Genome Sequence and Characterization of a Xanthorhodopsin-Containing, Aerobic Anoxygenic Phototrophic Rhodobacter Species, Isolated from Mesophilic Conditions at Yellowstone National Park

Abstract

The genus Rhodobacter consists of purple nonsulfur photosynthetic alphaproteobacteria known for their diverse metabolic capabilities. Here, we report the genome sequence and initial characterization of a novel Rhodobacter species, strain M37P, isolated from Mushroom hot spring runoff in Yellowstone National Park at 37 °C. Genome-based analyses and initial growth characteristics helped to define the differentiating characteristics of this species and identified it as an aerobic anoxygenic phototroph (AAP). This is the first AAP identified in the genus Rhodobacter. Strain M37P has a pinkish-red pigmentation that is present under aerobic dark conditions but disappears under light incubation. Whole genome-based analysis and average nucleotide identity (ANI) comparison indicate that strain M37P belongs to a specific clade of recently identified species that are genetically and physiologically unique from other representative Rhodobacter species. The genome encodes a unique xanthorhodopsin, not found in any other Rhodobacter species, which may be responsible for the pinkish-red pigmentation. These analyses indicates that strain M37P is a unique species that is well-adapted to optimized growth in the Yellowstone hot spring runoff, for which we propose the name Rhodobacter calidifons sp. nov.

A bacterium from a mountain lake harvests light using both proton-pumping xanthorhodopsins and bacteriochlorophyll-based photosystems

“…Recently, a BChl a –producing mesophilic Rhodobacter strain M37P was isolated from Yellowstone springs. It also contains an XR gene, but its expression has not yet been documented ( 45 ).…”

The Diversity and Extensive Presence of Culturable Anoxygenic Phototrophic Bacteria in Manitoba Marshes

“…Mentioned above strain EG17, a γ-Proteobacterium isolated from a hypersaline spring East German Creek, Manitoba is to date the sole known which synthesizes Bchl a regardless of oxygen presence [25]. However, there are a few AAP closely related to the PNSB Rhodobacter [37,38] suggesting the possibility of such expression of pigments may occur in some not yet taxonomically defined strains. These absorption spectra do not show definitively PNSB were using light energy aerobically, but it would be worthwhile to investigate in KP4 and FW5 (related to a species currently or formerly placed in the Rhodobacter genus [39]).…”

Abundance, Characterization and Diversity of Culturable Anoxygenic Phototrophic Bacteria in Manitoban Marshlands

“…The abovementioned strain EG17, a γ-Proteobacterium isolated from a hypersaline spring, East German Creek, Manitoba, is to date the sole known strain which synthesizes Bchl a regardless of the presence of oxygen [25]. However, there are a few AAP closely related to the PNSB Rhodobacter [37,38], suggesting the possibility that such expression of pigments may occur in some as of yet taxonomically undefined strains. These absorption spectra do not definitively show the PNSB used light energy aerobically, but this would be worthwhile to investigate in KP4 and FW5 (related to species currently or formerly placed in the Rhodobacter genus [39]).…”