scholarly journals The dlt operon confers resistance to cationic antimicrobial peptides in Clostridium difficile

Microbiology ◽  
2011 ◽  
Vol 157 (5) ◽  
pp. 1457-1465 ◽  
Author(s):  
Shonna M. McBride ◽  
Abraham L. Sonenshein
Keyword(s):  
Cell Wall ◽  
Clostridium Difficile ◽  
Antimicrobial Peptides ◽  
Positive Charge ◽  
Polymyxin B ◽  
Gram Positive ◽  
Cationic Antimicrobial Peptides ◽  
Teichoic Acids ◽  
Gram Positive Bacteria ◽  
Net Positive Charge

The dlt operon in Gram-positive bacteria encodes proteins that are necessary for the addition of d-alanine to teichoic acids of the cell wall. The addition of d-alanine to the cell wall results in a net positive charge on the bacterial cell surface and, as a consequence, can decrease the effectiveness of antimicrobials, such as cationic antimicrobial peptides (CAMPs). Although the roles of the dlt genes have been studied for some Gram-positive organisms, the arrangement of these genes in Clostridium difficile and the life cycle of the bacterium in the host are markedly different from those of other pathogens. In the current work, we determined the contribution of the putative C. difficile dlt operon to CAMP resistance. Our data indicate that the dlt operon is necessary for full resistance of C. difficile to nisin, gallidermin, polymyxin B and vancomycin. We propose that the d-alanylation of teichoic acids provides protection against antimicrobial peptides that may be essential for growth of C. difficile in the host.

scholarly journals A Functional dlt Operon, Encoding Proteins Required for Incorporation of d-Alanine in Teichoic Acids in Gram-Positive Bacteria, Confers Resistance to Cationic Antimicrobial Peptides in Streptococcus pneumoniae

2006 ◽  
Vol 188 (16) ◽  
pp. 5797-5805 ◽  
Author(s):  
Márta Kovács ◽  
Alexander Halfmann ◽  
Iris Fedtke ◽  
Manuel Heintz ◽  
Andreas Peschel ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Antimicrobial Peptides ◽  
Stop Codon ◽  
Start Codon ◽  
Phenotypic Analysis ◽  
Gram Positive ◽  
Cationic Antimicrobial Peptides ◽  
Teichoic Acids ◽  
Gram Positive Bacteria ◽  
Insertional Inactivation

ABSTRACT Streptococcus pneumoniae is one of the few species within the group of low-G +C gram-positive bacteria reported to contain no d-alanine in teichoic acids, although the dltABCD operon encoding proteins responsible for d-alanylation is present in the genomes of two S. pneumoniae strains, the laboratory strain R6 and the clinical isolate TIGR4. The annotation of dltA in R6 predicts a protein, d-alanine-d-alanyl carrier protein ligase (Dcl), that is shorter at the amino terminus than all other Dcl proteins. Translation of dltA could also start upstream of the annotated TTG start codon at a GTG, resulting in the premature termination of dltA translation at a stop codon. Applying a novel integrative translation probe plasmid with Escherichia coli ′lacZ as a reporter, we could demonstrate that dltA translation starts at the upstream GTG. Consequently, S. pneumoniae R6 is a dltA mutant, whereas S. pneumoniae D39, the parental strain of R6, and Rx, another derivative of D39, contained intact dltA genes. Repair of the stop codon in dltA of R6 and insertional inactivation of dltA in D39 and Rx yielded pairs of dltA-deficient and dltA-proficient strains. Subsequent phenotypic analysis showed that dltA inactivation resulted in enhanced sensitivity to the cationic antimicrobial peptides nisin and gallidermin, a phenotype fully consistent with those of dltA mutants of other gram-positive bacteria. In addition, mild alkaline hydrolysis of heat-inactivated whole cells released d-alanine from dltA-proficient strains, but not from dltA mutants. The results of our study suggest that, as in many other low-G+C gram-positive bacteria, teichoic acids of S. pneumoniae contain d-alanine residues in order to protect this human pathogen against the actions of cationic antimicrobial peptides.

scholarly journals BceAB-type antibiotic resistance transporters appear to act by target protection of cell wall synthesis

2019 ◽  
Author(s):  
Carolin M Kobras ◽  
Hannah Piepenbreier ◽  
Jennifer Emenegger ◽  
Andre Sim ◽  
Georg Fritz ◽  
...  
Keyword(s):  
Cell Wall ◽  
Antimicrobial Peptides ◽  
Gc Content ◽  
Critical Factor ◽  
Peptide Antibiotics ◽  
Cell Wall Synthesis ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Lipid Ii ◽  
High Level

ABSTRACTResistance against cell wall-active antimicrobial peptides in bacteria is often mediated by transporters. In low GC-content Gram-positive bacteria, a wide-spread type of such transporters are the BceAB-like systems, which frequently provide a high level of resistance against peptide antibiotics that target intermediates of the lipid II cycle of cell wall synthesis. How a transporter can offer protection from drugs that are active on the cell surface, however, has presented researchers with a conundrum. Multiple theories have been discussed, ranging from removal of the peptides from the membrane, internalisation of the drug for degradation, to removal of the cellular target rather than the drug itself. To resolve this much-debated question, we here investigated the mode of action of the transporter BceAB of Bacillus subtilis. We show that it does not inactivate or import its substrate antibiotic bacitracin. Moreover, we present evidence that the critical factor driving transport activity is not the drug itself, but instead the concentration of drug-target complexes in the cell. Our results, together with previously reported findings, lead us to propose that BceAB-type transporters act by transiently freeing lipid II cycle intermediates from the inhibitory grip of antimicrobial peptides, and thus provide resistance through target protection of cell wall synthesis. Target protection has so far only been reported for resistance against antibiotics with intracellular targets, such as the ribosome. However, this mechanism offers a plausible explanation for the use of transporters as resistance determinants against cell wall-active antibiotics in Gram-positive bacteria where cell wall synthesis lacks the additional protection of an outer membrane.

Cell Wall Teichoic Acids in the Taxonomy and Characterization of Gram-positive Bacteria

2011 ◽  
pp. 131-164 ◽  
Author(s):  
Natal’ya V. Potekhina ◽  
Galina M. Streshinskaya ◽  
Elena M. Tul'skaya ◽  
Alexander S. Shashkov
Keyword(s):  
Cell Wall ◽  
Gram Positive ◽  
Teichoic Acids ◽  
Gram Positive Bacteria ◽  
Wall Teichoic Acids

scholarly journals Alanine Esters of Enterococcal Lipoteichoic Acid Play a Role in Biofilm Formation and Resistance to Antimicrobial Peptides

2006 ◽  
Vol 74 (7) ◽  
pp. 4164-4171 ◽  
Author(s):  
Francesca Fabretti ◽  
Christian Theilacker ◽  
Lucilla Baldassarri ◽  
Zbigniew Kaczynski ◽  
Andrea Kropec ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Deletion Mutant ◽  
Lipoteichoic Acid ◽  
Polymyxin B ◽  
Resonance Spectroscopy ◽  
Wild Type ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Surface Molecules ◽  
Environmental Interactions

ABSTRACT Enterococcus faecalis is among the predominant causes of nosocomial infections. Surface molecules like d-alanine lipoteichoic acid (LTA) perform several functions in gram-positive bacteria, such as maintenance of cationic homeostasis and modulation of autolytic activities. The aim of the present study was to evaluate the effect of d-alanine esters of teichoic acids on biofilm production and adhesion, autolysis, antimicrobial peptide sensitivity, and opsonic killing. A deletion mutant of the dltA gene was created in a clinical E. faecalis isolate. The absence of d-alanine in the LTA of the dltA deletion mutant was confirmed by nuclear magnetic resonance spectroscopy. The wild-type strain and the deletion mutant did not show any significant differences in growth curve, morphology, or autolysis. However, the mutant produced significantly less biofilm when grown in the presence of 1% glucose (51.1% compared to that of the wild type); adhesion to eukaryotic cells was diminished. The mutant absorbed 71.1% of the opsonic antibodies, while absorption with the wild type resulted in a 93.2% reduction in killing. Sensitivity to several cationic antimicrobial peptides (polymyxin B, colistin, and nisin) was considerably increased in the mutant strain, confirming similar results from other studies of gram-positive bacteria. Our data suggest that the absence of d-alanine in LTA plays a role in environmental interactions, probably by modulating the net negative charge of the bacterial cell surface, and therefore it may be involved in the pathogenesis of this organism.

scholarly journals Commercial Preparations of Lipoteichoic Acid Contain Endotoxin That Contributes to Activation of Mouse Macrophages In Vitro

2001 ◽  
Vol 69 (2) ◽  
pp. 751-757 ◽  
Author(s):  
Jian Jun Gao ◽  
Qiao Xue ◽  
Eleanor G. Zuvanich ◽  
Kevin R. Haghi ◽  
David C. Morrison
Keyword(s):  
Cell Wall ◽  
Biological Activity ◽  
Polymyxin B ◽  
No Production ◽  
Raw 264.7 ◽  
Gram Positive ◽  
Raw 264.7 Macrophages ◽  
Gram Positive Bacteria ◽  
Mouse Macrophages ◽  
Ifn Γ

ABSTRACT Lipoteichoic acids (LTA), cell wall components of gram-positive bacteria, have been reported to induce various inflammatory mediators and to play a key role in gram-positive-microbe-mediated septic shock. In a large number of these studies, investigators used commercially available LTA purified from a variety of gram-positive bacteria, including Staphylococcus aureus, Bacillus subtilis, and Streptococcus sanguis. We report here that, although these commercially available LTA could be readily shown to stimulate production of nitric oxide (NO) in RAW 264.7 mouse macrophages, the activity was dramatically inhibited by polymyxin B, a relatively specific inhibitor of endotoxin biological activity. One-step purification of the commercially available S. aureus LTA using hydrophobic interaction chromatography resulted in two well-separated peak fractions, one highly enriched for LTA and a second highly enriched for endotoxin. The LTA-enriched fractions did not induce production of NO in RAW 264.7 macrophages, although they caused a dose-dependent induction of NO in the presence of low concentrations of gamma interferon (IFN-γ) (which by itself induced little NO), regardless of the presence of polymyxin B. In contrast, the endotoxin-enriched fractions by themselves inhibited in high levels of NO in RAW 264.7 macrophages but activity was almost completely inhibited in the presence of polymyxin B. Consistent with these findings, our data also indicate that commercial LTA preparations fromS. aureus, B. subtilis, and S. sanguis were not able to induce NO from lipopolysaccharide-hyporesponsive C3H/HeJ mouse peritoneal macrophages, but in the presence of IFN-γ, these LTA preparations were able to induce relatively high levels of NO from C3H/HeJ macrophages. These results indicate that commercially available LTA can contain contaminating and potentially significant levels of endotoxin that can be expected to contribute to the putative macrophage-stimulating effects of LTA as assessed by NO production. The fact that the purified LTA, by itself, was not able to induce significant levels of NO secretion in RAW 264.7 macrophages supports the conclusion that caution in attributing high-level biological activity to this microbial cell wall constituent should be exercised.

scholarly journals BceAB-Type Antibiotic Resistance Transporters Appear To Act by Target Protection of Cell Wall Synthesis

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Carolin M. Kobras ◽  
Hannah Piepenbreier ◽  
Jennifer Emenegger ◽  
Andre Sim ◽  
Georg Fritz ◽  
...  
Keyword(s):  
Cell Wall ◽  
Antimicrobial Peptides ◽  
Gc Content ◽  
Critical Factor ◽  
Peptide Antibiotics ◽  
Cell Wall Synthesis ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Lipid Ii

ABSTRACT Resistance against cell wall-active antimicrobial peptides in bacteria is often mediated by transporters. In low-GC-content Gram-positive bacteria, a common type of such transporters is BceAB-like systems, which frequently provide high-level resistance against peptide antibiotics that target intermediates of the lipid II cycle of cell wall synthesis. How a transporter can offer protection from drugs that are active on the cell surface, however, has presented researchers with a conundrum. Multiple theories have been discussed, ranging from removal of the peptides from the membrane and internalization of the drug for degradation to removal of the cellular target rather than the drug itself. To resolve this much-debated question, we here investigated the mode of action of the transporter BceAB of Bacillus subtilis. We show that it does not inactivate or import its substrate antibiotic bacitracin. Moreover, we present evidence that the critical factor driving transport activity is not the drug itself but instead the concentration of drug-target complexes in the cell. Our results, together with previously reported findings, lead us to propose that BceAB-type transporters act by transiently freeing lipid II cycle intermediates from the inhibitory grip of antimicrobial peptides and thus provide resistance through target protection of cell wall synthesis. Target protection has so far only been reported for resistance against antibiotics with intracellular targets, such as the ribosome. However, this mechanism offers a plausible explanation for the use of transporters as resistance determinants against cell wall-active antibiotics in Gram-positive bacteria where cell wall synthesis lacks the additional protection of an outer membrane.

Sign in / Sign up

Export Citation Format

Share Document