Title: 0165 - Phenotypic Characterization of a Streptococcus gordonii Lipoteichoic Acid-Deficient Mutant
Bruno Lima (Presenter)
University of Minnesota
Gerrit Vreeman, University of Minnesota
Karen Ross, University of Minnesota
Mark Herzberg, University of Minnesota
Objectives: Lipoteichoic acid (LTA) is a major component of the Gram-positive cell envelope. LTA affects bacterial interactions with eukaryotic cells, and in some infections, LTA functions as a virulence factor. Why LTA is important in the physiology of Gram-positive bacteria, however, remains elusive. Our lack of knowledge reflects in part the growth deficits that accompany LTA-defective mutants. The goal of this study is to investigate how LTA contributes to the physiology of the oral commensal, Streptococcus gordonii.
Methods: The LTA mutant was constructed by deleting SGO_1140, an LTA synthase homolog in S. gordonii. PCR and Western blot were utilized to confirm the deletion. To address the impact of LTA in S. gordonii physiology, and given that LTA is a membrane-bound, cell wall-associated exopolymer, the LTA mutant and wild-type strain were compared for growth profiles, coccal chain formation, biofilm development, coaggregation with other oral bacteria, and hemagglutination of red blood cells. The two strains were also compared for surface hydrophobicity and the expression pattern of cell-wall-associated proteins.
Results: As has been observed for other species of bacteria, the LTA-defective mutant presented a severe growth defect, when compared to the wild-type. Biofilm formation was also severely reduced by the lack of LTA. Hydrophobicity and coaggregation with other species of oral bacteria were not affected, and only a small defect was observed in the ability of the LTA mutant to hemagglutinate red blood cells. To our surprise, several cell-wall associated proteins were differentially expressed in the LTA mutant compared to wild type, including the lipoprotein adhesin ScaA.
Conclusions: A major polymer of the Gram-positive cell envelope, S. gordonii LTA plays a previously unrecognized role in the display of cell-wall-associated proteins, likely contributing to the defect in biofilm formation when mutated. We are currently working to identify those proteins and determine why LTA is required for their surface display.
This abstract is based on research that was funded entirely or partially by an outside source:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: none