Life has persisted for about 3.5 billion years (Gy) despite fluctuating environmental pressures and the aging and mortality of individuals. The disposable soma theory (DST) notoriously contributes to explain this persistence for lineages with a clear soma/germen distinction. Beyond such lineages however, the phylogenetic scope of application of the DST is less obvious. Typically, the DST is not expected to explain the survival of microbial species that comprise single-celled organisms apparently lacking a germen/soma distinction. Here, we present an evolutionary argument that generalizes the explanatory scope of DST to the entire microbial world and provides a novel characterization of the deep molecular and evolutionary roots supporting this expanded disposable soma theory of aging. Specifically, we argue that the germen/soma distinction arose early in evolution and identify DNA semi-conservative replication as a critical process through which two forms of rejuvenation could have evolved in the first microbes. Our hypothesis has fundamental and practical implications. First, whereas unicellular organisms were long thought of as potentially immortal, we suggest instead that all unicellular individuals (prokaryotes or protists alike) are very likely to age, either replicatively or physiologically, or both. Second, our theory introduces a profound reconsideration of microbial individuality, whereby, all microbial individuals, as seen by natural selection, present an obligate transient germen/soma distinction during their life cycles. Third, our work promotes the study of cellular division in prokaryotes and in protist mitosis to illuminate the evolutionary origin of the soma and germen division, traditionally studied in animals. These ideas set the stage for progress in the evolutionary theory of aging from a heretofore overlooked microbial perspective.

尽管不断变化的环境压力以及个人的衰老和死亡，生命仍然持续了约35亿年。众所周知，一次性躯体理论（DST）有助于以明显的躯体/德语区别来解释这种血统的持久性。但是，除了这些血统之外，DST的系统发育范围还不太明显。通常，DST不能解释包含明显缺乏细菌/体细胞区别的单细胞生物的微生物物种的生存。在这里，我们提出了一个进化论证，将DST的解释范围概括到整个微生物世界，并提供了支持这种扩展的一次性体细胞衰老理论的深层分子和进化根源的新颖表征。特别，我们认为，胚芽/胚芽的区别出现在进化的早期，并且将DNA半保守复制确定为一个关键过程，通过该过程，第一种微生物可以产生两种形式的复兴。我们的假设具有根本和实际意义。首先，虽然单细胞生物长期以来被认为是永生的，但我们建议所有单细胞个体（原核生物或原生生物都一样）极有可能衰老，无论是复制性的还是生理性的，或两者皆是。其次，我们的理论引入了对微生物个性的深刻反思，由此，从自然选择的角度来看，所有微生物个体在其生命周期中都表现出专一的暂时性菌种/胞体区别。第三，我们的工作促进了原核生物和原生质有丝分裂中细胞分裂的研究，以阐明传统上在动物中进行研究的体细胞和生殖细胞分裂的进化起源。从迄今为止被忽视的微生物角度来看，这些想法为衰老进化论的发展奠定了基础。