Role of RpoN from Labrenzia aggregata LZB033 ( Rhodobacteraceae ) in Formation of Flagella and Biofilms, Motility, and Environmental Adaptation

• Published in: Applied and environmental microbiology 2019-04, Vol.85 (7)
• Main Authors: Xu, Tingting, Yu, Min, Liu, Jingli, Lin, Heyu, Liang, Jinchang, Zhang, Xiao-Hua
• Format: Article
• Language: English
• Subjects: Adaptation; Adaptation, Physiological - physiology; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biodegradation; Biofilms; Biofilms - growth & development; Biosynthesis; Carbon; Carbon sources; Catabolism; Cellular stress response; Chemical analysis; China; Clonal deletion; Deletion mutant; Dimethylsulphoniopropionate; Environmental Microbiology; Fitness; Flagella; Flagella - metabolism; Gene deletion; Gene expression; Gene Expression Regulation, Bacterial; Gene Knockout Techniques; Gene sequencing; Genes; Genomes; Malic acid; Marine environment; Motility; Osmotic Pressure; Osmotic stress; Oxidative Stress; Physical fitness; Regulators; Rhodobacteraceae - cytology; Rhodobacteraceae - genetics; Rhodobacteraceae - growth & development; Rhodobacteraceae - metabolism; Ribonucleic acid; RNA; RNA Polymerase Sigma 54 - genetics; RNA Polymerase Sigma 54 - metabolism; RNA, Bacterial - isolation & purification; RpoN protein; Seawater; Sequence Analysis, RNA; Substrates; Sulfonium Compounds - metabolism; Survival; Swimming; Temperature; Transcription; Transcriptome; Water analysis
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.02844-18

LZB033 ( ), which produces dimethylsulfoniopropionate (DMSP) and reduces nitrate to nitrogen, was isolated from seawater of the East China Sea. Its genome encodes a large number of transcriptional regulators which may be important for its adaptation to diverse marine environments. The alternative σ factor (RpoN) is a central regulator of many bacteria, regulating the transcription of multiple genes and controlling important cellular functions. However, the exact role of RpoN in spp. is unknown. In this study, an in-frame deletion mutant was constructed in LZB033, and the function of RpoN was determined. To systematically identify RpoN-controlled genes, we performed a detailed analysis of gene expression differences between the wild-type strain and the Δ mutant using RNA sequencing. The expression of 175 genes was shown to be controlled by RpoN. Subsequent phenotypic assays showed that the Δ mutant was attenuated in flagellar biosynthesis and swimming motility, utilized up to 13 carbon substrates differently, lacked the ability to assimilate malic acid, and displayed markedly decreased biofilm formation. In addition, stress response assays showed that the Δ mutant was impaired in the ability to survive under different challenge conditions, including osmotic stress, oxidative stress, temperature changes, and acid stress. Moreover, both the DMSP synthesis and catabolism rates of LZB033 decreased after was knocked out. Our work provides essential insight into the regulatory function of RpoN, revealing that RpoN is a key determinant for LZB033 flagellar formation, motility, biofilm formation, and environmental fitness, as well as DMSP production and degradation. This study established an in-frame gene deletion method in the alphaproteobacterium LZB033 and generated an gene mutant. A comparison of the transcriptomes and phenotypic characteristics between the mutant and wild-type strains confirmed the role of RpoN in LZB033 flagellar formation, motility, biofilm formation, and carbon usage. Most importantly, RpoN is a key factor for survival under different environmental challenge conditions. Furthermore, the ability to synthesize and metabolize dimethylsulfoniopropionate (DMSP) was related to RpoN. These features revealed RpoN to be an important regulator of stress resistance and survival for LZB033 in marine environments.