Seasonality and Locality Affect the Diversity of Anopheles gambiae and Anopheles coluzzii Midgut Microbiota from Ghana

Symbiotic bacteria can have important implications in the development and competence of disease vectors. In Anopheles mosquitoes, the composition of the midgut microbiota is largely influenced by the larval breeding site, but the exact factors shaping this composition are currently unknown. Here, we examined whether the proximity to urban areas and seasons have an impact on the midgut microbial community of the two major malaria vectors in Africa, An. coluzzii and An. gambiae. Larvae and pupae were collected from selected habitats in two districts of Ghana during the dry and rainy season periods. The midgut microbiota of adults that emerged from these collections was determined by 454-pyrosequencing of the 16S ribosomal DNA. We show that in both mosquito species, Shewanellaceae constituted on average of 54% and 73% of the midgut microbiota from each site in the dry and rainy season, respectively. Enterobacteriaceae was found in comparatively low abundance below 1% in 22/30 samples in the dry season, and in 25/38 samples in the rainy season. Our data indicate that seasonality and locality significantly affect both the diversity of microbiota and the relative abundance of bacterial families with a positive impact of dry season and peri-urban settings.

共生细菌对病媒生物的发育及媒介效能具有重要影响。在按蚊（Anopheles）中，其中肠微生物群的组成极大地受幼虫孳生生境的影响，但目前尚不明确塑造该组成的确切因素。本研究以非洲两大疟疾媒介——科氏按蚊（An. coluzzii）与冈比亚按蚊（An. gambiae）——为研究对象，探讨了邻近城区程度与季节是否会对其中肠微生物群落产生影响。研究人员于旱季与雨季期间，在加纳两个行政区的选定生境中采集了幼虫与蛹。通过对16S核糖体DNA（16S ribosomal DNA）进行454焦磷酸测序（454-pyrosequencing），测定了由此类采集样本羽化得到的成蚊的中肠微生物群。研究结果显示，在两种按蚊中，旱季与雨季各采样点的中肠微生物群内，希瓦氏菌科（Shewanellaceae）的平均占比分别为54%与73%。肠杆菌科（Enterobacteriaceae）的相对丰度普遍较低：旱季的30份样本中有22份的丰度低于1%，雨季的38份样本中则有25份丰度低于1%。本研究数据表明，季节变化与采样地点均会显著影响微生物群多样性与细菌科的相对丰度，且旱季与城郊生境对上述指标具有正向促进作用。