Simultaneous loss of bacteriophage receptor and coaggregation mediator activities in Actinomyces viscosus MG-1

Abstract

Actinomyces bacteriophages were used as tools to study coaggregation between actinomyces and streptococci. Four bacteriophage isolates, phages AV-1, AV-2, AV-3, and 1281, bound to coaggregation group A Actinomyces viscosus and to group E A. naeslundii. No binding to groups B, C, D, or F was observed. Only A. viscosus MG-1 was capable of supporting a productive infection by these phages. Spontaneously occurring bacteriophage-resistant mutants of A. viscosus MG-1 were isolated and were shown to fall into two classes. Class I mutants were resistant to all four phages, whereas class II mutants were resistant only to phage AV-3. In each case, strains resistant to a particular phage were unable to bind that phage, suggesting that a loss or alteration of the cell surface phage receptor had occurred. Both classes of mutants were unable to coaggregate with streptococci representing coaggregation group 1 and had also lost the ability to mediate one type of coaggregation with group 4 streptococci. Class II mutants also were unable to coaggregate with group 2 streptococci. Lactose-inhibitable interactions with other streptococci (groups 3 and 4) were unchanged in the mutants. The simultaneous loss of sensitivity to phage AV-3 and the ability to coaggregate with coaggregation group 1 streptococci suggests the possibility of a relationship between these two cell surface structures.were tested for the presence of phage as described previ-228 on August 9, 2020 by guest http://iai.asm.org/ Downloaded from

Use of lytic bacteriophage for Actinomyces viscosus T14V as a probe for cell surface components mediating intergeneric coaggregation

“…Phages have been instrumental in the detection of dualfunction surface receptors on a variety of microbes (3,6,9,16,20,22,25). For instance, two recently isolated classes of phage-resistant mutants of Actinomyces viscosus MG-1 were altered simultaneously in their interbacterial adherence to certain strains of Streptococcus sanguis, indicating that the phage receptor and one of the adhesins on A. viscosus MG-1 are related in an as-yet-unspecified manner (24). The four phages used in that study were lytic only on A. viscosus MG-1.…”

“…Information on bacteriophages of oral bacteria is relatively scarce, as only a few phages infectious for these organisms have been described (7,10,18,21,23,24). This lack of knowledge is surprising in view of the potential roles such phages may play in regulating the oral microflora by lysing sensitive cells or selecting for resistant mutants which might have altered colonizing or pathogenic properties.…”

“…MATERIALS AND METHODS Media and growth conditions. Bacteria were grown in TYNP medium as described earlier (24). When used to grow phages, TYNP was supplemented with 10 mM MgCl2 and 0.1 mM CaCl2.…”

“…S. sanguis DL1, Hi, 34, and J22 represent streptococcal coaggregation groups 1, 2, 3, and 4, respectively (14). Phages Av-1, Av-2, Av-3, and 1281 of A. viscosus MG-1 have been described previously (7,24). Cultures and phages were stored frozen at -70°C in TYNP containing 7% dimethyl sulfoxide.…”

“…Phage stocks were prepared by infecting mid-logphase cultures at a multiplicity of infection of five. After overnight incubation, the resulting lysates were clarified by low-speed centrifugation and filtered as described above after the addition of Tween 20 to a final concentration of 0.05% (24). Phage titers were determined by the standard top agar overlay technique with 0.3 ml of cells per 3 ml of top agar (24).…”