Müller Albert L, Gu Wenyu, Patsalo Vadim, Deutzmann Jörg S, Williamson James R, Spormann Alfred M
Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305.
Department of Integrative Structural and Computational Biology, Department of Chemistry, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037.
Proc Natl Acad Sci U S A. 2021 Apr 20;118(16). doi: 10.1073/pnas.2025854118.
Most microorganisms in nature spend the majority of time in a state of slow or zero growth and slow metabolism under limited energy or nutrient flux rather than growing at maximum rates. Yet, most of our knowledge has been derived from studies on fast-growing bacteria. Here, we systematically characterized the physiology of the methanogenic archaeon during slow growth. was grown in continuous culture under energy (formate)-limiting conditions at different dilution rates ranging from 0.09 to 0.002 h, the latter corresponding to 1% of its maximum growth rate under laboratory conditions (0.23 h). While the specific rate of methanogenesis correlated with growth rate as expected, the fraction of cellular energy used for maintenance increased and the maintenance energy per biomass decreased at slower growth. Notably, proteome allocation between catabolic and anabolic pathways was invariant with growth rate. Unexpectedly, cells maintained their maximum methanogenesis capacity over a wide range of growth rates, except for the lowest rates tested. Cell size, cellular DNA, RNA, and protein content as well as ribosome numbers also were largely invariant with growth rate. A reduced protein synthesis rate during slow growth was achieved by a reduction in ribosome activity rather than via the number of cellular ribosomes. Our data revealed a resource allocation strategy of a methanogenic archaeon during energy limitation that is fundamentally different from commonly studied versatile chemoheterotrophic bacteria such as .
自然界中的大多数微生物在能量或营养通量有限的情况下，大部分时间处于生长缓慢或零生长以及新陈代谢缓慢的状态，而非以最大速率生长。然而，我们的大部分知识都来自对快速生长细菌的研究。在此，我们系统地描述了产甲烷古菌在缓慢生长过程中的生理特性。该古菌在能量（甲酸盐）限制条件下，于不同稀释率（范围从0.09至0.002 h⁻¹）的连续培养中生长，后者相当于其在实验室条件下最大生长速率（0.23 h⁻¹）的1%。虽然产甲烷的比速率如预期与生长速率相关，但用于维持的细胞能量比例增加，且每生物量的维持能量在生长较慢时降低。值得注意的是，分解代谢和合成代谢途径之间的蛋白质组分配与生长速率无关。出乎意料的是，除了测试的最低生长速率外，细胞在很宽的生长速率范围内都保持其最大产甲烷能力。细胞大小、细胞DNA、RNA和蛋白质含量以及核糖体数量也在很大程度上与生长速率无关。在缓慢生长期间，蛋白质合成速率的降低是通过核糖体活性的降低而非细胞核糖体数量的减少来实现的。我们的数据揭示了产甲烷古菌在能量限制期间的一种资源分配策略，这与常见研究的通用化能异养细菌（如 ）有着根本的不同。
