AGGREGATION OF ENZYMATICALLY MODIFIED STREPTOCOCCUS MITIS INDICATING INVOLVEMENT OF LECTIN‐LIGAND TYPE INTERACTION

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Abstract
The aggregation properties of S. mitis ATCC 903 cells modified by treatment with heat or different enzymes was investigated. Bacteria that had the ability to aggregate spontaneously lost this capacity by treatment with proteolytic enzymes, .beta.-galactosidase or heat. Cells subjected to different types of modification were mixed in various proportions; their aggregation properties were recorded. To discriminate between the 2 kinds of cells in the suspension, 1 partner in the aggregation reaction was labeled with 14C-palmitic acid. Bacteria treated with .beta.-galactosidase coaggregated with spontaneously aggregating cells (not modified) and with cells treated with heat. Heat-treated cells coaggregated with spontaneously aggregating cells and with cells treated with .beta.-galactosidase. Cells treated with trypsin did not coaggregate with spontaneously aggregating cells or cells treated with heat or .beta.-galactosidase. Evidently, 2 surface components are required for specific aggregation of S. mitis cells. Both components may be degraded or released from the bacterial surface by treatment with trypsin (and other proteolytic enzymes) as shown by the inability of these cells to take part in any coaggregation with spontaneously aggregating cells. Treatment with .beta.-galactosidase degrades a carbohydrate receptor constituting the terminal part of a glycoprotein. Heat treatment inactivates a protein lectin. The fact that heat-treated bacteria and bacteria treated with .beta.-galactosidase aggregate when mixed supports the assumption that 2 components take part in the aggregation reaction. [Aggregation plays a role in development of dental plaques.].

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