Role of RpoS in Virulence of Pathogens

Abstract

Understanding mechanisms of bacterial pathogenesis is critical for infectious disease control and treatment.Infection is a sophisticated process that requires the participation of global regulators to coordinate expression of not only genes coding for virulence factors but also those involved in other physiological processes, such as stress response and metabolic flux, to adapt to host environments. RpoS is a key response regulator to stress conditions in Escherichia coli and many other proteobacteria. In contrast to its conserved well-understood role in stress response, effects of RpoS on pathogenesis are highly variable and dependent on species. RpoS contributes to virulence through either enhancing survival against host defense systems or directly regulating expression of virulence factors in some pathogens, while RpoS is dispensable, or even inhibitory, to virulence in others. In this review, we focus on the distinct and niche-dependent role of RpoS in virulence by surveying recent findings in many pathogens.RpoS is an alternative sigma factor of RNA polymerase primarily found in Beta-and Gammaproteobacteria (31, 59). RNA core polymerase requires a sigma factor for promoter recognition and transcription initiation. In addition to housekeeping sigma factors that control transcription of essential genes, bacteria also possess alternative sigma factors that recognize the promoters of a specific set of genes. There are seven known sigma factors in the Gram-negative model bacterium Escherichia coli (67) and 18 in the Gram-positive bacterium Bacillus subtilis (52). The contribution of alternative sigma factors to virulence can be direct through regulated expression of virulence genes or indirect by enhancing survival against host defense and other stress conditions (70).Pathogenic bacteria experience many stresses during transmission and infection. For example, the enterohemorrhagic E. coli (EHEC) O157:H7 strain may face nutrient limitation and heat exposure in natural environments and acid stress and host defense after entry into human hosts. The ability to quickly adapt to changing environments is therefore critical for bacterial pathogens to successfully transmit and infect hosts. One of the most important adaptation factors in E. coli is RpoS (31, 59). The RpoS regulon, comprising 10% of E. coli genes (32,33,78,108,141), plays a critical role in survival of several stresses, including acid (124), heat (61), oxidative stress (116), starvation (79), and near-UV exposure (116). In E. coli, the levels of RpoS are low in exponential phase (32, 80), due to reduced transcription (80), attenuated translation (80), and, most importantly, rapid proteolysis mediated by RssB, a chaperone protein that binds to RpoS and directs the RssB-RpoS complex to the ClpXP protease (80,93,109,150). The degradation of RpoS is suppressed in stationary phase (11, 150), resulting in increased RpoS levels (80). Expression of RpoS is sensitive to environmental changes and is under the control of many regulatory factors, such as acetate, ppG...

Type II toxin–antitoxin systems are unevenly distributed among Escherichia coli phylogroups

“…s S activity and the rdar morphotype (red, dry and rough) (White & Surette, 2006;Dong & Schellhorn, 2010). Primarily, the authors observed a significantly lower prevalence of these two phenotypes in B2 than in B1 strains.…”

The stationary phase sigma factor, RpoS, regulates the production of a carbapenem antibiotic, a bioactive prodigiosin and virulence in the enterobacterial pathogen Serratia sp. ATCC 39006

“…RpoS has been shown to regulate virulence factors in E. coli, S. typhimurium and several other species involved in both animal and plant pathogenesis (Dong & Schellhorn, 2010). The pathogenesis of the S39006 rpoS mutant was investigated using potato and C. elegans as model hosts.…”

“…Role of rpoS in stress tolerance E. coli RpoS has been shown to play a critical role in coordinating the expression of genes involved in withstanding various stresses, including oxidative stress and starvation (Dong & Schellhorn, 2010). Therefore, the rpoS mutant was investigated for its ability to withstand different stresses.…”

Salmonella Pathogenicity Islands

“…RpoS, Salmonella türlerinin en önemli virülans faktörlerinden olup, besin yokluğu veya kısıtlaması ile pH ve sıcaklık değişimleri gibi stres faktörlerine maruz kaldığı zaman, bakterinin bu olumsuz koşullara dayanmasını ve canlı kalmasını sağlamaktadır 28 . Bu amaçla bakteri, durağan ve çoğalma fazında pek çok gen eksprese eder.…”