TY - JOUR
T1 - Resistance to acidic and alkaline environments in the endodontic pathogen Enterococcus faecalis
AU - Nakajo, K.
AU - Komori, R.
AU - Ishikawa, S.
AU - Ueno, T.
AU - Suzuki, Yoichi
AU - Iwami, Y.
AU - Takahashi, Nobuhiro
PY - 2006/10/1
Y1 - 2006/10/1
N2 - Background/aims: This study aimed to investigate the biochemical mechanisms employed by the endodontic pathogen Enterococcus faecalis to confer acid- and alkali-resistance and to compare these with the mechanisms of representative oral streptococci. Methods: E. faecalis JCM8728, Streptococcus mutans NCTC10449 and Streptococcus sanguinis ATCC10556 were used to assess both acid- and alkali-resistance by examining: (i) growth in complex media; (ii) stability of intracellular pH (pHin); (iii) cell durability to leakage of preloaded BCECF (2′,7′-bis-(2-carboxyethyl)-5,6-carboxy-fluorescein) ; and (iv) cell permeability to SYTOX-Green. Results: Growth was initiated by E. faecalis at pH 4.0-11.0, by S. mutans at pH 4.0-9.0 and by S. sanguinis at pH 5.0-9.0. The pHin was similar to the extracellular pH in S. mutans and S. sanguinis at pH 5-10, while the pHin of E. faecalis was maintained at approximately 7.5-8.5 when extracellular pH was 7.5-10 and was maintained at levels equivalent to the extracellular pH when pH < 7.5. Cell membranes of E. faecalis were resistant to BCECF leakage when extracellular pH was 2.5-12 and to SYTOX-Green permeability at pH 4-10. The cell membrane durability to extracellular pH in E. faecalis was higher than that observed in the Streptococcus strains. Conclusion: Compared to S. mutans, E. faecalis was found to be equally resistant to acid and more resistant to alkalis. The results suggest that pH-resistance in E. faecalis is attributed to membrane durability against acid and alkali, in addition to cell membrane-bound proton-transport systems. These characteristics may account for why E. faecalis is frequently isolated from acidic caries lesions and from persistently infected root canals where calcium hydroxide medication is ineffective.
AB - Background/aims: This study aimed to investigate the biochemical mechanisms employed by the endodontic pathogen Enterococcus faecalis to confer acid- and alkali-resistance and to compare these with the mechanisms of representative oral streptococci. Methods: E. faecalis JCM8728, Streptococcus mutans NCTC10449 and Streptococcus sanguinis ATCC10556 were used to assess both acid- and alkali-resistance by examining: (i) growth in complex media; (ii) stability of intracellular pH (pHin); (iii) cell durability to leakage of preloaded BCECF (2′,7′-bis-(2-carboxyethyl)-5,6-carboxy-fluorescein) ; and (iv) cell permeability to SYTOX-Green. Results: Growth was initiated by E. faecalis at pH 4.0-11.0, by S. mutans at pH 4.0-9.0 and by S. sanguinis at pH 5.0-9.0. The pHin was similar to the extracellular pH in S. mutans and S. sanguinis at pH 5-10, while the pHin of E. faecalis was maintained at approximately 7.5-8.5 when extracellular pH was 7.5-10 and was maintained at levels equivalent to the extracellular pH when pH < 7.5. Cell membranes of E. faecalis were resistant to BCECF leakage when extracellular pH was 2.5-12 and to SYTOX-Green permeability at pH 4-10. The cell membrane durability to extracellular pH in E. faecalis was higher than that observed in the Streptococcus strains. Conclusion: Compared to S. mutans, E. faecalis was found to be equally resistant to acid and more resistant to alkalis. The results suggest that pH-resistance in E. faecalis is attributed to membrane durability against acid and alkali, in addition to cell membrane-bound proton-transport systems. These characteristics may account for why E. faecalis is frequently isolated from acidic caries lesions and from persistently infected root canals where calcium hydroxide medication is ineffective.
KW - Acid-resistance
KW - Alkali-resistance
KW - Endodontic pathogen
KW - Enterococcus faecalis
UR - http://www.scopus.com/inward/record.url?scp=33747613542&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33747613542&partnerID=8YFLogxK
U2 - 10.1111/j.1399-302X.2006.00289.x
DO - 10.1111/j.1399-302X.2006.00289.x
M3 - Article
C2 - 16922926
AN - SCOPUS:33747613542
VL - 21
SP - 283
EP - 288
JO - Molecular Oral Microbiology
JF - Molecular Oral Microbiology
SN - 2041-1006
IS - 5
ER -