Critical Role of Dispensable Genes in Mycoplasma agalactiae Interaction with Mammalian Cells
Critical Role of Dispensable Genes in Mycoplasma agalactiae Interaction with Mammalian Cells
复制标题
DOI：
10.1128/iai.01195-09
复制
发表时间：
2010-04-01
影响因子：
3.1
通讯作者：
Citti, Christine
中科院分区：
文献类型：
--
作者：
Baranowski, Eric;Guiral, Sebastien;Citti, Christine
支原体是最小的细菌，其基因组几乎不超过维持自主生命所需的最小信息量。尽管表面上很简单，但几种支原体是人类和动物的成功病原体，它们与粘膜表面的上皮细胞建立了密切的相互作用。为了鉴定介导支原体与哺乳动物细胞相互作用的生物学功能，我们在反刍动物病原体无乳支原体中产生了转座子敲除突变体库，并使用该库来鉴定在细胞培养物中表现出生长缺陷表型的突变体。在与 HeLa 细胞共培养中，无乳分枝杆菌突变体的 CFU 滴度降低了 3 倍，甚至几乎完全灭绝。转座子插入位点的定位揭示了 18 个基因组区域，推测与无乳分枝杆菌与 HeLa 细胞的相互作用有关。其中一些区域编码具有膜脂蛋白特征的蛋白质和/或参与反刍动物系统发育上遥远的致病支原体的水平基因转移。具有最极端表型的两个突变体在指定为 NIF 位点的基因组区域中携带转座子，该区域编码 SufS 和 SufU 的同源物，这两种蛋白质可能参与革兰氏阳性细菌中的 [Fe-S] 簇生物合成。互补研究证实了 NIF 基因座的条件必要性，发现 NIF 基因座对于 HeLa 细胞和其他几种哺乳动物细胞系存在下的增殖至关重要，但对于无菌生长来说是可有可无的。虽然我们的结果提出了关于支原体基本功能的问题，但它们也提供了研究支原体作为最小病原体的作用的方法。
Mycoplasmas are minimal bacteria whose genomes barely exceed the smallest amount of information required to sustain autonomous life. Despite this apparent simplicity, several mycoplasmas are successful pathogens of humans and animals, in which they establish intimate interactions with epithelial cells at mucosal surfaces. To identify biological functions mediating mycoplasma interactions with mammalian cells, we produced a library of transposon knockout mutants in the ruminant pathogen Mycoplasma agalactiae and used this library to identify mutants displaying a growth-deficient pheonotype in cell culture. M. agalactiae mutants displaying a 3-fold reduction in CFU titers to nearly complete extinction in coculture with HeLa cells were identified. Mapping of transposon insertion sites revealed 18 genomic regions putatively involved in the interaction of M. agalactiae with HeLa cells. Several of these regions encode proteins with features of membrane lipoproteins and/or were involved in horizontal gene transfer with phylogenetically distant pathogenic mycoplasmas of ruminants. Two mutants with the most extreme phenotype carry a transposon in a genomic region designated the NIF locus which encodes homologues of SufS and SufU, two proteins presumably involved in [Fe-S] cluster biosynthesis in Gram-positive bacteria. Complementation studies confirmed the conditional essentiality of the NIF locus, which was found to be critical for proliferation in the presence of HeLa cells and several other mammalian cell lines but dispensable for axenic growth. While our results raised questions regarding essential functions in mycoplasmas, they also provide a means for studying the role of mycoplasmas as minimal pathogens.