A pivotal role for the response regulator DegU in controlling multicellular behaviour

Murray, Ewan J.; Kiley, Taryn B.; Stanley‐Wall, Nicola R.

doi:10.1099/mic.0.023903-0

Cited by 111 publications

(93 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…DegU is responsible for the expression of chemotaxis and (40,41,44,60). The data presented here suggest that the attenuation of the degU mutant in vivo is due to lysozyme sensitivity caused by the downregulation of pbpX and pgdA.…”

Section: Figmentioning

confidence: 76%

Listeria monocytogenes Is Resistant to Lysozyme through the Regulation, Not the Acquisition, of Cell Wall-Modifying Enzymes

et al. 2014

View full text Add to dashboard Cite

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is highly resistant to lysozyme, a ubiquitous enzyme of the innate immune system that degrades cell wall peptidoglycan. Two peptidoglycan-modifying enzymes, PgdA and OatA, confer lysozyme resistance on L. monocytogenes; however, these enzymes are also conserved among lysozyme-sensitive nonpathogens. We sought to identify additional factors responsible for lysozyme resistance in L. monocytogenes. A forward genetic screen for lysozyme-sensitive mutants led to the identification of 174 transposon insertion mutations that mapped to 13 individual genes. Four mutants were killed exclusively by lysozyme and not other cell wall-targeting molecules, including the peptidoglycan deacetylase encoded by pgdA, the putative carboxypeptidase encoded by pbpX, the orphan response regulator encoded by degU, and the highly abundant noncoding RNA encoded by rli31. Both degU and rli31 mutants had reduced expression of pbpX and pgdA, yet DegU and Rli31 did not regulate each other. Since pbpX and pgdA are also present in lysozyme-sensitive bacteria, this suggested that the acquisition of novel enzymes was not responsible for lysozyme resistance, but rather, the regulation of conserved enzymes by DegU and Rli31 conferred high lysozyme resistance. Each lysozyme-sensitive mutant exhibited attenuated virulence in mice, and a time course of infection revealed that the most lysozyme-sensitive strain was killed within 30 min of intravenous infection, a phenotype that was recapitulated in purified blood. Collectively, these data indicate that the genes required for lysozyme resistance are highly upregulated determinants of L. monocytogenes pathogenesis that are required for avoiding the enzymatic activity of lysozyme in the blood. Lysozyme is a ubiquitous bactericidal enzyme found in the blood, bodily secretions, and phagocytic cells of all animals (1-3). Lysozyme degrades the bacterial cell wall by hydrolyzing the ␤1-4 linkage between the N-acetylglucosamine (NAG) and Nacetylmuramic acid (NAM) residues that comprise the peptidoglycan backbone, often resulting in bacteriolysis (4). Not surprisingly, many pathogens have evolved mechanisms of lysozyme resistance (5, 6). The best-characterized mechanisms of lysozyme resistance involve the acetylation state of the peptidoglycan, catalyzed by the deacetylase PgdA and/or the acetyltransferase OatA. PgdA deacetylates the amino group of NAG, while OatA O-acetylates NAM, converting the sugar backbone into a poor lysozyme substrate (7,8). pgdA mutants of Streptococcus pneumoniae and oatA mutants of Staphylococcus aureus are lysozyme sensitive, and in each case, lysozyme-sensitive mutants are attenuated in animal models of infection (7-10).Listeria monocytogenes is a facultative intracellular pathogen of animals and humans that causes severe disease in pregnant women and immunocompromised individuals (11). Both PgdA and OatA contribute to lysozyme resistance in L. monocytogenes, and pgdA mutants are attenuated during oral a...

show abstract

Section: Figmentioning

confidence: 76%

Listeria monocytogenes Is Resistant to Lysozyme through the Regulation, Not the Acquisition, of Cell Wall-Modifying Enzymes

et al. 2014

View full text Add to dashboard Cite

show abstract

“…The DegU binding sites were identified in front of almost all regulated operons; however, only some of them were reported in the literature as parts of the DegU regulon. It is known that DegU in B. subtilis is an important regulator of many processes including chemotaxis, motility, extracellular secretion, quorum sensing and biofilm formation (Msadek et al, 1991;Murray et al, 2009;Gupta & Rao, 2014;Omer et al, 2015). It was reported that inactivation of DegU in B. amyloliquefaciens FZB42 led to impairing in efficient root colonization (Budiharjo et al, 2014).…”

Section: Gene Expression Profilingmentioning

confidence: 99%

Gene expression regulation in the plant growth promoting Bacillus atrophaeus UCMB-5137 stimulated by maize root exudates

Mwita

Chan

Pretorius

et al. 2016

Gene

View full text Add to dashboard Cite

Despite successful use of Plant Growth Promoting Rhizobacteria (PGPR) in agriculture, little is known about specific mechanisms of gene regulation facilitating the effective communication between bacteria and plants during plant colonization. Active PGPR strain B. atrophaeus UCMB-5137 was studied in this research. RNA sequencing profiles were generated in experiments where root exudate stimulations were used to mimic interactions between bacteria and plants. It was found that the gene regulation in B. atrophaeus UCMB-5137 in response to the root exudate stimuli differed from the reported gene regulation at similar conditions in B. amyloliquefaciens FZB42, which was considered as a paradigm PGPR. This difference was explained by hypersensitivity of UCMB-5137 to the root exudate stimuli impelling it to a sessile root colonization behavior through the CcpA-CodY-AbrB regulation. It was found that the transcriptional factor DegU also could play an important role in gene regulations during plant colonization. A significant stress caused by the root exudates on in vitro cultivated B. atrophaeus UCMB-5137 was noticed and discussed. Multiple cases of conflicted gene regulations showed scantiness of our knowledge on the regulatory network in Bacillus. Some of these conflicted regulations could be explained by interference of non-coding RNA (ncRNA). Search through differential expressed intergenic regions revealed 49 putative loci of ncRNA regulated by the root exudate stimuli. Possible target mRNA were predicted and a general regulatory network of B. atrophaeus UCMB-5137 genome was designed.1 Highlights  Plant colonizing PGPR Bacillus responded differently to the root exudate stimuli;  In UCMB-5137 the CcpA-CodY-AbrB regulation caused fast cell immobilization;  DegU regulon is important for plant colonization behavior in PGPR Bacillus;  ncRNA involved in regulation of plant colonization were identified;  A comprehensive model of gene regulation in UCMB-5137 was developed;

show abstract

“…ComA is an activator of many of the Rap proteins, thereby forming a complex regulatory network between the various QS pathways (18). Finally, RapG represses phosphorylated DegU (DegUϳP) (19), whose main functions are to promote the secretion of multiple enzymes and repress social motility (20). Recently, it was hypothesized that a plasmid-borne Rap (specifically, Rap carried by plasmid pLS20 [Rap pLS20 ]) may also interact directly with an Xre-type plasmidborne repressor (21).…”

mentioning

confidence: 99%

The RapP-PhrP Quorum-Sensing System of Bacillus subtilis Strain NCIB3610 Affects Biofilm Formation through Multiple Targets, Due to an Atypical Signal-Insensitive Allele of RapP

et al. 2014

View full text Add to dashboard Cite

The genome of Bacillus subtilis 168 encodes eight rap-phr quorum-sensing pairs. Rap proteins of all characterized Rap-Phr pairs inhibit the function of one or several important response regulators: ComA, Spo0F, or DegU. This inhibition is relieved upon binding of the peptide encoded by the cognate phr gene. Bacillus subtilis strain NCIB3610, the biofilm-proficient ancestor of strain 168, encodes, in addition, the rapP-phrP pair on the plasmid pBS32. RapP was shown to dephosphorylate Spo0F and to regulate biofilm formation, but unlike other Rap-Phr pairs, RapP does not interact with PhrP. In this work we extend the analysis of the RapP pathway by reexamining its transcriptional regulation, its effect on downstream targets, and its interaction with PhrP. At the transcriptional level, we show that rapP and phrP regulation is similar to that of other rap-phr pairs. We further find that RapP has an Spo0F-independent negative effect on biofilm-related genes, which is mediated by the response regulator ComA. Finally, we find that the insensitivity of RapP to PhrP is due to a substitution of a highly conserved residue in the peptide binding domain of the rapP allele of strain NCIB3610. Reversing this substitution to the consensus amino acid restores the PhrP dependence of RapP activity and eliminates the effects of the rapP-phrP locus on ComA activity and biofilm formation. Taken together, our results suggest that RapP strongly represses biofilm formation through multiple targets and that PhrP does not counteract RapP due to a rare mutation in rapP.T he behavior of bacterial communities is often regulated by quorum-sensing (QS) signaling pathways. In these pathways, a secreted molecular signal accumulates in the environment and activates a cognate receptor at sufficiently high concentrations. Gram-positive bacteria frequently utilize peptides as QS signals (1-3), thereby eliciting a variety of behaviors, including the secretion of various molecules (e.g., enzymes, antibiotics, surfactants, and exopolysaccharides [4]), the initiation of developmental processes (such as sporulation and biofilm formation), and horizontal gene transfer through transformation or conjugation (5-7).Members of the Rap-Phr family of QS systems in the Grampositive model Bacillus subtilis are involved in the regulation of competence, sporulation, and biofilm formation. The chromosome of strain B. subtilis 168 encodes eight full receptor signal systems and three orphan receptors from this family (6,8). In each of the full systems, the phr gene encodes a prepeptide, which is secreted through the major secretory system and then further processed outside the cell, resulting in the formation of a mature penta-or hexapeptide signal (9). The mature peptide is transported into the cell by the oligopeptide-permease (Opp) complex, where it interacts with its Rap targets within the cytoplasm (10). All characterized Rap proteins contain two domains (10-12), a tricopeptide repeat (TPR) domain that interacts with the signaling peptide and a second domain that f...

show abstract

A pivotal role for the response regulator DegU in controlling multicellular behaviour

Cited by 111 publications

References 67 publications

Listeria monocytogenes Is Resistant to Lysozyme through the Regulation, Not the Acquisition, of Cell Wall-Modifying Enzymes

Listeria monocytogenes Is Resistant to Lysozyme through the Regulation, Not the Acquisition, of Cell Wall-Modifying Enzymes

Gene expression regulation in the plant growth promoting Bacillus atrophaeus UCMB-5137 stimulated by maize root exudates

The RapP-PhrP Quorum-Sensing System of Bacillus subtilis Strain NCIB3610 Affects Biofilm Formation through Multiple Targets, Due to an Atypical Signal-Insensitive Allele of RapP

Contact Info

Product

Resources

About