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Oral Streptococcus species experience carbohydrate limitation interrupted by periods of substrate excess following food intake by the host. To investigate the competitiveness of various streptococcal species under fluctuating carbohydrate supply, 2-membered chemostat cultures were run.Under continuous limitation of glucose or sucrose, all 6 Streptococcus mutans test strains were outcompeted by Streptococcus sanguis P4A7 or Streptococcus milleri B448. This indicated that S. mutans had a lower affinity for glucose and sucrose than S. sanguis and S. milleri.Mixed cultures were then subjected to hourly pulses with glucose. Under these conditions S. mutans Ny344 competed successfully with S. milleri B448, but still lost the competition against S. sanguis P4A7. The streptococci responded to pulses by taking up glucose at the maximum rate almost instantaneously. S. sanguis P4A7 had the highest rate of glucose uptake while the qmax value of S. mutans Ny344 was higher than that Of S. milleri B448. This suggested a causal relationship between qmax and competitiveness.

The biokinetics of cell growth of Lactobacillus amylovorus DCE 471 and bacteriocin production by this strain were investigated as a function of the temperatures (28 to 44°C) and pH values (pH 4.2 to 6.4) that are characteristic of a sourdough fermentation process. The influence of temperature and pH on microbial behavior is described by using a successfully validated predictive model.

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The present study demonstrates that the best way to enhance DNA microarray assays, both in terms of analysis speed and in final spot intensity, is to dissolve the available molar amount of sample in the smallest possible buffer volume and to subsequently convect this solution continuously across the surface of the array. The presently proposed shear-driven flow system is pre-eminently suited for this task, as it allows to induce strongly enhanced lateral transport rates, independently of the degree of miniaturization of the hybridization chamber. This transport enhancement method, however, only increases the hybridization rate and not the final spot intensity, as neither can any of the other transport enhancement methods already proposed in literature. A series of experiments with synthetic single-stranded (ssDNA) samples and an accompanying mass balance analysis are presented to demonstrate these points.