suMMaRY: Bacterial community structure and the relationship between environmental variables and microbial communities in the surface sediments of tropical mangrove ecosystems were investigated in sanya, hainan island, China. Profiles of bacterial communities were generated using culture-independent PCR-denaturing gradient gel electrophoresis (dgge), and the results were interpreted with multivariate statistical analysis. Findings suggested that microbial communities varied with sample collection sites and seasons. The samples collected from the same sample sites at the same time had more similar microbial communities except samples sh3 and aB5, which also had unique sediment quality. Canonical correspondence analysis (CCa) revealed that the organic carbon concentration of the sediments accounted for a significant amount of the variability in the bacterial community composition. Phylogenetic analysis was used to identify the major groups of the predominant bacterial phylotypes. 16s rRna gene-V3 fragments from 17 individual dgge bands were sequenced and the corresponding bacteria were found in mangrove sediments for the first time based on BLasT results. Predominant bacterial phylotypes clustered with various taxonomic groups, including Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria and Firmicutes.Keywords: bacterial community, mangrove sediments, denaturing gradient gel electrophoresis, multivariate statistics.ResuMen: Estructura de la comunidad bacteriana en sedimentos de manglares en relación a variables medioambientales mediante análisis de fragmentos del gen 16S rRNA y electroforesis en geles desnaturalizantes. -La estructura de la comunidad bacteriana y la relación entre variables ambientales y las comunidades microbianas de la superficie de sedimentos de los ecosistemas tropicales de manglares fueron investigados en sanya, hainan island, China. Los perfiles de las comunidades bacterianas fueron obtenidos utilizando electroforesis de gradiente de gel desnaturalizante (dgge), cultivo-independiente, y los resultados fueron interpretados con un análisis estadístico multivariante. Los resultados sugerían que las comunidades microbianas variaban con los lugares de muestreo y las estaciones. Las muestras recogidas en el mismo lugar de muestreo y al mismo tiempo tenían comunidades microbianas similares, excepto las muestras sh3 y aB5, que tenían diferente calidad de sedimentos. el análisis de correspondencia (CCa) mostró que la concentración de carbono orgánico en sedimentos explicaba una parte importante de la variabilidad en la composición de la comunidad bacteriana. Los análisis filogenéticos fueron usados para identificar los grupos más importantes de filotipos predominantes de bacterias. se secuenciaron fragmentos 16 rRna gene-V3 de 17 bandas individuales de dgge y las bacterias correspondientes fueron encontradas por primera vez en sedimentos de manglares en base a resultados de BLasT. Los filotipos de bacterias predominantes se agrupaban con varios grupos taxonómicos que incluyen Proteobacte...

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Different water masses have distinct natural physical and chemical properties, which may influence the bacterial community structure. In the western pacific on both sides of the Luzon strait, which is covered with three water masses including the South China Sea (SCS) water mass, the Kuroshio water mass and the SCS-Kuroshio transition water mass, we selected 11 stations to estimate the spatial variation of surface water bacterial community composition using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified bacterial 16S ribosomal deoxyribonucleic acid (DNA) gene fragments and interpreted the results; its relationship with physical and chemical factors based on multivariate statistical analysis. A total of 343 bands at 105 different positions were detected in DGGE profiles and 18 distinct DGGE bands were sequenced. Sequence analysis revealed that most of the phylotypes were typical marine uncultured bacteria, and predominant bacteria came from three major phyla; Proteobacteria, Actinobacteria and Cyanobacteria. Apparent phylotype richness near the Luzon strait area varied between 24 and 35 bands (mean 31). Similarity and cluster analysis indicate that the distribution and composition of bacterial community at transition area were more affected by the SCS water mass than Kuroshio current. Redundancy analysis (RDA) revealed that temperature, salinity and the concentration of nitrate accounted for a significant amount of the variability in the bacterial community composition (P=0.004, P=0.014 and P=0.038, respectively, P<0.05).