Zhu Fang-Chao, Lian Chun-Ang, He Li-Sheng
Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China.
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 101408, China.
Microorganisms. 2020 Nov 27;8(12):1874. doi: 10.3390/microorganisms8121874.
Intestinal bacterial communities are highly relevant to the digestion, nutrition, growth, reproduction, and immunity of animals, but little is known about the composition and function of intestinal microbiota in deep-sea invertebrates. In this study, the intestinal microbiota of six holothurian were investigated, showing that their midguts were predominantly occupied by Izemoplasmatales bacteria. Using metagenomic sequencing, a draft genome of 1,822,181 bp was successfully recovered. After comparison with phylogenetically related bacteria, genes involved in saccharide usage and de novo nucleotide biosynthesis were reduced. However, a set of genes responsible for extracellular nucleoside utilization and 14 of 20 amino acid synthesis pathways were completely retained. Under oligotrophic condition, the gut-associated bacterium may make use of extracellular DNA for carbon and energy supplement, and may provide essential amino acids to the host. The clustered regularly interspaced short palindromic repeat (CRISPR) and restriction-modification (RM) systems presented in the genome may provide protection against invading viruses. A linear azol(in)e-containing peptide gene cluster for bacteriocin synthesize was also identified, which may inhibit the colonization and growth of harmful bacteria. Known virulence factors were not found by database searching. On the basis of its phylogenetic position and metabolic characteristics, we proposed that the bacterium represented a novel genus and a novel family within the Izemoplasmatales order and suggested it be named " Bathyoplasma sp. NZ". This was the first time describing host-associated Izemoplasmatales.
肠道细菌群落与动物的消化、营养、生长、繁殖和免疫密切相关，但对于深海无脊椎动物肠道微生物群的组成和功能却知之甚少。在本研究中，对六种海参的肠道微生物群进行了调查，结果表明它们的中肠主要被伊泽支原体目细菌占据。通过宏基因组测序，成功获得了一个1,822,181 bp的基因组草图。与系统发育相关细菌进行比较后发现，参与糖类利用和从头核苷酸生物合成的基因减少。然而，一组负责细胞外核苷利用的基因以及20种氨基酸合成途径中的14种被完全保留。在贫营养条件下，肠道相关细菌可能利用细胞外DNA补充碳源和能量，并可能为宿主提供必需氨基酸。基因组中呈现的成簇规律间隔短回文重复序列（CRISPR）和限制修饰（RM）系统可能提供针对入侵病毒的保护。还鉴定出一个用于合成细菌素的含线性氮杂环丁烷肽基因簇，其可能抑制有害细菌的定殖和生长。通过数据库搜索未发现已知的毒力因子。基于其系统发育位置和代谢特征，我们提出该细菌代表伊泽支原体目内的一个新属和一个新科，并建议将其命名为“Bathyoplasma sp. NZ”。这是首次描述与宿主相关的伊泽支原体目。
