Characteristics and Distribution of Actinophages Isolated from Thai Soil Samples

Indigenous streptomycetes isolated from soil samples collected from several parts of Thailand were used as hosts for isolation of phages. Twenty-four phages were obtained by an enrichment procedure. The phages were plaque purified and morphologically examined under a transmission electron microscope. It was observed that all phages had hexagonal heads and long non-contractile tails. Thus, they belonged to group B of Bradley's classification and type B1 in the Family Siphoviridae. The host range of the phages was determined against 163 streptomycete strains and was found to vary from narrow to broad. Ten phages were characterized based on their morphology, physiology, genome, proteins, antigenic relationship and biology. Phages No.1 and No.15, which had broad host ranges, showed dissimilar patterns in the one step growth experiment. The majority of phages gave maximum replication at neutral pH although phage No.15 preferred basic conditions. Phages No.30 and No.27 were closely related serologically. The number and size of fragments obtained after digestion with restriction enzymes showed that all phages were unique. The results showed that they were distinguished from previously reported phages.