Beauregard-Tousignant Samuel, Lazar Cassandre Sara
Biological Sciences Department, Université du Québec à Montréal (UQAM), Montreal, QC, Canada.
Interuniversity Research Group in Limnology/Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montreal, QC, Canada.
Front Microbiol. 2025 May 21;16:1568469. doi: 10.3389/fmicb.2025.1568469. eCollection 2025.
Aquifers in the continental subsurface have long been exploited for their resources. However, given the technical difficulties in accessing recurring subsurface samples, their community diversity and temporal dynamics remain largely misunderstood. Here, we investigated the effects of time and organic and inorganic carbon concentration variation on primary succession of microbial communities belonging to the Bacteria and Eukaryote domains colonizing rock surfaces and groundwater from a shallow fractured sandstone aquifer with a very high concentration of organic carbon and low concentration of nitrogen compounds. We attempted to recreate its physicochemical environment in a triplicate bioreactor setup and let the communities grow for 24 days. The sessile and planktonic communities were sampled daily in independent experiments and identified based on their 16S (Bacteria) or 18S (Eukaryote) rRNA genes. Time was the parameter with the strongest correlation both with alpha and beta diversity. The primary succession of all communities seems to have been divided into two temporal phases: in the first phase, approximately the two 1 days, the variations in community composition and diversity were high. In the second phase, the variation is more progressive and lasted until the end of the experiment. As expected in an aquifer rich in organic carbon, bacteria were mostly heterotrophs, except in the first few days where there were some chemolithotrophs, and eukaryotes were heterotrophs or likely mixotrophs. Unexpectedly, the alpha diversity of the sessile and planktonic communities varied following similar patterns, but the planktonic ones varied with a wider amplitude. Regarding carbon's effect, organic and inorganic carbon concentration variation explained a much smaller proportion of the variation in alpha and beta diversity than expected. We believe this is due to its high concentration throughout the incubation and to the strong limiting effect of other factors such as nitrogen concentration and pH. The communities of both Bacteria and Eukaryotes were more active than expected and their temporal dynamics and interactions should be further investigated in varying carbon, nitrogen and other nutrient concentrations to better understand how different perturbations can affect subsurface communities and, subsequently, us.
大陆地下的含水层长期以来一直因其资源而被开采。然而，鉴于获取反复出现的地下样本存在技术困难，其群落多样性和时间动态在很大程度上仍未得到充分理解。在此，我们研究了时间以及有机和无机碳浓度变化对定殖于岩石表面和来自浅层裂隙砂岩含水层（有机碳浓度非常高且氮化合物浓度低）的地下水的细菌和真核生物域微生物群落初级演替的影响。我们试图在一式三份的生物反应器设置中重现其物理化学环境，并让群落生长24天。在独立实验中每天对固着和浮游群落进行采样，并根据其16S（细菌）或18S（真核生物）rRNA基因进行鉴定。时间是与α和β多样性相关性最强的参数。所有群落的初级演替似乎都分为两个时间阶段：在第一阶段，大约前两天，群落组成和多样性的变化很大。在第二阶段，变化更为渐进，并持续到实验结束。正如在富含有机碳的含水层中所预期的那样，细菌大多是异养生物，除了最初几天有一些化能自养生物，而真核生物是异养生物或可能是兼养生物。出乎意料的是，固着和浮游群落的α多样性遵循相似模式变化，但浮游群落的变化幅度更大。关于碳的影响，有机和无机碳浓度变化对α和β多样性变化的解释比例比预期小得多。我们认为这是由于在整个培养过程中其浓度很高，以及其他因素如氮浓度和pH的强烈限制作用。细菌和真核生物的群落都比预期更活跃，它们的时间动态和相互作用应在不同的碳、氮和其他营养浓度下进一步研究，以更好地理解不同扰动如何影响地下群落，进而影响我们。
