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

Abstract

Abaas, S. & Holme. T. Aggregation of enzymatically modified Streptococcus mitis indicating involvement of lectin-ligand type interaction. Acta path. microbiol. immunol. a n d . Sect. B, 91: 3 I7 -324. 1983.The aggregation properties of Streptococcus 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, B-galactosidase or heat. Cells subjected to different types of modification were mixed in various proportions and their aggregation properties were recorded. To discriminate between the two kinds of cells in the suspension, one partner in the aggregation reaction was labelled with "C-palmitic acid. Bacteria treated with B-galactosidase coaggregated with spontaneously aggregating cells (not modified) and with cells treated with heat. Heattreated cells co-aggregated with spontaneously aggregating cells and with cells treated with Bgalactosidase. Cells treated with trypsin did not co-aggregate either with spontaneously aggregating cells or cells treated with heat or B-galactosidase. These findings are consistent with the hypothesis that two surface components are required for specific aggregation of S. mitis cells. We suggest that both components are 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 co-aggregation with spontaneously aggregating cells. Treatment with 6-galactosidase degrades a carbohydrate receptor constituing the terminal part of a glycoprotein. Heat treatment inactivates a protein lectin. The fact that heat-treated bacteria and bacteria treated with B-galactosidase aggregate when mixed supports the assumption that two components take part in the aggregation reaction.

INDUCTION OF AGGREGATION IN STREPTOCOCCUS MITIS BY CERTAIN IONS

“…Differences between induced and spontaneous aggregation are many. On the basis of the experimental results in the present study and earlier reports (2,4), the spontaneous aggregation seems to be a specific type of lectin-ligand interaction, as indicated by inhibition of the aggregation by galactosamine. Differences in aggregation kinetics in the spontaneous and induced aggregation, expressed as aggregation ratio, were observed.…”

“…In an earlier report the inhibition of spontaneous aggregation by trypsin, P-galactosidase or heat was demonstrated to be due to inactivation of lectin, ligand, or both (2). The failure of trypsin or P-galactosidase treatment of bacteria to inhibit the induced aggregation favours the hypothesis that ions of zinc, lanthanum, aluminium and cerium decrease the electrostatic forces of repulsion between surfaces of bacteria by a cation-bridging mechanism.…”

“…In conclusion, the results suggest that two types of qualitatively different aggregation mechanisms occur in Streplococcus mitis ATCC 903 under different conditions. One is a lectin-ligand type interaction (2,4). This mechanism is initially dependent on ionic strength (3).…”

“…Trypsin and p-galactosidase treatments have been shown to inhibit the spontaneous aggregation in S.mitis ATCC 903 (2). No such inhibitory effect was observed in aggregation induced by zinc, lanthanum or aluminium salts ( Table 3).…”