Faculty of Biosciences and Aquaculture, Bodø University College, 8049, Bodø, Norway.
Fish Physiol Biochem. 2010 Dec;36(4):883-91. doi: 10.1007/s10695-009-9364-0. Epub 2009 Oct 21.
This study identified phytase-producing bacteria that were previously isolated from the gastrointestinal tract of Atlantic cod, Gadus morhua and determined its effect on head kidney leukocytes. Out of the 216 bacterial strains tested, the two phytase producers were identified as Pseudomonas sp. and Psychrobacter sp. based on their 16S rDNA sequence. Crude phytase from these two bacterial strains was produced employing the shake flask method. Even though the total protein of the crude phytase was not significantly different for the two bacteria, the phytase activity of the crude enzyme produced by Pseudomonas sp. (97.1±16.7 U) was significantly higher than that of the enzyme from Psychrobacter sp. (75.9±2.4 U). When cod head kidney leukocytes were incubated with the crude phytase (50 μg ml(-1)), it resulted in enhanced cell proliferation, higher myeloperoxidase, and acid phosphatase activities. Extracellular responses-respiratory burst activity and hydrogen peroxide production were not enhanced by the crude enzyme. As a consequence, the growth of two pathogenic bacteria Aeromonas salmonicida and Vibrio anguillarum was not suppressed by the supernatants obtained from head kidney leukocytes incubated with the crude bacterial phytase. Thus, the enzyme from phytase-producing intestinal bacteria of Atlantic cod can stimulate intracellular head kidney leukocyte activities but not the production of extracellular substances that are involved in antibacterial response. These have implications on the potential use of bacterial phytase as feed supplement to boost cellular immune response of the fish and could be employed as a health management strategy in culture systems.
本研究从大西洋鳕鱼（Gadus morhua）的胃肠道中分离出了产植酸酶的细菌，并确定了其对头肾白细胞的影响。在测试的 216 株细菌中，根据 16S rDNA 序列，将两种产植酸酶的细菌鉴定为假单胞菌和Psychrobacter 菌。采用摇瓶法生产这两种细菌的粗植酸酶。尽管两种细菌的粗植酸酶总蛋白没有显著差异，但假单胞菌产生的粗酶的植酸酶活性（97.1±16.7 U）明显高于 Psychrobacter 菌（75.9±2.4 U）。当用粗植酸酶（50 μg ml(-1))孵育鳕鱼头肾白细胞时，细胞增殖增强，髓过氧化物酶和酸性磷酸酶活性更高。粗酶未增强细胞外反应-呼吸爆发活性和过氧化氢产生。因此，从用粗菌植酸酶孵育的头肾白细胞获得的上清液并未抑制两种致病性细菌鲑鱼气单胞菌和鳗弧菌的生长。因此，来自大西洋鳕鱼肠道产植酸酶的细菌的酶可以刺激细胞内头肾白细胞的活性，但不能刺激参与抗菌反应的细胞外物质的产生。这对细菌植酸酶作为饲料添加剂增强鱼类细胞免疫反应的潜在用途具有重要意义，并可作为养殖系统中的一种健康管理策略。
