Department of Marine Microbiology, Netherlands Institute of Ecology, NIOO-KNAW, Yerseke, The Netherlands.
FEMS Microbiol Ecol. 2010 Jul 1;73(1):55-67. doi: 10.1111/j.1574-6941.2010.00875.x. Epub 2010 Mar 30.
Diazotrophic (nitrogen-fixing) Cyanobacteria are often structurally dominant in coastal microbial mats but diazotrophs from other bacterial lineages are also present and active. The expression of nifH by four nonheterocystous Cyanobacteria and one member of the Gammaproteobacteria was followed over a 24-h cycle using quantitative reverse transcriptase-PCR. Daily nifH expression patterns were compared with the actual nitrogenase activity (NA) of the entire mat community. Lyngbya sp. was identified as the dominant cyanobacterium but, although recognized as a diazotroph, its cell-specific and abundance-related nifH expression was low. Unexpectedly, the other three cyanobacterial phylotypes dominated community nifH expression at all stations. Also, the gammaproteobacterium showed high levels of cell-specific nifH expression but its nifH copy number was low. Its contribution to the whole community nifH expression was therefore low. These results indicate that there were varying levels of cell-specific expression of nifH in the different mat types and more so, varying contributions to the overall nifH expression by the different diazotrophs. Furthermore, NA did not follow nifH expression patterns.
固氮（氮固定）蓝藻通常在沿海微生物席中结构上占优势，但其他细菌谱系的固氮生物也存在并活跃。使用定量逆转录 PCR 跟踪了四种非异形胞蓝藻和一种γ变形菌属成员的 nifH 表达在 24 小时周期内的变化。将每日 nifH 表达模式与整个席状群落的实际固氮酶活性（NA）进行了比较。确定 Lyngbya sp.为优势蓝藻，但尽管被认为是固氮生物，但它的细胞特异性和丰度相关 nifH 表达水平较低。出乎意料的是，其他三种蓝藻藻型在所有站位都主导着群落 nifH 表达。此外，γ变形菌属表现出高水平的细胞特异性 nifH 表达，但它的 nifH 拷贝数较低。因此，它对整个群落 nifH 表达的贡献较低。这些结果表明，不同席状类型中 nifH 的细胞特异性表达水平存在差异，而且不同固氮生物对整体 nifH 表达的贡献也存在差异。此外，NA 并不遵循 nifH 表达模式。
