Elioraea tepida, sp. nov., a Moderately Thermophilic Aerobic Anoxygenic Phototrophic Bacterium Isolated from the Mat Community of an Alkaline Siliceous Hot Spring in Yellowstone National Park, WY, USA

Strain MS-P2T was isolated from microbial mats associated with Mushroom Spring, an alkaline siliceous hot spring in Yellowstone National Park, WY, USA. The isolate grows chemoheterotrophically by oxygen-dependent respiration, and light stimulates photoheterotrophic growth under strictly oxic conditions. Strain MS-P2T synthesizes bacteriochlorophyll a and the carotenoid spirilloxanthin. However, photoautotrophic growth did not occur under oxic or anoxic conditions, suggesting that this strain should be classified as an aerobic anoxygenic phototrophic bacterium. Strain MS-P2T cells are motile, curved rods about 0.5 to 1.0 μm wide and 1.0 to 1.5 μm long. The optimum growth temperature is 45–50 °C, and the optimum pH for growth is circum-neutral (pH 7.0–7.5). Sequence analysis of the 16S rRNA gene revealed that strain MS-P2T is closely related to Elioraea species, members of the class Alphaproteobacteria, with a sequence identity of 96.58 to 98%. The genome of strain MS-P2T is a single circular DNA molecule of 3,367,643 bp with a mol% guanine-plus-cytosine content of 70.6%. Based on phylogenetic, physiological, biochemical, and genomic characteristics, we propose this bacteriochlorophyll a-containing isolate is a new species belonging to the genus Elioraea, with the suggested name Elioraeatepida. The type-strain is strain MS-P2T (= JCM33060T = ATCC TSD-174T).

Draft Genome Sequence of the Anoxygenic Phototrophic Bacterium Rhodoferax sp. Strain U11-2br, Isolated from a Mountain Lake on the Ulagan Plateau

We report the draft genome sequence of an anoxygenic phototrophic bacterium, Rhodoferax sp. strain U11-2br, which was isolated from a freshwater mountain lake on the Ulagan Plateau (Altai, Russia). The assembly contains 4,514,979 bp, with a GC content of 59.9%.

Draft Genome Sequence of the Anoxygenic Phototrophic Bacterium Rhodomicrobium sp. Strain Az07, Isolated from a Brackish Canal

Rhodomicrobium sp. strain Az07 was isolated from a brackish canal. The organism is more halotolerant than previously described species of the genus Rhodomicrobium . The Illumina MiSeq system was used to sequence the genome of the isolated strain. The assembly contains 3,291,400 bp, 106 contigs, and a GC content of 62.7%.

Draft Genome Sequence of the Aerobic Anoxygenic Phototrophic Bacterium Roseobacter sp. Strain OBYS 0001, Isolated from Coastal Seawater in Otsuchi Bay, Japan

Here, we report the draft genome sequence of the aerobic anoxygenic phototrophic bacterium Roseobacter sp. strain OBYS 0001, isolated from coastal seawater in Ostuchi Bay, Japan. This genome sequence could be useful for our understanding of the variation in photosynthesis-related genes among aerobic anoxygenic phototrophs.

An Aerobic Anoxygenic Phototrophic Bacterium Fixes CO2 via the Calvin-Benson-Bassham Cycle

Aerobic anoxygenic phototrophic bacteria (AAnPB) are photoheterotrophs, which use light as auxiliary energy and require organic carbon (OC) for growth. Herein, we report the unusual strain B3, which is a true AAnPB because it requires oxygen for growth, harbours genes for cbb3- and bd-type cytochromes and acsF, and produces bacteriochlorophyll. The B3 genome encodes the complete metabolic pathways for AAnPB light utilization, CO2 fixation via Calvin-Benson-Bassham (CBB) cycle and oxidation of sulfite and H2, and the transcriptome indicated that all components of these pathways were fully transcribed. Expression of the marker genes related to photosynthesis, including pufM for light harnessing and rbcL for CO2 fixation, and the activity of RubisCO, the key enzyme in the Calvin-Benson-Bassham (CBB) cycle, increased in response to decreased OC supply. Large amounts of cell biomass were obtained in liquid BG11 medium under illumination. The strain thus likely photoautotrophically grows using sulfite or H2 as an electron donor. Similar GC contents between photosynthesis, the CBB cycle and 16S rRNA genes and the consistency of their phylogenetic topologies implied that light harnessing and carbon fixation genes evolved vertically from an anaerobic phototrophic ancestor of Rhodospirillaceae in Alphaproteobacteria. In conclusion, strain B3 represents a novel AAnPB characterized by photoautotrophy using the CBB cycle. This kind of AAnPB may be ecologically significant in the global carbon cycle.

A New Thermophilic Ene-Reductase from the Filamentous Anoxygenic Phototrophic Bacterium Chloroflexus aggregans

Aiming at expanding the biocatalytic toolbox of ene-reductase enzymes, we decided to explore photosynthetic extremophile microorganisms as unique reservoir of (new) biocatalytic activities. We selected a new thermophilic ene-reductase homologue in Chloroflexus aggregans, a peculiar filamentous bacterium. We report here on the functional and structural characterization of this new enzyme, which we called CaOYE. Produced in high yields in recombinant form, it proved to be a robust biocatalyst showing high thermostability, good solvent tolerance and a wide range of pH optimum. In a preliminary screening, CaOYE displayed a restricted substrate spectrum (with generally lower activities compared to other ene-reductases); however, given the amazing metabolic ductility and versatility of Chloroflexus aggregans, further investigations could pinpoint peculiar chemical activities. X-ray crystal structure has been determined, revealing conserved features of Class III (or thermophilic-like group) of the family of Old Yellow Enzymes: in the crystal packing, the enzyme was found to assemble as dimer even if it behaves as a monomer in solution. The description of CaOYE catalytic properties and crystal structure provides new details useful for enlarging knowledge, development and application of this class of enzymes.

Draft Genome Sequence of a Filamentous Anoxygenic Phototrophic Bacterium, “Candidatus Roseilinea sp. Strain NK_OTU-006,” Recovered from Metagenomic Data of a Hot Spring Microbial Mat

ABSTRACT We report here the metagenome-assembled draft genome of an uncultured filamentous anoxygenic phototroph of the phylum Chloroflexota (formerly Chloroflexi), “Candidatus Roseilinea sp. strain NK_OTU-006,” recovered from hot spring-associated microbial mats. The 3.6-Mb genome is estimated to be 94% complete and comprises 117 contigs encoding 3,203 predicted genes, including a full-length rRNA operon.

Draft Genome Sequence of the Anoxygenic Phototrophic Bacterium Phaeospirillum fulvum MGU-K5

ABSTRACT Phaeospirillum fulvum MGU-K5 is an anoxygenic, purple, photoheterotrophic, nonsulfur alphaproteobacterium. Unlike most purple nonsulfur bacteria, MGU-K5 is unable to grow aerobically under chemoorganotrophic conditions. Here, we present the draft genome sequence of P. fulvum to provide insights into its physiology.