George Christaline, Lim Chloe Xue Qi, Tong Yan, Pointing Stephen Brian
Yale-NUS College, National University of Singapore, Singapore, Singapore.
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Front Microbiol. 2023 Jun 16;14:1189468. doi: 10.3389/fmicb.2023.1189468. eCollection 2023.
The Sembawang Hot Spring in Singapore lies at the foot of a major regional geological feature called the Bentong-Raub Suture Zone. Amid an extensively managed surface geothermal park, an undisturbed hot spring emerges with source water at 61°C, pH 6.8, and 1 mg/L dissolved sulfide. A small main pool at the source supported orange-green benthic flocs, whereas the outflow channel with gradually less extreme environmental stress supported extensive vivid green microbial mats. Microscopy revealed that cyanobacterial morphotypes were distinct in flocs and mats at several intervals along the environmental gradient, and we describe a spiraling pattern in the oscillatorian cyanobacteria that may reflect response to poly-extreme stress. Estimation of diversity using 16S rRNA gene sequencing revealed assemblages that were dominated by phototrophic bacteria. The most abundant taxa in flocs at 61°C/1 mg/L sulfide were sp. and , whilst the mats at 45.7-55.3°C/0-0.5 mg/L sulfide were dominated by cyanobacterium MTP1 and sp. Occurrence of diverse chemoautotrophs and heterotrophs reflected known thermal ranges for taxa, and of note was the high abundance of thermophilic cellulolytic bacteria that likely reflected the large allochthonous leaf input. A clear shift in ASV-defined putative ecotypes occurred along the environmental stress gradient of the hot spring and overall diversity was inversely correlated to environmental stress. Significant correlations for abiotic variables with observed biotic diversity were identified for temperature, sulfide, and carbonate. A network analysis revealed three putative modules of biotic interactions that also reflected the taxonomic composition at intervals along the environmental gradient. Overall, the data indicated that three distinct microbial communities were supported within a small spatial scale along the poly-extreme environmental gradient. The findings add to the growing inventory of hot spring microbiomes and address an important biogeographic knowledge gap for the region.
新加坡的三巴旺温泉位于一个名为本通 - 劳勿缝合带的主要区域地质构造脚下。在一个经过广泛管理的地表地热公园中，一处未受干扰的温泉涌出，源水温度为61°C，pH值为6.8，溶解硫化物含量为1毫克/升。源头有一个小主池，池中生长着橙绿色的底栖絮凝物，而流出通道的环境压力逐渐减小，这里生长着大量鲜艳的绿色微生物垫。显微镜观察显示，在沿环境梯度的几个区间内，絮凝物和微生物垫中的蓝藻形态类型各不相同，我们描述了颤藻属蓝藻中的一种螺旋模式，这可能反映了对多重极端压力的响应。利用16S rRNA基因测序估计多样性，结果显示群落以光合细菌为主。在61°C/1毫克/升硫化物条件下的絮凝物中，最丰富的分类群是 属和 属，而在45.7 - 55.3°C/0 - 0.5毫克/升硫化物条件下的微生物垫则以蓝藻MTP1和 属为主。多种化能自养生物和异养生物的出现反映了已知分类群的温度范围，值得注意的是，嗜热纤维素分解菌的高丰度可能反映了大量外来树叶的输入。沿着温泉的环境压力梯度，以扩增子序列变体（ASV）定义的假定生态型发生了明显变化，总体多样性与环境压力呈负相关。确定了温度、硫化物和碳酸盐等非生物变量与观察到的生物多样性之间的显著相关性。网络分析揭示了三个假定的生物相互作用模块，这些模块也反映了沿环境梯度各区间的分类组成。总体而言，数据表明在沿着多重极端环境梯度的小空间尺度内支持着三个不同的微生物群落。这些发现增加了温泉微生物群落不断增长的清单，并填补了该地区一个重要的生物地理知识空白。
