An aerolysin-like enterotoxin from Vibrio splendidus may be involved in intestinal tract damage and mortalities in turbot, Scophthalmus maximus (L.), and cod, Gadus morhua L., larvae.
An aerolysin-like enterotoxin from Vibrio splendidus may be involved in intestinal tract damage and mortalities in turbot, Scophthalmus maximus (L.), and cod, Gadus morhua L., larvae.
复制标题
DOI：
10.1111/j.1365-2761.2011.01331.x
复制
发表时间：
2012-02
影响因子：
2.5
通讯作者：
H. L. Macpherson;Ø. Bergh;T. Birkbeck
中科院分区：
文献类型：
--
作者：
H. L. Macpherson;Ø. Bergh;T. Birkbeck
脾弧菌是一种病原体，当使用活饲料（轮虫或蒿）饲养幼虫时，可在早期阶段造成重大损失。由于溶血细菌经常与幼虫饲养损失有关，我们研究了脾弧菌溶血素在幼虫感染中的作用。从10000多个脾弧菌转座子突变体中，获得了两种不同类型的溶血素阴性突变体。两者都失去了对幼鱼的毒力，免疫组织化学表明，所研究的转座子突变体在大菱鲆幼鱼肠道中的定殖水平与野生型生物相似，但没有引起野生型生物的损伤或肠炎迹象。其中一个转座子插入位点位于一个与气溶素高度同源的基因中，气溶素是由几种气单胞菌产生的细胞溶解毒素。我们称之为弧菌气溶素的溶血素具有与气溶素相似的特性，渗透保护研究表明，它在红细胞膜上形成与气溶素相似直径的孔。第二个转座子突变体的Tn10插入位点位于相邻的toxr样基因中，表明这可能控制了弧菌溶气素的表达。气单胞菌引起的人类胃肠炎被认为是由于气溶素的产生引起胃肠道细胞中循环amp依赖性氯化物的分泌。对海鱼幼鱼肠道的损害可能以类似的方式发生，并且在幼鱼肠道发育中的细菌菌群中发现的几种弧菌可能会分泌类似溶气素的毒素，导致幼鱼在饲养早期死亡。建议对活饲料的血琼脂板进行常规细菌学筛查，并采取措施降低饲养系统中溶血细菌的浓度。
Vibrio splendidus is a pathogen that can cause major losses during the early stages of larval turbot rearing when live feed (rotifers or Artemia) is used. As haemolytic bacteria have often been associated with larval rearing losses, we studied the role of the V. splendidus haemolysin in infection of larvae. From a bank of over 10,000 transposon mutants of V. splendidus, two different types of haemolysin-negative mutants were obtained. Both had lost virulence for larval fish, and immunohistochemistry showed that the transposon mutant studied colonized the turbot larval intestinal tract at a similar level to the wild-type organism but did not cause damage or signs of enteritis found with the wild-type organism. One transposon insertion site was located within a gene with high homology to aerolysin, the cytolytic toxin produced by several Aeromonas spp. The haemolysin, which we have termed vibrioaerolysin, had properties similar to aerolysin and osmotic protection studies showed that it formed pores in the membranes of erythrocytes of similar diameter to those of aerolysin. The Tn10 insertion site of the second transposon mutant was in an adjacent ToxR-like gene, suggesting that this might control expression of the vibrioaerolysin. The gastroenteritis caused by Aeromonas spp. in humans is considered to be due to production of aerolysin causing cyclic AMP-dependent chloride secretion in cells of the gastrointestinal tract. Damage to the intestinal tract of marine fish larvae could occur in a similar way, and it is possible that several Vibrio spp. found in the developing bacterial flora of the larval fish gut can secrete aerolysin-like toxins leading to death of larvae in the early rearing stages. Routine bacteriological screening on blood agar plates of live feed is recommended with measures to reduce the concentrations of haemolytic bacteria in rearing systems.