Title : New insights into beta glucan enhanced immunity in largemouth bass by transcriptome and intstinal microbial composition
Abstract:
b-glucan is widely used in aquaculture due to its immunostimulatory effects, but the specific effect and potential regulatory mechanism on largemouth bass (Micropterus salmoides) are still unclear. Here, we evaluated the effects of bglucan on growth, resistance to Aeromonas schubertii, intestinal health, and transcriptome of largemouth bass to reveal the potential regulators, metabolic pathways, and altered differential microbiota. Four experimental diets were designed with b-glucan supplementation levels of 0 (control), 100 (LA-100), 200 (MA-200), and 300 (HA-300) mg kg-1, and each diet was fed to largemouth bass (79.30 ± 0.50 g) in triplicate for 70 days, followed by a 3-day challenge experiment. Results showed that different b-glucan supplementations had no significant effects on growth performance and whole-body composition. Fish fed a diet with 300 mg kg-1 b-glucan significantly increased the activity of lysozyme than those fed diets with 0 and 100 mg kg-1 b-glucan. In addition, the survival rate of largemouth bass in b-glucan supplementation groups was significantly higher than the control group at 12- and 24-h challenge by Aeromonas schubertii. Transcriptome analysis showed that a total of 1,245 genes were differentially expressed [|log2(fold change)| ≥1, q-value ≤0.05], including 109 immune-related differentially expressed genes (DEGs). Further analysis revealed that significantly upregulated and downregulated DEGs associated with immunity were mapped into 12 and 24 pathways, respectively. Results of intestinal microflora indicated that fish fed a diet with 300 mg kg-1 b-glucan had higher bacterial richness and diversity as evaluated by Sobs, Chao, Ace, and Simpson indices, but no significant differences were found in the comparison groups. Furthermore, 300 mg kg-1 b-glucan significantly increased the relative abundance of Mycoplasma and decreased Frontiers in Immunology 01 frontiersin.org OPEN ACCESS EDITED BY Mingchun Ren, Freshwater Fisheries Research Center (CAFS), China REVIEWED BY Chang’An Wang, Heilongjiang River Fisheries Research Institute (CAFS), China Yishan Lu, Guangdong Ocean University, China *CORRESPONDENCE Bo Shi [email protected] SPECIALTY SECTION This article was submitted to Comparative Immunology, a section of the journal Frontiers in Immunology RECEIVED 01 November 2022 ACCEPTED 28 November 2022 PUBLISHED 14 December 2022 CITATION Zhang Y, Guo M, Li N, Dong Z, Cai L, Wu B, Xie J, Liu L, Ren L and Shi B (2022) New insights into bglucan-enhanced immunity in largemouth bass Micropterus salmoides by transcriptome and intestinal microbial composition. Front. Immunol. 13:1086103. doi: 10.3389/fimmu.2022.1086103 COPYRIGHT © 2022 Zhang, Guo, Li, Dong, Cai, Wu, Xie, Liu, Ren and Shi. This is an openaccess article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. TYPE Original Research PUBLISHED 14 December 2022 DOI 10.3389/fimmu.2022.1086103 Proteobacteria (mainly Escherichia-Shigella and Escherichia coli) and Bacillus anthracis in largemouth bass intestinal microflora. The findings of this study provided new insights that will be valuable in future studies to elucidate the mechanism of immunity enhancement by b-glucan.
Keywords: largemouth bass, b-Glucan, growth, immunity, Aeromonas schubertii
