Community structures of actively growing bacteria shift along a north-south transect in the western North Pacific

Bacterial community structures and their activities in the ocean are tightly coupled with organic matter fluxes and thus control ocean biogeochemical cycles. Bromodeoxyuridine (BrdU), halogenated nucleoside and thymidine analogue, has been recently used to monitor actively growing bacteria (AGB) in natural environments. We labelled DNA of proliferating cells in seawater bacterial assemblages with BrdU and determined community structures of the bacteria that were possible key species in mediating biochemical reactions in the ocean. Surface seawater samples were collected along a north-south transect in the North Pacific in October 2003 and subjected to BrdU magnetic beads immunocapture and PCR-DGGE (BUMP-DGGE) analysis. Change of BrdU-incorporated community structures reflected the change of water masses along a north-south transect from subarctic to subtropical gyres in the North Pacific. We identified 25 bands referred to AGB as BrdU-incorporated phylotypes, belonging to Alphaproteobacteria (5 bands), Betaproteobacteria (1 band), Gammaproteobacteria (4 bands), Cytophaga-Flavobacterium-Bacteroides (CFB) group bacteria (5 bands), Gram-positive bacteria (6 bands), and Cyanobacteria (4 bands). BrdU-incorporated phylotypes belonging to Vibrionales, Alteromonadales and Gram-positive bacteria appeared only at sampling stations in a subtropical gyre, while those belonging to Roseobacter-related bacteria and CFB group bacteria appeared at the stations in both subarctic and subtropical gyres. Our result revealed phylogenetic affiliation of AGB and their dynamic change along with north-south environmental gradients in open oceans. Different species of AGB utilize different amount and kinds of substrates, which can affect the change of organic matter fluxes along transect

A Red Beneckea from Laguna Figueroa, Baja California

A new bacterium (nitrate-respiring, prodigiosin-producing, marine curved rod with a sheathed flagellum) has been isolated from anaerobic mud underlying a microbial meat. This brightly pigmented red bacterium, referred to as strain BV1 (Baja California vibrio, isolate 1) was taken from a closed, hypersaline basin at Laguna Figueroa (or Laguna Mormona), Baja California de Norte, Mexico. It is closely related to the recently described Beneckea gazogenes (Harwood, 1978), which was isolated from an estuarine habitat, the Sippewissett salt marsh at Woods Hole, Massachusetts, U.S.A. Strain BV1 and B-gazogenes are both oxidase positive facultative anaerobic curved rods which bear a single polar flagellum, and synthesize the red-orange tri-pyrrole pigment prodigiosin. The bacterium, which fluoresces green when excited with UV light (lambda = 455 nm), deposits pigment extracellularly in copious quantities. The extracellular pigment deposits fluoresce red-yellow. Both BV1 and B. gazogenes are able to grow utilizing xylose, cellobiose or arabinose, products of plant biosynthesis, as sole carbon sources. BV1 differs from B. gazogenes in cell size, pattern of pigment production, nutritional characteristics, the ability to perform anaerobic respiration using nitrate as a terminal electron acceptor, sensitivity to a newly discovered lytic phage and to the antibiotic vibriostat O/129

The phylogeny of endolithic microbes associated with marine basalts

We examined the phylogenetic diversity of microbial communities associated with marine basalts, using over 300 publicly available 16S rDNA sequences and new sequence data from basalt enrichment cultures. Phylogenetic analysis provided support for 11 monophyletic clades originating from ocean crust (sediment, basalt and gabbro). Seven of the ocean crust clades (OCC) are bacterial, while the remaining four OCC are in the Marine Group I (MGI) Crenarchaeota. Most of the OCC were found at diverse geographic sites, suggesting that these microorganisms have cosmopolitan distributions. One OCC in the Crenarchaeota consisted of sequences derived entirely from basalts. The remaining OCC were found in both basalts and sediments. The MGI Crenarchaeota were observed in all studies where archaeal diversity was evaluated. These results demonstrate that basalts are occupied by cosmopolitan clades of microorganisms that are also found in marine sediments but are distinct from microorganisms found in other marine habitats, and that one OCC in the ubiquitous MGI Crenarchaeota clade may be an ecotype specifically adapted to basalt

Abundance and activity of Chloroflexi-type SAR202 bacterioplankton in the meso- and bathypelagic waters of the (sub)tropical Atlantic

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