Community composition of the marine bacterioplankton in Kongsfjorden (Spitsbergen) as revealed by 16S rRNA gene analysis

Phylogenetic diversity of the marine bacterioplankton in Kongsfjorden (Spitsbergen) was investigated by 16S rRNA gene analysis. Community fingerprint analysis by PCR-denaturing gradient gel electrophoresis revealed that there was no apparent difference of bacterioplankton community composition between sampling locations in the fjord. A higher biodiversity was observed in bottom water of station 3 in the central part of the fjord. By 16S rRNA gene clone library analysis, sequences detected both in surface and bottom water of station 3 fell into eight putative divisions, including Proteobacteria (Alpha, Beta, Gamma and Delta), Bacteroidetes, Actinobacteria, Verrucomicrobia and unidentified bacteria, in addition to chloroplasts of algae. Sequences representing Planctomycetes were only observed in bottom water. Compared to the preponderance of clones representing Gammaproteobacteria (36.5%) and Alphaproteobacteria (29.4%) in bottom water, Alphaproteobacteria (43.6%) and algae (27.7%) constituted two dominant fractions in surface water. Cloned sequences showed 82.1-100% similarity to those described sequences. It suggests that, attributing to the influence of ocean currents as well as freshwater input in the summer, the bacterial community in Kongsfjorden may consist of a mixture of cosmopolitan and uniquely endemic phylotypes.National Natural Science Foundation of China [40676002, 40876097]; China's Action Plan for the International Polar Year (IPY

Relationships between Arctic and Antarctic Shewanella strains evaluated by a polyphasic taxonomic approach

As a result of the recent application of DNA-based technologies to investigate bacterial diversity in the polar marine environment, bacterial strains sharing significant 16S rRNA gene sequence similarities were isolated from both the Arctic and the Antarctic sea waters. Three selected marine bacterial isolates (BSw20248, BSw20661 and BSw10166) from two Arctic regions (the Greenland Sea and Canada Basin) and from Antarctica (Prydz Bay) were studied to determine their evolutionary relationships and phylogenetic position using a polyphasic taxonomic approach, including phenotypic characterization and genotypic analyses. These bacterial isolates proved to belong to the same species and were identified as Shewanella frigidimarina. Differences in phenotypic properties observed among them revealed a diversity of ecotypes for adaptation to the changing ecological or geographical conditions. It provided the evidence that Shewanella frigidimarina has a bipolar, or even global, distribution in the marine environment.National Natural Science Foundation of China [40576002, 40676002, 40876097]; High-Tech Research and Development Program of China [2008AA09Z408]; Program for Changjiang Scholars and Innovative Research Team in University [40821063]; Science and Technology Committee of Shanghai, China [052307053]; China's Action Plan for the International Polar Year (IPY

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and beta-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSw10175 belonging to Actinobacteria phylum, these isolates were classified as gamma-Proteobacteria, suggesting that gamma-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus Shewanella dominated in cultivable bacterioplankton in the Pry-dz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria ( >99%), but also between polar marine bacteria and bacteria from other aquatic environments ( >=98.8%), including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level

Culture-independent and -dependent methods to investigate the diversity of planktonic bacteria in the northern Bering Sea

National Natural Science Foundation of China [40676002, 40930847, 31070442, 41076130, 41076131]; Emphasis Project Fund of National Scientific and Technical Support Plan [2006BAB18B07]; International Science and Technology Cooperation Program [2008DFA20420]; U.S. National Science Foundation [NSF-OPP-ARC-0454454]; Public Science and Technology Research Funds Projects of Ocean [201105022]Planktonic bacteria are abundant in the Bering Sea. However, very little is known about their diversity and the roles of various bacteria in the ocean. Bacterioplankton diversity in the northern Bering Sea was investigated using a combination of molecular and cultivation-based methods. Community fingerprint analysis using polymerase chain reaction-denaturing gradient gel electrophoresis revealed an apparent difference in the bacterioplankton community composition between sampling locations in the area. The bacterial communities were characterized by two 16S rRNA gene clone libraries for surface and bottom water at shallow station NEC5 (< 60 m in depth) on the continental shelf. Sequences fell into 21 major lineages of the domain Bacteria, including Proteobacteria (Alpha, Beta, Gamma, and Delta), Bacteroidetes, Actinobacteria, Firmicutes, Acidobacteria, Planctomycetes, Verrucomicrobia, Fusobacteria, Chlamydiae, Chloroflexi, Chlorobi, Spirochaetes, Cyanobacteria (or algal chloroplasts), and candidate divisions OP8, OP11, TM6, TM7, and WS3. Significant differences were found between the two clone libraries. Actinobacteria formed the dominant bacterial lineage in both surface and bottom water, and the Alphaproteobacteria was another dominant fraction in surface water. A total of 232 heterotrophic bacterial strains were isolated and 81% showed extracellular proteolytic activity. Phylogenetic analysis revealed that the isolates fell into three bacterial groups, including the Gammaproteobacteria, Actinobacteria, and Firmicutes. The most common genus in both the bacterial isolates and protease-producing bacteria was Pseudoalteromonas. Divergence of bacterial community composition in the northern Bering Sea was mainly characterized by the dominance of Actinobacteria and reflected a bacterial community different from that currently known for marine bacterioplankton communities in other polar regions

Molecular diversity of the microbial community in coloured snow from the Fildes Peninsula (King George Island, Maritime Antarctica)

Snow in Antarctica is a vast terrestrial ecosystem and plays a key role that has likely been underestimated. Algae are the key primary producers on the coloured snow surface, and they support a microbial community that includes bacteria, fungi and/or invertebrates. We analysed microbial communities that co-exist in green and red snow samples from the Fildes Peninsula by Illumina sequencing, Antarctica, as well as the influence of snow physicochemical properties. We detected several species of green algae from Chlorophyta and Ochrophyta as well as fungi and cercozoans. The three red snow samples (RS1, RS2 and RS3) were represented by mixed eukaryotic microalgae fromSanguina,Chloromonasand Trebouxiophyceae. The green snow sample GS5 exhibited lake-to-snow colonisation composed of Trebouxiophyceae, Ulvophyceae and Chrysophyta representatives. The red snow RS4, predominantly byChlainomonassp. from slush layers, which presented a different microbial community from the other red snow samples, was sampled close to green snow sample GS5 near Lake Changhu. The environmental parameters were involved into descriptive differences among these coloured snow samples. The two snow algaeChlainomonasandSanguinawere firstly reported from Antarctica, which indicates distinguished snow algae colonisation that is closely connected with the melting snow at the lake ice-cover. Meanwhile, consistent with previous bacterial community profiles, Proteobacteria and Bacteroidetes were mostly represented in all the coloured snow samples. Polaromonas(Betaproteobacteria) was the most abundant genus, and its presence was reportedly essential for the sustained growth of snow algae.Flavobacteriumfrom Bacteroidetes was the most frequently detected genera in GS5, but the Sphingobacteriia with only a few reads were an interestingly minority in GS5. The snow-algae-associated bacteria were closely related to psychrophilic strains or sequences from low-temperature environments. Many possible factors influence on the coloured snow microbial communities would require attentions, to help understand their occurrence mechanisms, their biogeographic distributions in polar regions

Phylogenetic diversity of sediment bacteria in the northern Bering Sea

National Natural Science Foundation of China [40676002, 40930847, 41076131, 30940002]; US National Science Foundation [NSF-OPP-ARC-0454454]; Emphasis Project Fund [2006BAB18B07]; International Science and Technology Cooperation Program [2008DFA20420]; ChiThe bacterial diversity in sediments from the northern Bering Sea was investigated by culture-independent approaches. Community fingerprint analysis by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that sediment at two deep stations (DBSE and DBS1, > 400 m in depth) harbored a bacterial community distinct from the sediments collected at shallow stations (< 150 m in depth) on the continental shelf. Three 16S rRNA gene clone libraries for sediments collected from shallow to deep water stations (NEC5, DBSE and DBS1, respectively) were established. Sediment collected at the deepest station DBS1 showed the highest diversity index value. Sequences fell into 19 major lineages of the domain Bacteria: Alpha-, Beta-, Gamma-, Delta- and Epsilonproteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, Firmicutes, Planctomycetes, Nitrospirae, Verrucomicrobia, Chloroflexi, Chlorobi, Spirochaetes, Cyanobacteria (or chloroplasts), and candidate divisions OP8, TM6, and WS3. A small fraction of retrieved sequences (1.8%) did not fall into any taxonomic division. Deltaproteobacteria (30%) was the dominant phylum in the three libraries, followed by Gammaproteobacteria (21%) and Acidobacteria (16%). The percentages of cloned sequences with the highest similarity to reported sequences below 97 and 93% were 48.1 and 24.3%, respectively. A large number of phylotypes affiliated with bacteria that play important roles in the carbon, sulfur, and nitrogen cycles suggest an important link of bacteria to the matter cycling in these subarctic sediments

Community composition of the marine bacterioplankton in Kongsfjorden (Spitsbergen) as revealed by 16S rRNA gene analysis

Phylogenetic diversity of the marine bacterioplankton in Kongsfjorden (Spitsbergen) was investigated by 16S rRNA gene analysis. Community fingerprint analysis by PCR-denaturing gradient gel electrophoresis revealed that there was no apparent difference of bacterioplankton community composition between sampling locations in the fjord. A higher biodiversity was observed in bottom water of station 3 in the central part of the fjord. By 16S rRNA gene clone library analysis, sequences detected both in surface and bottom water of station 3 fell into eight putative divisions, including Proteobacteria (Alpha, Beta, Gamma and Delta), Bacteroidetes, Actinobacteria, Verrucomicrobia and unidentified bacteria, in addition to chloroplasts of algae. Sequences representing Planctomycetes were only observed in bottom water. Compared to the preponderance of clones representing Gammaproteobacteria (36.5%) and Alphaproteobacteria (29.4%) in bottom water, Alphaproteobacteria (43.6%) and algae (27.7%) constituted two dominant fractions in surface water. Cloned sequences showed 82.1-100% similarity to those described sequences. It suggests that, attributing to the influence of ocean currents as well as freshwater input in the summer, the bacterial community in Kongsfjorden may consist of a mixture of cosmopolitan and uniquely endemic phylotypes.National Natural Science Foundation of China [40676002, 40876097]; China's Action Plan for the International Polar Year (IPY