National Veterinary Institute Uppsala, Sweden.
Front Cell Infect Microbiol. 2012 Sep 6;2:116. doi: 10.3389/fcimb.2012.00116. eCollection 2012.
Strains within a bacterial species typically have a set of conserved core genes and a variable set of accessory genes. The accessory genes often appear to move laterally between strains, thereby forming new trait combinations. Sometimes, genetic material also moves laterally between species, thereby resulting in diffuse borders between them. The growing number of genome sequences offers new possibilities to study these processes. Ten species for which abundant genomic data exists were here selected for analysis of the species border integrity. The average core genome similarities and relative core genome sizes (RCGSs) were determined for strain pairs within the species and for strain pairs crossing the species border. The variability within the species as well as the border integrity varies for different bacterial species. Some have very distinct borders while others are more or less indefinable. From the growing amount of genomic data, it becomes even clearer that the concept of bacterial species is, in many cases, far from absolute.
细菌种内的菌株通常具有一组保守的核心基因和一组可变的辅助基因。辅助基因通常在菌株之间横向转移，从而形成新的性状组合。有时，遗传物质也在物种之间横向转移，从而导致它们之间的边界变得模糊。越来越多的基因组序列为研究这些过程提供了新的可能性。选择了十种基因组数据丰富的物种来分析物种边界的完整性。确定了种内菌株对和跨越物种边界的菌株对的平均核心基因组相似性和相对核心基因组大小 (RCGS)。不同的细菌物种在种内的变异性和边界完整性有所不同。有些物种的边界非常明显，而有些则或多或少难以界定。从越来越多的基因组数据中可以更清楚地看出，在许多情况下，细菌物种的概念远非绝对。
