Phage adsorption to Streptococcus thermophilus.: Influence of environmental factors and characterization of cell receptors

Five autochthonal bacteriophages were used to characterize the adsorption process to Streptococcus thermophilus cells. For this purpose, the influence of several factors was studied. Calcium ions were necessary to complete cell lysis and plaque formation, but, they were not required for adsorption process. The adsorption rates were almost normal for all cases within the temperature range assayed (0-50 degreesC) and the adsorption kinetics were similar on viable and non-viable, cells. The phages adsorbed on S. thermophilus cells even at pH = 4, but adsorption rate reached its maximum at pH values from 6 to 7. Furthermore, several chemical and enzymatic treatments were applied to the cell walls in order to investigate the nature of cells receptors. TCA 5% and mutanolysin 50 U ml(-1) reduced appreciably the adsorption of phages, indicating that phage receptors were carbohydrates in nature. SDS 1% and proteinase K 0.10 mg ml(-1) treatments did not change the adsorption ability of phage particles. Experiments with different saccharides to inactivate the phages indicated that several of them were involved in the adsorption process. The reversibility of phage binding was also investigated, indicating that the first step of lytic cycle was an irreversible mechanism. (C) 2002 Elsevier Science Ltd. All rights reserved.