Abstract
Many bacteria in biofilm surround themselves by an extracellular matrix composed mainly of extracellular polysaccharide (EP), proteins such as amyloid-like fibers (ALF) and nucleic acids. While the importance of EP in attachment and acceleration of biofilm by a number of different bacterial species is well established, the contribution of ALF to attachment in multispecies biofilm remains unknown. The study presented here aimed to investigate the role of TasA, a precursor for ALF, in cell-cell interactions in dual-species biofilms of Bacillus subtilis and Streptococcus mutans. Expression of major B. subtilis matrix operons was significantly up-regulated in the presence of S. mutans during different stages of biofilm formation, suggesting that the two species interacted and modulated gene expression in each other. Wild-type B. subtilis expressing TasA adhered strongly to S. mutans biofilm, while a TasA-deficient mutant was less adhesive and consequently less abundant in the dual-species biofilm. Dextran, a biofilm polysaccharide, induced aggregation of B. subtilis and stimulated adhesion to S. mutans biofilms. This effect was only observed in the wild-type strain, suggesting that interactions between TasA and dextran-associated EP plays an important role in inter-species interactions during initial stages of multispecies biofilm development.
Highlights
Biofilm is defined as a complex structure of microorganisms adhering to each other and/or to surfaces, embedded in an extracellular matrix[1]
The aims of the current study were to determine the direct interaction between the model bacteria B. subtilis and S. mutans and to identify the role of TasA, a precursor for amyloid-like fibers (ALF) produced by B. subtilis, in the formation of this co-species biofilm
The first aim of this study was to determine whether an interaction between B. subtilis and S. mutans cells may result in formation of dual-species biofilm
Summary
Biofilm is defined as a complex structure of microorganisms adhering to each other and/or to surfaces, embedded in an extracellular matrix[1]. Recent studies have shown that many biofilm-producing microorganisms can produce amyloid-like fibers (ALF)[7]. Among these microorganisms are Bacillus subtilis (Romero, Aguilar et al.22), Streptococcus mutans (Oli, Otoo et al 2012), Escherichia coli[8,9], Staphylococcus aureus[9] and Pseudomonas aeruginosa[10]. The role of ALF in mono-species biofilm formation has been studied before, its role in multispecies microbial communities remains unclear[11]. The dental biofilm is a classic example of diverse, complex multispecies biofilm It appears that one of the most predominant class in the oral biofilm is bacilli[12]. Association of B. subtilis to dental diseases remains unclear[13,14]
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