A comprehensive assessment of bacterial diversity and community composition in arctic and antarctic pack ice was conducted through cultivation and cultivation-independent molecular techniques. We sequenced 16S rRNA genes from 115 and 87 pure cultures of bacteria isolated from arctic and antarctic pack ice, respectively. Most of the 33 arctic phylotypes were >97% identical to previously described antarctic species or to our own antarctic isolates. At both poles, the ␣-and ␥-proteobacteria and the Cytophaga-Flavobacterium group were the dominant taxonomic bacterial groups identified by cultivation as well as by molecular methods. The analysis of 16S rRNA gene clone libraries from multiple arctic and antarctic pack ice samples revealed a high incidence of closely overlapping 16S rRNA gene clone and isolate sequences. Simultaneous analysis of environmental samples with fluorescence in situ hybridization (FISH) showed that ϳ95% of 4,6-diamidino-2-phenylindole (DAPI)-stained cells hybridized with the general bacterial probe EUB338. More than 90% of those were further assignable. Approximately 50 and 36% were identified as ␥-proteobacteria in arctic and antarctic samples, respectively. Approximately 25% were identified as ␣-proteobacteria, and 25% were identified as belonging to the Cytophaga-Flavobacterium group. For the quantification of specific members of the sea ice community, new oligonucleotide probes were developed which target the genera Octadecabacter, Glaciecola, Psychrobacter, Marinobacter, Shewanella, and Polaribacter. High FISH detection rates of these groups as well as high viable counts corroborated the overlap of clone and isolate sequences. A terrestrial influence on the arctic pack ice community was suggested by the presence of limnic phylotypes.Pack ice in the Arctic and Antarctic, with its vast extension and high biological productivity (3,34,35,36,56), constitutes one of the most significant polar ecosystems. Several similarities exist between the sea ice regimes in the north and the south; however, there are also fundamental differences in formation, development, thickness, maturity, and ice crystal structure (57). Moreover, the Arctic Ocean, in contrast to the Southern Ocean, is strongly influenced by warm Atlantic waters and has a high terrestrial input due to its nearly complete enclosure by landmasses. Whether these differences influence the colonization of sea ice and the development of microbial sea ice communities is still an open question.Phylogenetic diversity studies of sea ice bacterial communities have focused mainly on the Antarctic (8, 18). In particular, land-fast ice surrounding the McMurdo base and pack ice between the Casey and Davis bases has been investigated. Sampling was limited to spring and summer seasons. The few arctic sea ice samples considered came from Baffin Bay (18), the Chukchi Sea (41), and Barrow, Alaska (31). Cultivation approaches provided the initial view of diversity of sea ice bacteria, mainly in the Antarctic, and revealed several novel genera and species t...

Abstract.A methane surplus relative to the atmospheric equilibrium is a frequently observed feature of ocean surface water. Despite the common fact that biological processes are responsible for its origin, the formation of methane in aerobic surface water is still poorly understood. We report on methane production in the central Arctic Ocean, which was exclusively detected in Pacific derived water but not nearby in Atlantic derived water. The two water masses are distinguished by their different nitrate to phosphate ratios. We show that methane production occurs if nitrate is depleted but phosphate is available as a P source. Apparently the low N:P ratio enhances the ability of bacteria to compete for phosphate while the phytoplankton metabolite dimethylsulfoniopropionate (DMSP) is utilized as a C source. This was verified by experimentally induced methane production in DMSP spiked Arctic sea water. Accordingly we propose that methylated compounds may serve as precursors for methane and thermodynamic calculations show that methylotrophic methanogenesis can provide energy in aerobic environments.

Abstract. The bacterially mediated aerobic methane oxidation (MO x ) is a key mechanism in controlling methane (CH 4 ) emissions from the world's oceans to the atmosphere. In this study, we investigated MO x in the Arctic fjord Storfjorden (Svalbard) by applying a combination of radio-tracerbased incubation assays ( 3 H-CH 4 and 14 C-CH 4 ), stable C-CH 4 isotope measurements, and molecular tools (16S rRNA gene Denaturing Gradient Gel Electrophoresis (DGGE) fingerprinting, pmoA-and mxaF gene analyses). Storfjorden is stratified in the summertime with melt water (MW) in the upper 60 m of the water column, Arctic water (ArW) between 60 and 100 m, and brine-enriched shelf water (BSW) down to 140 m. CH 4 concentrations were supersaturated with respect to the atmospheric equilibrium (about 3-4 nM) throughout the water column, increasing from ∼ 20 nM at the surface to a maximum of 72 nM at 60 m and decreasing below. MO x rate measurements at near in situ CH 4 concentrations (here measured with 3 H-CH 4 raising the ambient CH 4 pool by < 2 nM) showed a similar trend: low rates at the sea surface, increasing to a maximum of ∼ 2.3 nM day −1 at 60 m, followed by a decrease in the deeper ArW/BSW. In contrast, rate measurements with 14 C-CH 4 (incubations were spiked with ∼ 450 nM of 14 C-CH 4 , providing an estimate of the CH 4 oxidation at elevated concentration) showed comparably low turnover rates (< 1 nM day −1 ) at 60 m, and peak rates were found in ArW/BSW at ∼ 100 m water depth, concomitant with increasing 13 C values in the residual CH 4 pool. Our results indicate that the MO x community in the surface MW is adapted to relatively low CH 4 concentrations. In contrast, the activity of the deep-water MO x community is relatively low at the ambient, summertime CH 4 concentrations but has the potential to increase rapidly in response to CH 4 availability. A similar distinction between surface and deepwater MO x is also suggested by our molecular analyses. The DGGE banding patterns of 16S rRNA gene fragments of the surface MW and deep water were clearly different. A DGGE band related to the known type I MO x bacterium Methylosphaera was observed in deep BWS, but absent in surface MW. Furthermore, the Polymerase Chain Reaction (PCR) amplicons of the deep water with the two functional primers sets pmoA and mxaF showed, in contrast to those of the surface MW, additional products besides the expected one of 530 base pairs (bp). Apparently, different MO x communities have developed in the stratified water masses in Storfjorden, which is possibly related to the spatiotemporal variability in CH 4 supply to the distinct water masses.

Bacteria in the water beneath the sea ice of the eastern Weddell Sea were homogeneously distributed. Direct counts resembled values from sprmg and autumn, whereas viable cell counts, total ATP concentrations, as well as heterotrophic assimilation and extracellular enzymatic activities were very low, implying a metabolic inactive bactenoplankton The consolidated sea ice had a very heterogeneous horizontal distribution of microbes on large as well as small scales but vertical profiles in low and densely populated ice cores exhibited similar patterns. A close relation between bacterial colonization of sea ice and genetic ice classes was revealed. Sea ice of the 'predominantly congelation ice' had the lowest bacterial biomass and displayed very low heterotrophic activities which were comparable to those of the water column. Samples of older sea ice belonging to the 'mainly frazil' and 'mixed ice' had maximal numbers of bacteria. They often included high proportions of culturable cells and dividing cells as well as large bacteria The bacteria of these ice classes were active and contributed significantly to the productivity in the Weddell Sea during winter 'Predominantly frazil ice' was less colonized; however, selective bacterial growth was also indicated in this typical winter ice by an increase m the proportions of culturable and psychrophihc bacteria with advancing age of the ice Psychrophilic bacteria dominated in consohdated sea-ice whereas facultative psychrophiles prevailed in young sea-ice and water, corroborating a strict partitiomng m a microbial sea-ice and a seawater regime. Generally, temperature does not appear to be the significant factor for the development of bacterial communities in the surface layer of the eastern Weddell Sea m winter smce the metabolically active bacterial flora develops in the very cold sea-ice environment. The organic matter supply and its unproved usabihty obviously controls bacterial activity as well as the selective enrichment of psychrophiles.

Roughly 60% of the Earth's outer surface is comprised of oceanic crust formed by volcanic processes at mid-ocean ridges (MORs). Although only a small fraction of this vast volcanic terrain has been visually surveyed and/or sampled, the available evidence suggests that explosive eruptions are rare on MORs, particularly at depths below the critical point for

The danger of a petroleum hydrocarbon spillage in the polar, ice-covered regions is increasing due to oil exploration in Arctic offshore areas and a growing interest in using the Northern Sea Route (NSR) as an alternative transportation route for Arctic oil and gas. However, little is known about the potential impact of accidental oil spills on this environment. We investigated the impact of crude oil on microbial community composition in six different Arctic sea-ice samples incubated with crude oil at 1 degrees C in microcosms for one year. Alterations in the composition of bacterial communities were analyzed with the culture-independent molecular methods DGGE (denaturing gradient gel electrophoresis) and FISH (fluorescence in situ hybridization). DGGE, FISH and cultivation methods revealed a strong shift in community composition toward the gamma-proteobacteria in sea-ice and melt pool samples incubated with crude oil. Marinobacter spp., Shewanella spp. and Pseudomonas spp. were the predominant phylotypes in the oil-treated microcosms. The ability of indigenous sea-ice bacteria to degrade hydrocarbons at low temperature (1 degrees C) was tested using four representative strains cultivated from sea-ice enriched with crude oil. [14C]Hexadecane was degraded by the sea-ice isolates at 20-50% capacity of the mesophilic type strain Marinobacter hydrocarbonoclasticus, a known hydrocarbon degrader, incubated at 22 degrees C.

Volatile organic compounds emitted by different marine arctic strains of the Cytophaga-Flavobacterium-Bacteroides group were investigated by using a modified closed-loop stripping apparatus (CLSA). Seven of nine strains emitted volatiles, dominated by methyl ketones, in specific patterns. The methyl ketones were aliphatic saturated, or unsaturated, and comprised 12 to 18 C-atoms, sometimes with terminal Me branches. They were identified by GC/MS, retention-index calculations, derivatization with dimethyl disulfide for C=C bond location, and GC/FTIR to elucidate their uniform (Z)-configuration. The proposed structures of all methyl ketones were subsequently confirmed by synthesis, while the absolute configuration of chiral volatiles was elucidated by stereoselective synthesis. From retrobiosynthetic considerations, it was found that strain ARK10267 uses mainly valine, and strain ARK10063 mainly isoleucine for formation of starters for the ketone biosynthesis, which is correlated to fatty acid biosynthesis. Four strains (ARK10223, ARK10044, ARK10141, and ARK10146) use leucine. These separations are supported by phylogenetic affiliations based on 16S rRNA. Strain ARK10255b, in the course of this study found to be not a member of the Cytophaga-Flavobacterium-Bacteroides phylum, did not emit aliphatic ketones of medium chain length, but methionine-derived 4-(methylsulfanyl)butan-2-one and corresponding 4-(methylsulfanyl)butan-2-ol. Most of the compounds described have not been reported previously from nature.

Chemical screening of the ethyl acetate extract from the marine-derived Streptomyces sp. isolate Mei37 resulted in five isoquinolinequinones, four new derivatives, mansouramycin A-D (1, 3-5), and the known 3-methyl-7-(methylamino)-5,8-isoquinolinedione (2). Their structures were elucidated by NMR and MS techniques and by comparison with related compounds. Cytotoxicity profiling of the mansouramycins in a panel of up to 36 tumor cell lines indicated significant cytotoxicity of several derivatives, with pronounced selectivity for non-small cell lung cancer, breast cancer, melanoma, and prostate cancer cells.