School of Life Sciences, Guizhou Normal University, Guiyang, 550001, Guizhou, China.
CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China.
BMC Microbiol. 2020 May 29;20(1):137. doi: 10.1186/s12866-020-01806-7.
Karst caves are considered as extreme environments with nutrition deficiency, darkness, and oxygen deprivation, and they are also the sources of biodiversity and metabolic pathways. Microorganisms are usually involved in the formation and maintenance of the cave system through various metabolic activities, and are indicators of changes environment influenced by human. Zhijin cave is a typical Karst cave and attracts tourists in China. However, the bacterial diversity and composition of the Karst cave are still unclear. The present study aims to reveal the bacterial diversity and composition in the cave and the potential impact of tourism activities, and better understand the roles and co-occurrence pattern of the bacterial community in the extreme cave habitats.
The bacterial community consisted of the major Proteobacteria, Actinobacteria, and Firmicutes, with Proteobacteria being the predominant phylum in the rock, soil, and stalactite samples. Compositions and specialized bacterial phyla of the bacterial communities were different among different sample types. The highest diversity index was found in the rock samples with a Shannon index of 4.71. Overall, Zhijin cave has relatively lower diversity than that in natural caves. The prediction of function showed that various enzymes, including ribulose-bisphosphate carboxylase, 4-hydroxybutyryl-CoA dehydratase, nitrogenase NifH, and Nitrite reductase, involved in carbon and nitrogen cycles were detected in Zhijin cave. Additionally, the modularity indices of all co-occurrence network were greater than 0.40 and the species interactions were complex across different sample types. Co-occurring positive interactions in the bacteria groups in different phyla were also observed.
These results uncovered that the oligotrophic Zhijin cave maintains the bacterial communities with the diverse metabolic pathways, interdependent and cooperative co-existence patterns. Moreover, as a hotspot for tourism, the composition and diversity of bacterial community are influenced by tourism activities. These afford new insights for further exploring the adaptation of bacteria to extreme environments and the conservation of cave ecosystem.
喀斯特洞穴被认为是营养缺乏、黑暗和缺氧的极端环境，也是生物多样性和代谢途径的来源。微生物通常通过各种代谢活动参与洞穴系统的形成和维持，并且是受人类影响的环境变化的指标。织金洞是一个典型的喀斯特洞穴，吸引了中国的游客。然而，喀斯特洞穴的细菌多样性和组成仍不清楚。本研究旨在揭示洞穴中的细菌多样性和组成以及旅游活动的潜在影响，并更好地了解细菌群落在极端洞穴栖息地中的作用和共生模式。
细菌群落由主要的变形菌门、放线菌门和厚壁菌门组成，其中变形菌门是岩石、土壤和钟乳石样本中的主要门。不同样本类型的细菌群落组成和特化细菌门不同。岩石样本的多样性指数最高，香农指数为 4.71。总体而言，织金洞的多样性低于天然洞穴。功能预测表明，检测到了各种酶，包括核酮糖二磷酸羧化酶、4-羟基丁酸辅酶 A 脱水酶、固氮酶 NifH 和亚硝酸盐还原酶，它们参与碳氮循环。此外，所有共生网络的模块指数均大于 0.40，不同样本类型的物种相互作用复杂。还观察到不同门的细菌群落在不同样本类型中的共生正相互作用。
这些结果表明，贫营养的织金洞维持着具有多样代谢途径、相互依存和协同共存模式的细菌群落。此外，作为旅游热点，细菌群落的组成和多样性受到旅游活动的影响。这些为进一步探索细菌对极端环境的适应以及洞穴生态系统的保护提供了新的见解。
