the impact of overexpression of sigma factors on morphological changes, growth pattern, and biofilm formation in mycobacterium marinum ccug 20998

Introduction: bacteria have at least one sigma factor (σ-factor) that transcribes the genes required for cell viability. usually, transcription of σ-factors occurs and changes in response to a variety of environmental stresses. expression of σ-factors is one of the strategies which is used in response to different stress conditions. this study was aimed to evaluate the effects of overexpression of σ-factors genes including σa, σb, σd, σe, σf, σg, σh, σj, σk, σl, and σm on morphology, growth pattern and biofilm formation in mycobacterium marinum ccug 20998. methods: in this study, the genes for major σ-factors were cloned in the expression vector paghd1, containing 11 kb hind iii fragment of pag1 and tetz determinants. a quantitative real-time pcr (qrt-pcr) assay was used to quantify σ-factor mrna levels of σ-factors in exponential and stationary phases. the overexpression in real-time experiments was normalized to the σa expression level. the effect of expression was evaluated on biofilm formation in this bacterium. results: some selected σ-factors used in this study were overexpressed. the σb had the highest expression level during the exponential and stationary phases. the σ-factors σd, σg, and σh showed lower expression level compared with σe, σf, and σk. the lowest expression belonged to σl and σm σ-factors. also, overexpression of σe and σk led to more biofilm formation in comparison with other σ-factors in m. marinum ccug 20998. conclusion: the overexpression of some σ-factors can affect growth, morphology and biofilm formation in m. marinum ccug 20998.