Microbial diversity is essential for the maintenance of the normal structure and function of bioregenerative life support systems (BLSS). As a typical nutrient-deficient environment (NDE), the BLSS does not provide sufficient types of available substrates for microbial communities, and its internal microbial diversity is usually not high due to interspecific competitive exclusion. However, it is reported that microbial diversity is abnormally high in the International Space Station (ISS) after long-term exposure to low-dose ionizing radiation (LDIR). It remains a mystery why LDIR leads to the formation and maintenance of high microbial diversity. In this study, a series of artificial microbial communities have been cultivated in NDE without and with LDIR, respectively. These communities are composed of three common microbial species (Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa) in the ISS. By comparing and analyzing the differences in the microbial physiological and behavioral response characteristics in the two scenarios, a reasonable hypothesis was put forward to elucidate the formation and maintenance mechanisms of high microbial diversity in NDE with LDIR. Then a set of kinetic models were developed based on this hypothesis, observed phenomena, and experimental data. Finally, these kinetic models were sufficiently validated and the hypothesis was fully confirmed through large-scale digital simulations. Briefly, two fundamental succession mechanisms of the microbial communities are supposed to exist in NDE with LDIR: substrate-based negative feedback regulation (SNFR) and microbial delayed responses. These two decisive succession mechanisms can give rise to asynchronously convergent fluctuations of microbial populations and significantly alleviate the interspecific competitions. Such a species-for-quantity strategy drives the microbial communities to form and maintain species diversity with higher richness and evenness. This study can lay the theoretical foundation and provide new ideas for the construction of advanced BLSS featured with more robust structures and stronger function.

微生物多样性对于维持生物再生生命支持系统 (BLSS) 的正常结构和功能至关重要。作为典型的营养缺乏环境（NDE），BLSS 没有为微生物群落提供足够类型的可用底物，并且由于种间竞争排斥，其内部微生物多样性通常不高。然而，据报道，在长期暴露于低剂量电离辐射（LDIR）后，国际空间站（ISS）的微生物多样性异常高。为什么 LDIR 导致高微生物多样性的形成和维持仍然是个谜。在这项研究中，分别在没有和有 LDIR 的 NDE 中培养了一系列人工微生物群落。这些群落由三种常见的微生物物种组成（大肠杆菌、 枯草芽孢杆菌 和 铜绿假单胞菌）在国际空间站。通过比较和分析两种情景下微生物生理和行为反应特征的差异，提出了合理的假设，以阐明LDIR在NDE中高微生物多样性的形成和维持机制。然后基于这一假设、观察到的现象和实验数据开发了一组动力学模型。最后，这些动力学模型得到了充分验证，并通过大规模数字模拟充分证实了这一假设。简而言之，微生物群落的两种基本演替机制应该存在于具有 LDIR 的 NDE 中：基于底物的负反馈调节 (SNFR) 和微生物延迟响应。这两种决定性的演替机制可以引起微生物种群的异步收敛波动，并显着减轻种间竞争。这种以物种换数量的策略驱使微生物群落形成和维持具有更高丰富度和均匀度的物种多样性。本研究可为构建结构更稳健、功能更强的先进BLSS奠定理论基础并提供新思路。