Alterations of the gut microbiome of largemouth bronze gudgeon (Coreius guichenoti) suffering from furunculosis.

Yuanli Zhao,Cheng Ji,Tongtong Li,Lanli Zhang,Xujie Zhang,François-Joël Gatesoupe,Qianqian Zhang,Zhixin Shen,Meng Long,Xinhua Liu,Aihua Li

doi:10.1038/srep30606

Abstract

High-throughput sequencing was applied to compare the intestinal microbiota in largemouth bronze gudgeon either healthy or affected by furunculosis. Proteobacteria, Actinobacteria, Tenericutes, Firmicutes and Bacteroidetes were detected as the predominant bacterial phyla in the gut of both diseased and healthy fish. The abundance of Proteobacteria differed significantly between the two groups of fish, mainly due to the overwhelming prevalence of Aeromonas in the diseased fish (81% ± 17%), while the genus was unevenly spread among the apparently healthy fish (33% ± 33%). The bacterial diversity in the intestine of diseased fish was markedly lower than in healthy fish. Analysis revealed the significant dissimilarity between the gut microbiota of diseased and healthy fish. The bacterial profiles in the gut were further characterized with the 28 phylotypes that were shared by the two groups. In diseased fish, two shared OTUs (OTU0001 and OTU0013) were closely related to Aeromonas salmonicida, their total proportion exceeding 70% of the sequences in diseased fish, while averaging 5.2% ± 4.6% in the healthy fish. This result suggested the presence of healthy carriers of pathogenic A. salmonicida among the farmed fish, and the gut appeared as a probable infection source for furunculosis in largemouth bronze gudgeon.

Highlights

Gut microbiota can play important roles in nutrition and health, and it may be considered as an integral component of the host[1,2,3,4]
The importance of the intestinal tract as infection source in fish was previously evidenced in the case of motile Aeromonas septicemia, as the pathogenic clone of Aeromonas hydrophila that caused the disease was detected in the intestine before systemic infection[23]
The first issue was to compare the relative abundances of gut bacteria in diseased and healthy fish, in view to evaluate the changes in microbiota that may be caused by the disease

Summary

Introduction

Gut microbiota can play important roles in nutrition and health, and it may be considered as an integral component of the host[1,2,3,4]. Recent studies have revealed the important contributions of gut microbiota to vertebrate health and disease, stimulating the interest in understanding how gut microbial communities are assembled and how they impact host fitness[8]. Other studies have reported that this bacterium could infect non-salmonid fishes[19,20,21,22] This infection has been diagnosed in largemouth bronze gudgeon (unpublished data), and it might cause the disease outbreaks that decimated the natural population. The prevention of this widespread disease was difficult due to the lack of knowledge about the infection sources and routes, and further investigation in this area is of the utmost importance. Zebrafish were challenged with bacterial isolates corresponding to the pathogenic phylotypes to assess virulence, and to check the reproducibility of furunculosis symptoms

Objectives

Methods

Results

Conclusion