凡纳滨对虾肠道铁载体高产菌株筛选与饲料添加应用效果的研究

Screening a high-yield intestinal iron carrier strain of Litopenaeus vannamei and effect of feed addition

中文关键词: 铁载体菌株  凡纳滨对虾  肠道菌群  消化酶活性  非特异性免疫

英文关键词: Siderophore strain  Litopenaeus vannamei  Intestinal flora  Digestive enzyme activity  Nonspecific immunity

中文摘要:

      本研究筛选了凡纳滨对虾(Litopenaeus vannamei)肠道铁载体高产菌株，并探究了饲料中添加铁载体高产菌株对凡纳滨对虾的生理功效。结果显示，从凡纳滨对虾肠道中筛选出一株铁载体产量高达74.87%的菌株SDVGH3，经鉴定属于泛菌属(Pantoea sp.)，产生的铁载体属于异羟肟酸型，该菌株无溶血性，对大部分抗生素敏感；优化了该菌株铁载体产量的培养条件：最适温度为28℃，pH为7.5，盐度为0，装液量为10 mL，Fe3+浓度为0.01 mmol/L；采用滤纸片扩散法检测了菌株抑制病原菌的特性，显示能抑制5种凡纳滨对虾致病菌。通过在饲料中添加SDVGH3菌液，凡纳滨对虾增重率和饲料利用率明显升高，血细胞数量、吞噬率和血浆酚氧化酶、抗菌活性均有不同程度的升高，副溶血弧菌(Vibrio parahaemolyticus)攻毒后，实验组的死亡率显著低于对照组，1010 CFU/g实验组的死亡率最低，为61.4%；添加107 CFU/g SDVGH3菌液处理组，凡纳滨对虾肠道菌群多样性显著提高，弧菌属(Vibrio sp.)在肠道菌群中所占比例明显下降。研究表明，铁载体高产菌株SDVGH3能明显促进凡纳滨对虾生长、免疫防御能力，增强肠道菌群健康，具有应用于水产养殖中的潜力。

英文摘要:

      In this study, a high-yielding siderophore strain, SDVGH3, was screened from the gut of Litopenaeus vannamei using a combination of the CAS plate method and liquid-phase detection. Strain SDVGH3 is a Pantoea sp. gram-negative, facultative anaerobe. The SDVGH3 colony was cream-yellow and round. The strain was non-hemolytic and sensitive to 18 antibiotics. The siderophore extracted by XAD-2 large-aperture resin adsorption belongs to the isohydroxamic acid type, and its yield reached 74.87%. The filter-paper method was used to test the antibacterial characteristics of the strain. The degree of inhibition of the five pathogenic bacteria of L. vannamei was as follows: Vibrio parahaemolyticus > V. harveyi > V. anguillarum > Staphylococcus aureus > V. alginolyticus. The optimal culture conditions of SDVGH3 are as follows: 10 mL of culture medium in a 50 mL triangle flask; concentration of Fe3+ in the medium of 0.01 mmol/L; salinity of 0; initial pH value of 7.5; and culture temperature of 28℃. This study investigated the effects of SDVGH3 bacterial solution at concentrations of 1010 and 107 CFU/g on growth performance, immune defense indices, and intestinal microflora of L. vannamei. The results show that feed supplemented with 1010 CFU/g SDVGH3 bacterial solution significantly promoted growth and enhanced the immune capacity of L. vannamei. The feed supplemented with 107 CFU/g SDVGH3 bacterial solution significantly increased the intestinal floral diversity of L. vannamei, and significantly decreased the proportion of Vibrio in the intestinal flora. The strain SDVGH3 screened in this study is part of the indigenous probiotics in the intestinal tract of L. vannamei and has an inhibitory effect on the main pathogenic bacteria of L. vannamei. The supplementation of feed with strain SDVGH3 can promote the growth of L. vannamei, improve its immune capacity, and improve its diversity of intestinal flora, providing a theoretical basis for the application of high-yielding siderophore strains in the culture of L. vannamei.