Involvement of signal peptidase I in Streptococcus sanguinis biofilm formation

Abstract

Biofilm accounts for 65–80 % of microbial infections in humans. Considerable evidence links biofilm formation by oral microbiota to oral disease and consequently systemic infections. Streptococcus sanguinis, a Gram-positive bacterium, is one of the most abundant species of the oral microbiota and it contributes to biofilm development in the oral cavity. Due to its altered biofilm formation, we investigated a biofilm mutant, ΔSSA_0351, that is deficient in type I signal peptidase (SPase) in this study. Although the growth curve of the ΔSSA_0351 mutant showed no significant difference from that of the wild-type strain SK36, biofilm assays using both microtitre plate assay and confocal laser scanning microscopy (CLSM) confirmed a sharp reduction in biofilm formation in the mutant compared to the wild-type strain and the paralogous mutant ΔSSA_0849. Scanning electron microscopy (SEM) revealed remarkable differences in the cell surface morphologies and chain length of the ΔSSA_0351 mutant compared with those of the wild-type strain. Transcriptomic and proteomic assays using RNA sequencing and mass spectrometry, respectively, were conducted on the ΔSSA_0351 mutant to evaluate the functional impact of SPase on biofilm formation. Subsequently, bioinformatics analysis revealed a number of proteins that were differentially regulated in the ΔSSA_0351 mutant, narrowing down the list of SPase substrates involved in biofilm formation to lactate dehydrogenase (SSA_1221) and a short-chain dehydrogenase (SSA_0291). With further experimentation, this list defined the link between SSA_0351-encoded SPase, cell wall biosynthesis and biofilm formation.

Genetics ofsanguinis-Group Streptococci in Health and Disease

“…Rather the process is elaborate and ensures the role of S. sanguinis as a pioneer colonizer. This correlates with the observation that signal peptidase I is required for biofilm development (40). In general, signal peptidases are membrane-bound endo-proteases that cleave the signal peptide portion from the majority of secreted proteins (41).…”

“…Deletion of SSA_0351 abolishes biofilm formation but does not affect planktonic growth. Although the substrates for signal peptidase processing are not experimentally verified, in silico prediction identified 168 potential candidates, including several adhesins (40). Further characterization of signal peptidase processed surface proteins will most likely identify new proteins involved in the adhesion process.…”

Seaweeds as nutraceuticals for health and nutrition

“…Many species of bacteria secrete a combination of polysaccharides, proteins, and extracellular DNA that forms a protective layer under which they can thrive. It is estimated that biofilms are present in 65% to 85% of all bacterial infections (Aynapudi et al 2017). These films can form in wounds and inside the lungs.…”

Streptococcus Sanguinis Biofilm Formation & Interaction with Oral Pathogens

“…Several genes have been reported to impact biofilm formation by unknown mechanisms in S. sanguinis , including purB , purL , pyrE , thrB , adcA , spi , sptR and sptS [ 58 , 73 , 74 ]. It is interesting that genes ( purB , purL and pyrE ) related to nucleotide biosynthesis are involved in the biofilm formation network.…”