The last universal cellular ancestor (LUCA) is the most recent population of organisms from which all cellular life on Earth descends. The reconstruction of the genome and phenotype of the LUCA is a major challenge in evolutionary biology. Given that all life forms are associated with viruses and/or other mobile genetic elements, there is no doubt that the LUCA was a host to viruses. Here, by projecting back in time using the extant distribution of viruses across the two primary domains of life, bacteria and archaea, and tracing the evolutionary histories of some key virus genes, we attempt a reconstruction of the LUCA virome. Even a conservative version of this reconstruction suggests a remarkably complex virome that already included the main groups of extant viruses of bacteria and archaea. We further present evidence of extensive virus evolution antedating the LUCA. The presence of a highly complex virome implies the substantial genomic and pan-genomic complexity of the LUCA itself.

最后一个通用细胞祖先（LUCA）是地球上所有细胞生命都从其降落的最新生物种群。LUCA的基因组和表型的重建是进化生物学中的主要挑战。鉴于所有生命形式都与病毒和/或其他流动遗传成分有关，毫无疑问，LUCA是病毒的宿主。在这里，通过使用跨生命，细菌和古细菌这两个主要域的现存病毒及时回溯，并追溯一些关键病毒基因的进化历史，我们尝试重建LUCA病毒。即使是这种重建的保守形式，也显示出非常复杂的病毒，其中已经包含了主要的现存细菌和古细菌病毒。我们进一步提出了在LUCA之前广泛传播病毒的证据。高度复杂的病毒体的存在意味着LUCA本身的基因组和泛基因组的复杂性。