In vitro inhibition of oral streptococci binding to the acquired pellicle by algal lectins.

AIMS: The initial colonization of the tooth by streptococci involves their attachment to adsorbed components of the acquired pellicle. Avoiding this adhesion may be successful in preventing caries at early stages. Salivary mucins are glycoproteins that when absorbed onto hydroxyapatite may provide binding sites for certain bacteria. Algal lectins may be especially interesting for oral antiadhesion trials because of their great stability and high specificity for mucins. This work aimed to evaluate the potential of two algal lectins to inhibit the adherence of five streptococci species to the acquired pellicle in vitro. METHODS AND RESULTS: The lectins used were extracted from Bryothamnion triquetrum (BTL) and Bryothamnion seaforthii (BSL). Fluorescence microscopy was applied to visualize the ability of fluorescein isothiocyanate-labelled lectins to attach to the pellicle and revealed a similar capability for both lectins. Streptococcal adherence assays were performed using saliva-coated microtitre plates. BSL inhibited more than 75% of Streptococcus sanguis, Streptococcus mitis, Streptococcus sobrinus and Streptococcus mutans adherence, achieving 92% to the latter. BTL only obtained statistically significant results on S. mitis and S. sobrinus, whose adherence was decreased by 32.5% and 54.4%, respectively. CONCLUSION: Algal lectins are able to inhibit streptococcal adherence. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results support the proposed application of lectins in antiadhesion therapeutics.

Isolation and characterization of a new agglutinin from the red marine alga Hypnea cervicornis J. Agardh.

The biochemical characterization of a new lectin (Hypnea cervicornis agglutinin or HCA) isolated from the Brazilian red alga H. cervicornis is reported. The haemagglutinating activity of the lectin was only inhibited by the glycoprotein porcine stomach mucin at a minimum inhibitory concentration of 19 microg x mL(-1). No haemagglutination inhibition was detected after the addition of simple sugars. The MALDI-TOF molecular masses of native and reduced and carbamidomethylated HCA were, respectively, 9196.6 Da and 9988.2 Da, indicating that the primary structure of the protein is crosslinked by 7 disulfide bonds. This unusual structural feature among lectins, along with its N-terminal sequence and amino-acid composition, clearly shows that HCA belongs to a protein family distinct from the isolectins Hypnin A1 and A2 isolated from the related Japanese alga Hypnea japonica. On the other hand, HCA displayed a high degree of similarity to the agglutinin from the Brazilian species Hypnea musciformis. Our data indicate the occurrence of structural diversity among lectins of closely related species living in distant ecosystems, i.e., the Pacific coast of Japan and the Atlantic coast of Brazil, and support the hypothesis that the lectin content (lectinome) might serve as a biomarker for taxonomical purposes.

Purification and characterization of a new lectin from the red marine alga Hypnea musciformis.

A lectin from the red marine alga Hypnea musciformis (HML) was purified by extraction with 20 mM PBS, precipitation with 70% saturated ammonium sulphate, ion-exchange DEAE-Cellulose chromatography and RP-HPLC. The 9.3 kDa polypeptide agglutinates erythrocytes from various sources and shows oligomerization tendencies under certain MALDI-TOF/MS conditions. Preliminary N-terminal sequencing and biological assays strongly suggest that the HML may belong to a new class of algae lectins.

The amino acid sequence of the agglutinin isolated from the red marine alga Bryothamnion triquetrum defines a novel lectin structure.

The primary structure of a lectin isolated from the red alga Bryothamnion triquetrum was established by combination of Edman degradation of sets of overlapping peptides and mass spectrometry. It contains 91 amino acids and two disulphide bonds. The primary structure of the B. triquetrum lectin does not show amino acid sequence similarity with known plant and animal lectin structures. Hence, this protein may be the paradigm of a novel lectin family.

Coliforms and Salmonella in seawater near to domestic sewage sources in Fortaleza (Ceará, Brazil).

The bacteriological conditions of the coastal region of Fortaleza (Ceará, Brasil), including the coastal zones of the Ceará and Cocó rivers, were examined. The study was conducted during June, September and December 1993, and March 1994. The region was divided into two areas: (i) Direct Influence Area (DIA), consisting of 20 sampling stations located near to discharge zones of the submarine pipeline system, where collections were carried out at the surface, and (ii) Indirect Influence Area (IIA), located near to the coastal zone, including Barra do Ceará, Kartódromo, Volta de Jurema, Mucuripe, Farol and Caça e Pesca beaches, totalling 26 sampling stations. The most probable number (MPN) of both total and fecal coliforms in DIA was positive only in station number 6, near to the sewage discharge exit. The following bacteria were identified: Citrobacter sp., Enterobacter aerogenes and Escherichia coli. Kartódromo beach was contaminated throughout the sampling period. Results of total fecal MPN was essentially lower than 3.0 x 10(2) coliforms/100 ml at Caça e Pesca beach. In December, at both DIA and IIA, Salmonella was identified in several samples. In DIA, the spatial distribution for Salmonella suggests that there should be a coastal sea current from east to west along the coastline. In IIA, Salmonella was identified at Kartódromo and Farol beaches throughout the sampling period.