Gene expression profile and pathogenicity of biofilm-forming Prevotella intermedia strain 17

Abstract

BackgroundPrevotella intermedia (P. intermedia), a gram-negative, black-pigmented anaerobic rod, has been implicated in the development of chronic oral infection. P. intermedia strain 17 was isolated from a chronic periodontitis lesion in our laboratory and described as a viscous material producing strain. The stock cultures of this strain still maintain the ability to produce large amounts of viscous materials in the spent culture media and form biofilm-like structures. Chemical analyses of this viscous material showed that they were mainly composed of neutral sugars with mannose constituting 83% of the polysaccharides. To examine the biological effect of the extracellular viscous materials, we identified and obtained a naturally-occurring variant strain that lacked the ability to produce viscous materials in vitro from our stock culture collections of strain 17, designated as 17-2. We compared these two strains (strains 17 versus 17-2) in terms of their capacities to form biofilms and to induce abscess formation in mice as an indication of their pathogenicity. Further, gene expression profiles between these two strains in planktonic condition and gene expression patterns of strain 17 in solid and liquid cultures were also compared using microarray assays.ResultsStrain 17 induced greater abscess formation in mice as compared to that of the variant. Strain 17, but not 17-2 showed an ability to interfere with the phagocytic activity of human neutrophils. Expression of several genes which including those for heat shock proteins (DnaJ, DnaK, ClpB, GroEL and GroES) were up-regulated two to four-fold with statistical significance in biofilm-forming strain 17 as compared to the variant strain 17-2. Strain 17 in solid culture condition exhibited more than eight-fold up-regulated expression levels of several genes which including those for levanase, extracytoplasmic function-subfamily sigma factor (σE; putative) and polysialic acid transport protein (KpsD), as compared to those of strain 17 in liquid culture media.ConclusionThese results demonstrate that the capacity to form biofilm in P. intermedia contribute to their resistance against host innate defence responses.

Exopolysaccharide Productivity and Biofilm Phenotype on Oral Commensal Bacteria as Pathogenesis of Chronic Periodontitis

“…Our previous studies showed that P. nigrescens as well as P. intermedia with mannose-rich EPS showed stronger ability to induce abscesses in mice than those of a naturally occurring variant or chemically-induced mutant that lack the ability to produce EPS. TEM observations revealed that test strains with mannose-rich EPS appeared to be recognized by human neutrophils but not internalized (Yamane et al, 2005;Yamanaka et al, 2009). Leid et al (2002) have shown that human neutrophils can easily penetrate S. aureus biofilms but fail to phagocytose the bacteria.…”

“…While sucrose-derived homopolysaccharides are well known substrates which mediate adhesion of bacteria to the tooth surface and co-aggregation interactions between species of oral bacteria in the dental plaque (Russell, 2009), recent studies suggest that each bacterium produces distinctive EPS components in a sucrose-independent manner and can form so called single species biofilm (Branda et al, 2005). In the oral cavity, several species of oral bacteria are known to produce their own EPS with this manner (Okuda et al, 1987;Dyer and Bolton, 1985;Kaplan et al, 2004;Yamane et al, 2005;Yamanaka et al, 2009;Yamanaka et al, 2010). In this chapter, we will describe a possibility that a single species biofilm in the oral cavity can cause persistent chronic periodontitis along with the importance of dental plaque formation and maturation with sucrose-derived polysaccharides.…”

Neutrophil Role in Periodontal Disease

“…One important microbial defense mechanism is the evasion of phagocytosis. Prevotella strains were recognized by neutrophils but not phagocytosed, depending on whether they produced mannose-rich exopolysaccharides as part of their extracellular matrix [65]. S. aureus is able to survive after being phagocytosed by neutrophils [66].…”

Subgingival Biofilm Structure

“…Prevotella nigrescens produces a heteropolysaccharide that is composed mainly of mannose, but also contains other sugars, including glucose and fructose [42]. A mannose-rich polysaccharide has also been identified from P. intermedia [43,44]. The polysaccharides produced by P. nigrescens and P. intermedia contribute to biofilm formation and the resistance to neutrophil phagocytosis.…”