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.

Draft Genome Sequences of Putative Aerobic Anoxygenic Phototrophic Bacterial Strains Jannaschia sp. Strains AI_61 and AI_62, Isolated from Seawater around a Coastal Aquaculture Area

Here, we report the draft genome sequences of putative aerobic anoxygenic phototrophic bacterial strains Jannaschia sp. AI_61 and AI_62, isolated from seawater around a coastal aquaculture in Ainan, Ehime, Japan. These genome sequences could be useful for our understanding of the variation of aerobic anoxygenic phototrophs in the genus.

Discovery of Siderophore and Metallophore Production in the Aerobic Anoxygenic Phototrophs

Aerobic anoxygenic phototrophs have been isolated from a rich variety of environments including marine ecosystems, freshwater and meromictic lakes, hypersaline springs, and biological soil crusts, all in the hopes of understanding their ecological niche. Over 100 isolates were chosen for this study, representing 44 species from 27 genera. Interactions with Fe3+ and other metal(loid) cations such as Mg2+, V3+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Se4+ and Te2+ were tested using a chromeazurol S assay to detect siderophore or metallophore production, respectively. Representatives from 20 species in 14 genera of α-Proteobacteria, or 30% of strains, produced highly diffusible siderophores that could bind one or more metal(loid)s, with activity strength as follows: Fe > Zn > V > Te > Cu > Mn > Mg > Se > Ni > Co. In addition, γ-proteobacterial Chromocurvus halotolerans, strain EG19 excreted a brown compound into growth medium, which was purified and confirmed to act as a siderophore. It had an approximate size of ~341 Da and drew similarities to the siderophore rhodotorulic acid, a member of the hydroxamate group, previously found only among yeasts. This study is the first to discover siderophore production to be widespread among the aerobic anoxygenic phototrophs, which may be another key method of metal(loid) chelation and potential detoxification within their environments.

Diversity of Aerobic Anoxygenic Phototrophs and Rhodopsin-Containing Bacteria in the Surface Microlayer, Water Column and Epilithic Biofilms of Lake Baikal

The diversity of aerobic anoxygenic phototrophs (AAPs) and rhodopsin-containing bacteria in the surface microlayer, water column, and epilithic biofilms of Lake Baikal was studied for the first time, employing pufM and rhodopsin genes, and compared to 16S rRNA diversity. We detected pufM-containing Alphaproteobacteria (orders Rhodobacterales, Rhizobiales, Rhodospirillales, and Sphingomonadales), Betaproteobacteria (order Burkholderiales), Gemmatimonadetes, and Planctomycetes. Rhodobacterales dominated all the studied biotopes. The diversity of rhodopsin-containing bacteria in neuston and plankton of Lake Baikal was comparable to other studied water bodies. Bacteroidetes along with Proteobacteria were the prevailing phyla, and Verrucomicrobia and Planctomycetes were also detected. The number of rhodopsin sequences unclassified to the phylum level was rather high: 29% in the water microbiomes and 22% in the epilithon. Diversity of rhodopsin-containing bacteria in epilithic biofilms was comparable with that in neuston and plankton at the phyla level. Unweighted pair group method with arithmetic mean (UPGMA) and non-metric multidimensional scaling (NMDS) analysis indicated a distinct discrepancy between epilithon and microbial communities of water (including neuston and plankton) in the 16S rRNA, pufM and rhodopsin genes.

Genome Sequence of the Acidophilic Nonsulfur Purple Photosynthetic Alphaproteobacterium Rhodovastum atsumiense, a Divergent Member of the Acetobacteraceae Family

The genome sequence of the acidophile Rhodovastum atsumiense was determined for comparison with that of Rhodopila globiformis. Both genomes are unusually large for purple bacteria (7.10 Mb and 7.25 Mb, respectively), and they have an average nucleotide identity of 72%. This value is remarkably similar to the average nucleotide identity values for Acidisphaera, Elioraea, and Paracraurococcus, all aerobic anoxygenic phototrophs.

Aerobic anoxygenic phototrophs are highly abundant in hypertrophic and polyhumic waters

ABSTRACT Aerobic anoxygenic phototrophs (AAPs) are a group of photoheterotrophic bacteria common in natural waters. Here, AAP abundance and contribution to total bacterial abundance and biomass were investigated to test whether the trophic status of a lake or content of coloured dissolved organic matter (CDOM) play a role in determining AAP distribution and abundance in shallow inland lakes, with special focus on hypertrophic and polyhumic waters. Twenty-six different shallow lakes in Hungary were monitored. AAP abundance and biomass were determined by epifluorescence microscopy. The lakes exhibit a broad range of CDOM (2–7000 mg Pt L−1) and phytoplankton biomass (2–1200 μg L−1 chlorophyll a concentration). Very high AAP abundance (up to 3 × 107 cells mL−1) was observed in polyhumic and hypertrophic shallow lakes. AAP abundance was influenced by phytoplankton biomass and CDOM content, and these effects were interrelated. As determined, 40 μg L−1 chlorophyll a and 52 mg Pt L−1 CDOM are threshold levels above which these effects have a synergistic relationship. Hence, the observed high AAP abundance in some soda pans is a consequence of combined hypertrophy and high CDOM content. AAP contribution was influenced by total suspended solids (TSS) content: the success of AAP cells could be explained by high TSS levels, which might be explained by the decrease of their selective grazing control.