other OTUs had the closest relatives, which have not been reported to be AAP bacteria. Physiological comparisons among the isolates revealed differences in preferences for nutrient concentrations, BChl contents, and light-harvesting proteins. These results suggest that diverse and previously unknown AAP bacteria inhabit river biofilms.

Diversity of purple phototrophic bacteria, inferred from pufM gene, within epilithic biofilm in Tama River, Japan.

The diversity of purple phototrophic bacteria in algae-dominated biofilm of a streambed in Tama River, Japan was investigated. Clone library analysis of the pufM gene encoding a subunit of the photochemical reaction center of purple bacteria detected 18 operational taxonomic units (OTUs) in several classes of Proteobacteria. Most of the OTUs showed less than 85% identity to the PufM amino acid sequences of known phototrophic bacteria. These results suggest that phylogenetically divergent and unknown purple phototrophic bacteria are present in the epilithic biofilm of the river.