Grothjan Jacob J, Young Erica B
Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States.
School of Freshwater Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States.
Front Microbiol. 2022 Mar 14;13:791079. doi: 10.3389/fmicb.2022.791079. eCollection 2022.
Processes influencing recruitment of diverse bacteria to plant microbiomes remain poorly understood. In the carnivorous pitcher plant model system, individual pitchers open to collect rainwater, invertebrates and a diverse microbial community, and this detrital food web is sustained by captured insect prey. This study examined how potential sources of bacteria affect the development of the bacterial community within pitchers, how the host plant tissue affects community development and how established vs. assembling communities differ. In a controlled greenhouse experiment, seven replicate pitchers were allocated to five treatments to exclude specific bacterial sources or host tissue: milliQ water only, milliQ + insect prey, rainwater + prey, established communities + prey, artificial pitchers with milliQ + prey. Community composition and functions were examined over 8-40 weeks using bacterial gene sequencing and functional predictions, measurements of cell abundance, hydrolytic enzyme activity and nutrient transformations. Distinct community composition and functional differences between artificial and real pitchers confirm an important influence of host plant tissue on community development, but also suggest this could be partially related to host nutrient uptake. Significant recruitment of bacteria to pitchers from air was evident from many taxa common to all treatments, overlap in composition between milliQ, milliQ + prey, and rainwater + prey treatments, and few taxa unique to milliQ only pitchers. Community functions measured as hydrolytic enzyme (chitinase, protease) activity suggested a strong influence of insect prey additions and were linked to rapid transformation of insect nutrients into dissolved and inorganic sources. Bacterial taxa found in 6 of 7 replicate pitchers within treatments, the "core microbiome" showed tighter successional trajectories over 8 weeks than all taxa. Established pitcher community composition was more stable over 8 weeks, suggesting a diversity-stability relationship and effect of microinvertebrates on bacteria. This study broadly demonstrates that bacterial composition in host pitcher plants is related to both stochastic and specific bacterial recruitment and host plants influence microbial selection and support microbiomes through capture of insect prey.
影响多种细菌进入植物微生物群的过程仍知之甚少。在食肉猪笼草模型系统中，单个猪笼草开口以收集雨水、无脊椎动物和多样的微生物群落，这个碎屑食物网由捕获的昆虫猎物维持。本研究考察了细菌的潜在来源如何影响猪笼草内细菌群落的发育、宿主植物组织如何影响群落发育以及已建立的群落与正在形成的群落有何不同。在一个受控的温室实验中，将七个重复的猪笼草分配到五种处理中，以排除特定的细菌来源或宿主组织：仅用超纯水、超纯水 + 昆虫猎物、雨水 + 猎物、已建立的群落 + 猎物、装有超纯水 + 猎物的人工猪笼草。在8至40周的时间里，使用细菌基因测序和功能预测、细胞丰度测量、水解酶活性和养分转化来检查群落组成和功能。人工猪笼草和真实猪笼草之间不同的群落组成和功能差异证实了宿主植物组织对群落发育有重要影响，但也表明这可能部分与宿主养分吸收有关。从所有处理共有的许多分类群、超纯水、超纯水 + 猎物和雨水 + 猎物处理之间组成的重叠以及仅装有超纯水的猪笼草中独特的分类群很少可以明显看出，空气中的细菌大量进入猪笼草。以水解酶（几丁质酶、蛋白酶）活性衡量的群落功能表明添加昆虫猎物有很大影响，并且与昆虫养分迅速转化为溶解态和无机态来源有关。在处理中的7个重复猪笼草中有6个发现的细菌分类群，即“核心微生物群”，在8周内显示出比所有分类群更紧密的演替轨迹。已建立的猪笼草群落组成在8周内更稳定，表明存在多样性 - 稳定性关系以及微型无脊椎动物对细菌的影响。这项研究广泛表明，宿主猪笼草中的细菌组成与随机和特定的细菌招募都有关系，并且宿主植物通过捕获昆虫猎物影响微生物选择并支持微生物群。
