| The bacterioplankton play an important role in primary production in oceanic environments,they also involve in the process of biogeochemical cycle and energy flow on the earth. Certainprotein-coding genes could be used to assess the diversity of bacteria group with considerableecological function. In current study we constructed clone libraries of pufM, dmdA, dddP,GTAs(g5) genes in the water samples collectedfrom two gulfs-Ardley Cove and Great Wall Baynear the Fildes Peninsula in Antarctic offshore. The pufM gene codes the M subunit ofphotosynthetic center in aerobic anoxygenic phototrophic bacteria, dmdA and dddP encode thecatabolic enzymes of DMSP which is osmolyte in marine algae cells, and GTAs is a cluster ofgenes derived from prophages in Rhodobacterales. In addition, a comparative study were carriedout between pufM and GTAs(g5) gene sequences retrieved in current study and their counterpartsin Kongsfjorden, Svalbard. The results indicated:1) In Antarctica offshore water, most of the pufM genes in the clone libraries were fromRhodobacterales,clustered in α-Proteobacteria. In addition, a small propotion of pufM genes hadsporadic occurence under several orders of β-Proteobacteria and γ-Proteobacteria. The pufMdiversity in Antarctic nearshore was high overall, while the Great Wall Cove had a higherphylogenetic diversity than Ardley Cove.2) The dmdA genes in Antarctic coastal water were from Roseobacter-clade-affilatedspecies in Rhodobacterales. The source of dddP genes contained two main clades, one wasaffilated with two orders in α-Proteobacteria,RhodobacteralesandSphingomonadales,the otherswere close to Psychrobacter belongs to Pseudomonadalesin the γ-Proteobacteria. Both genes hadlow phylogenetic diversity, it was suspected that the primers used in this study had a bias tocertain bacteria groups The dmdA genetic diversity in Great Way Bay was similar with that ofArdley Cove, while dddP diversity in Great Wall Bay outnumbered the other gulf greatly.3) Besides, the g5genes were all from Rhodobacterales. The GTAs in two gulfs differedlittle and had a high diversity.4) In contrast with the planktonic bacteria in Kongsfjorden of Arctic, the phylogeneticanalysis of pufM geneand GTAs(g5) indicated that the diversity of pufM and GTAs(g5) inAntarctic coastal areas was slightly higher than the outer of Kongsfjorden-st1station, and muchhigher than the inner part of Kongsfjorden-st5station. It elucidated an impact of environmental variables and hydrology conditions on the bacterioplankton community in bipolar oceans, andthe diversity of pufM gene have an obvious positive correlation with silicate and phosphate.5) At the same time, the pufM gene retrieved from Kongsfjorden were all fromRhodobacteraceae, in the class of α-Proteobacteria, dominated by Sulfitobacter-related bacteria.According to the results in Arctic and Antarctic, we speculated the pufM primers used in thisstudy may targeted limited groups of aerobic anoxygenic phototrophic bacteria, there was stillquite a few pufM gene orthologs uncovered. The g5genes from Kongsfjorden were fromRhodobacteralesentirely, Both thediversity indexes of pufM and g5genes in st1were higher thanst5.We found that the surface water of Antarctic coastal areas had an abundant ofRoseobacter-clade-affilated and some aerobic anoxygenic phototrophic baceria by the analysis ofgenetic diversity with pufM, dmdA, dddP genes and gene transfer agents. It demonstrated thatRoseobacter and other related species in Rhodobacteraceaehave good adaption to polar marineenvironments. Due to pressing time, our study did not refer to the expression level of these genesin different environmental conditions(e. g., salinity, temperature, dissolved organic matter etc.).A further study is required with the methods of transcriptomics including RT-PCR to examinetheir expression in order to understand the metabolic regulation and ecological role in ecosystemof these genes and their hosted bacteria. |
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