Rhodobacter amnigenus sp. nov. and Rhodobacter ruber sp. nov., isolated from freshwater habitats

Abstract

Two bacterial strains, designated HSP-20T and CCP-1T, isolated from freshwater habitats in Taiwan, were characterized by polyphasic taxonomy. Both strains were Gram-stain-negative, aerobic, non-motile and rod-shaped. Cells of strains HSP-20T and CCP-1T formed pink and dark red coloured colonies, respectively. Both strains contained bacteriochlorophyll a, and showed optimum growth under anaerobic conditions by photoheterotrophy, but no growth by photoautotrophy. Phylogenetic analyses based on 16S rRNA gene and whole-genome sequences indicated that both strains belonged to the genus Rhodobacter . Analysis of 16S rRNA gene sequences showed that strains HSP-20T and CCP-1T shared 98.3 % sequence similarity and were closely related to Rhodobacter tardus CYK-10T (96.0 %) and Rhodobacter flagellatus SYSU G03088T (96.0 %), respectively. Both strains shared common chemotaxonomic characteristics including Q-10 as the major isoprenoid quinone, C18 : 1 ω7c as the predominant fatty acid, and phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine as the main polar lipids. The DNA G+C content of both strains was 66.2 mol%. The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between these two novel isolates and their closest relatives were below the cut-off values of 95–96, 90 and 70 %, respectively, used for species demarcation. On the basis of phenotypic and genotypic properties and phylogenetic inference, both strains should be classified as novel species within the genus Rhodobacter , for which the names Rhodobacter amnigenus sp. nov. (=BCRC 81193T=LMG 31334T) and Rhodobacter ruber sp. nov. (=BCRC 81189T=LMG 31335T) are proposed.

Species-level classification provides new insights into the biogeographical patterns of microbial communities in shallow saline lakes

“…The two highly abundant Betaproteobacteria shown to be either restricted to or prevalent in low-salinity lakes (< 10‰) were the genera of free-living freshwater bacteria Polynucleobacter and Limnohabitans 61 . In addition, several indicator species from Alphaproteobacteria ( Rhodobacter spp, Caulobacter spp, and Tabrizicola spp), Actinomycetes ( Rhodoluna lacicola ), Bacteroidota ( Aquirufa spp, Algoriphagus sanaruensis ), and Cyanobacteriota ( Planktothrix agardhii ) are also reported for freshwater habitats 62–66 . Besides these planktonic freshwater taxa, the indicator value analysis demonstrated presence of a high number of shared soil-derived bacterial groups.…”