A role for histone-like protein H1 (H-NS) in the regulation of hemolysin expression by Serratia marcescens

Abstract

The histone-like protein H1 (H-NS) is an abundant structural component of the bacterial nucleoid and influences many cellular processes including recombination, transcription and transposition. Mutations in the hns gene encoding H-NS are highly pleiotropic, affecting the expression of many unrelated genes. We have studied the role of H-NS on the regulation of hemolysin gene expression in Serratia marcescens. The Escherichia coli hns mutant carrying S. marcescens hemolysin genes on a plasmid constructed by ligation of the 3.2-kb HindIIISacI fragment of pR02 into pBluescriptIIKS, showed a high level of expression of this hemolytic factor. To determine the osmoregulation of wild-type and hns defective mutants the cells were grown to midlogarithmic phase in LB medium with 0.06 or 0.3 M NaCl containing ampicillin and kanamycin, whereas to analyze the effect of pH on hemolysin expression, the cells were grown to late-logarithmic phase in LB medium buffered with 0.1 M Tris-HCl, pH 4.5 to 8.0. To assay growth phase-related hemolysin production, bacterial cells were grown in LB medium supplemented with ampicillin and kanamycin. The expression of S. marcescens hemolysin genes in wild-type E. coli and in an hns-defective derivative at different pH and during different growth phases indicated that, in the absence of H-NS, the expression of hemolysin did not vary with pH changes or growth phases. Furthermore, the data suggest that H-NS may play an important role in the regulation of hemolysin expression in S. marcescens and its effect may be due to changes in DNA topology influencing transcription and thus the amount of hemolysin expression. Implications for the mechanism by which H-NS influences gene expression are discussed.

Active Cytotoxic Necrotizing Factor 1 Associated with Outer Membrane Vesicles from Uropathogenic Escherichia coli

“…The authors attributed this to the pleiotropic effects of the hns mutation. Other studies have reported H-NS to be involved in downregulation of toxins in different gramnegative bacteria including some proteins in the ToxR regulatory cascade in Vibrio cholerae (27), hemolysin in Serratia marcescens (9), and products of the spv virulence locus in Salmonella enterica serovar Typhimurium (28) and of two structural genes (mxiC and icsB) in Shigella flexneri (31).…”

The use of biodiversity as source of new chemical entities against defined molecular targets for treatment of malaria, tuberculosis, and T-cell mediated diseases: a review

“…Mutations in hns gene have been shown to be involved in high level expression of cholera toxin in Vibrio cholerae (Nye et al 2000). More recently, H-NS has been shown to modulate expression of hemolysin, an important virulence factor of the opportunistic pathogen Serratia marcescens (Franzon & Santos 2004). In addition, deletion of the hns gene has been shown to confer drug resistance to E. coli by repressing multidrug exporter genes (Nishino & Yamaguchi 2004).…”

Identification of Rv3852 as a nucleoid-associated protein in Mycobacterium tuberculosis

“…The best studied NAPs are Fis (factor for inversion stimulation), H-NS (histone-like nucleoid structuring), HU (heat unstable) and IHF (integration host factor), although the existence of other similar proteins is becoming increasingly apparent (Luijsterburg et al, 2008). Their structural and functional properties have been related to chromatin compaction (by bending, bridging and wrapping DNA) and global transcriptional regulation of several genes, including virulence genes of bacterial pathogens (Beloin & Dorman, 2003;Berlutti et al, 1998;Falconi et al, 2001;Franzon & Santos, 2004; Harrison et al, 1994; Mangan et al, 2006;Nye et al, 2000;Schechter et al, 2003;Stonehouse et al, 2008; Wilson et al, 2001). Most of these proteins have been reported to bind to non-specific DNA sequences (Bailly et al, 1995;Krylov et al, 2001;Yamada et al, 1991), to exhibit low sequence or structural conservation (Luijsterburg et al, 2008), and to induce DNA bending and other alterations (Dhavan et al, 2002;Koh et al, 2008; Schneider et al, 2001;Spurio et al, 1997;Swinger & Rice, 2004).…”