Mycoplasmas are atypical bacteria with small genomes that necessitate colonization of their respective animal or plant hosts as obligate parasites, whether as pathogens, or commensals. Some can grow axenically in specialized complex media yet show only host-cell-dependent growth in cell culture, where they can survive chronically and often through interactions involving surface colonization or internalization. To develop a mycoplasma-based system to identify genes mediating such interactions, we exploited genetically tractable strains of the goat pathogen Mycoplasma mycoides (Mmc) with synthetic designer genomes representing the complete natural organism (minus virulence factors; JCVI-syn1.0) or its reduced counterpart (JCVI-syn3B) containing only those genes supporting axenic growth. By measuring growth of surviving organisms, physical association with cultured human cells (HEK-293T, HeLa), and induction of phagocytosis by human myeloid cells (dHL-60), we determined that JCVI-syn1.0 contained a set of eight genes (MMSYN1-0179 to MMSYN1-0186, dispensable for axenic growth) conferring survival, attachment, and phagocytosis phenotypes. JCVI-syn3B lacked these phenotypes, but insertion of these genes restored cell attachment and phagocytosis, although not survival. These results indicate that JCVI-syn3B may be a powerful living platform to analyze the role of specific gene sets, from any organism, on the interaction with diverse mammalian cells in culture.

中文翻译：

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最小细菌细胞 JCVI-syn3B 作为研究细菌和哺乳动物细胞之间相互作用的基础

支原体是具有小基因组的非典型细菌，需要作为专性寄生虫（无论是作为病原体还是共生体）在各自的动物或植物宿主中定殖。有些可以在专门的复杂培养基中生长，但在细胞培养中仅表现出宿主细胞依赖性生长，在细胞培养中它们可以长期存活，并且通常通过涉及表面定植或内化的相互作用。为了开发基于支原体的系统来识别介导此类相互作用的基因，我们利用了山羊病原体蕈状支原体( Mmc ) 的遗传易处理菌株，以及代表完整自然生物体（减去毒力因子；JCVI-syn1.0）或其合成设计基因组。还原对应物（JCVI-syn3B）仅包含那些支持无菌生长的基因。通过测量存活生物体的生长、与培养的人类细胞（HEK-293T、HeLa）的物理关联以及人类骨髓细胞（dHL-60）吞噬作用的诱导，我们确定 JCVI-syn1.0 包含一组八个基因（MMSYN1-0179至MMSYN1-0186（对于无菌生长是可有可无的）赋予存活、附着和吞噬表型。 JCVI-syn3B 缺乏这些表型，但插入这些基因可以恢复细胞附着和吞噬作用，但不能恢复存活。这些结果表明，JCVI-syn3B 可能是一个强大的生活平台，用于分析任何生物体的特定基因集在与培养中的不同哺乳动物细胞相互作用中的作用。