Institute for Genomic Sciences and Department of Microbiology and Immunology, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
J Bacteriol. 2011 Aug;193(16):4199-213. doi: 10.1128/JB.00449-11. Epub 2011 Jun 24.
Bacillus megaterium is deep-rooted in the Bacillus phylogeny, making it an evolutionarily key species and of particular importance in understanding genome evolution, dynamics, and plasticity in the bacilli. B. megaterium is a commercially available, nonpathogenic host for the biotechnological production of several substances, including vitamin B(12), penicillin acylase, and amylases. Here, we report the analysis of the first complete genome sequences of two important B. megaterium strains, the plasmidless strain DSM319 and QM B1551, which harbors seven indigenous plasmids. The 5.1-Mbp chromosome carries approximately 5,300 genes, while QM B1551 plasmids represent a combined 417 kb and 523 genes, one of the largest plasmid arrays sequenced in a single bacterial strain. We have documented extensive gene transfer between the plasmids and the chromosome. Each strain carries roughly 300 strain-specific chromosomal genes that account for differences in their experimentally confirmed phenotypes. B. megaterium is able to synthesize vitamin B(12) through an oxygen-independent adenosylcobalamin pathway, which together with other key energetic and metabolic pathways has now been fully reconstructed. Other novel genes include a second ftsZ gene, which may be responsible for the large cell size of members of this species, as well as genes for gas vesicles, a second β-galactosidase gene, and most but not all of the genes needed for genetic competence. Comprehensive analyses of the global Bacillus gene pool showed that only an asymmetric region around the origin of replication was syntenic across the genus. This appears to be a characteristic feature of the Bacillus spp. genome architecture and may be key to their sporulating lifestyle.
巨大芽孢杆菌在芽孢杆菌的系统发育中根深蒂固，使其成为一个进化关键种，对于理解芽孢杆菌的基因组进化、动态和可塑性具有特别重要的意义。巨大芽孢杆菌是一种可商业获得的、非致病性的宿主，可用于生物技术生产多种物质，包括维生素 B(12)、青霉素酰化酶和淀粉酶。在这里，我们报告了两个重要的巨大芽孢杆菌菌株——无质粒菌株 DSM319 和携带 7 个本土质粒的 QM B1551 的首个完整基因组序列的分析。5.1-Mbp 染色体携带约 5300 个基因，而 QM B1551 质粒则代表了一个组合的 417kb 和 523 个基因，这是在单个细菌菌株中测序的最大质粒阵列之一。我们记录了质粒和染色体之间广泛的基因转移。每个菌株携带大约 300 个菌株特异性染色体基因，这些基因解释了它们实验确认表型的差异。巨大芽孢杆菌能够通过一种不依赖于氧的腺苷钴胺素途径合成维生素 B(12)，现在已经完全重建了该途径以及其他关键的能量和代谢途径。其他新基因包括第二个 ftsZ 基因，它可能负责该物种成员的大细胞大小，以及气室基因、第二个β-半乳糖苷酶基因以及遗传能力所需的大部分但不是全部基因。对全球芽孢杆菌基因库的综合分析表明，只有复制起点周围的一个不对称区域在属内是同线性的。这似乎是芽孢杆菌属基因组结构的一个特征，可能是其孢子形成生活方式的关键。
