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

Abstract:

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.