Biotechnology Institute (IBTEC) & Biosciences Institute at Botucatu (IBB), Sao Paulo State University (UNESP), Sao Paulo, Brazil.
School of Biosciences and Veterinary Medicine, University of Camerino, Italy.
Genome Biol Evol. 2019 Jan 1;11(1):1-10. doi: 10.1093/gbe/evy255.
Symbiosis is now recognized as a driving force in evolution, a role that finds its ultimate expression in the variety of associations bonding insects with microbial symbionts. These associations have contributed to the evolutionary success of insects, with the hosts acquiring the capacity to exploit novel ecological niches, and the symbionts passing from facultative associations to obligate, mutualistic symbioses. In bacterial symbiont of insects, the transition from the free-living life style to mutualistic symbiosis often resulted in a reduction in the genome size, with the generation of the smallest bacterial genomes thus far described. Here, we show that the process of genome reduction is still occurring in Asaia, a group of bacterial symbionts associated with a variety of insects. Indeed, comparative genomics of Asaia isolated from different mosquito species revealed a substantial genome size and gene content reduction in Asaia from Anopheles darlingi, a South-American malaria vector. We thus propose Asaia as a novel model to study genome reduction dynamics, within a single bacterial taxon, evolving in a common biological niche.
共生关系现在被认为是进化的驱动力之一，其在昆虫与微生物共生体之间的各种关联中得到了最终的体现。这些关联促进了昆虫的进化成功，使宿主获得了利用新生态位的能力，而共生体则从兼性共生关系转变为专性互利共生关系。在昆虫的细菌共生体中，从自由生活方式到互利共生的转变通常会导致基因组大小的减少，从而产生了迄今为止描述的最小的细菌基因组。在这里，我们表明，在与各种昆虫相关的细菌共生体 Asaia 中，基因组减少的过程仍在发生。事实上，对从不同蚊子物种中分离出的 Asaia 进行比较基因组学分析表明，在南美疟疾传播媒介 Anopheles darlingi 中的 Asaia 中，基因组大小和基因含量有了很大的减少。因此，我们提出 Asaia 作为一个新的模型，在一个共同的生物栖息地内，研究单一细菌分类群内的基因组减少动态。
