Proteinaceous determinants of surface colonization in bacteria: bacterial adhesion and biofilm formation from a protein secretion perspective

Abstract

Bacterial colonization of biotic or abiotic surfaces results from two quite distinct physiological processes, namely bacterial adhesion and biofilm formation. Broadly speaking, a biofilm is defined as the sessile development of microbial cells. Biofilm formation arises following bacterial adhesion but not all single bacterial cells adhering reversibly or irreversibly engage inexorably into a sessile mode of growth. Among molecular determinants promoting bacterial colonization, surface proteins are the most functionally diverse active components. To be present on the bacterial cell surface, though, a protein must be secreted in the first place. Considering the close association of secreted proteins with their cognate secretion systems, the secretome (which refers both to the secretion systems and their protein substrates) is a key concept to apprehend the protein secretion and related physiological functions. The protein secretion systems are here considered in light of the differences in the cell-envelope architecture between diderm-LPS (archetypal Gram-negative), monoderm (archetypal Gram-positive) and diderm-mycolate (archetypal acid-fast) bacteria. Besides, their cognate secreted proteins engaged in the bacterial colonization process are regarded from single protein to supramolecular protein structure as well as the non-classical protein secretion. This state-of-the-art on the complement of the secretome (the secretion systems and their cognate effectors) involved in the surface colonization process in diderm-LPS and monoderm bacteria paves the way for future research directions in the field.

Role of Extracellular Proteases in Biofilm Disruption of Gram Positive Bacteria with Special Emphasis on Staphylococcus aureus Biofilms

“…These surface associated proteins can also help in biofilm establishment in a polysaccharide independent background. The biofilm-associated protein Bap mentioned previously is involved in S. aureus adherence to abiotic surface, intercellular adhesion, and biofilm accumulation [1,5,7,19]. The Bap-homologous protein Bhp may be involved in biofilm accumulation in S. epidermidis [7].…”

“…The biofilm-associated protein Bap mentioned previously is involved in S. aureus adherence to abiotic surface, intercellular adhesion, and biofilm accumulation [1,5,7,19]. The Bap-homologous protein Bhp may be involved in biofilm accumulation in S. epidermidis [7]. Some other Staphylococcal surface proteins or cell wall associated proteins that have been implicated in surface attachment/adhesion and possibly biofilm formation include: SasX and SasC (structurally uncharacterized), FnBPs (Fibronectin binding proteins), ClfB and Protein A [5].…”

“…Among the many different exopolysaccharides that are known β-1,6-linked N-acetyl glucosamine forms the most common component of the biofilm matrix of many different bacteria [3]. Besides exopolysaccharides, surface proteins and protienaceous components also play an important role in biofilm formation [7]. Most of the surface proteins involved in biofilm formation share several structural and functional features [7,8].…”

“…Besides exopolysaccharides, surface proteins and protienaceous components also play an important role in biofilm formation [7]. Most of the surface proteins involved in biofilm formation share several structural and functional features [7,8]. The first member of this group was described in a Staphylococcus aureus bovine mastitis isolate and was named Bap, for biofilm associated protein [1].…”

“…Extracellular proteases are usually activated in a complex cascade involving auto-processing and proteolytic maturation [8]. Initial belief that biofilm matrix is made up mostly of polysaccharides, has been questioned with recent findings that demonstrate that surface and secreted proteins and extracellular DNA (eDNA) are also important factors in biofilm formation, stability, and regulation [6,7]. In this light, the role of proteases becomes clearer and recent reports have shown that the application of various proteases to bacterial cultures have often resulted in the reduction of biofilm formation and in the dispersal of established biofilms [9,10].…”