A non‐coding RNA from the intercellular adhesion (ica) locus of Staphylococcus epidermidis controls polysaccharide intercellular adhesion (PIA)‐mediated biofilm formation

Abstract

Polysaccharideintercellular adhesin (PIA)associated biofilm formation is mediated by the intercellular adhesin (ica) locus and represents a major pathomechanism of Staphylococcus epidermidis. Here, we report on a novel long non-coding (nc)RNA, named IcaZ, which is approximately 400 nucleotides in size. icaZ is located downstream of the ica repressor gene icaR and partially overlaps with the icaR 3ʹ UTR. icaZ exclusively exists in icapositive S. epidermidis, but not in S. aureus or other staphylococci. Inactivation of the gene completely abolishes PIA production. IcaZ is transcribed as a primary transcript from its own promoter during early-and mid-exponential growth and its transcription is induced by low temperature, ethanol and salt stress. IcaZ targets the icaR 5ʹ UTR and hampers icaR mRNA translation, which alleviates repression of icaADBC operon transcription and results in PIA production. Interestingly, other than in S. aureus, posttranscriptional control of icaR mRNA in S. epidermidis does not involve icaR mRNA 5ʹ/3ʹ UTR base pairing. This suggests major structural and functional differences in icaADBC operon regulation between the two species that also involve the recruitment of ncRNAs. Together, the IcaZ ncRNA represents an unprecedented novel species-specific player involved in the control of PIA production in NBSP S. epidermidis.

The staphylococcal exopolysaccharide PIA – Biosynthesis and role in biofilm formation, colonization, and infection

“…Moreover, recent findings also add non-protein factors to the list of PIA regulators. IcaZ, a non-coding 400-nucleotide RNA, which is encoded downstream of icaR , was found to inhibit icaR mRNA translation, leading to increased PIA production [95] . IcaZ is found inclusively in ica -positive S. epidermidis but no other staphylococcal species [95] .…”

“…IcaZ, a non-coding 400-nucleotide RNA, which is encoded downstream of icaR , was found to inhibit icaR mRNA translation, leading to increased PIA production [95] . IcaZ is found inclusively in ica -positive S. epidermidis but no other staphylococcal species [95] . Additionally, a regulatory RNA named RsaE binds in its processed form to the 5′UTR of the icaR mRNA, also increasing PIA production [96] .…”

Biofilm released cells can easily be obtained in a fed-batch system using ica+ but not with ica- isolates

“…The results obtained herein demonstrated that a fed-batch system is only reliable in obtaining Brc from S. epidermidis biofilms for some isolates, especially from those who can form thick and strong biofilms. While all ica + isolates used herein were found to be high biofilm producing strains, it should be noted that some ica + isolates lack a functional intact operon (Cafiso et al, 2004;Cue, Lei & Lee, 2012), and the mere presence of the gene might not be related to its expression (Freitas et al, 2017;Lerch et al, 2019). As such, to assess the feasibility of this method in more strains, it is important not only to determine the presence of ica but to assess if the operon is functional, as mutations in major biofilm regulators may influence the dynamics of Brc production (Cue, Lei & Lee, 2012).…”

“…Importantly, this bacterium, which was previously seen as a commensal microorganism due to its benign relationship with the host (Cogen, Nizet & Gallo, 2008;Gardiner et al, 2017), is nowadays accepted as an important opportunistic pathogen, of particular concern in ill and immunocompromised patients (Otto, 2009). S. epidermidis infections are more likely to happen upon invasive procedures involving indwelling medical devices, in which the physiological barriers are compromised, since this bacterium is a ubiquitous inhabitant of the skin and mucosae in humans (Ziebuhr et al, 2006) and has a strong ability to form biofilms on the surface of medical devices (Cerca et al, 2005c;Laverty, Gorman & Gilmore, 2013). Bacteria within biofilms are undoubtedly more resistant to antibiotics (Albano et al, 2019;Cerca et al, 2005a;Dias et al, 2018) and to the host immune defense (Cerca et al, 2006;Gray et al, 1984;Yao, Sturdevant & Otto, 2005), contributing to the persistence and recurrence of infections (Mah, 2012;Schommer et al, 2011;Singh & Ray, 2014).…”

Peer Review #1 of "Biofilm released cells can easily be obtained in a fed-batch system using ica+ but not with ica- isolates (v0.1)"

“…The results obtained herein demonstrated that a fed-batch system is only reliable in obtaining Brc from S. epidermidis biofilms for some isolates, especially from those who can form thick and strong biofilms. While all ica + isolates used herein were found to be high biofilm producing strains, it should be noted that some ica + isolates lack a functional intact operon (Cafiso et al, 2004;Cue et al, 2012), and the mere presence of the gene might not be related to its expression (Freitas et al, 2017;Lerch et al, 2019). As such, to assess the feasibility of this method in more strains, it is important not only to determine the presence of ica but to assess if the operon is functional, as mutations in major biofilm regulators may influence the dynamics of Brc production (Cue et al, 2012).…”