Department of Microbiology, Cornell University, Ithaca, New York 14853, USA.
Annu Rev Microbiol. 2012;66:197-212. doi: 10.1146/annurev-micro-090110-102827.
Large cell size is not restricted to a particular bacterial lifestyle, dispersal method, or cell envelope type. What is conserved among the very large bacteria are the quantity and arrangement of their genomic resources. All large bacteria described to date appear to be highly polyploid. This review focuses on Epulopiscium sp. type B, which maintains tens of thousands of genome copies throughout its life cycle. Only a tiny proportion of mother cell DNA is inherited by intracellular offspring, but surprisingly DNA replication takes place in the terminally differentiated mother cell as offspring grow. Massive polyploidy supports the acquisition of unstable genetic elements normally not seen in essential genes. Further studies of how large bacteria manage their genomic resources will provide insight into how simple cellular modifications can support unusual lifestyles and exceptional cell forms.
大细胞尺寸并不局限于特定的细菌生活方式、分散方法或细胞膜类型。在非常大的细菌中，其基因组资源的数量和排列是保守的。迄今为止描述的所有大型细菌似乎都是高度多倍体。本综述重点介绍 Epulopiscium sp. 型 B，其在整个生命周期中维持数万份基因组拷贝。只有一小部分母细胞 DNA 被细胞内后代继承，但令人惊讶的是，当后代生长时，DNA 复制发生在终末分化的母细胞中。大规模的多倍体支持不稳定遗传元素的获取，这些元素通常在必需基因中看不到。进一步研究大型细菌如何管理其基因组资源，将有助于了解简单的细胞修饰如何支持不同寻常的生活方式和特殊的细胞形态。
