Multiple Factors are Involved in Regulation of Extracellular Membrane Vesicle Biogenesis in Streptococcus mutans

In this study, functional genomics, along within vitro biofilm models, was used to identify factors that regulate MV biogenesis. Our results showed that when added to growth medium, MVs significantly enhanced biofilm formation byS. mutans, especially during growth in sucrose. This effect occurred in the presence and absence of added human saliva. Functional genomics revealed several genes, includingsfp, which have a major effect onS. mutans MVs. InBacillus sp.sfp encodes a 4 ’‐phosphopantetheinyl transferase that contributes to surfactin biosynthesis and impacts vesiculogenesis. InS. mutans, sfp resides within the TnSmu2 Genomic Island that supports pigment production associated with oxidative stress tolerance. Compared to the UA159 parent, theΔsfp mutant, TW406, demonstrated a 1.74 ‐fold (P<0.05) higher MV yield as measured by BCA protein assay. This mutant also displayed increased susceptibility to low pH and oxidative stressors, as demonstrated by acid killing and hydrogen peroxide challenge assays. Deficiency ofbacA, a putative surfactin synthetase homolog within TnSmu2, and especiallydac andpdeA that encode a di ‐adenylyl cyclase and a phosphodiesterase, respectively, also significantly increased MV yield (P<0.05). However, elimination ofbacA2, a bacitracin synthetase homolog, resulted in a>1.5 ‐fold (P<0.05) reduction of MV yield. These results demonstrate thatS. mutans MV properties are regulated by genes within and outside of the TnSmu2 island, ...
Source: Molecular Oral Microbiology - Category: Microbiology Authors: Tags: ORIGINAL ARTICLE Source Type: research