Huddy Robert J, Coyne Vernon E
Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa.
PLoS One. 2014 Jan 22;9(1):e86623. doi: 10.1371/journal.pone.0086623. eCollection 2014.
Probiotics have been widely reported to increase the growth rate of commercially important fish and shellfish by enhancing the digestion of ingested feed through the production of extracellular enzymes such as proteases and alginases. In order to investigate this further, the objective of this study was to localise the bacterial probiont Vibrio midae SY9 and one of the extracellular proteases it produces in the digestive tract of the South African abalone Haliotis midae. This was accomplished by inserting a promotorless gfp gene into the chromosome of the bacterium which was incorporated in an artificial, fishmeal-based abalone feed. In situ histological comparison of abalone fed either a basal diet or the basal diet supplemented with V. midae SY9::Tn10.52 using a cocktail of DNA probes to the gfp gene localised the probiont to the crop/stomach and intestinal regions of the H. midae digestive tract. Generally, the ingested probiotic bacterium occurred in association with feed and particulate matter within the crop/stomach and intestinal regions, as well as adhered to the wall of the crop/stomach. Histological immunohistochemical examination using polyclonal anti-VmproA antibodies localised an extracellular protease produced by V. midae SY9 to the H. midae crop/stomach and intestine where it appeared to be associated with feed and/or other particulate matter in the abalone gut. Thus the data suggests that V. midae SY9 colonises and/or adheres to the mucous lining of the abalone gut. Furthermore, the close association observed between the bacterium, its extracellular protease and ingested feed particles supports the theory that V. midae SY9 elevates in situ digestive enzyme levels and thus enhances feed digestion in farmed abalone.
益生菌已被广泛报道可通过产生胞外酶（如蛋白酶和藻酸酶）增强摄入饲料的消化，从而提高具有商业重要性的鱼类和贝类的生长速度。为了进一步研究这一点，本研究的目的是在南非鲍鱼（Haliotis midae）的消化道中定位益生菌米氏弧菌（Vibrio midae）SY9及其产生的一种胞外蛋白酶。这是通过将无启动子的绿色荧光蛋白（gfp）基因插入该细菌的染色体来实现的，该细菌被掺入基于鱼粉的人工鲍鱼饲料中。使用针对gfp基因的DNA探针混合物，对喂食基础饲料或添加了米氏弧菌SY9::Tn10.52的基础饲料的鲍鱼进行原位组织学比较，将益生菌定位到南非鲍鱼消化道的嗉囊/胃和肠道区域。一般来说，摄入的益生菌与嗉囊/胃和肠道区域内的饲料和颗粒物相关联，并且附着在嗉囊/胃壁上。使用多克隆抗VmproA抗体进行的组织学免疫组化检查将米氏弧菌SY9产生的一种胞外蛋白酶定位到南非鲍鱼的嗉囊/胃和肠道，在那里它似乎与鲍鱼肠道中的饲料和/或其他颗粒物相关联。因此，数据表明米氏弧菌SY9定殖和/或附着在鲍鱼肠道的黏液内衬上。此外，观察到的细菌、其胞外蛋白酶和摄入的饲料颗粒之间的紧密关联支持了这样一种理论，即米氏弧菌SY9提高了原位消化酶水平，从而增强了养殖鲍鱼的饲料消化。
