The Raw datasets of the study A novel two-component system MprA/B (MprA/B1) was involved in regulation of metabolism, antibiotics resistance and virulence in Nocardia seriolae

<em>Nocardia seriolae </em>is one of the most important bacterial pathogens in cultured fish, causing serious necrotic granulomas in tissues. As a Gram-positive bacterium belonging to the order Actinomycetales, the pathogenic mechanism of <em>N. seriolae </em>is complex and not well defined. Two-component systems (TCS) function as signal transducers in prokaryotes that respond to different environmental stimuli. In this study, a novel two-component system gene, <em>mprA/B</em> homolog (<em>mprA/B</em>1), was identified in <em>N. seriolae</em> and a double gene-deficient mutant was generated. The Δ<em>mprA/B</em>1 strain exhibited faster growth and a more turbid bacterial suspension in trypticase soy broth (TSB). Transmission electron microscopy revealed an extra irregular polysaccharide layer outside the cell wall in the Δ<em>mprA/B</em>1 strain. Moreover, the Δ<em>mprA/B</em>1 strain showed a significantly increased sensitivity to macrolides and rifampicin. In a cell line, both strains were able to invade and survive intracellularly and induce cell apoptosis, but the Δ<em>mprA/B</em>1 strain showed lower cell invasion and intracellular survival rates. In largemouth bass, the Δ<em>mprA/B</em>1 strain showed significantly less tissue bacterial load and attenuated virulence. RNA sequencing identified 492 upregulated and 851 downregulated genes in the Δ<em>mprA/B</em>1 strain, and the gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment showed that many upregulated genes were involved in sugar and amino acid metabolic processes, and many downregulated genes were involved in drug efflux pump and virulence factor. These findings provide functional insights into the role of MprA/B in <em>N. seriolae</em>.<br>

杀鱼诺卡氏菌（Nocardia seriolae）是养殖鱼类最重要的细菌性致病菌之一，可引发组织出现严重的坏死性肉芽肿。作为隶属于放线菌目（Actinomycetales）的革兰氏阳性菌，其致病机制复杂且尚未被完全阐明。双组分系统（Two-component systems, TCS）是原核生物中响应不同环境刺激的信号转导元件。本研究在杀鱼诺卡氏菌中鉴定出一种新型双组分系统基因——mprA/B同源基因（mprA/B1），并构建了该基因的双基因缺失突变株。ΔmprA/B1菌株在胰蛋白胨大豆肉汤（trypticase soy broth, TSB）中生长速度更快，菌液浊度更高。透射电子显微镜观察发现，ΔmprA/B1菌株的细胞壁外多出一层不规则的多糖层。此外，ΔmprA/B1菌株对大环内酯类药物及利福平的敏感性显著升高。在细胞系中，野生株与突变株均可侵入宿主细胞并在胞内存活，同时诱导细胞凋亡，但ΔmprA/B1菌株的细胞侵袭率与胞内存活率均更低。在大口黑鲈模型中，ΔmprA/B1菌株的组织载菌量显著降低，毒力减弱。RNA测序结果显示，ΔmprA/B1菌株中共鉴定出492个上调基因与851个下调基因；基因本体（Gene Ontology, GO）与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）通路富集分析表明，大量上调基因参与糖与氨基酸代谢过程，而大量下调基因则与药物外排泵及毒力因子相关。本研究结果为阐明MprA/B在杀鱼诺卡氏菌中的功能提供了新的研究视角。