A Meta-Transcriptomics Survey Reveals Changes in the Microbiota of the Chinese Mitten Crab Eriocheir sinensis Infected with Hepatopancreatic Necrosis Disease.

Huaishun Shen,Yanan Zang,Yuanchao Ma,Ali Serwadda,Kun Song,Tianhao Dai

doi:10.3389/fmicb.2017.00732

Abstract

Infection of the freshwater Chinese mitten crab Eriocheir sinensis with hepatopancreatic necrosis disease (HPND) has been a major problem in the crab-cultivated Chinese Province of Jiangsu since 2015. To explore the etiology of HPND, meta-transcriptomic libraries of the hepatopancreata from crabs with and without HPND were constructed. Comparison analyses showed that there were no statistically significant differences in viral and microsporidial communities in the hepatopancreata of diseased and healthy crabs. Bacteroidetes, Proteobacteria, and Firmicutes were the most dominant bacterial phyla in the hepatopancreata of healthy crabs, with a combined prevalence of 93%. However, a decrease in bacterial diversity and a striking shift in the microbial composition were found in the hepatopancreata of crabs infected with HPND. Tenericutes was the most prevalent bacterial phylum in diseased crabs (31.82%), whereas its prevalence was low in healthy crabs (0.02%). By contrast, the prevalence of Bacteroidetes was significantly lower in crabs with HPND (3.49%) than in crabs without HPND (41.04%). We also found that the prevalence of Actinobacteria was higher in crabs with HPND (16.70%) than in crabs without the disease (4.03%). The major bacterial family within the Tenericutes phylum in crabs with HPND was detected by polymerase chain reaction and determined to be Mycoplasmataceae. In conclusion, there were striking changes in the microbiota of diseased and healthy crabs. Specifically, the prevalence of bacteria belonging to Tenericutes and Actinobacteria phyla increased, whereas the prevalence of bacteria belonging to the Bacteroidetes phylum decreased in crabs with HPND, clearly pointing to an association with HPND.

Highlights

The freshwater Chinese mitten crab E. sinensis is an economically important crustacean cultured in the Chinese provinces of Jiangsu, Anhui, Hubei, and Liaoning (Shen et al, 2014)
Considering that RNA viruses can associate with certain diseases in E. sinensis (Zhang et al, 2004; Zhang and Bonami, 2007, 2012; Shen et al, 2015), and microsporidia were found in crabs infected with hepatopancreatic necrosis disease (HPND) (Ding et al, 2016), we analyzed the meta-transcriptomes of hepatopancreata from crabs with and without HPND to identify potential pathogens from viruses, bacteria, and eukaryotes
There was no significant difference in the virome of both groups, we identified a new nodavirus, which was more abundant in the hepatopancreata of diseased crabs than in healthy crabs

Summary

Introduction

The freshwater Chinese mitten crab E. sinensis is an economically important crustacean cultured in the Chinese provinces of Jiangsu, Anhui, Hubei, and Liaoning (Shen et al, 2014). Hepatopancreatic necrosis disease (HPND, “shuibiezi” in Chinese), which affects E. sinensis, has been a major problem in the crab-cultivated area of Jiangsu Province since 2015. The majority of the diseased crabs do not die immediately; instead, they continue to molt, albeit at a later stage of breeding. These crabs are of little/no economic value, and they eventually die. A previous study reported that microsporidia were detected in the hepatopancreata of crabs infected with HPND (Ding et al, 2016).

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Conclusion