Complete genome sequence of the bacteriochlorophyll a-containing Roseibacterium elongatum type strain (DSM 19469(T)), a representative of the Roseobacter group isolated from Australian coast sand

Hydrogenase Gene Distribution and H2 Consumption Ability within the Thiomicrospira Lineage

Thiomicrospira were originally characterized as sulfur-oxidizing chemolithoautotrophs. Attempts to grow them on hydrogen failed for many years. Only recently we demonstrated hydrogen consumption among two of three tested Thiomicrospira and posited that hydrogen consumption may be more widespread among Thiomicrospira than previously assumed. Here, we investigate and compare the hydrogen consumption ability and the presence of group 1 [NiFe]-hydrogenase genes (enzyme catalyzes H₂↔2H⁺ + 2e^-) for sixteen different Thiomicrospira species. Seven of these Thiomicrospira species encoded group 1 [NiFe]-hydrogenase genes and five of these species could also consume hydrogen. All Thiomicrospira species exhibiting hydrogen consumption were from hydrothermal vents along the Mid-Atlantic ridge or Eastern Pacific ridges. The tested Thiomicrospira from Mediterranean and Western Pacific vents could not consume hydrogen. The [NiFe]-hydrogenase genes were categorized into two clusters: those resembling the hydrogenase from Hydrogenovibrio are in cluster I and are related to those from Alpha- and other Gammaproteobacteria. In cluster II, hydrogenases found exclusively in Thiomicrospira crunogena strains are combined and form a monophyletic group with those from Epsilonproteobacteria suggesting they were acquired through horizontal gene transfer. Hydrogen consumption appears to be common among some Thiomicrospira, given that five of the tested sixteen strains carried this trait. The hydrogen consumption ability expands their competitiveness within an environment.

Genome sequence of the Roseovarius mucosus type strain (DSM 17069(T)), a bacteriochlorophyll a-containing representative of the marine Roseobacter group isolated from the dinoflagellate Alexandrium ostenfeldii

Roseovarius mucosus Biebl et al. 2005 is a bacteriochlorophyll a-producing representative of the marine Roseobacter group within the alphaproteobacterial family Rhodobacteraceae, which was isolated from the dinoflagellate Alexandrium ostenfeldii. The marine Roseobacter group was found to be abundant in the ocean and plays an important role for global and biogeochemical processes. Here we describe the features of the R. mucosus strain DFL-24(T) together with its genome sequence and annotation generated from a culture of DSM 17069(T). The 4,247,724 bp containing genome sequence encodes 4,194 protein-coding genes and 57 RNA genes. In addition to the presence of four plasmids, genome analysis revealed the presence of genes associated with host colonization, DMSP utilization, cytotoxins, and quorum sensing that could play a role in the interrelationship of R. mucosus with the dinoflagellate A. ostenfeldii and other marine organisms. Furthermore, the genome encodes genes associated with mixotrophic growth, where both reduced inorganic compounds for lithotrophic growth and a photoheterotrophic lifestyle using light as additional energy source could be used.