The increased intracellular concentration of this stress protein at pH 8.2 may prevent protein aggregation
and misfolding due to an increased intracellular pH. Bacterial GroEL is highly homologous with human HSP 60. It was shown to cross-react with human HSP 60 on endothelial cells and induces autoimmune responses that may play a role in the process of vascular endothelial injury, a key event in the pathogenesis of atherosclerosis . A recent study by Lee and colleagues  reported that F. Selleckchem Crizotinib nucleatum GroEL induces a number of risk factors in a mouse model of atheroscleorosis. The increased production of GroEL under SB273005 alkaline pH environments may support the association between periodontal diseases and atherosclerosis. The intracellular concentration of RecA, which is associated with the maintenance and repair of DNA, was found to increase at pH 8.2 (Table 1). Both acidic (pH 8.0) pH environments denature DNA via depurination leading to the separation of double-stranded DNA [70, 71]. Repair of the DNA gap relies on recombinational DNA proteins, including RecA . The increased production of RecA may reflect the rise in intracellular
check details pH at pH 8.2. Interestingly, our Western blotting results did not detect altered concentration of RecA in cells grown at pH 7.4 and 8.2. The production of RecA under different growth pH may therefore require further investigation although some may argue that Western blotting technique is of semi-quantitative in nature . Changes in translational protein expression The intracellular concentration of seven
proteins classified in the category of protein synthesis including five elongation factors (EF-Tu and EF-Ts) and two ribosomal S2 subunits decreased significantly by at least ten-fold at pH 8.2 (Table 1). Bacterial elongation factors EF-Tu and EF-Ts interact with each other and are essential for growth in E. coli. These proteins are often reported to be differentially expressed by bacterial cells exposed to stressful environments. It is interesting to note that the abundance of elongation factors EF-Ts decreased 2-fold in F. nucleatum when exposed to pH 7.8  but remained www.selleck.co.jp/products/Decitabine.html affected when the bacterium was cultured under oxidative stress . Elongation factor EF-Tu has been reported to posses chaperone-like properties . Len and co-workers  reported an increased production of EF-Tu at low pH by acid-stressed Streptococcus mutans. The down-regulation of EF-Tu and translational proteins in the present study may indicate reduced rate of protein synthesis at pH 8.2. Conclusions To our knowledge, this is the first study to investigate alterations in both cytoplasmic and membrane protein production in F. nucleatum alkaline induced biofilms. Our results indicate that the biofilm cells may be more metabolically efficient, primarily via alterations in glucose and glutamate catabolism.