A Functional Reciprocal Relationship Between the Host Defense Mechanisms of Oysters and the Bio-control Methods for Protection of Bacillary Necrosis of Larval Oysters Caused by Pathogenic Vibrio Species

在本研究中，作者确定并讨论了巨型太平洋牡蛎（Crassostrea gigas）宿主防御过程与保护致病性弧菌引起的牡蛎幼虫细菌性坏死的生物防治方法之间的功能互惠关系。在许多双壳类软体动物的孵化场，大量的幼虫死亡往往是由海洋弧菌物种感染引起的。感染的幼虫表现出典型的细菌性坏死，包括异常游动和纤毛和绒毛脱落。因此，认为致病性弧菌菌株产生的蛋白酶在细菌性坏死的发病机制中起主要作用。使用抗生素已被证明是控制这种疾病和提高牡蛎幼虫存活率的有效方法。然而，不建议使用抗生素治疗，因为抗生素会影响培养海水中的细菌菌群，也会导致r…更具耐药性的致病菌的表达。因此，为了开发抗生素的替代方法来预防细菌性坏死，作者研究了卵大球蛋白对巨型太平洋牡蛎幼虫存活的影响。卵大球蛋白是母鸡蛋清中的一种糖蛋白，众所周知，它能结合并强烈抑制蛋白酶的数量。作者还研究了有潜力作为弧菌感染生物防治剂的菌株的使用。用致病性管氏弧菌（ATCC19106）感染太平洋牡蛎幼虫。tubiashii对牡蛎幼虫具有很强的致病性，在10^5 cfu（菌落形成单位）/ml浓度下实验暴露24 h后死亡率为100%。与此相反，以10^5 cfu/ml的浓度攻毒牡蛎幼虫，在感染24 h后，添加浓度为10 μg/ml的卵巨球蛋白可使其存活率显著提高96.5%。卵巨球蛋白组活幼虫运动活跃，纤毛和绒毛未坏死。卵巨球蛋白的添加明显抑制了明胶-海水培养液中管氏弧菌的生长，但孵育24 h后管氏弧菌的活菌数没有下降到初始剂量水平。本研究结果表明，卵巨球蛋白通过非杀菌性抑制结核分枝杆菌的生长，几乎完全保护了牡蛎幼虫免受结核分枝杆菌感染，而不影响牡蛎的存活。少

In the present study, the author determined and discussed a functional reciprocal relationship between the host defense process of the giant Pacific oyster, Crassostrea gigas, and the bio-control methods for protection of bacillary necrosis of larval oysters caused by pathogenic Vibrio species. In many hatcheries of bivalve molluscs, mass larval mortalities often induced by marine Vibrio species infections have been reported. Infected larvae showed typical cases of bacillary necrosis including anomalous swimming and the detachment of cilia and vela. As a result, it is considered that proteases produced by the pathogenic Vibrio strains play a major role in the pathogenesis of bacillary necrosis. The use of antibiotics has been shown to be an effective method for controlling this disease and improving the survival of larval oysters. However, antibiotic treatment is not recommended because it is can affect bacterial flora in the culture sea water and can also result in the expression of r … More esistant pathogenic bacteria. Therefore, in order to develop altenative methods to antibiotics for preventing bacillary necrosis, the author examined the effects of ovomacroglobulin, which is a glycoprotein in the hen's egg whites and is well known to bind and inhibit strongly the number of proteases, on the larval survival of the giant Paciftc oyster. The author also investigated the use of bacterial strains that have potentiality as bio-control agents for Vibrio infection. The pathogenic Vibrio tubiashii (ATCC19106) was used to infect larvae of the Pacific oyster. V. tubiashii showed strong pathogenicity to oyster larvae, causing 100 % mortality aftar experimental exposure for 24 h at a concentration of 10^5 cfu (colony-forming units)/ml. In contrast, the addition of ovomacroglobulin at a concentration of 10 μg/ml to larval oysters, challenged with V. tubiashii at 10^5 cfu/ml, led to a marked increase in larval survivel of 96.5% at 24 h after infection. Live larvae were actively motile, and their cilia and vela were not necrotized in the ovomacroglobulin-added group. The addition of ovomacroglobulin clearly suppressed the growth of V. tubiashii in gelatin-seawater broth, but the number of viable V. tubiashii 24 h after incubation did not decrease to the initial dose level. Findings obtained in this study indicate that ovomacroglobulin almost completely protect larval oysters from V. tubiashii infection by non-bactericidally inhibiting the growth of V. tubiashii without affecting the survival of the oysters. Less