Comparison of aminopeptidase activities in four strains of mutans group oral streptococci

Abstract

In this study, native cells of Streptococcus mutans VA-29R and Streptococcus rattus FA-1 displayed significantly higher aminopeptidase activity than did cells of Streptococcus cricetus AHT or Streptococcus sobrinus 6715 toward the nitroanilide derivatives of leucine, alanine, methionine, arginine, and lysine. These differences in cellular aminopeptidase activity led us to investigate the subcellular localization of the aminopeptidase in these mutans group streptococci. Following conversion of native cells to protoplasts by treatment with lysozyme, most of the aminopeptidase activity detected in the native-cell preparations remained associated with the intact protoplasts. After lysis of protoplasts and differential centrifugation, most of the total cellular aminopeptidase activity was recovered with the cytoplasmic fraction. Membrane-associated aminopeptidases represented only minor activities in these mutans group streptococci. Although the four strains showed no differences with respect to a predominant cytoplasmic localization for the aminopeptidase activities, the levels of activity in the cytoplasmic fractions from S. cricetus AHT and S. sobrinus 6715 were significantly lower than those measurable in the corresponding fractions from S. mutans VA-29R and S. rattus FA-1. These results support the conclusion that the differences in aminopeptidase activity expressed by these streptococci reflect quantitative differences rather than differences in enzyme subcellular localization.

Bacterial adhesion on the titanium and zirconia abutment surfaces

“…Also, reduced levels of detection obtained may be related to degradation of bacterial DNA in the surfaces of specimens. Cell killing and degradation of DNA by proteolytic enzymes and/or endonucleases were demonstrated in previous studies (Cowman & Baron 1993;Cascales et al 2007). The association of other DNA-based methods, such as real-time PCR, may add important new information and supplement the data recorded by DNA checkerboard.…”

Use of checkerboard DNA–DNA hybridization to evaluate the internal contamination of dental implants and comparison of bacterial leakage with cast or pre‐machined abutments

“…The significant decrease in the number of bacteria from samples collected 14 days after implant inoculation was considered to be related to degradation of bacterial DNA. Cell killing and degradation by bacteriocin as well as degradation of DNA by proteolytic enzymes and endonucleases have been demonstrated in several studies (Loyola‐Rodriguez et al 1992; Cowman & Baron 1993; Cascales et al 2007). A recent investigation has shown that bacteria seem to influence each other during the storage period, possibly altering DNA to an extent that causes the DNA‐hybridization method to fail in recognizing its targets (Katsoulis et al 2005).…”

Bacterial leakage along the implant–abutment interface: culture and DNA Checkerboard hybridization analyses

“…In the present investigation, the reduced detection levels observed may be in part related to degradation of the bacterial DNA collected from the internal surfaces of the implants. Cell killing and degradation of DNA by proteolytic enzymes and/or endonucleases has been demonstrated in previous studies (Cowman & Baron 1993;Cascales et al 2007). Katsoulis et al (2005) showed that bacteria seem to influence each other, possibly altering DNA to the extent of causing the DNA-hybridization method to fail in recognizing its targets.…”