Physicochemical characterization of phage adsorption toLactobacillus helveticusATCC 15807 cells

Characterization of the adsorption process by the phages hv and ATCC 15807‐B1 to Lactobacillus helveticus ATCC 15807 was carried out. For this purpose, the influence of Ca2+ ions, temperature and physiological cell state were studied. The ability of several saccharides and related compounds to inactivate the phages hv and ATCC 15807‐B1 was determined to investigate their potential role as phage receptors. Furthermore, several chemical treatments on the sensitive strain cells were carried out to study their influence on phage adsorption. Cell lysis and plaque formation were independent of Ca2+ ions for phage hv, but the cation was indispensable for completion of the lytic cycle of phage ATCC 15807‐B1. However, for this phage, Ca2+ was not necessary for the adsorption process. The adsorption rates were almost normal for both phages within the temperature range examined (0 – 50 °C) and the adsorption kinetics were practically identical on viable and non‐viable cells. The saccharides and related compounds used did not produce inactivation of the phages, suggesting that they were not essential components of phage receptor structures. Lactobacillus helveticus ATCC 15807 cells treated with SDS 1%, SDS 0·5% ‐EDTA 50 mmol l−1 or NaOH 50 mmol l−1 exhibited reduced adsorption of the phages, indicating possible damage or extraction of receptors from the cell wall. Phage adsorption presents an extremely attractive target for interfering in the lytic cycle of phages.