The influence of weight and gender on intestinal bacterial community of wild largemouth bronze gudgeon (Coreius guichenoti, 1874)

Li et al. BMC Microbiology (2016) 16:191 DOI 10.1186/s12866-016-0809-1 RESEARCH ARTICLE Open Access The influence of weight and gender on intestinal bacterial community of wild largemouth bronze gudgeon (Coreius guichenoti, 1874) Xuemei Li1, Qingyun Yan2, Einar Ringø3, Xingbing Wu1, Yongfeng He1 and Deguo Yang1* Abstract Background: Largemouth bronze gudgeon (Coreius guichenoti) is of economic importance in China, distributed in upstream regions of the Yangtze River in China. But it has recently dramatically declined and is close to elimination. However, there is little knowing about the character of its intestinal microbiota. This study was conducted to elucidate the intestinal microbiota of wild largemouth bronze gudgeon with different body weight and gender. Results: Thirty wild largemouth bronze gudgeon were measured for body length and body weight, and identified for male and female according to gonadal development, and thereafter the intestinal microbiota’s were assessed by MiSeq sequencing of 16S rRNA genes. The results revealed that phyla Proteobacteria and Tenericutes were dominant in wild largemouth bronze gudgeon intestine independent of the body weight. Shannon’s and Inverse Simpson’s diversity indexes were significant (P < 0.05) different between male and female fish. The phylum profile in the intestine of male fish revealed that phylum Proteobacteria was dominant, in contrast to female fish where five phyla Tenericutes, Proteobacteria, Firmicutes, Fusobacteria and Spirochaetes were dominant. The genus profile revealed that genera Shewanella and Unclassified bacteria were dominant in male fish, while genus Mycoplasma was dominant in female fish. Conclusions: Our results revealed that the intestinal microbial community of wild largemouth bronze gudgeon was dominated by the phyla Proteobacteria and Tenericutes regardless of the different body weight, but the communities are significant different between male and female fish. These results provide a theoretical basis to understand the biological mechanisms relevant to the protection of the endangered fish species. Keywords: Coreius guichenoti, Intestinal microbiota, Fish gender, Yangtze River Background Largemouth bronze gudgeon (Coreius guichenoti, Sauvage et Dabry, 1874) is a freshwater fish of the Cyprinidae family, distributed in upstream regions of the Yangtze River. It is of economic importance in China and the largest weight they can reach is 4.0 kg [1, 2]. The fish species is benthic and potamodromous and is typically found in river with torrential flow and they always live in cluster and produce * Correspondence: 1 Key Laboratory of Freshwater Biodiversity Conservation, Ministry of Agriculture of China Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, No.8, 1st Wudayuan Road, Donghu Hi-Tech Development Zone, Wuhan, Hubei 430223, China Full list of author information is available at the end of the article pelagic eggs in flows from March to June every year [3]. However, the species has recently dramatically declined and is close to elimination [4] due to overfishing and construction of hydroelectrically projects, which have blocked the migration routes, causing habitat fragmentation, and losses of spawning grounds and habitat destruction [5, 6]. Over the recent years, the development of omics technologies has boosted our insights on the structure and function of the complex gastrointestinal (GI) microbiota of fish [7–11]. It has been revealed that colonization of microorganisms in the GI tract of fish results in the establishment of a symbiotic relationship between the host and gut microbiota [10, 12], and the fish GI microbiota © 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Li et al. BMC Microbiology (2016) 16:191 can contribute to nutrition, health and development [13–15]. In addition, the GI microbiota is important in the defense against adhesion and colonization of pathogenic bacteria [16, 17]. The shaping of the fish intestinal microbiota is a complex process, and a number of factors have been reported to modulate its composition, e.g. host genetics, developmental stage, gut structure, environmental factors, diet and dietary components [10, 12, 18, 19]. However, no information is available on the intestinal microbiota of largemouth bronze gudgeon, a fish species of economic importance in of the Yangtze River. The ongoing positive growth trend of the ecological protection and species conservation is expected to continue, reflecting the rising demand for largemouth bronze gudgeon rearing in indoor tanks to carry artificial reproduction. Considering the important roles of intestinal microbiota during fish life, the aims of the present study were to elucidate the intestinal bacterial community of wild caught male and female largemouth bronze gudgeon with different body weight from Yangtze River by sequencing of 16S rRNA genes. The evaluation of sex-dependent effects the gut microbiota is of importance to study as less information is available on aquatic animal [20] compared to endothermic animals [21–24]. The results of the present study may be vital for successful propagation of the fish in indoor artificial culture as well as the influence of gender on drug delivery as discussed by Freire et al. [25]. Results We obtained 963,883 valid sequences from the 30 fish intestines. After quality filtering and normalization; totally 672,240 high-quality bacterial sequences were obtained, equivalent to an average of 22,408 reads per Page 2 of 8 sample, when representative sequences were classified using RDP classifier. We calculated the number of operational taxonomical units (OTUs), and they were analyzed for each sample with a 97 % sequence similarity cutoff value. Figure 1 shows the rarefaction curve at an OTU definition of 97 % identity. The Good’s coverage of the four samples ranged from 99.70 to 99.86 % (Table 1). Intestinal microbial community in fish with different body weight To provide an overview of the sequence reads associated with wild caught largemouth bronze gudgeon intestine, the 30 samples were divided into three groups according to fish body weight: large fish (>2 kg, 4 samples), medium fish (between 1 and 2 kg, 17 samples) and small fish (<1 kg, 9 samples). In small fish, the Shannon and Inverse Simpson diversity indexes were 0.38 ± 0.21 and 0.21 ± 0.14, respectively, while the indexes were (...truncated)