Agglutination of Streptococcus suis by sialic acid-binding lectins.

The 35 Streptococcus suis capsular-type reference strains as well as 45 field strains of type 2 were tested with sialic acid-binding lectins from Sambucus nigra (SNA I), Triticum vulgaris, Maackia amurensis, Homarus americanus, and Limax flavus. Only types 1, 1/2, 2, 14, 15, and 16 agglutinated with SNA I and/or the T. vulgaris lectin. All field strains agglutinated only with SNA I. Reaction with SNA I was probably due to the sialic acid moiety since it disappeared after sialidase treatment. These results confirm the presence of sialic acid in S. suis with the possible terminal sequence N-acetylneuraminic acid-alpha(2,6)GalNAc.

Agglutination of "Streptococcus milleri" by lectins.

The agglutination of 218 clinical isolates and three ATCC type strains of "Streptococcus milleri" was tested with 25 different lectins from plants and fungi. An agglutination reaction with one or more lectins was observed with 42 isolates when the cells were untreated. After trypsinisation of the bacteria, 109 strains yielded a positive reaction and after boiling the bacterial cells at pH2, 218 isolates were agglutinated. As an overall result of our experiments with untreated, trypsinised and boiled cells, 17, 37 and 45 different agglutination patterns, respectively, were obtained. The lectins from Datura stramonium, Robinia pseudoacacia and Dolichos biflorus agglutinated isolates belonging only to Lancefield group C, being non-reactive with other isolates. These lectins were also found to be specific for "large colony type" streptococci of group C. The use of lectin agglutination in epidemiological and ecological studies of "S. milleri" is discussed.

The agglutination of beta-haemolytic streptococci by lectins.

The ability of 25 lectins, isolated from different plants and fungi, to agglutinate 95 clinical isolates of beta-haemolytic streptococci was examined. Cell suspensions were untreated, trypsin-treated or boiled at pH 2.0. None of the 95 untreated cell suspensions gave a visible reaction with any of the lectins. When the cells were trypsinised, 42 strains were agglutinated with one or more lectin and after boiling at pH 2, all the strains were agglutinated. After treatment with trypsin, 20 different agglutination patterns were observed, and after boiling, 19 patterns, four of which were similar. A correlation was found between Lancefield group C and some of these patterns. Some lectins reacted specifically with group C streptococci; DBA and WFA, both specific for D-GalNAc, DSA, a GlcNAc-specific lectin, and RPA, which showed a complex specificity, reacted only with group C strains. Furthermore, the lectin of Maackia amurensis reacted with 50% of group B streptococci only. Agglutination assays with lectins were reproducible, easy to perform, relatively inexpensive and, therefore, applicable to studies of cell-wall structure and epidemiology of beta-haemolytic streptococci.

Isolation and characterization of a seed lectin from elderberry (Sambucus nigra L.) and its relationship to the bark lectins.

A third elderberry (Sambucus nigra L.) lectin (SNA-III) has been isolated from dry seeds by affinity chromatography on immobilized 2-acetamido-2-deoxy-D-galactose. This lectin is a blood-group, nonspecific glycoprotein containing 21% of carbohydrate, and is rich in asparagine (or aspartic acid), serine, glutamine (or glutamic acid), and glycine. Gel filtration on Superose 12 yielded a single symmetrical peak corresponding to mol. wt. 50,000, SDS-poly(acrylamide) gel (SDS-PAGE) electrophoresis showed a single polypeptide band of 33 kDa, indicating that the native protein is a dimer of identical subunits. Hapten-inhibition assays of the agglutination of red blood cells showed that 2-acetamido-2-deoxy-D-galactose is the best inhibitor, being twice as potent as D-galactose, melibiose, and 2-amino-2-deoxy-D-galactose. A comparison of SNA-III to the previously described elderberry-bark lectins, SNA-I and SNA-II, indicated that the seed lectin is well distinct from them.

Stress-induced accumulation of wheat germ agglutinin and abscisic Acid in roots of wheat seedlings.

Wheat germ agglutinin (WGA) levels in roots of 2-day-old wheat seedlings increased up to three-fold when stressed by air-drying. Similar results were obtained when seedling roots were incubated either in 0.5 molar mannitol or 180 grams per liter polyethylene glycol 6000, with a peak level of WGA after 5 hours of stress. Longer periods of osmotic treatment resulted in a gradual decline of WGA in the roots. Since excised wheat roots incorporate more [(35)S]cysteine into WGA under stress conditions, the observed increase of lectin levels is due to de novo synthesis. Measurement of abscisic acid (ABA) levels in roots of control and stressed seedlings indicated a 10-fold increase upon air-drying. Similarly, a five- and seven-fold increase of ABA content of seedling roots was found after 2 hours of osmotic stress by polyethylene glycol 6000 and mannitol, respectively. Finally, the stress-induced increase of WGA in wheat roots could be inhibited by growing seedlings in the presence of fluridone, an inhibitor of ABA synthesis. These results indicate that roots of water-stressed wheat seedlings (a) contain more WGA as a result of an increased de novo synthesis of this lectin, and (b) exhibit higher ABA levels. The stress-induced increase of lectin accumulation seems to be under control of ABA.