INRS-Institut Armand-Frappier, 531 boul. des Prairies, Laval, Québec, Canada.
Microb Ecol. 2012 May;63(4):726-35. doi: 10.1007/s00248-011-9960-2. Epub 2011 Oct 18.
Nitrate is a serious problem in closed-circuit public aquariums because its accumulation rapidly becomes toxic to many lifeforms. A moving bed biofilm denitrification reactor was installed at the Montreal Biodome to treat its 3,250-m(3) seawater system. Naturally occurring microorganisms from the seawater affluent colonized the reactor carriers to form a denitrifying biofilm. Here, we investigated the functional diversity of this biofilm by retrieving gene sequences related to narG, napA, nirK, nirS, cnorB, and nosZ. A total of 25 sequences related to these genes were retrieved from the biofilm. Among them, the corresponding napA1, nirK1, cnorB9, and nosZ3 sequences were identical to the corresponding genes found in Hyphomicrobium sp. NL23 while the narG1 and narG2 sequences were identical to the two corresponding narG genes found in Methylophaga sp. JAM1. These two bacterial strains were previously isolated from the denitrifying biofilm. To assess the abundance of denitrifiers and nitrate respirers in the biofilm, the gene copy number of all the narG, napA, nirS, and nirK sequences found in biofilm was determined by quantitative PCR. napA1, nirK1, narG1, and narG2, which were all associated with either Methylophaga sp. JAM1 or Hyphomicrobium sp. NL23, were the most abundant genes. The other genes were 10 to 10,000 times less abundant. nirK, cnorB, and nosZ but not napA transcripts from Hyphomicrobium sp. NL23 were detected in the biofilm, and only the narG1 transcripts from Methylophaga sp. JAM1 were detected in the biofilm. Among the 19 other genes, the transcripts of only two genes were detected in the biofilm. Our results show the predominance of Methylophaga sp. JAM1 and Hyphomicrobium sp. NL23 among the denitrifiers detected in the biofilm. The results suggest that Hyphomicrobium sp. NL23 could use the nitrite present in the biofilm generated by nitrate respirers such as Methylophaga sp. JAM1.
硝酸盐是封闭循环公共水族馆中的一个严重问题，因为其积累会迅速对许多生物产生毒性。一个移动床生物膜反硝化反应器被安装在蒙特利尔生物博物馆，以处理其 3250 立方米的海水系统。来自海水富营养物的天然存在的微生物殖民了反应器载体，形成了反硝化生物膜。在这里，我们通过检索与 narG、napA、nirK、nirS、cnorB 和 nosZ 相关的基因序列来研究该生物膜的功能多样性。从生物膜中总共检索到 25 个与这些基因相关的序列。其中，对应的 napA1、nirK1、cnorB9 和 nosZ3 序列与在 Hyphomicrobium sp. NL23 中发现的相应基因相同，而 narG1 和 narG2 序列与在 Methylophaga sp. JAM1 中发现的两个相应 narG 基因相同。这两个细菌菌株以前是从反硝化生物膜中分离出来的。为了评估生物膜中反硝化菌和硝酸盐呼吸菌的丰度，通过定量 PCR 确定了生物膜中所有发现的 narG、napA、nirS 和 nirK 序列的基因拷贝数。与 Methylophaga sp. JAM1 或 Hyphomicrobium sp. NL23 相关的 napA1、nirK1、narG1 和 narG2 是最丰富的基因。其他基因的丰度则低 10 到 10000 倍。在生物膜中检测到来自 Hyphomicrobium sp. NL23 的 nirK、cnorB 和 nosZ 但没有 napA 转录物，并且仅在生物膜中检测到来自 Methylophaga sp. JAM1 的 narG1 转录物。在其他 19 个基因中，仅检测到两个基因的转录物。我们的结果表明，在生物膜中检测到的反硝化菌中，Methylophaga sp. JAM1 和 Hyphomicrobium sp. NL23 占主导地位。结果表明，Hyphomicrobium sp. NL23 可以利用硝酸盐呼吸菌（如 Methylophaga sp. JAM1）在生物膜中产生的亚硝酸盐。
