Staphylococcus aureus Develops an Alternative, ica- Independent Biofilm in the Absence of the arlRS Two-Component System

Abstract

The biofilm formation capacity of Staphylococcus aureus clinical isolates is considered an important virulence factor for the establishment of chronic infections. Environmental conditions affect the biofilm formation capacity of S. aureus, indicating the existence of positive and negative regulators of the process. The majority of the screening procedures for identifying genes involved in biofilm development have been focused on genes whose presence is essential for the process. In this report, we have used random transposon mutagenesis and systematic disruption of all S. aureus two-component systems to identify negative regulators of S. aureus biofilm development in a chemically defined medium (Hussain-Hastings-White modified medium [HHWm]). The results of both approaches coincided in that they identified arlRS as a repressor of biofilm development under both steady-state and flow conditions. The arlRS mutant exhibited an increased initial attachment as well as increased accumulation of poly-N-acetylglucosamine (PNAG). However, the biofilm formation of the arlRS mutant was not affected when the icaADBC operon was deleted, indicating that PNAG is not an essential compound of the biofilm matrix produced in HHWm. Disruption of the major autolysin gene, atl, did not produce any effect on the biofilm phenotype of an arlRS mutant. Epistatic experiments with global regulators involved in staphylococcal-biofilm formation indicated that sarA deletion abolished, whereas agr deletion reinforced, the biofilm development promoted by the arlRS mutation.Staphylococcus aureus is a gram-positive bacterium responsible for many infections ranging from folliculitis and foodborne intoxications to severe endocarditis, osteomyelitis, or septicemia. S. aureus can live harmlessly on many skin surfaces, especially around the nose, mouth, genitals, and rectum. This organism shares with other pathogens the ability to adhere to catheters and other indwelling devices and form multicellular communities embedded in an exopolysaccharidic matrix known as a biofilm (for reviews, see references 22 and 11). Inside the biofilm, S. aureus becomes more resistant to antibiotic treatments and the actions of the immune system (2, 23). As a consequence, staphylococcal-biofilm-associated infections of this type are difficult to eradicate, and most of them can be eliminated only by the removal and substitution of the contaminated implant.With the exception of the icaADBC operon, discovered by heterologous complementation of a biofilm-negative Staphylococcus carnosus isolate with a genomic library of Staphylococcus epidermidis RP62A (29), early genetic studies of the staphylococcal-biofilm formation process have been performed using transposon mutagenesis on a biofilm-positive isolate and the ensuing selection of biofilm-deficient mutants by a microtiter plate assay (6,13,24,27,28,37,38,42,46,49). These studies have been crucial for identifying S. aureus genes whose presence is essential for primary attachment and/or biofilm development under the environmen...

Biofilm Formation by Staphylococcus haemolyticus

“…Furthermore, the detachment results indicate that ß-1,6-linked polysaccharides are probably not the major matrix component of PIA-independent biofilms. PIA-independent biofilm formation has also been reported in S. epidermidis, S. aureus, and S. lugdunensis (15,18,41,43,46). Only two isolates in our study showed Ͼ75% detachment when they were treated with NaIO 4 , which is comparable to the level of detachment observed for S. epidermidis RP62A (43).…”

Identification of a Novel Essential Two-Component Signal Transduction System, YhcSR, inStaphylococcus aureus

“…It has been recently reported that insertional mutation of either yhcS or yhcR has no effect on the viability of S. aureus (37). This contradictory result may be due to the functional untruncated proteins generated from the insertional knockout mutants.…”

Biofilm formation of Brazilian meticillin-resistant Staphylococcus aureus strains: prevalence of biofilm determinants and clonal profiles

“…As a result, agr-dysfunctional strains have a tendency to form biofilms in vitro, which has been attributed to, among other factors, the decreased production of proteases responsible for digestion of biofilm extracellular matrix, overexpression of protein A and the increased accumulation of fibronectin-binding proteins (Toledo-Arana et al, 2005;Merino et al, 2009;Vergara-Irigaray et al, 2009;Ferreira et al, 2013). The literature differs as regards the association between the type of agr and biofilm production (Cafiso et al, 2007;Lim et al, 2013).…”