University of Minnesota, St. Paul, Minnesota, USA.
Appl Environ Microbiol. 2012 Mar;78(5):1397-403. doi: 10.1128/AEM.06468-11. Epub 2011 Dec 30.
Rhodococcus sp. strain Mel was isolated from soil by enrichment and grew in minimal medium with melamine as the sole N source with a doubling time of 3.5 h. Stoichiometry studies showed that all six nitrogen atoms of melamine were assimilated. The genome was sequenced by Roche 454 pyrosequencing to 13× coverage, and a 22.3-kb DNA region was found to contain a homolog to the melamine deaminase gene trzA. Mutagenesis studies showed that the cyanuric acid hydrolase and biuret hydrolase genes were clustered together on a different 17.9-kb contig. Curing and gene transfer studies indicated that 4 of 6 genes required for the complete degradation of melamine were located on an ∼265-kb self-transmissible linear plasmid (pMel2), but this plasmid was not required for ammeline deamination. The Rhodococcus sp. strain Mel melamine metabolic pathway genes were located in at least three noncontiguous regions of the genome, and the plasmid-borne genes encoding enzymes for melamine metabolism were likely recently acquired.
从土壤中通过富集培养筛选得到一株嗜甲基单胞菌（Rhodococcus sp. strain Mel），该菌可以以三聚氰胺作为唯一氮源在最小培养基中生长，倍增时间为 3.5 h。化学计量研究表明三聚氰胺的所有 6 个氮原子都被同化了。通过罗氏 454 焦磷酸测序对该菌基因组进行测序，覆盖度达到 13×，发现了一个包含三聚氰胺脱氨酶基因 trzA 同源物的 22.3-kb DNA 区域。突变研究表明，氰尿酸水解酶和缩二脲水解酶基因簇位于另一个不同的 17.9-kb 连续体上。消除和基因转移研究表明，6 个完全降解三聚氰胺所需的基因中的 4 个位于一个约 265-kb 的自我可转移的线性质粒（pMel2）上，但该质粒不是三聚氰胺脱氨所必需的。嗜甲基单胞菌（Rhodococcus sp. strain Mel）三聚氰胺代谢途径的基因至少位于基因组的三个不连续区域，编码三聚氰胺代谢酶的质粒基因可能是最近获得的。
