Intercellular Communication via thecomX-Inducing Peptide (XIP) ofStreptococcus Mutans

Abstract

21Gram-positive bacteria utilize exported peptides to coordinate genetic and physiological 41. CC-BY-NC-ND 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/148320 doi: bioRxiv preprint first posted online Jun. 9, 2017; IMPORTANCE 42The comX-inducing peptide (XIP) of Streptococcus mutans is a key regulatory element 49The results have important implications in the context of the ecology, virulence and evolution of 50 a ubiquitous human pathogen and related organisms.

Competence inhibition by the XrpA peptide encoded within the comX gene of Streptococcus mutans

“…Our working model must also account for the fact that XrpA fragments can elicit effects when provided exogenously. Therefore, we are testing the hypothesis that XrpA peptides, which may be released into the extracellular space through lysis, can be actively internalized, perhaps after processing, to elicit their effects on ComR – similar to what has been proposed for XIP (Kaspar et al ., ). Mass spectrometry studies are currently ongoing to localize XrpA and other S. mutans encoded peptides that affect competence (Ahn et al ., ).…”

“…XIP has been detected in culture supernates, supporting the hypothesis that XIP is a diffusible intercellular signal (Desai et al ., ; Khan et al ., ; Wenderska et al ., ), although the mechanism by which XIP is released into the environment can involve active transport (Chang and Federle, ) or cell lysis (Kaspar et al ., ), depending on the species of bacteria. Recently, it was confirmed experimentally that XIP is able to act as a diffusible intercellular communication molecule and that signaling can occur within biofilm populations (Shields and Burne, ; Kaspar et al ., ).…”

Expanding the Vocabulary of Peptide Signals in Streptococcus mutans

“…The model for XIP release and processing may differ in S. mutans . While three independent research groups have detected XIP in supernatant fluids of S. mutans (Desai et al, 2012; Khan et al, 2012; Wenderska et al, 2012), the mechanisms for secretion or processing have not been identified in this organism to date (Kaspar et al, 2017). Notably, in Streptococcus thermophilus (Gardan et al, 2013), the Eep protease processes ComS to XIP, but an equivalent function for proteases in S. mutans with characteristics similar to Eep has not been demonstrated (Khan et al, 2012).…”

“…This was in contrast to early biofilms (5–7 h), where robust comX activity was measured and the majority of the population responded. In a second study, a co-culturing system was designed such that one S. mutans strain (a “sender”) would overproduce the XIP peptide precursor ComS, exporting large amounts of XIP to the extracellular space so that a receiver strain, which was unable to produce XIP (Δ comS ), would internalize the XIP via the Opp transport system and a response could be measured (Kaspar et al, 2017). This study concluded that XIP had the potential to act as a diffusible signal and that the XIP released by a sender could activate a nearby responder in biofilm populations.…”

“…Release of XIP to bacterial kin could also be a part of this process—release of both a source of genetic material (eDNA) and activating peptide at the same time is a logical approach so that DNA is available as cells become fully competent. Support for this new idea arises from failed competence activation of a reporter strain grown in supernatant of a S. mutans strain lacking the major autolysin AtlA (Kaspar et al, 2017). Why would S. mutans lack a dedicated peptide export system that seems common in other streptococci?…”