In Salmonella Typhimurium (S. Typhimurium), lipopolysaccharide (LPS) anchored on the bacterial outer membrane is a major immune stimulus that can broadly activate immune cells and induce innate immune responses. wzxE is involved in bacterial LPS biosynthesis but has rarely been reported in Salmonella; wzxE encodes a flipase that can flip the precursor of LPS across the membrane into the periplasm space. Our preliminary data showed that the wzxE transposon mutant of S. Typhimurium could not significantly adhere to and invade into HEp-2 cells, but the mechanism remains unknown. In this study, we infected human LS174T, Caco-2, HeLa, and THP-1 cells with the wild-type S. Typhimurium strain SL1344, its wzxE mutant, and its complemented strain. wzxE depletion significantly attenuated bacterial adhesion and internalization in the four cell types. In addition, the postinfectious production of interleukin-8 (IL-8) was significantly decreased in the Caco-2 cells infected with the wzxE mutant. Bacterial LPS stained with polymyxin B probe also exhibited a reduced signal in the wzxE mutant. The silver staining of purified LPS demonstrated a significant reduction of the O-antigen (OAg) chain in the wzxE mutant. To confirm the role of OAg in the wzxE mutant during infection, we treated the HT-29 cells with the S. Typhimurium strain SL1344, its wzxE mutant, and their purified LPS, which revealed significantly decreased IL-8 secretion in the HT-29 cells treated with purified LPS from the wzxE mutant and with the wzxE mutant. In conclusion, wzxE mediates LPS biosynthesis and plays a major role in bacterial pathogenesis by regulating OAg flipping.

在鼠伤寒沙门氏菌（S. Typhimurium）中，锚定在细菌外膜上的脂多糖（LPS）是一种主要的免疫刺激，可以广泛激活免疫细胞并诱导先天免疫反应。wzxE参与细菌LPS的生物合成，但在沙门氏菌中很少报道; wzxE编码一种可将脂多糖的前体跨膜翻转进入周质空间的酶。我们的初步数据表明，S。的wzxE转座子突变体。鼠伤寒沙门氏菌不能显着粘附并侵袭HEp-2细胞，但其机制尚不清楚。在这项研究中，我们用野生型S感染了人LS174T，Caco-2，HeLa和THP-1细胞。鼠伤寒菌株SL1344，其wzxE突变体及其互补菌株。wzxE耗竭显着减弱了四种细胞类型中的细菌粘附和内在化。此外，在感染了wzxE突变体的Caco-2细胞中，白细胞介素8（IL-8）的感染后产量显着下降。用多粘菌素B探针染色的细菌LPS在wzxE中也显示出减少的信号突变体。纯化的LPS的银染表明wzxE突变体中O抗原（OAg）链显着减少。为了确认OAg在感染期间wzxE突变体中的作用，我们用S处理了HT-29细胞。鼠伤寒沙门氏菌SL1344菌株，其wzxE突变体，以及它们的纯化LPS，其显著显示与纯化LPS从处理的HT-29细胞中降低IL-8分泌wzxE突变体，并与wzxE突变体。总之，wzxE通过调节OAg翻转介导LPS的生物合成，并在细菌发病机理中起主要作用。