Entomology and Nematology Department, University of Florida, Gainesville, Florida, USA.
Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA.
Microbiol Spectr. 2023 Jun 15;11(3):e0265222. doi: 10.1128/spectrum.02652-22. Epub 2023 Apr 19.
Cholera has been a human scourge since the early 1800s and remains a global public health challenge, caused by the toxigenic strains of the bacterium Vibrio cholerae. In its aquatic reservoirs, V. cholerae has been shown to live in association with various arthropod hosts, including the chironomids, a diverse insect family commonly found in wet and semiwet habitats. The association between V. cholerae and chironomids may shield the bacterium from environmental stressors and amplify its dissemination. However, the interaction dynamics between V. cholerae and chironomids remain largely unknown. In this study, we developed freshwater microcosms with chironomid larvae to test the effects of cell density and strain on V. cholerae-chironomid interactions. Our results show that chironomid larvae can be exposed to V. cholerae up to a high inoculation dose (10 cells/mL) without observable detrimental effects. Meanwhile, interstrain variability in host invasion, including prevalence, bacterial load, and effects on host survival, was highly cell density-dependent. Microbiome analysis of the chironomid samples by 16S rRNA gene amplicon sequencing revealed a general effect of V. cholerae exposure on microbiome species evenness. Taken together, our results provide novel insights into V. cholerae invasion dynamics of the chironomid larvae with respect to various doses and strains. The findings suggest that aquatic cell density is a crucial driver of V. cholerae invasion success in chironomid larvae and pave the way for future work examining the effects of a broader dose range and environmental variables (e.g., temperature) on V. cholerae-chironomid interactions. Vibrio cholerae is the causative agent of cholera, a significant diarrheal disease affecting millions of people worldwide. Increasing evidence suggests that the environmental facets of the V. cholerae life cycle involve symbiotic associations with aquatic arthropods, which may facilitate its environmental persistence and dissemination. However, the dynamics of interactions between V. cholerae and aquatic arthropods remain unexplored. This study capitalized on using freshwater microcosms with chironomid larvae to investigate the effects of bacterial cell density and strain on V. cholerae-chironomid interactions. Our results suggest that aquatic cell density is the primary determinant of V. cholerae invasion success in chironomid larvae, while interstrain variability in invasion outcomes can be observed under specific cell density conditions. We also determined that V. cholerae exposure generally reduces species evenness of the chironomid-associated microbiome. Collectively, these findings provide novel insights into V. cholerae-arthropod interactions using a newly developed experimental host system.
自 19 世纪初以来，霍乱一直是人类的灾难，仍然是一个全球性的公共卫生挑战，由产毒菌株霍乱弧菌引起。在其水生水库中，已经证明霍乱弧菌与各种节肢动物宿主（包括摇蚊科）共生，摇蚊科是一种常见于湿地和半湿地栖息地的多样化昆虫科。霍乱弧菌与摇蚊的共生关系可能使细菌免受环境胁迫，并放大其传播。然而，霍乱弧菌和摇蚊之间的相互作用动态在很大程度上仍然未知。在这项研究中，我们使用带有摇蚊幼虫的淡水微宇宙来测试细胞密度和菌株对霍乱弧菌-摇蚊相互作用的影响。我们的结果表明，摇蚊幼虫可以暴露于高达高接种剂量（10 个细胞/mL）的霍乱弧菌而没有观察到有害影响。同时，宿主入侵的菌株间变异性，包括流行率、细菌负荷和对宿主生存的影响，高度依赖于细胞密度。通过 16S rRNA 基因扩增子测序对摇蚊样本进行的微生物组分析显示，霍乱弧菌暴露对微生物组物种均匀度有普遍影响。总的来说，我们的结果提供了关于不同剂量和菌株的霍乱弧菌入侵摇蚊幼虫动态的新见解。研究结果表明，水生细胞密度是霍乱弧菌在摇蚊幼虫中成功入侵的关键驱动因素，并为未来研究在更广泛的剂量范围和环境变量（例如温度）对霍乱弧菌-摇蚊相互作用的影响铺平了道路。霍乱弧菌是霍乱的病原体，这是一种严重的腹泻病，影响着全世界数百万人。越来越多的证据表明，霍乱弧菌生命周期的环境方面涉及与水生节肢动物的共生关联，这可能有助于其环境持久性和传播。然而，霍乱弧菌与水生节肢动物之间相互作用的动态仍然未知。本研究利用带有摇蚊幼虫的淡水微宇宙来研究细菌细胞密度和菌株对霍乱弧菌-摇蚊相互作用的影响。我们的结果表明，水生细胞密度是霍乱弧菌在摇蚊幼虫中成功入侵的主要决定因素，而在特定的细胞密度条件下，可以观察到入侵结果的菌株间变异性。我们还确定，霍乱弧菌暴露通常会降低摇蚊相关微生物组的物种均匀度。总的来说，这些发现使用新开发的实验宿主系统为霍乱弧菌-节肢动物相互作用提供了新的见解。
