Phylogenetic identification and substrate uptake patterns of sulfate-reducing bacteria by MAR-FISH

我们采用显微放射自显影术和荧光原位杂交(MAR-FISH)与16S rRNA家族和属特异性探针相结合的方法，同时测定了以氧、硝酸盐或硫酸盐为电子受体的下水道生物膜中硫酸盐还原细菌(SRB)的系统发育鉴定和底物摄取模式。MAR-FISH分析表明，与660探针杂交的硫球藻是该污水生物膜中SRB的优势亚群，占总SRB的23%。用660探针检测，约有9%和27%的硫球藻能以氧和硝酸盐为电子受体摄取丙酸，这可能解释了该物种在各种含氧环境中的高丰度。此外，在缺氧条件下，超过40%的脱硫球藻将醋酸盐结合到细胞中。SRB也是该下水道生物膜中利用H_2和固定CO_2微生物种群的重要成员，约占与EUB338探针杂交的利用H_2细菌总数的42%。16S rDNA比较分析表明，与Desulfommicrobium subgeium和Desultfovibrians destefficans MB谱系相关的两个SRB种群是该生物膜中重要的H_2利用者。不同系统发育SRB亚群的底物吸收特性与迄今所描述的特性进行了比较。这些结果进一步揭示了生活在下水道生物膜中的SRB种群的16S rRNA系统发育多样性和生理多样性之间的相关性。

We simultaneously determined the phylogenetic identification and substrate uptake patterns of sulfate-reducing bacteria (SRB) inhabiting a sewer biofilm with oxygen, nitrate, or sulfate as electron acceptors by combining microautoradiography and fluorescenct in situ hybridization (MAR-FISH) with family- and genus-specific 16S rRNA probes. The MAR-FISH analysis revealed that Desulfobulbus hybridized with probe 660 was a dominant SRB subgroup in this sewer biofilm, which accounted for 23% of total SRB. Approximately 9% and 27% of Desulfobulbus detected with probe 660 could take up [^<14>C]propionate with oxygen and nitrate as electron acceptor, respectively, which might explain the high abundance of this species in various oxic environments. Furthermore, more than 40% of Desulfobulbus incorporated acetate into cells under anoxic conditions. SRB were also numerically important members of H_2-utilizing and [^<14>C]CO_2-fixing microbial populations in this sewer biofiim, which roughly acccunted for 42% of total H_2-utilizing bacteria hybridized with probe EUB338. A comparative 16S rDNA analysis revealed that two SRB populations, related to the Desulfomicrobium hypogeium and the Desultfovibrio desulfuricans MB lineages, were found to be important H_2-utilizers in this biofilms. Substrate uptake characteristics of different phylogenetic SRB subgroups was compared with the characteristics described to date. These results provide further insight into the correlation between 16S rRNA phylogenetic diversity and physiological diversity of SRB populations inhabiting sewer biofilms.