The Impact of Overexpression of Sigma Factors on Morphological Changes, Growth Pattern, and Biofilm Formation in Mycobacterium marinum CCUG 20998

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.
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.
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 to other σ-factors in M. marinum CCUG 20998.
The overexpression of some σ-factors can affect growth, morphology and biofilm formation in M. marinum CCUG 20998.