Adaptation of Streptococcus mutans and Enterococcus hirae to acid stress in continuous culture.
AUTOR(ES)
Belli, W A
RESUMO
Streptococcus mutans GS-5 and IB1600 adapted to growth in acidic environments in continuous culture at slow (generation time = 8.3 h) or fast (generation time = 2.4 h) rates of growth in complex medium with a restricted glucose supply. The extent of adaptation was indicated by changes in minimum pH values attained by harvested cells suspended in dense suspensions with excess glucose and by increased levels of ATPase activity assayed in permeabilized cells. Also, adapted cells better withstood potentially lethal acidification. Cells harvested from cultures growing at pH values close to 5 reduced suspension pH to lower values than cells from cultures maintained at pH 7. Cells from pH 6 cultures were intermediate. The IB1600 strain had a higher level of constitutive acid resistance than the GS-5 strain and also was better able to adapt to growth in acidified media. Both had less adaptive capacity than Enterococcus hirae ATCC 9790. Adaptation occurred rapidly, mainly within a single generation in continuous culture, while deadaptation occurred more slowly over multiple generations. The capacity of S. mutans to adapt to acid conditions is likely to be important in the ecology of dental plaque and also for the cariogenicity of the organism.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=182857Documentos Relacionados
- Application of a competition model to the growth of Streptococcus mutans and Streptococcus sanguis in binary continuous culture.
- Streptococcus mutans fructosyltransferase (ftf) and glucosyltransferase (gtfBC) operon fusion strains in continuous culture.
- Effect of fructose and other carbohydrates on the surface properties, lipoteichoic acid production, and extracellular proteins of Streptococcus mutans Ingbritt grown in continuous culture.
- Effect of growth conditions on levels of components of the phosphoenolpyruvate:sugar phosphotransferase system in Streptococcus mutans and Streptococcus sobrinus grown in continuous culture.
- Effect of ionophores and pH on growth of Streptococcus bovis in batch and continuous culture.