This study was undertaken to identify ecological factors that favour opportunistic pathogenic species in the subgingival microflora. In a first approach, human serum as a substitute for gingival exudate, was used for batch-wise enrichment of subgingival plaque. The microflora resulting after 5-6 enrichment steps consisted of black-pigmented and non-black-pigmented Bacteroides species, Peptostreptococcus micros and Fusobacterium nucleatum as the main organisms. It is noted that the same group of species was found to be enriched independent upon the origin of the subgingival plaque sample. It was suggested that these organisms are favoured by the increased flow of gingival exudate during inflammation. The consortium of organisms was capable of selective degradation of serum (glyco-)proteins. Four different types of degradation occurred. After a prolonged period of growth complete degradation of immunoglobulins, haptoglobin, transferrin and complement C3c was observed. Partial degradation of immunoglobulins, haptoglobin, transferrin, albumin, alpha 1-antitrypsin and complement C3c and C4 was generally observed after 48 h of growth. Besides, immunoglobulin protease activity yielding Fc and Fab fragments was found. The consortium was also capable of consuming carbohydrate side-chains as indicated by an altered electrophoretic mobility of the serum glycoproteins.
Aims: To assess the in¯uence of sporulation media on heat resistance, and the use of stress recovery media to measure preservation injury of spores of ®ve representative spoilage bacilli. Methods and Results: Bacillus spores prepared on nutrient agar supplemented with Ca 2+ , Mg 2+ , Mn 2+ , Fe 2+ and K + were more heat-resistant than spores obtained from nutrient agar with Mn 2+ . This increased heat resistance correlated with a decrease in the protoplast water content as determined by buoyant density sedimentation. The degree of preservation injury severity could be assessed on media containing NaCl at moderate pH and organic acids at acid pH. Ca-DPA, K + or proline were added to the recovery media to demonstrate that heat probably caused injury to both spore germination and the outgrowth system. Signi®cance and Impact of the Study 2 : The metal content of sporulation media can strongly effect the validity of preservation resistance studies. The distinctive recovery media developed here can be relevant for assessing and comparing new preservation technologies.
. 1997. Flow cytometry in combination with fluorescent molecular markers 5-(and 6-) carboxyfluorescein succinimidylester (CFSE) and propidium iodide (PI) have been applied to determine lag times, numbers of cell divisions and injury after mild heat (50°C, 5 min) and nisin treatments (0·1 and 1·0 mg ml −1 ) of Lactobacillus plantarum. Initial labelling with covalently bound dye CFSE (20 and 100 mg ml −1 ) allowed determination of lag times and cell proliferation for up to eight generations. Double-labelling with CFSE and PI (5 mg ml −1 ) provided additional information about damage levels and distributions within populations. Subpopulations surviving treatment could be identified easily and selectively sorted.
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