School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.
School of Science, Auckland University of Technology, Private Bag 92006, Auckland, New Zealand.
BMC Microbiol. 2023 Sep 29;23(1):275. doi: 10.1186/s12866-023-03025-2.
Gut microbiota play a key role in the nutrition of many marine herbivorous fishes through hindgut fermentation of seaweed. Gut microbiota composition in the herbivorous fish Kyphosus sydneyanus (family Kyphosidae) varies between individuals and gut sections, raising two questions: (i) is community composition stable over time, especially given seasonal shifts in storage metabolites of dietary brown algae, and (ii) what processes influence community assembly in the hindgut?
We examined variation in community composition in gut lumen and mucosa samples from three hindgut sections of K. sydneyanus collected at various time points in 2020 and 2021 from reefs near Great Barrier Island, New Zealand. 16S rRNA gene analysis was used to characterize microbial community composition, diversity and estimated density. Differences in community composition between gut sections remained relatively stable over time, with little evidence of temporal variation. Clostridia dominated the proximal hindgut sections and Bacteroidia the most distal section. Differences were detected in microbial composition between lumen and mucosa, especially at genus level.
High variation in community composition and estimated bacterial density among individual fish combined with low variation in community composition temporally suggests that initial community assembly involved environmental selection and random sampling/neutral effects. Community stability following colonisation could also be influenced by historical contingency, where early colonizing members of the community may have a selective advantage. The impact of temporal changes in the algae may be limited by the dynamics of substrate depletion along the gut following feeding, i.e. the depletion of storage metabolites in the proximal hindgut. Estimated bacterial density, showed that Bacteroidota has the highest density (copies/mL) in distal-most lumen section V, where SCFA concentrations are highest. Bacteroidota genera Alistipes and Rikenella may play important roles in the breakdown of seaweed into useful compounds for the fish host.
肠道微生物群通过对海藻的后肠发酵，在许多海洋草食性鱼类的营养中发挥着关键作用。草食性鱼类 Kyphosus sydneyanus（Kyphosidae 科）的肠道微生物群落组成在个体和肠道部位之间存在差异，这提出了两个问题：（i）在给定季节变化的情况下，特别是在饮食褐藻的储存代谢物方面，群落组成是否稳定，以及（ii）哪些过程影响后肠的群落组装？
我们检查了 2020 年和 2021 年期间从新西兰大堡礁附近的珊瑚礁中收集的三个后肠部位的肠道腔和黏膜样本中群落组成的变化。16S rRNA 基因分析用于表征微生物群落组成、多样性和估计密度。随着时间的推移，肠道部位之间的群落组成差异相对稳定，几乎没有时间变化的证据。厚壁菌门在近端后肠部位占主导地位，拟杆菌门在最远端部位占主导地位。在腔和黏膜之间检测到微生物组成的差异，特别是在属水平上。
个体之间的群落组成和估计细菌密度的高度变异性以及随时间变化的群落组成的低变异性表明，初始群落组装涉及环境选择和随机采样/中性效应。定植后群落的稳定性也可能受到历史偶然性的影响，群落中的早期定植成员可能具有选择优势。藻类时间变化的影响可能受到喂养后肠道中底物消耗的动态限制，即近端后肠中储存代谢物的消耗。估计的细菌密度表明，Bacteroidota 在远端腔部 V 中具有最高密度（拷贝/mL），那里的 SCFA 浓度最高。拟杆菌门属 Alistipes 和 Rikenella 可能在将海藻分解为鱼类宿主有用的化合物方面发挥重要作用。
