Abstract
Streptococcus pyogenes frequently causes purulent infections in humans. Biofilm formation is an important virulence property of S. pyogenes because of decreased susceptibility of bacteria to antibiotic treatment. Biofilm is composed of various types of matrix including glycocalyx which is an important exocellular matrix material related to bacterial sugar metabolism. A putative antiterminator protein, LicT (Spy0571), is one of the components of the glucose-independent β-gluco-side-specific phosphotransferase system (PTS). Although the PTS, a carbohydrate metabolic system, may play a role in biofilm formation, the relationship between LicT and biofilm formation has not yet been elucidated. Here, we evaluated whether LicT affected biofilm formation in modified chemically defined medium (CDMM) supplemented with glucose or β-glucoside:salicin. We created licT- and licT-complemented mutant strains from S. pyogenes 1529. Although the licT mutant strain tended to have higher growth rate than wild-typestrain in CDMM with glucose, it had a significant lower growth rate than the wild-type strain in CDMM with salicin. In addition, the licT mutant exhibited lower biofilm formation in CDMM containing salicin than the wild-type strain by 96 well plate analysis and confocal laser scanning microscopic analysis. Our results suggest that LicT plays an important role in biofilm formation of S. pyogenes.
Highlights
Streptococcus pyogenes is a gram-positive bacterium that infects the upper respiratory tract, including the tonsils and pharynx, and is responsible for pharyngitis, tonsillitis, rheumatic fever, and glomerulonephritis
A previous study revealed that S. pyogenes strains recovered from patients with treatment failure form biofilms in vitro with variable efficiency and that compared to planktonic cultures, S. pyogenes organized in biofilms have higher minimum inhibitory concentrations for all standard antibiotics used in a treatment [5]
Β-Glucosides including salicin are carbohydrates that are largely derived from plant sources. β-Glucoside utilization systems have been described in several bacteria [16]
Summary
Streptococcus pyogenes is a gram-positive bacterium that infects the upper respiratory tract, including the tonsils and pharynx, and is responsible for pharyngitis, tonsillitis, rheumatic fever, and glomerulonephritis. Bacteria alter the transcription of carbohydrate utilization genes and virulence factor production in response to changes in the environmental conditions encountered during infection in humans [7]. Pathogenic bacteria have developed molecular strategies to directly link the regulation of carbohydrate utilization and virulence factors such as biofilm formation. Antiterminator proteins are involved in the transcriptional regulation of β-glucoside-specific genes from various bacteria [9]. These antiterminator proteins bind to a ribonucleic antiterminator site present in a specific mRNA secondary structure and prevent the formation of a hairpin terminator structure that terminates transcription [10]. The binding of an antiterminator protein to mRNA permits transcription through the disrupted terminator structure into the β-glucoside-specific genes that are not normally transcribed. We focused on the role of LicT and evaluated whether LicT affected biofilm formation
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