Zhang Jun-Jie, Hu Wei-Lin, Yang Youyun, Li Hongxia, Picardeau Mathieu, Yan Jie, Yang X Frank
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, P.R. China.
Mol Microbiol. 2018 Apr 6. doi: 10.1111/mmi.13967.
Leptospira spp. comprise both pathogenic and free-living saprophytic species. Little is known about the environmental adaptation and survival mechanisms of Leptospira. Alternative sigma factor, σ (RpoN) is known to play an important role in environmental and host adaptation in many bacteria. In this study, we constructed an rpoN mutant by allele exchange, and the complemented strain in saprophytic L. biflexa. Transcriptome analysis revealed that expression of several genes involved in nitrogen uptake and metabolism, including amtB1, glnB-amtB2, ntrX and narK, were controlled by σ . While wild-type L. biflexa could not grow under nitrogen-limiting conditions but was able to survive under such conditions and recover rapidly, the rpoN mutant was not. The rpoN mutant also had dramatically reduced ability to survive long-term in water. σ appears to regulate expression of amtB1, glnK-amtB2, ntrX and narK in an indirect manner. However, we identified a novel nitrogen-related gene, LEPBI_I1011, whose expression was directly under the control of σ (herein renamed as rcfA for RpoN-controlled factor A). Taken together, our data reveal that the σ regulatory network plays an important role in the long-term environmental survival of Leptospira spp.
钩端螺旋体属包括致病性和自由生活的腐生菌。人们对钩端螺旋体的环境适应性和生存机制知之甚少。已知替代西格玛因子σ（RpoN）在许多细菌的环境和宿主适应性中起重要作用。在本研究中，我们通过等位基因交换构建了一个rpoN突变体，并在腐生双曲钩端螺旋体中构建了互补菌株。转录组分析表明，几个参与氮吸收和代谢的基因，包括amtB1、glnB-amtB2、ntrX和narK，其表达受σ调控。野生型双曲钩端螺旋体在氮限制条件下不能生长，但能够在这种条件下存活并迅速恢复，而rpoN突变体则不能。rpoN突变体在水中长期存活的能力也显著降低。σ似乎以间接方式调节amtB1、glnK-amtB2、ntrX和narK的表达。然而，我们鉴定了一个新的氮相关基因LEPBI_I1011，其表达直接受σ（在此重新命名为rcfA，即RpoN控制因子A）的控制。综上所述，我们的数据表明，σ调控网络在钩端螺旋体属的长期环境生存中起重要作用。
