Turbot (Scophthalmus maximus) culture has become one of the most commercial flatfish species for recirculating aquaculture in north China. The rapid expansion of intensive aquaculture increased the risk of disease outbreaks. Probiotics have attracted great interest due to their positive effects on host and are considered environmentally friendly alternatives to chemicals and vaccination to prevent infectious diseases. The present study was conducted to understand the effects of lactic acid bacteria screened from fishery catch as probiotics on growth, immune response and gut microbiome of S. maximus.
A four week experiment was conducted in a turbot recirculating culture system. Leuconostoc mesenteroides HY2 strain was administrated in juvenile turbot culture water. The mRNA levels of TLR3, CXCL8 and IFIH1 in different organs were analyzed using RT-PCR technology. The structure and diversity of intestinal flora were analyzed using 16sRNA technology, in which community composition and diversity indexes (Shannon, Simpson, abundance-based coverage estimator and Chao1), principal co-ordinates analysis (PCoA) as well as cluster analysis were performed.
The specific growth rate of turbot in L treatment was significantly higher (P<0.05) than in control. The expression levels of TLR3, IL-8 and IFIH1 were almost all significantly (P<0.05) up-regulated in intestine, liver, spleen, kidney, brain and skin in L treatment after four weeks culture (Fig. 1). A total of 42 phyla in intestinal flora were identified and its composition and biomarkers showed significant difference in two groups (Fig. 2). The administration of HY2 strain was capable of improving turbot growth by enhancing the immune system. Some bacteria groups in intestine acted as biomarkers indicating the variation of the structure and diversity of intestinal flora, which may help to promote absorption and/or trigger immune function.