Project description:Understanding how pathogens respond to antimicrobial peptides, and how this compares to currently available antibiotics, is crucial to optimizing antibiotic therapy. Staphylococcus aureus has several known resistance mechanisms against human cationic antimicrobial peptides (CAMPs). We aim to determine how S. aureus responds to sheep and frog CAMPs, and whether this response is associated with resistance. Gene expression changes in Staphylococcus aureus Newman cells exposed to linear CAMPs were analyzed by DNA microarray. Three antimicrobial peptides were used in the analysis, two of them are derived from frog, temporin L and dermaseptin K4-S4(1-16), one is from sheep, ovispirin-1. The peptides induced the VraSR cell-wall regulon and several other genes which are also upregulated in cells treated with vancomycin and other cell wall-active antibiotics. In addition to this similarity, three genes/operons were particularly strongly induced by the peptides: vraDE, SA0205 and SAS016, encoding an ABC transporter, a putative membrane-bound lysostaphin-like peptidase and a small functionally unknown protein, respectively. Ovispirin-1 and dermaseptin K4-S4(1-16), which disrupt lipid bilayers by the carpet mechanism, were strong inducers of the vraDE operon. We show that high level induction by ovispirin-1 was dependent on the amide modification of the peptide C-terminus. This suggests that the amide group has a crucial role in the activation of the Aps sensory system, the regulator of vraDE. In contrast, temporin L, which disrupts lipid bilayers by forming pores, was clearly a weaker inducer of vraDE despite the C-terminal amide modification. Sensitivity testing with CAMPs and other antimicrobials suggested that VraDE is a transporter dedicated to resist bacitracin. We also showed that SA0205 belongs to the VraSR regulon. Furthermore, VraSR was shown to be important for resistance against a wide range of cell wall-active antibiotics and other antimicrobial agents including the amide-modified ovispirin-1, bacitracin, teicoplanin, cefotaxime and 10 other β-lactam antibiotics, chlorpromazine, thioridazine and EGTA.

Project description:Understanding how pathogens respond to antimicrobial peptides, and how this compares to currently available antibiotics, is crucial to optimizing antibiotic therapy. Staphylococcus aureus has several known resistance mechanisms against human cationic antimicrobial peptides (CAMPs). We aim to determine how S. aureus responds to sheep and frog CAMPs, and whether this response is associated with resistance. Gene expression changes in Staphylococcus aureus Newman cells exposed to linear CAMPs were analyzed by DNA microarray. Three antimicrobial peptides were used in the analysis, two of them are derived from frog, temporin L and dermaseptin K4-S4(1-16), one is from sheep, ovispirin-1. The peptides induced the VraSR cell-wall regulon and several other genes which are also upregulated in cells treated with vancomycin and other cell wall-active antibiotics. In addition to this similarity, three genes/operons were particularly strongly induced by the peptides: vraDE, SA0205 and SAS016, encoding an ABC transporter, a putative membrane-bound lysostaphin-like peptidase and a small functionally unknown protein, respectively. Ovispirin-1 and dermaseptin K4-S4(1-16), which disrupt lipid bilayers by the carpet mechanism, were strong inducers of the vraDE operon. We show that high level induction by ovispirin-1 was dependent on the amide modification of the peptide C-terminus. This suggests that the amide group has a crucial role in the activation of the Aps sensory system, the regulator of vraDE. In contrast, temporin L, which disrupts lipid bilayers by forming pores, was clearly a weaker inducer of vraDE despite the C-terminal amide modification. Sensitivity testing with CAMPs and other antimicrobials suggested that VraDE is a transporter dedicated to resist bacitracin. We also showed that SA0205 belongs to the VraSR regulon. Furthermore, VraSR was shown to be important for resistance against a wide range of cell wall-active antibiotics and other antimicrobial agents including the amide-modified ovispirin-1, bacitracin, teicoplanin, cefotaxime and 10 other β-lactam antibiotics, chlorpromazine, thioridazine and EGTA. The effects of the three different antimicrobial peptides on gene expression of S. aureus Newman were studied by using whole genome oligo-DNA microarrays. Bacteria were grown in BHI medium to the early exponential phase (OD600=0.6) and antimicrobial peptides were added at sublethal concentrations. Samples were taken for RNA isolations after treating the cultures with the peptides for 10 minutes. Control cultures without peptide additions were treated similarly and in parallel.

Project description:Serine protease inhibitors (serpins) are a diverse family of proteins that is conserved across taxa. The diversity of Amblyomma americanum serpins (AAS) is far more complex than previously thought as revealed by discovery of 57 and 33 AAS transcripts that are respectively expressed in male and female A. americanum ticks, with 30 found in both. While distinct reproductively, both male and female metastriate ticks, such as A. americanum, require a blood meal. Thus, 30 AAS sequences found in both male and female ticks could play important role(s) in regulating tick feeding and thus represent attractive candidates for anti-tick vaccine development. Of significant interest, 19 AAS sequences expressed in male and female ticks are also part of the 48 AAS sequences expressed in fed female tick salivary glands or midguts; two organs through which the tick interacts with host blood and immune response factors. Considered the most important domain for serpin function, the reactive center loop (RCL) is further characterized by a single 'P1' site amino acid residue, which is central to determining the protease regulated by the serpin. In this study, a diversity of 17 different P1 site amino acid residues were predicted, suggesting that A. americanum serpins potentially regulate a large number of proteolytic pathways. Our data also indicate that some serpins in this study could regulate target protease common to all tick species, in that more than 40% of AAS show 58-97% inter-species amino acid conservation. Of significance, 24% of AAS showed 62-100% inter-species conservation within the functional RCL domain, with 10 RCLs showing ?90-100% conservation. In vertebrates, serpins with basic residues at the P1 site regulate key host defense pathways, which the tick must evade to feed successfully. Interestingly, we found that AAS sequences with basic or polar uncharged residues at the putative P1 site are more likely to be conserved across tick species. Another notable observation from our data is that AAS sequences found only in female ticks and those found in both males and females, but not those found only in male ticks, were highly conserved in other tick species. While descriptive, this study provides the basis for more in-depth studies exploring the roles of serpins in tick feeding physiology.

Dataset Information

Two novel non-cationic defensin-like antimicrobial peptides from haemolymph of the female tick, Amblyomma hebraeum.

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