Lactobacillus reuteri -produced cyclic dipeptides quench agr -mediated expression of toxic shock syndrome toxin-1 in staphylococci

Abstract

The production of the staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) by Staphylococcus aureus has been associated with essentially all cases of menstruation-associated toxic shock syndrome (TSS). In this work, we show that the human vaginal isolate Lactobacillus reuteri RC-14 produces small signaling molecules that are able to interfere with the staphylococcal quorum-sensing system agr, a key regulator of virulence genes, and repress the expression of TSST-1 in S. aureus MN8, a prototype of menstrual TSS S. aureus strains. Quantitative real-time PCR data showed that transcription from the Ptst promoter, as well as the P2 and P3 promoters of the agr system from all four agr subgroups of S. aureus, was strongly inhibited in response to growth with L. reuteri RC-14 cultural supernatant. Alterations in the transcriptional levels of two other virulence-associated regulators sarA and saeRS were also observed, indicating a potential overall influence of L. reuteri RC-14 signals on the production of virulence factors in S. aureus. S. aureus promoter-lux reporter strains were used to screen biochemically fractionated L. reuteri RC-14 supernatant, and the cyclic dipeptides cyclo(L-Phe-L-Pro) and cyclo(L-Tyr-L-Pro) were identified as the signaling molecules. The results from this work contribute to a better understanding of interspecies cell-to-cell communication between Lactobacillus and Staphylococcus, and provide a unique mechanism by which endogenous or probiotic strains may attenuate virulence factor production by bacterial pathogens.diketopiperazine | two-component systems

The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus

“…Although mutation of the repressor of toxins (rot) transcriptional regulator was reported to have little effect on TSST-1 expression, overexpression of Rot in trans strongly repressed TSST-1 (15). In addition to these experiments, prior work from our laboratory has demonstrated that interspecies communication between Lactobacillus reuteri and S. aureus can result in a dramatic repression of TSST-1 expression (18). Although this phenotype correlated with repression of agr, and deletion of agr in S. aureus MN8 reduced TSST-1 expression, TSST-1 could be further repressed in the agr-null background by the L. reuteri signaling molecules.…”

“…The tst gene promoter (P tst ) was previously cloned into the luciferase reporter plasmid pAmilux (18,24). The pAmilux::P tst plasmid was transformed into the different MN8 clones.…”

“…E. coli cells were made competent using the RbCl 2 method (3). Transformation of plasmids into S. aureus was carried out as described previously (18), and S. aureus RN4220 (19) and E. coli SA30B (20) were used as cloning intermediates to methylate DNA prior to electroporation in S. aureus MN8.…”

“…Although this phenotype correlated with repression of agr, and deletion of agr in S. aureus MN8 reduced TSST-1 expression, TSST-1 could be further repressed in the agr-null background by the L. reuteri signaling molecules. This additional repression of TSST-1 correlated with decreased transcription of the S. aureus exotoxin expression (Sae) system and increased transcription of stand-alone transcriptional regulator SarA (18). The aim of the present study was to investigate the role of both Sae and SarA in production of TSST-1 in S. aureus MN8, a prototypic menstrual TSS S. aureus strain.…”

Purification and identification of two antifungal cyclic dipeptides from Bacillus cereus subsp. thuringiensis associated with a rhabditid entomopathogenic nematode especially against Fusarium oxysporum

“…The stereochemistry of the compounds play an important role in biological activity. Li et al 49 reported the production of two stereoisomeric CDPs, cyclo(L-Tyr-L-Pro) and cyclo(L-Tyr-D-Pro) from Lactobacillus reuteri, where cyclo(L-Tyr-L-Pro) is more effective against S. aureus which causes menstruation-associated toxic shock syndrome (TSS) in human.…”