Comparison between the gut microbiome of healthy fish and fish experimentally infected with Streptococcus agalactiae

Author(s)

Bruna Rafaela dos Santos Silva

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2020-02-07

Examining board members

Wanderley Dias da Silveira; Gerson Nakazato; José Luiz Proença Módena

• Advisor: Wanderley Dias da Silveira

Abstract

The pathogen Streptococcus agalactiae is a microorganism associated to fish disease, both in freshwater and seawater. Septicemia due to S. agalactiae is one of the major diseases affecting Nile tilapia (Oreochromis niloticus) husbandry. In this study, we compared the intestinal microbiome of healthy fish (n = 27) and fish experimentally infected with S. agalactiae (n = 28). For both groups, bacteria attached to the mucosa (M) and free in feces (F) were analyzed. The microbiome was established with 16S rRNA next-generation sequencing (NGS). The average number of taxa detected in the infected group (M + F) was lower (45.87 ± 30.13) than in the control group (M + F) (67.70 ± 21.10) (p <0.01). Combined analysis of mucosa and feces and isolated analysis of feces only or mucosa only revealed OTUs more associated with samples from infected animals when compared to healthy animals. The number of taxa associated with the infected group ranged from 19 to 61. When comparing the fecal and mucosa samples combined and fecal samples only, the genus Streptococcus was more than 4,000 times more abundant in the infected group compared to the healthy group. However, such genus was only about 500 times more abundant in mucosa samples. The taxon Lactobacillus, also associated with the infected group, had similar abundances in all sample categories, ranging from 249.2 to 524.37. The genus Pleisomonas showed a similar profile in the various categories of samples, with abundances ranging from 9.01 to 12.3 times. The results demonstrate that S. agalactiae infection reduces the intestinal microbiota variability. Furthermore, some microorganisms as Streptococcus, Lactobacillus and Pleisomonas proliferate in this situation (AU)

• FAPESP's process: 17/22288-7 - Comparison between the gut microbiome of healthy fish and fish experimentally infected with Streptococcus agalactiae
• Grantee: Bruna Rafaela dos Santos Silva
• Support Opportunities: Scholarships in Brazil - Master