A new isolate of Streptomyces lateritius (Z1-26) with antibacterial activity against fish pathogens and immune enhancement effects on crucian carp (Carassius auratus)

The Streptomyces lateritius Z1-26 was isolated from soil samples which showed broad-spectrum antibacterial activity against a broad range of fish pathogens. The In Vivo Imaging System (IVIS) monitored that strain Z1-26 could survive and colonize in the gills and abdomen of crucian carp. The effects of dietary supplementation with strain Z1-26 were evaluated with respect to the growth performance, antioxidant capacity, and immune response of crucian carp. The results showed that the Z1-26-fed fish had a significantly higher growth rate than the fish fed the control diet. The immune and antioxidant parameters revealed that the non-specific immune indicators (AKP, SOD, and LZM) of the serum, the expression of immune-related genes (IgM, C3, and LZM), and antioxidant-related genes (Nrf2 and Keap1) of the immune organs were significantly increased, whereas the expression of pro-inflammatory factors (IL-1 beta, IL-8, and TNF-alpha) of the immune organs was significantly down-regulated in crucian carp fed strain Z1-26 compared with fish fed a control diet. Moreover, fish fed with Z1-26 supplemented diets showed a significantly improved survival rate after Aeromonas hydrophila infection. In addition, the whole genome analysis showed that strain Z1-26 possesses 28 gene clusters, including 6 polyketide synthetase (PKS), 4 non-ribosomal peptide-synthetase (NRPS), 1 bacteriocin, and 1 lantipeptide. In summary, these results indicated that strain Z1-26 could improve the growth performance and disease resistance in crucian carp, and has the potential to be developed as a candidate probiotics for the control of bacterial diseases in aquaculture.