Environmental Microbial and Food Safety Laboratory, Henry A. Wallace Beltsville Agricultural Research Center, Agricultural Research Service, USDA, 10300 Baltimore Avenue, Bldg. 173, BARC-E, Beltsville, MD 20705-2350, USA.
Arch Microbiol. 2012 Jun;194(6):541-8. doi: 10.1007/s00203-012-0791-4. Epub 2012 Jan 26.
opgB gene of Salmonella enterica serovar Typhimurium was identified earlier in a genome-wide screen for mice virulence (Valentine et al. in Infect Immun 66:3378-3383, 1998). Although mutation in opgB resulted in avirulent Salmonella strain, how this gene contributes to pathogenesis remains unclear. Based on DNA homology, opgB is predicted to be responsible for adding phosphoglycerate residues to osmoregulated periplasmic glucans (OPGs) giving them anionic characteristics. In Escherichia coli, yet another gene, opgC, is also reported to contribute to anionic characteristics of OPGs by adding succinic acid residues. We constructed opgB, opgC, and opgBC double mutants of S. enterica serovar Typhimurium strain SL1344. As predicted opgBC mutant synthesized neutral OPGs that were devoid of any anionic substituents. However, opgB, opgC, and opgBC mutations had no significant impact on mice virulence as well as on competitive organ colonization. In low osmotic conditions, opgB, opgC, and opgBC mutants exhibited delay in growth initiation in the presence of sodium deoxycholate. Anionic substituents of OPGs from Salmonella although appear to be needed to overcome resistance of deoxycholate in hypoosmotic growth media, no evidence was found for their role in mice virulence.
先前在全基因组范围内筛选鼠源伤寒沙门氏菌毒力的研究中鉴定出了鼠伤寒沙门氏菌的 opgB 基因（Valentine 等人，Infect Immun 66:3378-3383, 1998）。虽然 opgB 基因突变导致了无毒性的沙门氏菌菌株，但该基因如何导致发病机制尚不清楚。根据 DNA 同源性，opgB 预计负责在渗透压调节的周质葡聚糖（OPGs）上添加磷酸甘油酸残基，从而使它们具有阴离子特性。在大肠杆菌中，另一个基因 opgC 也被报道通过添加琥珀酸残基来促进 OPGs 的阴离子特性。我们构建了鼠伤寒沙门氏菌 SL1344 株的 opgB、opgC 和 opgBC 双突变体。正如预测的那样，opgBC 突变体合成了中性 OPGs，没有任何阴离子取代基。然而，opgB、opgC 和 opgBC 突变对鼠源毒力以及竞争器官定植均无显著影响。在低渗透压条件下，opgB、opgC 和 opgBC 突变体在存在脱氧胆酸钠时生长起始延迟。沙门氏菌 OPGs 的阴离子取代基似乎需要克服低渗生长介质中脱氧胆酸钠的抗性，但没有发现它们在鼠源毒力中的作用证据。
