Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
Appl Environ Microbiol. 2011 Feb;77(4):1352-8. doi: 10.1128/AEM.02048-10. Epub 2010 Dec 17.
Nitrate respiration is a common and strain-specific property in Thermus thermophilus encoded by the nitrate respiration conjugative element (NCE) that can be laterally transferred by conjugation. In contrast, nitrite respiration and further denitrification steps are restricted to a few isolates of this species. These later steps of the denitrification pathway are under the regulatory control of an NCE-encoded transcription factor, but nothing is known about their coding sequences or its putative genetic linkage to the NCE. In this study we examine the genetic linkage between nitrate and nitrite respiration through lateral gene transfer (LGT) assays and describe a cluster of genes encoding the nitrite-nitric oxide respiration in T. thermophilus PRQ25. We show that the whole denitrification pathway can be transferred from the denitrificant strain PRQ25 to an aerobic strain, HB27, and that the genes coding for nitrite and nitric oxide respiration are encoded near the NCE. Sequence data from the draft genome of PRQ25 confirmed these results and allowed us to describe the most compact nor-nir cluster known thus far and to demonstrate the expression and activities of the encoded enzymes in the HB27 denitrificant derivatives obtained by LGT. We conclude that this NCE nor-nir supercluster constitutes a whole denitrification island that can be spread by lateral transfer among Thermus thermophilus strains.
硝酸盐呼吸是嗜热栖热菌中普遍存在的一种菌株特异性特性，由硝酸盐呼吸共轭元件（NCE）编码，可通过共轭进行横向转移。相比之下，亚硝酸盐呼吸和进一步的反硝化步骤仅限于该物种的少数分离株。该反硝化途径的这些后续步骤受 NCE 编码的转录因子的调控，但对于其编码序列或其与 NCE 的潜在遗传联系知之甚少。在这项研究中，我们通过横向基因转移（LGT）实验研究了硝酸盐和亚硝酸盐呼吸之间的遗传联系，并描述了嗜热栖热菌 PRQ25 中编码亚硝酸盐-一氧化氮呼吸的基因簇。我们表明，整个反硝化途径可以从脱硝菌株 PRQ25 转移到需氧菌株 HB27，并且编码亚硝酸盐和一氧化氮呼吸的基因位于 NCE 附近。PRQ25 的草图基因组序列数据证实了这些结果，并允许我们描述迄今为止已知的最紧凑的 nor-nir 簇，并证明通过 LGT 获得的 HB27 脱硝衍生物中编码酶的表达和活性。我们得出结论，这个 NCE nor-nir 超级簇构成了一个完整的反硝化岛，可以通过嗜热栖热菌菌株之间的横向转移进行传播。
