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Exploration of the mechanisms of biofilm formation by Enterococcus faecalis in glucose starvation environments
Author(s) -
Ran SJ,
Jiang W,
Zhu CL,
Liang JP
Publication year - 2015
Publication title -
australian dental journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.701
H-Index - 71
eISSN - 1834-7819
pISSN - 0045-0421
DOI - 10.1111/adj.12324
Subject(s) - biofilm , enterococcus faecalis , extracellular polymeric substance , microbiology and biotechnology , polysaccharide , extracellular , bacteria , chemistry , viability assay , atpase , tryptic soy broth , confocal laser scanning microscopy , biochemistry , biology , cell , gene , enzyme , escherichia coli , genetics
Background Enterococcus faecalis is the most common single species present in teeth after failed root canal therapy. This is mainly due to its ability to maintain viability for a long time in filled root canals where nutrients are normally sparse. The aim of this study was to explore the mechanism of E. faecalis survival and biofilm formation in glucose‐starved environments. Methods Enterococcus faecalis ATCC 33186 was inoculated in energy starvation media for biofilm formation. Confocal laser scanning microscopy and fluorescent DNA ‐binding agents were employed to assess biofilm‐forming ability. The physiochemical properties of the biofilm cell wall were investigated by measuring the hydrophobicity, extracellular polysaccharide and ATP ase activity. The expression of stress and virulence genes was quantified by real‐time quantitative polymerase chain reaction. Results The ability for biofilm formation decreased with a decreasing concentration of glucose. The cell surface hydrophobicity increased dramatically with decreasing glucose concentration. Water‐soluble exopolysaccharide ( WSE ) synthesis decreased in glucose starvation media, whereas water‐insoluble exopolysaccharide ( WIE ) synthesis increased. A marked decrease in ATP ase activity was observed only in a no glucose medium. In addition, transcription of ace, fsrB and gelE genes increased under glucose starvation stress while atpE, salB and esp genes were down‐regulated. Conclusions Enterococcus faecalis survival and biofilm formation under glucose starvation stress may be attributed to an increase in cell‐surface hydrophobicity and additionally to the up‐regulation of some genes involved in stress response and biofilm formation. These characteristics may explain why E. faecalis can maintain viability for a long time in an energy‐starved environment and why it is frequently isolated from persistently infected root canals.