Marine Microbiology Group (MMG), Department of Animal and Microbial Biodiversity, Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), 07190 Esporles, Spain.
Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany.
ISME J. 2024 Jan 8;18(1). doi: 10.1093/ismejo/wrae215.
To understand how extreme halophiles respond to recurrent disturbances, we challenged the communities thriving in salt-saturated (~36% salts) ~230 L brine mesocosms to repeated dilutions down to 13% (D13 mesocosm) or 20% (D20 mesocosm) salts each time mesocosms reached salt saturation due to evaporation (for 10 and 17 cycles, respectively) over 813 days. Depending on the magnitude of dilution, the most prevalent species, Haloquadratum walsbyi and Salinibacter ruber, either increased in dominance by replacing less competitive populations (for D20, moderate stress conditions), or severely decreased in abundance and were eventually replaced by other congeneric species better adapted to the higher osmotic stress (for D13, strong stress conditions). Congeneric species replacement was commonly observed within additional abundant genera in response to changes in environmental or biological conditions (e.g. phage predation) within the same system and under a controlled perturbation of a relevant environmental parameter. Therefore, a genus is an ecologically important level of diversity organization, not just a taxonomic rank, that persists in the environment based on congeneric species replacement due to relatively high functional overlap (gene sharing), with important consequences for the success of the lineage, and similar to the success of a species via strain-replacement. Further, our results showed that successful species were typically accompanied by the emergence of their own viral cohorts, whose intra-cohort diversity appeared to strongly covary with, and likely drive, the intra-host diversity. Collectively, our results show that brine communities are ecologically resilient and continuously adapting to changing environments by transitioning to alternative stable states.
为了了解极端嗜盐生物如何应对反复出现的干扰，我们挑战了在盐饱和（36%盐）230L 盐沼中茁壮成长的群落，每次由于蒸发而使盐沼达到盐饱和时（分别进行了 10 和 17 个循环），将其分别稀释至 13%（D13 盐沼）或 20%（D20 盐沼）盐。取决于稀释的幅度，最常见的物种 Haloquadratum walsbyi 和 Salinibacter ruber 要么通过取代竞争力较弱的种群而增加优势地位（对于 D20，中度胁迫条件），要么丰度严重下降，最终被其他更适应更高渗透压的同属物种所取代（对于 D13，强胁迫条件）。在同一系统内，由于环境或生物条件（例如噬菌体捕食）的变化，以及在相关环境参数的受控扰动下，同属种的替代通常在其他丰富属内观察到。因此，一个属是一个具有重要生态意义的多样性组织水平，不仅仅是一个分类等级，它基于同属种的替代而在环境中持续存在，因为相对较高的功能重叠（基因共享），这对谱系的成功具有重要意义，类似于通过菌株替代而实现的物种成功。此外，我们的研究结果表明，成功的物种通常伴随着其自身病毒群的出现，其种内多样性似乎与宿主内多样性强烈相关，并可能驱动宿主内多样性。总之，我们的研究结果表明，盐水群落具有生态弹性，通过过渡到替代稳定状态，不断适应变化的环境。
