The bacterial and temperature factors leading to yellow blotch/band disease (YBD), which affects the major reef-building Caribbean corals Montastrea spp., have been investigated. Groups of bacteria isolated from affected corals and inoculated onto healthy corals caused disease signs similar to those of YBD. The 16S rRNA genes from these bacteria were sequenced and found to correspond to four Vibrio spp. Elevating the water temperature notably increased the rate of spread of YBD on inoculated corals and induced greater coral mortality. YBD-infected corals held at elevated water temperatures had 50% lower zooxanthella densities, 80% lower division rates, and a 75% decrease in chlorophyll a and c 2 pigments compared with controls. Histological sections indicated that the algal pyrenoid was fragmented into separate segments, along with a reconfiguration and swelling of the zooxanthellae, as well as vacuolization. YBD does not appear to produce the same physiological response formerly observed in corals undergoing temperature-related bleaching. Evidence indicates that YBD affects primarily the symbiotic algae rather than coral tissue.

Coastal salt marshes are highly sensitive wetland ecosystems that can sustain long-term impacts from anthropogenic events such as oil spills. In this study, we examined the microbial communities of a Gulf of Mexico coastal salt marsh during and after the influx of petroleum hydrocarbons following the Deepwater Horizon oil spill. Total hydrocarbon concentrations in salt marsh sediments were highest in June and July 2010 and decreased in September 2010. Coupled PhyloChip and GeoChip microarray analyses demonstrated that the microbial community structure and function of the extant salt marsh hydrocarbon-degrading microbial populations changed significantly during the study. The relative richness and abundance of phyla containing previously described hydrocarbon-degrading bacteria ( Proteobacteria, Bacteroidetes, and Actinobacteria ) increased in hydrocarbon-contaminated sediments and then decreased once hydrocarbons were below detection. Firmicutes, however, continued to increase in relative richness and abundance after hydrocarbon concentrations were below detection. Functional genes involved in hydrocarbon degradation were enriched in hydrocarbon-contaminated sediments then declined significantly (p<0.05) once hydrocarbon concentrations decreased. A greater decrease in hydrocarbon concentrations among marsh grass sediments compared to inlet sediments (lacking marsh grass) suggests that the marsh rhizosphere microbial communities could also be contributing to hydrocarbon degradation. The results of this study provide a comprehensive view of microbial community structural and functional dynamics within perturbed salt marsh ecosystems.

The characterization of microbial assemblages within solid gas hydrate, especially those that may be physiologically active under in situ hydrate conditions, is essential to gain a better understanding of the effects and contributions of microbial activities in Gulf of Mexico (GoM) hydrate ecosystems. In this study, the composition of the Bacteria and Archaea communities was determined by 16S rRNA phylogenetic analyses of clone libraries derived from RNA and DNA extracted from sediment-entrained hydrate (SEH) and interior hydrate (IH). The hydrate was recovered from an exposed mound located in the northern GoM continental slope with a hydrate chipper designed for use on the manned-submersible Johnson Sea Link (water depth, 550 m). Previous geochemical analyses indicated that there was increased metabolic activity in the SEH compared to the IH layer (B. N. Orcutt, A. Boetius, S. K. Lugo, I. R. Macdonald, V. A. Samarkin, and S. Joye, Chem. Geol. 205:239-251). Phylogenetic analysis of RNA-and DNA-derived clones indicated that there was greater diversity in the SEH libraries than in the IH libraries. A majority of the clones obtained from the metabolically active fraction of the microbial community were most closely related to putative sulfate-reducing bacteria and anaerobic methane-oxidizing archaea. Several novel bacterial and archaeal phylotypes for which there were no previously identified closely related cultured isolates were detected in the RNA-and DNA-derived clone libraries. This study was the first phylogenetic analysis of the metabolically active fraction of the microbial community extant in the distinct SEH and IH layers of GoM gas hydrate.Marine gas hydrates, which are ice-like crystalline solids, are composed of rigid water molecules with trapped gas molecules, primarily methane and other hydrocarbons. Gas hydrate reservoirs, which are distributed in the sediments of active and passive continental slope margins, as well as in terrestrial (i.e., permafrost) regions (38), are a proposed fossil fuel energy source (10). Additionally, the estimated global volume of submarine methane hydrates exceeds 10 16 m 3 (7, 10), highlighting the impact of hydrates on global carbon cycling, climate conditions, and seafloor stability (16,18,28,31,35). The formation of gas hydrates is dependent upon suitable gas, temperature, and pressure conditions (reviewed in reference 38). Geological and chemical conditions in the northern continental slope of the Gulf of Mexico (GoM) promote the formation of gas hydrates where seepage of hydrocarbon gases forms extensive surface-breaching mounds on the seafloor, as well as vast veinfilling hydrates in hemipelagic sediments (27).Geochemical characteristics, including gas composition and isotopic ratios of surface breaching hydrate, in the GoM have been well documented (19,33,34,38). Growth and dissolution of GoM hydrate mounds have also been observed, with changes in mound size and shape evident over a period of months (19). Such hydrate growth patterns increase fluid and solid (i.e....

Uranium contamination is an environmental concern at the Department of Energy's Field Research Center in Oak Ridge, Tennessee. In this study, we investigated whether phosphate biomineralization, or the aerobic precipitation of U(VI)-phosphate phases facilitated by the enzymatic activities of microorganisms, offers an alternative to the more extensively studied anaerobic U(VI) bioreduction. Three heterotrophic bacteria isolated from FRC soils were studied for their ability to grow and liberate phosphate in the presence of U(VI) and an organophosphate between pH 4.5 and 7.0. The objectives were to determine whether the strains hydrolyzed sufficient phosphate to precipitate uranium, to determine whether low pH might have an effect on U(VI) precipitation, and to identify the uranium solid phase formed during biomineralization. Two bacterial strains hydrolyzed sufficient organophosphate to precipitate 7395% total uranium after 120 h of incubation in simulated groundwater. The highest rates of uranium precipitation and phosphatase activity were observed between pH 5.0 and 7.0. EXAFS spectra identified the uranyl phosphate precipitate as an autunite/meta-autunite group mineral. The results of this study indicate that aerobic heterotrophic bacteria within a uranium-contaminated environment that can hydrolyze organophosphate, especially in low pH conditions, may play an important role in the bioremediation of uranium.

Aerobic heterotrophs were isolated from subsurface soil samples obtained from the U.S. Department of Energy's (DOE) Field Research Center (FRC) located at Oak Ridge, Tenn. The FRC represents a unique, extreme environment consisting of highly acidic soils with cooccurring heavy metals, radionuclides, and high nitrate concentrations. Four hundred isolates obtained from contaminated soil were assayed for heavy metal resistance, and a smaller subset was assayed for tolerance to uranium. The vast majority of the isolates were gram-positive bacteria and belonged to the high-G؉C-and low-G؉C-content genera Arthrobacter and Bacillus, respectively. Genomic DNA from a randomly chosen subset of 50 Pb-resistant (Pb r ) isolates was amplified with PCR primers specific for P IB -type ATPases (i.e., pbrA/cadA/zntA). A total of 10 pbrA/cadA/zntA loci exhibited evidence of acquisition by horizontal gene transfer. A remarkable dissemination of the horizontally acquired P IB -type ATPases was supported by unusual DNA base compositions and phylogenetic incongruence. Numerous Pb r P IB -type ATPase-positive FRC isolates belonging to the genus Arthrobacter tolerated toxic concentrations of soluble U(VI) (UO 2 2؉ ) at pH 4. These unrelated, yet synergistic, physiological traits observed in Arthrobacter isolates residing in the contaminated FRC subsurface may contribute to the survival of the organisms in such an extreme environment. This study is, to the best of our knowledge, the first study to report broad horizontal transfer of P IB -type ATPases in contaminated subsurface soils and is among the first studies to report uranium tolerance of aerobic heterotrophs obtained from the acidic subsurface at the DOE FRC.The remediation of hazardous mixed-waste sites, particularly those cocontaminated with heavy metals and radionuclides, is one of the most costly environmental challenges currently faced by the United States and other countries. Interactions between microorganisms, radionuclides, and metals that promote their precipitation and immobilization in situ are promising strategies for treatment and cleanup of the contaminated subsurface (1, 15). At mixed-waste sites where the concentrations of metal contaminants can reach toxic levels, the metal resistance of indigenous microbial populations could be critical for the success of in situ biostimulation efforts. For example, while a number of microbes can carry out reductive precipitation of radionuclides (e.g., Desulfovibrio sp., Geobacter sp., and Shewanella sp.) (28,44,63), the sensitivity of these organisms to heavy metals could possibly limit their in situ activities. Thus, the metal sensitivity of some radionuclide-reducing microbes suggests that the acquisition of metal resistance traits (e.g., P IB -type ATPases that regulate the transport of heavy metals) might be conducive to facilitating and/or enhancing microbial metabolism during subsequent biostimulation activities in metal-and radionuclide-contaminated subsurface environments.The P-type ATPases represent a chromosomally en...

In this study, the composition of the metabolically active fraction of the microbial community occurring in Gulf of Mexico marine sediments (water depth, 550 to 575 m) with overlying filamentous bacterial mats was determined. The mats were mainly composed of either orange-or white-pigmented Beggiatoa spp. Complementary 16S ribosomal DNA (crDNA) was obtained from rRNA extracted from three different sediment depths (0 to 2, 6 to 8, and 10 to 12 cm) that had been subjected to reverse transcription-PCR amplification. Domainspecific 16S PCR primers were used to construct 12 different 16S crDNA libraries containing 333 Archaea and 329 Bacteria clones. Analysis of the Archaea clones indicated that all sediment depths associated with overlying orange-and white-pigmented microbial mats were almost exclusively dominated by ANME-2 (95% of total Archaea clones), a lineage related to the methanogenic order Methanosarcinales. In contrast, bacterial diversity was considerably higher, with the dominant phylotype varying by sediment depth. An equivalent number of clones detected at 0 to 2 cm, representing a total of 93%, were related to the ␥ and ␦ classes of Proteobacteria, whereas clones related to ␦-Proteobacteria dominated the metabolically active fraction of the bacterial community occurring at 6 to 8 cm (79%) and 10 to 12 cm (85%). This is the first phylogenetics-based evaluation of the presumptive metabolically active fraction of the Bacteria and Archaea community structure investigated along a sediment depth profile in the northern Gulf of Mexico, a hydrocarbon-rich cold-seep region.

In this study, the immobilization of toxic uranium [U(VI)] mediated by the intrinsic phosphatase activities of naturally occurring bacteria isolated from contaminated subsurface soils was examined. The phosphatase phenotypes of strains belonging to the genera, Arthrobacter, Bacillus and Rahnella, previously isolated from subsurface soils at the US Department of Energy's (DOE) Oak Ridge Field Research Center (ORFRC), were determined. The ORFRC represents a unique, extreme environment consisting of highly acidic soils with co-occurring heavy metals, radionuclides and high nitrate concentrations. Isolates exhibiting phosphatase-positive phenotypes indicative of constitutive phosphatase activity were subsequently tested in U(VI) bioprecipitation assays. When aerobically grown in synthetic groundwater (pH 5.5) amended with 10 mM glycerol-3-phosphate (G3P), phosphatase-positive Bacillus and Rahnella spp. strains Y9-2 and Y9602 liberated sufficient phosphate to precipitate 73% and 95% of total soluble U added as 200 microM uranyl acetate respectively. In contrast, an Arthrobacter sp. X34 exhibiting a phosphatase-negative phenotype did not liberate phosphate from G3P or promote U(VI) precipitation. This study provides the first evidence of U(VI) precipitation via the phosphatase activity of naturally occurring Bacillus and Rahnella spp. isolated from the acidic subsurface at the DOE ORFRC.

The biotransformation of n-tetradecylbenzyldimethylammonium chloride (C 14 BDMA-Cl), a quaternary ammonium compound (QAC), under aerobic conditions by an enriched microbial community growing on benzalkonium chlorides (BACs) was investigated. Biotransformation of C 14 BDMA-Cl commenced with cleavage of the C alkyl −N bond and formation of benzyldimethylamine (BDMA). BDMA was further degraded, but in contrast to a previously reported BAC biotransformation pathway, neither benzylmethylamine (BMA) nor benzylamine (BA) was detected as a BDMA biotransformation product. Kinetic assays further confirmed that BMA and BA were not intermediates of C 14 BDMA-Cl transformation by the enriched community. Thus, BDMA is thought to be transformed to dimethylamine and benzoic acid via debenzylation. The biomass-normalized rate of C 14 BDMA-Cl biotransformation was 0.09 μmol/[mg of volatile suspended solids (VSS)•h]. The Microtox acute toxicity EC 50 value of BDMA was 500 times higher than that of C 14 BDMA-Cl. Thus, the aerobic biotransformation of C 14 BDMA-Cl to BDMA results in substantial toxicity reduction. Phylogenetic analysis of Bacteria diversity indicated that the majority of the sequenced clones (98% of the clone library) belonged to the genus Pseudomonas.