Kinetics of lactose‐reversible coadhesion of Actinomyces naeslundii WVU 398A and Streptococcus oralis 34 on the surface of hexadecane droplets

Abstract

Most investigations of mechanisms accounting for intergeneric coaggregation have emphasized stereospecific rather than nonspecific interactions. The purpose of this investigation was to determine the relative importance of lectin-carbohydrate and nonspecific hydrophobic and ionic interactions, using a model based on strains with one of the most well understood specific coaggregation mechanisms, the lactose-reversible coaggregation of Actinomyces naeslundii and Streptococcus oralis. The kinetics of coadhesion and desorption of coadherent bacteria were studied using S. oralis 34 bound to hexadecane droplets as an affinity support for the adhesion of A. naeslundii WVU 398A. Light, confocal microscopy and transmission electron microscopy confirmed that A. naeslundii cells adhered only to the S. oralis cells, not to exposed hexadecane between the streptococci. Coadhesion was inhibited by lactose concentrations as low as 2.0 mM. The rate of coadhesion was halved at 60 mM lactose. The hydrophobicity inhibitors bovine serum albumin and defatted bovine serum albumin and the salts LiCl and KCl failed to inhibit coadhesion in the hexadecane assay, and bovine serum albumin also failed to inhibit coaggregation in a bacterial aggregation assay on glass slides. High concentrations of the salts achieved a 50% rate decrease in A. naeslundii adhesion to the S. oralis-coated droplets only when they were combined with > 20 mM lactose. Sodium dodecyl sulfate (SDS) and Tween 20 inhibition was tested by the slide coaggregation assay because they tended to emulsify the droplets; SDS was inhibitory. Lactose selectively desorbed A. naeslundii from S. oralis-coated droplets at low concentrations equivalent to those that inhibited coadhesion. Neither LiCl nor KCl desorbed A. naeslundii from the droplets, even at 500 mM. At low concentrations, SDS but not Tween 20 eluted both A. naeslundii and S. oralis from the droplets. Although the SDS results might suggest a degree of cooperative charge interactions, the results support the hypothesis that stereospecific, beta-galactoside-sensitive interactions have a much greater impact than nonspecific interactions on the coadhesion of A. naeslundii and S. oralis.

Co-adhesion of Oral Microbial Pairs under Flow in the Presence of Saliva and Lactose

“…Alternatively, Ellen et al (1994) described the lactose-reversible co-adhesion of Actinomyces naeslundii WVU 398A and S. oralis 34 as a predominantly stereospecific interaction. However, specific interactions are also mediated by Lifshitz-Van der Waals, acid-base, and electrostatic interactions between highly localized and spatially well-organized groups (Van Oss, 1990;Busscher et al, 1992a).…”

Occurrence of lectins and hydrophobicity of bacteria obtained from biofilm of hospital catheters and water pipes

“…Hydrophobic interactions have been widely studied in environmental bacteriology, while specific interactions have been mostly explored in medical bacteriology. Studies on the involvement of both hydrophobic interactions and lectin production in bacterial adhesion are rare ( Ellen et al . 1994 ).…”

Probing of Microbial Biofilm Communities for Coadhesion Partners

“…The underlying mechanisms mediating coaggregation and coadhesion were assumed to be identical (24), but it has been questioned whether an in-suspension coaggregation assay can accurately reflect what happens in vivo, e.g., in dental plaque biofilms (23). In consequence, various types of assays have been developed to better mimic coadhesion, and these approaches have added to the present understanding of biofilm formation (15,23,(25)(26)(27)(28)(29)(30). The coadhesion assay, presented here, reveals additional interbacterial adhesive interactions that are not detectable by coaggregation.…”