Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada T6G 2H7.
Proc Natl Acad Sci U S A. 2010 Nov 9;107(45):19520-4. doi: 10.1073/pnas.1012931107. Epub 2010 Oct 25.
The acute diarrheal disease cholera is caused by the marine bacterium Vibrio cholerae. A type VI secretion system (T6SS), which is structurally similar to the bacteriophage cell-puncturing device, has been recently identified in V. cholerae and is used by this organism to confer virulence toward phagocytic eukaryotes, such as J774 murine macrophages and Dictyostelium discoideum. We tested the interbacterial virulence of V. cholerae strain V52, an O37 serogroup with a constitutively active T6SS. V52 was found to be highly virulent toward multiple Gram-negative bacteria, including Escherichia coli and Salmonella Typhimurium, and caused up to a 100,000-fold reduction in E. coli survival. Because the T6SS-deficient mutants V52ΔvasK and V52ΔvasH showed toxicity defects that could be complemented, virulence displayed by V. cholerae depends on a functional T6SS. V. cholerae V52 and strains of the O1 serogroup were resistant to V52, suggesting that V. cholerae has acquired immunity independently of its serogroup. We hypothesize that the T6SS, in addition to targeting eukaryotic host cells, confers toxicity toward other bacteria, providing a means of interspecies competition to enhance environmental survival. Thus, the V. cholerae T6SS may enhance the survival of V. cholerae in its aquatic ecosystem during the transmission of cholera and between epidemics.
霍乱这种急性腹泻疾病是由海洋细菌霍乱弧菌引起的。一种结构上类似于噬菌体细胞穿孔装置的 VI 型分泌系统（T6SS）最近在霍乱弧菌中被发现，并且该生物体利用该系统将毒性赋予吞噬真核生物，例如 J774 鼠巨噬细胞和盘基网柄菌。我们测试了霍乱弧菌 V52 菌株的细菌间毒性，V52 是 O37 血清群，具有组成型活性的 T6SS。发现 V52 对多种革兰氏阴性菌（包括大肠杆菌和鼠伤寒沙门氏菌）具有高度毒性，可导致大肠杆菌存活率降低 100000 倍。因为 T6SS 缺陷突变体 V52ΔvasK 和 V52ΔvasH 显示出可以互补的毒性缺陷，所以霍乱弧菌的毒性依赖于功能正常的 T6SS。V. cholerae V52 和 O1 血清群的菌株对 V52 具有抗性，表明霍乱弧菌已经独立于其血清群获得了免疫力。我们假设 T6SS 除了靶向真核宿主细胞外，还对其他细菌具有毒性，提供了一种种间竞争的手段，以增强环境生存能力。因此，霍乱弧菌的 T6SS 可能会增强霍乱弧菌在其水生态系统中的传播和流行之间的生存能力。
