Diversity And Temporal-spatial Variability Of Sediment Bacterial Communities In Jiaozhou Bay

The composition, distribution and the dynamics of bacterial community in the sediment of Jiaozhou Bay China) were examined using both the 16S rDNA PCR-denaturing gradient gel electrophoresis (DGGE) and the 16S rRNA gene clone library analyses. The benthic bacterial communities in the sediment of Jiaozhou Bay displayed a highly diversified composition including members from 17 bacterial phylum and some unclassified sequences (0.9%). Proteobacteria, Acidobacteria, Bacteroidetes, Planctomycetes, Actinobacteria, Verrucomicrobia, Chloroflexi and Nitrospirae were the rather dominant groups and members of Firmicutes, Fusobacteria, Cyanobacteri, Gemmatimonadete, Spirochaetes, Elusimicrobia, Deferribacteres, Lentisphaerae and Deinococcus-Thermus were also found in sediment of Jiaozhou Bay.Sediment samples were collected at 10 stations in four seasons from Jiaozhou Bay. Total genomic DNA was extracted from each sample and used as template to amplify 16S rRNA V3 region gene with universal V3 specific primers. PCR-denaturing gradient gel electrophoresis (DGGE) was then performed to study the spatial and temporal variations of bacteria communities. Considering all the ten stations of Jiaozhou Bay as a whole, variations in bacterial community composition were obvious and particularly evident temporally. Less pronounced changes were also detected spatially. The analysis of bacterial communities was used to divide the 10 sampling stations into three types: stations A3, A5, and B2 were relatively in similar situations and were classified as one type; stations C3, D3, D6, and D7 represented another type. Stations C1, C4, and D1 formed the third peculiar type and they were different each other. The dynamics of bacterial communities at station D1 were the most irregular and were not temporally driven at all. Multivariate statistical analysis was used combing the DGGE bands with the sediment physico-chemical properties such as total nitrogen and total carbon content. It revealed again the strong and obvious variation of bacterial communities in temporal. Besides, changes in bacterial communities driven by environmental factors also occurred, especially in some outer bay stations.Four stations were selected according to DGGE result and the geographical factors. The construction of 16S rDNA clone libraries and Restriction Fragment Length Polymorphism (RFLP) analysis were applied not only to give a comprehensive view of the diversity and composition of bacterial communities in these stations but also to investigate a detail spatial-temporal variability of bacterial communities. For each of the 16 samples collected from the four stations and four seasons, comprehensive full-length 16S rDNA clone libraries were built. In total, 2560 positive clones were retained, and 1231 different RFLP patterns occurred in all the 5120 RFLP patterns. The number of distinct operational taxonomic units (OTUs) was 746 based on a taxa cutoff set at 97% similarity.It also revealed a high diversity and temporal-spatial difference in bacterial communities of each sample by the construction of clone libraries. UniFrac analyses showed that bacterial community shifted more obviously in spatial than in temporal when in this relatively small scale. It also indicated that similar environmental features selecting for similar bacterial communities, and the validity of the station selection by DGGE result was tested and proved here. The influence of seasons on bacterial communities in the four stations was quite irregular and this result reflects from another perspective that the bacterial community variations in Jiaozhou Bay result from a combination of many factors such as spatial, temporal and sedimentological factors. The high diversity Shannon-Wiener index and species richness (Schaol) estimates indicated that our sampling stations might have a higher bacterial diversity.Moreover, comparative phylogenetic analysis of the closest relatives of the sequences obtained in Jiaozhou Bay implied the presence of influences of human activities such as the influence of harbor, aquaculture and heavy metal contamination, which exhibited spatial and temporal specificities.