Regulation of Virulence Gene Expression in Bacteria: A Review

Dessie Abera

doi:10.7176/jbah/11-3-02

Abstract

Bacterial diseases are the leading cause of death worldwide through the involvement of virulence determinants. Virulence genes encode virulence factors which are essential for pathogenesis and infectious disease development in bacteria. The virulence factor concept helps for further investigations in the fields of microbial pathogenesis. The objective of this paper is to review regulation of virulence gene expression in bacteria. Virulence genes can be acquired via spontaneous mutations or through horizontal gene transfer mechanisms. Bacteria sense and respond to environmental stimuli in the host during infection. Successful host infection can be possible by coordinated expression of multitude of virulence genes. They adapt in the host by modulating its gene expression. Pathogenic bacteria possess many regulatory networks that control the production of virulence factors which enable the bacteria to survive and proliferate in the host. The most common forms of regulation of genome expression are by involvement of transcription factors, post-transcriptional modifications, ribo-regulation, environmental flux sensing, stress response and biofilm formation through quorum sensing. Virulence gene expression is carefully controlled to ensure correct spatiotemporal production of virulence factors. Regulation of virulence gene expression is very complex and influenced by environmental factors. Major regulatory control mechanisms used by pathogenic bacteria are alternative sigma factors and the two component regulatory systems. They do not always express virulence factors because it is energetically costly and reduces bacterial fitness. Therefore, they need to regulate their virulence properly in order to maximize their fitness and it is a key invasion strategy of pathogens. Keywords: Bacteria, Expression, Regulation, Virulence gene DOI: 10.7176/JBAH/11-3-02 Publication date: February 28 th 2021

Highlights

Bacteria monitor their extracellular physicochemical conditions and respond by modifying their genome expression (Ishihama, 2010)
Expressions of virulence genes in bacteria is regulated carefully to produce at the right time and location because the expression of virulence genes is energetically costly for the organism and properly controlled in order to maximize their fitness
The regulation of virulence gene expression is very complex and regulation of these genes is influenced by environmental factors

Summary

Introduction

Bacteria monitor their extracellular physicochemical conditions and respond by modifying their genome expression (Ishihama, 2010). The bacterial pathogens within the host senses and adapts to the prevailing conditions by modulating its gene expression (Thomas and Wigneshweraraj, 2014). They regulate their virulence factors by the use of a number of common motifs (Wilson et al, 2002). Successful host infection depends on the coordinated expression of multitude of virulence factors of pathogenic bacteria and their genes involved in the infection process (Caldelari et al, 2013). The expression of the virulence gene of the microbe are regulated in response to environmental signals like temperature, availability of key metal ions, concentration of anions such as bicarbonate or phosphate, pH, oxygen tension, and osmolarity encountered inside the infected host to initiate the appropriate and coordinate the adaptive response in gene expression (Winzer and Williams, 2001; Casadevall and Pirofski, 2009; Thomas and Wigneshweraraj, 2014)

Objectives

Conclusion