The influence of surface proteins on the probiotic effects of Lactobacillus pentosus HC-2 in the Litopenaeus vannamei hepatopancreas

Unveiling the Bacterial Community across the Stomach, Hepatopancreas, Anterior Intestine, and Posterior Intestine of Pacific Whiteleg Shrimp

The gastrointestinal (GI) tract of shrimp, which is comprised of the stomach, hepatopancreas, and intestine, houses microbial communities that play crucial roles in immune defense, nutrient absorption, and overall health. While the intestine's microbiome has been well-studied, there has been limited research investigating the stomach and hepatopancreas. The present study addresses this gap by profiling the bacterial community in these interconnected GI segments of Pacific whiteleg shrimp. To this end, shrimp samples were collected from a local aquaculture farm in South Korea, and 16S rRNA gene amplicon sequencing was performed. The results revealed significant variations in bacterial diversity and composition among GI segments. The stomach and hepatopancreas exhibited higher Proteobacteria abundance, while the intestine showed a more diverse microbiome, including Cyanobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Chloroflexi, and Verrucomicrobia. Genera such as Oceaniovalibus, Streptococcus, Actibacter, Ilumatobacter, and Litorilinea dominated the intestine, while Salinarimonas, Sphingomonas, and Oceaniovalibus prevailed in the stomach and hepatopancreas. It is particularly notable that Salinarimonas, which is associated with nitrate reduction and pollutant degradation, was prominent in the hepatopancreas. Overall, this study provides insights into the microbial ecology of the Pacific whiteleg shrimp's GI tract, thus enhancing our understanding of shrimp health with the aim of supporting sustainable aquaculture practices.

Rhodobacter azotoformans supplementation improves defense ability of Chinese mitten crab Eriocheir sinensis against citrobacteriosis

Rhodobacter probiotics are considered as good alternatives to antibiotics for aquaculture. Yet the beneficial effects of Rhodobacter on Chinese mitten crab Eriocheir sinensis are still unclear, and more functions of Rhodobacter supplementation need to be clarified. In this study, a 60-day feeding trial was performed to investigate the protective effects of R. azotoformans against citrobacteriosis in E. sinensis by growth performance, serum immunity, hepatopancreatic antioxidant capability, intestinal flora, and resistance to Citrobacter freundii challenge assays. The results showed that R. azotoformans supplementation significantly and dose-dependently increased weight gain and specific growth rate as well as activities of serum immune and hepatopancreatic antioxidant enzymes, leading to notable improvement in the growth performance, serum immunity and hepatopancreatic antioxidant status of E. sinensis. Besides, R. azotoformans supplementation significantly enhanced intestinal microbial abundance and diversity in E. sinensis, and conferred significant protection of the crabs against C. freundii challenge with seven-day survival rates of 70.0%-100.0%. To the best of our knowledge, this is the first study to reveal the protective effects of R. azotoformans against citrobacteriosis in E. sinensis.

Lactobacillus acidophilus and L. plantarum improve health status, modulate gut microbiota and innate immune response of marron (Cherax cainii)

This study aimed to investigate the combined effects of two most potent probiotic bacteria Lactobacillus acidophilus and Lactobacillus plantarum on overall health and immune status of freshwater crayfish, marron under laboratory conditions. A total of 36 marron were distributed into six different tanks and two different feeding groups, control and probiotic-fed group. After acclimation, control group was fed with basal diet while probiotic group was fed 109 CFU/mL per kg of bacterial supplemented feed for 60 days. The results showed no significant differences in weight gain, however, probiotic feed significantly enhanced some hemolymph parameters and biochemical composition of tail muscle. Histology data revealed better hepatopancreas health and higher microvilli counts in the marron gut fed probiotic diet. The probiotic bacteria triggered significant shift of microbial communities at different taxa level, mostly those reported as beneficial for crayfish. The probiotic diet also enriched the metabolic functions and genes associated with innate immune response of crayfish. Further correlation analysis revealed significant association of some taxa with increased activity for hemolymph and immune genes. Therefore, dietary Lactobacillus supplementation can modulate the overall health and immunity as well as gut microbial composition and interaction network between gut microbiota and immune system in crayfish.