U.S. Department of Agriculture, Agricultural Research Service, Dover, Delaware, USA.
Appl Environ Microbiol. 2012 Oct;78(20):7455-66. doi: 10.1128/AEM.01594-12. Epub 2012 Aug 17.
This study shows that naturally occurring Vibrio predatory bacteria (VPB) exert a major role in controlling pathogenic vibrios in seawater and shellfish. The growth and persistence of Vibrio parahaemolyticus and Vibrio vulnificus were assessed in natural seawater and in the Eastern oyster, Crassostrea virginica. The pathogens examined were V. vulnificus strain VV1003, V. parahaemolyticus O1:KUT (KUT stands for K untypeable), and V. parahaemolyticus O3:K6 and corresponding O3:K6 mutants deficient in the toxRS virulence regulatory gene or the rpoS alternative stress response sigma factor gene. Vibrios were selected for streptomycin resistance, which facilitated their enumeration. In natural seawater, oysters bioconcentrated each Vibrio strain for 24 h at 22°C; however, counts rapidly declined to near negligible levels by 72 h. In natural seawater with or without oysters, vibrios decreased more than 3 log units to near negligible levels within 72 h. Neither toxRS nor rpoS had a significant effect on Vibrio levels. In autoclaved seawater, V. parahaemolyticus O3:K6 counts increased 1,000-fold over 72 h. Failure of the vibrios to persist in natural seawater and oysters led to screening of the water samples for VPB on lawns of V. parahaemolyticus O3:K6 host cells. Many VPB, including Bdellovibrio and like organisms (BALOs; Bdellovibrio bacteriovorus and Bacteriovorax stolpii) and Micavibrio aeruginosavorus-like predators, were detected by plaque assay and electron microscopic analysis of plaque-purified isolates from Atlantic, Gulf Coast, and Hawaiian seawater. When V. parahaemolyticus O3:K6 was added to natural seawater containing trace amounts of VPB, Vibrio counts diminished 3 log units to nondetectable levels, while VPB increased 3 log units within 48 h. We propose a new paradigm that VPB are important modulators of pathogenic vibrios in seawater and oysters.
本研究表明，天然捕食性弧菌（VPB）在控制海水中和贝类中的致病性弧菌方面发挥着重要作用。在天然海水中和东方牡蛎（Crassostrea virginica）中评估了副溶血性弧菌和创伤弧菌的生长和持久性。检查的病原体是创伤弧菌菌株 VV1003、副溶血性弧菌 O1:KUT（KUT 代表不可分型）以及副溶血性弧菌 O3:K6 和相应的 O3:K6 突变体，它们缺乏 toxRS 毒力调节基因或 rpoS 替代应激反应 sigma 因子基因。弧菌被选择对链霉素产生抗性，这便于对其进行计数。在 22°C 下，天然海水中的牡蛎在 24 小时内生物浓缩了每种弧菌菌株；然而，72 小时后计数迅速降至接近可忽略的水平。在有或没有牡蛎的天然海水中，弧菌在 72 小时内减少了 3 个对数单位以上，接近可忽略的水平。ToxRS 和 rpoS 对弧菌水平均无显著影响。在高压灭菌海水中，副溶血性弧菌 O3:K6 在 72 小时内增加了 1000 倍。由于弧菌无法在天然海水中和牡蛎中持续存在，因此对水样进行了筛选，以在副溶血性弧菌 O3:K6 宿主细胞的草坪上检测捕食性弧菌。通过噬菌斑测定法和对来自大西洋、墨西哥湾和夏威夷海水的噬菌斑纯化分离物的电子显微镜分析，检测到了许多捕食性弧菌，包括蛭弧菌和类似生物（蛭弧菌和噬杆菌）和 Aeruginosavorus 样捕食性微弧菌。当将副溶血性弧菌 O3:K6 添加到含有痕量 VPB 的天然海水中时，弧菌数量减少了 3 个对数单位，达到不可检测的水平，而 VPB 在 48 小时内增加了 3 个对数单位。我们提出了一个新的范式，即 VPB 是海水中和牡蛎中致病性弧菌的重要调节剂。
