Santini Talitha C, Gramenz Lucy, Southam Gordon, Zammit Carla
UWA School of Agriculture and Environment, The University of Western Australia, Crawley, WA, Australia.
School of Earth and Environmental Sciences, The University of Queensland, St Lucia, QLD, Australia.
Front Microbiol. 2022 Jun 2;13:920056. doi: 10.3389/fmicb.2022.920056. eCollection 2022.
Salt lakes are globally significant microbial habitats, hosting substantial novel microbial diversity and functional capacity. Extremes of salinity and pH both pose major challenges for survival of microbial life in terrestrial and aquatic environments, and are frequently cited as primary influences on microbial diversity across a wide variety of environments. However, few studies have attempted to identify spatial and geochemical contributions to microbial community composition, functional capacity, and environmental tolerances in salt lakes, limiting exploration of novel halophilic and halotolerant microbial species and their potential biotechnological applications. Here, we collected sediment samples from 16 salt lakes at pH values that ranged from pH 4 to 9, distributed across 48,000 km of the Archaean Yilgarn Craton in southwestern Australia to identify associations between environmental factors and microbial community composition, and used a high throughput culturing approach to identify the limits of salt and pH tolerance during iron and sulfur oxidation in these microbial communities. Geographical distance between lakes was the primary contributor to variation in microbial community composition, with pH identified as the most important geochemical contributor to variation in microbial community composition. Microbial community composition split into two clear groups by pH: dominated microbial communities in acidic saline lakes, whereas dominated microbial communities in alkaline saline lakes. Iron oxidation was observed at salinities up to 160 g L NaCl at pH values as low as pH 1.5, and sulfur oxidation was observed at salinities up to 160 g L NaCl between pH values 2-10, more than doubling previously observed tolerances to NaCl salinity amongst cultivable iron and sulfur oxidizers at these extreme pH values. OTU level diversity in the salt lake microbial communities emerged as the major indicator of iron- and sulfur-oxidizing capacity and environmental tolerances to extremes of pH and salinity. Overall, when bioprospecting for novel microbial functional capacity and environmental tolerances, our study supports sampling from remote, previously unexplored, and maximally distant locations, and prioritizing for OTU level diversity rather than present geochemical conditions.
盐湖是全球重要的微生物栖息地，拥有大量新的微生物多样性和功能能力。盐度和pH值的极端情况对陆地和水生环境中微生物的生存都构成了重大挑战，并且经常被认为是影响各种环境中微生物多样性的主要因素。然而，很少有研究试图确定盐湖中空间和地球化学对微生物群落组成、功能能力和环境耐受性的影响，这限制了对新型嗜盐和耐盐微生物物种及其潜在生物技术应用的探索。在这里，我们从澳大利亚西南部太古宙伊尔加恩克拉通48000公里范围内的16个pH值在4到9之间的盐湖中采集了沉积物样本，以确定环境因素与微生物群落组成之间的关联，并使用高通量培养方法来确定这些微生物群落在铁和硫氧化过程中盐和pH耐受性的极限。湖泊之间的地理距离是微生物群落组成变化的主要因素，pH值被确定为微生物群落组成变化中最重要的地球化学因素。微生物群落组成按pH值分为两个明显的组：酸性盐湖中以 为主导的微生物群落，而碱性盐湖中以 为主导的微生物群落。在低至pH 1.5的条件下，盐度高达160 g/L NaCl时观察到铁氧化，在pH值2 - 10之间，盐度高达160 g/L NaCl时观察到硫氧化，这比之前在这些极端pH值下可培养的铁和硫氧化剂中观察到的对NaCl盐度的耐受性增加了一倍多。盐湖微生物群落中的OTU水平多样性成为铁和硫氧化能力以及对极端pH值和盐度的环境耐受性的主要指标。总体而言，在对新型微生物功能能力和环境耐受性进行生物勘探时，我们的研究支持从偏远、以前未探索过且距离最远的地点进行采样，并优先考虑OTU水平多样性而非当前的地球化学条件。
