Biochemical change exhibited by oral streptococci resulting from laboratory subculturing

Abstract

The intent of this study was to assess the effects of continued laboratory subculturing on selected biochemical properties of oral streptococci freshly isolated from dental plaque. Six fresh isolates (3 Streptococcus mutans and 3 non-mutans) and 2 laboratory strains were subcultured daily for a total of 225 transfers, and cells were harvested every 75 transfers from duplicate batch cultures grown with glucose at a constant pH. Eleven biochemical properties were assayed with cells, membranes and cell-free extracts and the results subjected to statistical analysis for differences between the duplicate cultures and the various subcultures. In addition, the activity of 19 hydrolytic enzymes was assayed with the semiquantitative apiZYM system (Analytab products). The activity of zero-time samples varied by as much as 241-fold for a single property with particularly low activity for EIIglc of the phosphoenolpyruvate phosphotransferase system and cell-associated extracellular polysaccharide synthesis. The 3 S. mutans fresh isolates had higher activity in 8 of the 11 assays compared with the 3 non-mutans strains, with extracellular polysaccharide synthesis the most significant trait. Statistical analysis of the 2816 assays of the 11 traits for the 8 test strains at the 4 selected time intervals revealed considerable change in the activity of the test parameters. The most notable changes in the S. mutans strains over the 225 subcultures were significant increases in glycolytic activity and decreases in hydrophobicity and extracellular polysaccharide synthesis activity. Of the measured properties, lactate dehydrogenase and cell-associated extracellular polysaccharide synthesis activity were the most stable and H+/ATPase activity was the most variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Construction and characterization of a recombinant ureolytic Streptococcus mutans and its use to demonstrate the relationship of urease activity to pH modulating capacity

“…These results can be explained by considering the relative rates at which ureolysis and glycolysis occur. The approximate rate of glycolysis by S. mutans has previously been determined to fall in the range of between 0.08–0.25 U/mg cell dry weight [25, 26]. In S. mutans AC04 grown in 5 or 10 μM NiCl 2 , which possesses a ureolytic capacity of approximately 0.13 and 0.16 μmol urea hydrolyzed/min/mg cell dry weight, (0.26 and 0.32 μmol NH 3 produced/min/mg) respectively, glycolysis appears to occur at a slightly faster rate than ureolysis (Fig.…”

Dispensable genes and foreign DNA in Streptococcus mutans

“…However, it is recognized within the S. mutans research community that phenotypic changes have occurred in stocks of long-established laboratory strains. For example, stocks of Ingbritt and GS5 held in different laboratories display variation in properties (Ellwood et al, 1976;Gibbons et al, 1966;Tao et al, 1993) and there are reports of changes during multiple laboratory subcultures (Cvitkovitch & Hamilton, 1994;McBride et al, 1984;Russell & Smith, 1986).This study provides two examples where consequential genetic changes may have been precipitated by laboratory manipulation. Strain LT11, which was derived by chemical mutagenesis of UA159 (Tao et al, 1993), has lost TnSmu2 and the IS3 elements detected in its parent UA159 (Table 1).…”

Differences in Acidogenicity of <i>S. sobrinus</i> and <i>S. rattus</i> Are Linked to the Catalytic Efficiency of the Glycolytic Key Enzyme Phosphofructokinase

“…Making use of two model strains, this study shows that possibly strain-specific differences in acidogenicity may be biochemically detected by measuring the catalytic properties of their respective PFKs. However, laboratory subculturing over a long period may lead to changes in the glycolytic rate [Cvitkovitch and Hamilton, 1994]. Hence, the in vivo situation may differ from the in vitro model system described here.…”