Gene analysis of a biofilm-forming Streptococcus intermedius clinical isolate

Abstract

Most bacteria in natural environments form communities, which are commonly referred to as biofilms. Previously, we reported that biofilm-forming oral bacteria have an impact on pathogenesis and play a key role in development of persistent infections. We investigated how genes relate to biofilm-formation. We determined the capacity of biofilm-formation of Streptococcus intermedius (S. intermedius) clinical isolate (strain H39) by a crystal violet (CV) assay using a 96-well microtiter plate. Because CV analysis showed that the addition of glucose to the culture medium increased the biofilm-forming capacity of strain H39, we attempted to determine the gene involved in glucose metabolism and biofilm-formation in this strain. We isolated the homolog to the pgcA gene, which codes α-phosphoglucomutase in Bacillus subtilis from strain H39. Moreover, we isolated a mutant strain, which is a recombinant of this gene. Scanning electron microscopy indicated that this strain has a mesh-like structure around its cells, which is typical of biofilm-forming bacteria. Inactivation of the pgcA gene was not enough to stop biofilm-formation of strain H39. These results suggest that the genetic basis of biofilm-formation in S. intermedius is multifaceted and that the composition of the polymeric biofilm matrix is complex. Further studies are needed to elucidate the genetic basis for biofilm-formation.