CHARACTERIZATION OF BACTERIAL SOFT ROT STRAINS AND THEIR SPECIFIC PHAGES ISOLATED FROM SOIL AT TAIF

Abstract

In this study some bacteriophage(s) specific to some plant pathogenic bacteria (the causal agent of soft rot
diseases), were isolated and characterized from soil of Taif, KSA. Soil samples were randomly collected from some
rhizosphere soils cultivated with various plant species including potato. Ten bacterial isolates were obtained from soil
and used as hosts for enrichment and isolation of the virulent bacteriophages. The spot test and turbidity tests were used
to detect the presence of the phage of interest in the suspension. The area of clear zones were represented by threes
levels, i.e., weak lysis (+) (three isolates), moderate lysis (++) (one isolate) and high lysis (+++) (two isolates). The
phage(s) was propagated and partially purified for determining the morphology of viral particles via electron
microscopy. Sperm shape virus-like particles with long tail and icosahedral head were shown in the electron
micrographs of partially purified phages specific to the two selected bacterial isolates (# 08 and # 10). These two
bacterial isolates were then biologically and molecularly identified. The nucleotide sequences of 16S rRNA gene of the
two bacterial isolates was determined and final sequences of 942 and 940 nts for the 16S rRNA gene of two soft rot
bacteria (# 08 and # 10), respectively were recorded. Data of the phylogentic trees show that the two bacterial isolates (#
08 and # 10) could be strains of Pseudomonas stutzeri (LC053456.1) and Bacillus pumilus (LC053854.1).