scholarly journals The Bacillus subtilis Extracytoplasmic-Function σX Factor Regulates Modification of the Cell Envelope and Resistance to Cationic Antimicrobial Peptides

2004 ◽  
Vol 186 (4) ◽  
pp. 1136-1146 ◽  
Author(s):  
Min Cao ◽  
John D. Helmann
Keyword(s):  
Bacillus Subtilis ◽  
Antimicrobial Peptides ◽  
Cell Envelope ◽  
Resistance Mechanism ◽  
Penicillin Binding Protein ◽  
Wild Type ◽  
Amino Groups ◽  
Cationic Antimicrobial Peptides ◽  
Teichoic Acids ◽  
Positively Charged

ABSTRACT Bacillus subtilis contains seven extracytoplasmic-function σ factors that activate partially overlapping regulons. We here identify four additional members of the σX regulon, pbpX (penicillin-binding protein), ywnJ, the dlt operon (d-alanylation of teichoic acids), and the pss ybfM psd operon (phosphatidylethanolamine biosynthesis). Modification of teichoic acids by esterification with d-alanine and incorporation of phosphatidylethanolamine into the cell membrane have a common consequence: in both cases positively charged amino groups are introduced into the cell envelope. The resulting reduction in the net negative charge of the cell envelope has been previously implicated as a resistance mechanism specific for cationic antimicrobial peptides. Consistent with this notion, we find that both sigX and dltA mutants are more sensitive to nisin than wild-type cells. We conclude that activation of the σX regulon serves to alter cell surface properties to provide protection against antimicrobial peptides.

Cationic antimicrobial peptides elicit a complex stress response in Bacillus subtilis that involves ECF-type sigma factors and two-component signal transduction systems

Microbiology ◽  
2005 ◽  
Vol 151 (5) ◽  
pp. 1577-1592 ◽  
Author(s):  
Milla Pietiäinen ◽  
Marika Gardemeister ◽  
Maria Mecklin ◽  
Soile Leskelä ◽  
Matti Sarvas ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Bacillus Subtilis ◽  
Antimicrobial Peptides ◽  
Stress Responses ◽  
Signal Transduction Pathways ◽  
Synthetic Analogue ◽  
Cationic Antimicrobial Peptides ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems

Stress responses of Bacillus subtilis to membrane-active cationic antimicrobial peptides were studied. Global analysis of gene expression by DNA macroarray showed that peptides at a subinhibitory concentration activated numerous genes. A prominent pattern was the activation of two extracytoplasmic function sigma factor regulons, SigW and SigM. Two natural antimicrobial peptides, LL-37 and PG-1, were weak activators of SigW regulon genes, whereas their synthetic analogue poly-l-lysine was clearly a stronger activator of SigW. It was demonstrated for the first time that LL-37 is a strong and specific activator of the YxdJK two-component systems, one of the three highly homologous two-component systems sensing antimicrobial compounds. YxdJK regulates the expression of the YxdLM ABC transporter. The LiaRS (YvqCE) TCS was also strongly activated by LL-37, but its activation is not LL-37 specific, as was demonstrated by its activation with PG-1 and Triton X-100. Other strongly LL-37-induced genes included yrhH and yhcGHI. Taken together, the responses to cationic antimicrobial peptides revealed highly complex regulatory patterns and induction of several signal transduction pathways. The results suggest significant overlap between different stress regulons and interdependence of signal transduction pathways mediating stress responses.

scholarly journals Exogenous and Endogenous Phosphoethanolamine Transferases Differently Affect Colistin Resistance and Fitness in Pseudomonas aeruginosa

2021 ◽  
Vol 12 ◽  
Author(s):  
Matteo Cervoni ◽  
Alessandra Lo Sciuto ◽  
Chiara Bianchini ◽  
Carmine Mancone ◽  
Francesco Imperi
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Lipid A ◽  
Cell Envelope ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Transferase Activity ◽  
Colistin Resistance ◽  
Phosphoethanolamine Transferases ◽  
Positively Charged ◽  
Inducible Gene

Colistin represents a last-line treatment option for infections caused by multidrug resistant Gram-negative pathogens, including Pseudomonas aeruginosa. Colistin resistance generally involves the modification of the lipid A moiety of lipopolysaccharide (LPS) with positively charged molecules, namely phosphoethanolamine (PEtN) or 4-amino-4-deoxy-L-arabinose (Ara4N), that reduce colistin affinity for its target. Several lines of evidence highlighted lipid A aminoarabinosylation as the primary colistin resistance mechanism in P. aeruginosa, while the contribution of phosphoethanolamination remains elusive. PEtN modification can be due to either endogenous (chromosomally encoded) PEtN transferase(s) (e.g., EptA in P. aeruginosa) or plasmid borne MCR enzymes, commonly found in enterobacteria. By individually cloning eptA and mcr-1 into a plasmid for inducible gene expression, we demonstrated that MCR-1 and EptA have comparable PEtN transferase activity in P. aeruginosa and confer colistin resistance levels similar to those provided by lipid A aminoarabinosylation. Notably, EptA, but not MCR-1, negatively affects P. aeruginosa growth and, to a lesser extent, cell envelope integrity when expressed at high levels. Mutagenesis experiments revealed that PEtN transferase activity does not account for the noxious effects of EptA overexpression, that instead requires a C-terminal tail unique to P. aeruginosa EptA, whose function remains unknown. Overall, this study shows that both endogenous and exogenous PEtN transferases can promote colistin resistance in P. aeruginosa, and that PEtN and MCR-1 mediated resistance has no impact on growth and cell envelope homeostasis, suggesting that there may be no fitness barriers to the spread of mcr-1 in P. aeruginosa.

scholarly journals Analysis of Outgrowth of Bacillus subtilis Spores Lacking Penicillin-Binding Protein 2a

1998 ◽  
Vol 180 (24) ◽  
pp. 6493-6502 ◽  
Author(s):  
Thomas Murray ◽  
David L. Popham ◽  
Christine B. Pearson ◽  
Arthur R. Hand ◽  
Peter Setlow
Keyword(s):  
Bacillus Subtilis ◽  
Cell Elongation ◽  
Binding Protein ◽  
Divalent Cations ◽  
Cross Linking ◽  
Penicillin Binding Protein ◽  
Wild Type ◽  
Spore Outgrowth ◽  
Partial Redundancy

ABSTRACT The loss of Bacillus subtilis penicillin-binding protein (PBP) 2a, encoded by pbpA, was previously shown to slow spore outgrowth and result in an increased diameter of the outgrowing spore. Further analyses to define the defect inpbpA spore outgrowth have shown that (i) outgrowingpbpA spores exhibited only a slight defect in the rate of peptidoglycan (PG) synthesis compared to wild-type spores, but PG turnover was significantly slowed during outgrowth of pbpAspores; (ii) there was no difference in the location of PG synthesis in outgrowing wild-type and pbpA spores once cell elongation had been initiated; (iii) outgrowth and elongation of pbpAspores were dramatically affected by the levels of monovalent or divalent cations in the medium; (iv) there was a partial redundancy of function between PBP2a and PBP1 or -4 during spore outgrowth; and (v) there was no difference in the structure of PG from outgrowing wild-type spores or spores lacking PBP2a or PBP2a and -4; but also (vi) PG from outgrowing spores lacking PBP1 and -2a had transiently decreased cross-linking compared to PG from outgrowing wild-type spores, possibly due to the loss of transpeptidase activity.

scholarly journals The dlt Operon of Bacillus cereus Is Required for Resistance to Cationic Antimicrobial Peptides and for Virulence in Insects

2009 ◽  
Vol 191 (22) ◽  
pp. 7063-7073 ◽  
Author(s):  
Z. Abi Khattar ◽  
A. Rejasse ◽  
D. Destoumieux-Garzón ◽  
J. M. Escoubas ◽  
V. Sanchis ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Bacillus Cereus ◽  
Cell Walls ◽  
Type Strain ◽  
Pathogenic Bacteria ◽  
Wild Type Strain ◽  
Wild Type ◽  
Gram Positive ◽  
Cationic Antimicrobial Peptides ◽  
Humoral Immune

ABSTRACT The dlt operon encodes proteins that alanylate teichoic acids, the major components of cell walls of gram-positive bacteria. This generates a net positive charge on bacterial cell walls, repulsing positively charged molecules and conferring resistance to animal and human cationic antimicrobial peptides (AMPs) in gram-positive pathogenic bacteria. AMPs damage the bacterial membrane and are the most effective components of the humoral immune response against bacteria. We investigated the role of the dlt operon in insect virulence by inactivating this operon in Bacillus cereus, which is both an opportunistic human pathogen and an insect pathogen. The ΔdltBc mutant displayed several morphological alterations but grew at a rate similar to that for the wild-type strain. This mutant was less resistant to protamine and several bacterial cationic AMPs, such as nisin, polymyxin B, and colistin, in vitro. It was also less resistant to molecules from the insect humoral immune system, lysozyme, and cationic AMP cecropin B from Spodoptera frugiperda. ΔdltBc was as pathogenic as the wild-type strain in oral infections of Galleria mellonella but much less virulent when injected into the hemocoels of G. mellonella and Spodoptera littoralis. We detected the dlt operon in three gram-negative genera: Erwinia (Erwinia carotovora), Bordetella (Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica), and Photorhabdus (the entomopathogenic bacterium Photorhabdus luminescens TT01, the dlt operon of which did not restore cationic AMP resistance in ΔdltBc ). We suggest that the dlt operon protects B. cereus against insect humoral immune mediators, including hemolymph cationic AMPs, and may be critical for the establishment of lethal septicemia in insects and in nosocomial infections in humans.

scholarly journals Effects of net charge and the number of positively charged residues on the biological activity of amphipathic α-helical cationic antimicrobial peptides

Biopolymers ◽  
2007 ◽  
Vol 90 (3) ◽  
pp. 369-383 ◽  
Author(s):  
Ziqing Jiang ◽  
Adriana I. Vasil ◽  
John D. Hale ◽  
Robert E. W. Hancock ◽  
Michael L. Vasil ◽  
...  
Keyword(s):  
Biological Activity ◽  
Antimicrobial Peptides ◽  
Net Charge ◽  
Cationic Antimicrobial Peptides ◽  
Charged Residues ◽  
Positively Charged

scholarly journals The Absence of FtsH Metalloprotease Activity Causes Overexpression of the σW-Controlled pbpE Gene, Resulting in Filamentous Growth of Bacillus subtilis

2003 ◽  
Vol 185 (3) ◽  
pp. 973-982 ◽  
Author(s):  
Stephan Zellmeier ◽  
Ulrich Zuber ◽  
Wolfgang Schumann ◽  
Thomas Wiegert
Keyword(s):  
Bacillus Subtilis ◽  
Filamentous Growth ◽  
Penicillin Binding Protein ◽  
Wild Type ◽  
Double Knockout ◽  
Ftsh Protease ◽  
Its Gene ◽  
Membrane Bound ◽  
Metalloprotease Activity ◽  
Energy Dependent

ABSTRACT FtsH is a membrane-bound and energy-dependent metalloprotease in bacteria which is involved in the posttranslational control of the activity of a variety of important transcription factors and in the degradation of uncomplexed integral membrane proteins. For Bacillus subtilis, little is known about the target proteins of FtsH protease. Its gene is not essential, but knockout strains display a pleiotropic phenotype including sensitivity toward salt and heat stress, defects in sporulation and competence, and largely filamentous growth. Comparison of the intracellular proteomes of wild-type and ftsH knockout strains revealed that at least nine proteins accumulated in the absence of ftsH, four of which could be identified. Two of these proteins turned out to be members of the σW regulon. Accumulation of one of these σW-controlled proteins, the penicillin-binding protein PBP4*, was analyzed in more detail. We could show that PBP4* is not a proteolytic substrate of FtsH and that its overproduction is due to the enhanced transcription of its gene (pbpE) in ftsH null mutants. The filamentous growth phenotype of ΔftsH strains was abolished in a ΔftsH ΔpbpE double knockout. In ftsH wild-type strains with the pbpE gene under regulatable control, pbpE overexpression caused filamentation of the cells. DNA macroarray analysis revealed that most genes of the σW regulon are transcribed at elevated levels in an ftsH mutant. The influence of FtsH on σW-controlled genes is discussed.

scholarly journals Haemophilus ducreyi SapA Contributes to Cathelicidin Resistance and Virulence in Humans

2010 ◽  
Vol 78 (3) ◽  
pp. 1176-1184 ◽  
Author(s):  
Kristy L. B. Mount ◽  
Carisa A. Townsend ◽  
Sherri D. Rinker ◽  
Xiaoping Gu ◽  
Kate R. Fortney ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Mutant Strain ◽  
Virulence Factor ◽  
Formation Rate ◽  
Resistance Mechanism ◽  
Bacterial Virulence ◽  
Haemophilus Ducreyi ◽  
Wild Type ◽  
Human Volunteers ◽  
Antimicrobial Peptide Resistance

ABSTRACT Haemophilus ducreyi is an extracellular pathogen of human epithelial surfaces that resists human antimicrobial peptides (APs). The organism's genome contains homologs of genes sensitive to antimicrobial peptides (sap operon) in nontypeable Haemophilus influenzae. In this study, we characterized the sap-containing loci of H. ducreyi 35000HP and demonstrated that sapA is expressed in broth cultures and H. ducreyi-infected tissue; sapA is also conserved among both class I and class II H. ducreyi strains. We constructed a nonpolar sapA mutant of H. ducreyi 35000HP, designated 35000HPsapA, and compared the percent survival of wild-type 35000HP and 35000HPsapA exposed to several human APs, including α-defensins, β-defensins, and the cathelicidin LL-37. Unlike an H. influenzae sapA mutant, strain 35000HPsapA was not more susceptible to defensins than strain 35000HP was. However, we observed a significant decrease in the survival of strain 35000HPsapA after exposure to LL-37, which was complemented by introducing sapA in trans. Thus, the Sap transporter plays a role in resistance of H. ducreyi to LL-37. We next compared mutant strain 35000HPsapA with strain 35000HP for their ability to cause disease in human volunteers. Although both strains caused papules to form at similar rates, the pustule formation rate at sites inoculated with 35000HPsapA was significantly lower than that of sites inoculated with 35000HP (33.3% versus 66.7%; P = 0.007). Together, these data establish that SapA acts as a virulence factor and as one mechanism for H. ducreyi to resist killing by antimicrobial peptides. To our knowledge, this is the first demonstration that an antimicrobial peptide resistance mechanism contributes to bacterial virulence in humans.

scholarly journals Induction by Cationic Antimicrobial Peptides and Involvement in Intrinsic Polymyxin and Antimicrobial Peptide Resistance, Biofilm Formation, and Swarming Motility of PsrA in Pseudomonas aeruginosa

2008 ◽  
Vol 190 (16) ◽  
pp. 5624-5634 ◽  
Author(s):  
W. James Gooderham ◽  
Manjeet Bains ◽  
Joseph B. McPhee ◽  
Irith Wiegand ◽  
Robert E. W. Hancock
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Outer Membrane ◽  
Biofilm Formation ◽  
Metabolic Energy ◽  
Wild Type ◽  
Swarming Motility ◽  
Cationic Antimicrobial Peptides ◽  
Antimicrobial Peptide Resistance

ABSTRACT Pseudomonas aeruginosa is an important opportunistic pathogen that causes infections that can be extremely difficult to treat due to its high intrinsic antibiotic resistance and broad repertoire of virulence factors, both of which are highly regulated. It is demonstrated here that the psrA gene, encoding a transcriptional regulator, was upregulated in response to subinhibitory concentrations of cationic antimicrobial peptides. Compared to the wild type and the complemented mutant, a P. aeruginosa PAO1 psrA::Tn5 mutant displayed intrinsic supersusceptibility to polymyxin B, a last-resort antimicrobial used against multidrug-resistant infections, and the bovine neutrophil antimicrobial peptide indolicidin; this supersusceptibility phenotype correlated with increased outer membrane permeabilization by these agents. The psrA mutant was also defective in simple biofilm formation, rapid attachment, and swarming motility, all of which could be complemented by the cloned psrA gene. The role of PsrA in global gene regulation was studied by comparing the psrA mutant to the wild type by microarray analysis, demonstrating that 178 genes were up- or downregulated ≥2-fold (P ≤ 0.05). Dysregulated genes included those encoding certain known PsrA targets, those encoding the type III secretion apparatus and effectors, adhesion and motility genes, and a variety of metabolic, energy metabolism, and outer membrane permeability genes. This suggests that PsrA might be a key regulator of antimicrobial peptide resistance and virulence.

scholarly journals The d-Alanine Residues ofStaphylococcus aureus Teichoic Acids Alter the Susceptibility to Vancomycin and the Activity of Autolytic Enzymes

2000 ◽  
Vol 44 (10) ◽  
pp. 2845-2847 ◽  
Author(s):  
Andreas Peschel ◽  
Cuong Vuong ◽  
Michael Otto ◽  
Friedrich Götz
Keyword(s):  
Structural Changes ◽  
Cell Envelope ◽  
Glycopeptide Antibiotics ◽  
Wild Type ◽  
Teichoic Acids ◽  
In The Wild ◽  
Autolytic Activity ◽  
Increased Sensitivity ◽  
High Concentrations ◽  
Mutant Cells

ABSTRACT Recently, Staphylococcus aureus strains with intermediate resistance to vancomycin, the antibiotic of last resort, have been described. Multiple changes in peptidoglycan turnover and structure contribute to the resistance phenotype. Here, we describe that structural changes of teichoic acids in the cell envelope have a considerable influence on the susceptibility to vancomycin and other glycopeptides. S. aureus cells lackingd-alanine esters in teichoic acids exhibited an at least threefold-increased sensitivity to glycopeptide antibiotics. Furthermore, the autolytic activity of the d-alanine mutant was reduced compared to the wild-type, and the mutant was more susceptible to the staphylolytic enzyme lysostaphin. Vancomycin inhibited autolysis at very high concentrations but neither in the wild-type nor in the mutant was the autolytic activity influenced in the range of the MIC. Mutant cells had a considerably higher capacity to bind vancomycin.

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