State Key Laboratory of Applied Microbiology (Ministry-Guangdong Province Jointly Breeding Base), South China, Guangdong Institute of Microbiology, Guangzhou, People's Republic of China.
Antonie Van Leeuwenhoek. 2011 Nov;100(4):607-17. doi: 10.1007/s10482-011-9615-9. Epub 2011 Jul 6.
Streptomyces vietnamensis, a recently designated species isolated from tropical forest soil, was found to be a new granaticin producer. The granaticin biosynthetic gene cluster (gra) and flanking genes from S. vietnamensis were cloned and sequenced by a sequential cloning strategy. All biosynthetic genes were found as expected. The high overall homology of the gra cluster from S. vietnamensis to that of Streptomyces violaceoruber Tü22 indicated a recent common ancestor of the two clusters. However, a flanking gene orf35 was missing from the gra cluster of S. vietnamensis, and high frequency of insertions and deletions of short fragment (shorter than 63 bp) were observed throughout the sequenced region compared to that of S. violaceoruber Tü22. These revealed a rapid evolution of the gra cluster and suggested that small insertions and deletions might be one of the basic evolution mechanisms for streptomycete genomes. The phylogenetic incongruence between 16S rDNA and the gra cluster and the scattered distribution of the granaticin producers within Streptomyces implicated horizontal gene transfer (HGT) being involved in the gra cluster dispersion. The remnants of orf35 found in S. vietnamensis present a scenario on how the antibiotic gene clusters evolved after HGT. The contemporary gra cluster residing in S. vietnamensis could be interpreted as a combination of HGT and highly variable vertical transmission.
从热带森林土壤中分离到的新种越光霉素链霉菌被发现是一种新的格兰那丁产生菌。采用连续克隆策略克隆并测序了来自越光霉素链霉菌的格兰那丁生物合成基因簇（gra）及其侧翼基因。所有生物合成基因都如预期的那样存在。越光霉素链霉菌的 gra 簇与紫罗兰色链霉菌 Tü22 的 gra 簇具有很高的整体同源性，表明这两个簇有一个最近的共同祖先。然而，越光霉素链霉菌的 gra 簇缺失了一个侧翼基因 orf35，与紫罗兰色链霉菌 Tü22 相比，整个测序区域都观察到短片段（短于 63bp）的插入和缺失频率很高。这揭示了 gra 簇的快速进化，并表明小的插入和缺失可能是链霉菌基因组基本进化机制之一。16S rDNA 与 gra 簇之间的系统发育不一致以及格兰那丁产生菌在链霉菌中的分散分布表明水平基因转移（HGT）参与了 gra 簇的分散。在越光霉素链霉菌中发现的 orf35 的残余物呈现了一种抗生素基因簇在 HGT 后如何进化的情景。当代存在于越光霉素链霉菌中的 gra 簇可以被解释为 HGT 和高度可变的垂直传播的结合。
