Isolation and Characterization of Pseudomonas aeruginosa and its Virulent Bacteriophages.

BACKGROUND AND OBJECTIVE: Pseudomonas aeruginosa is a free living bacterium in widely different areas such as plants, soil, water and other moist locations. It is pathogenic to plants and humans. P. aeruginosa causes several disease symptoms to plants such as wet rot and curved leaves. The virulent bacterial viruses of P. aeruginosa were found to be of widespread occurrence in nature and isolated from widely different sources. Bacterial viruses were applied to control pathogenic bacteria in different fields and successfully. Therefore, this work aimed to study the different characteristics of P. aeruginosa lytic phage isolates. Moreover, the bio-control of P. aeruginosa by lytic phage isolates was also studied. MATERIAL AND METHODS: Different physical and molecular characteristics were assayed and determined of P. aeruginosa lytic bacteriophages. Also, the effect of phage isolates on P. aeruginosa as a bio-control under lab condition was studied. RESULTS: Pseudomonas aeruginosa pathogenic bacterium was isolated from a sewage water sample. Two lytic bacteriophages specific to P. aeruginosa were isolated from same sewage water sample and designated Pa1 and Pa2. Both phage isolates (Pa1 and Pa2) found to be stable in 90°C and different pH low and high levels. The total count of P. aeruginosa decreased after 48 h in broth treated with lytic phages. RAPD-PCR amplification was indicated that the two phage isolates (Pa1 and Pa2) are belonging to two different phage types. CONCLUSION: The results of this study indicated that both lytic phage isolates could be used as a biological control agents against the plant pathogen P. aeuroginosa.

Biochemical and Molecular Characteristics of Pc1 Virulent Phage Isolate Infecting Pectobacterium carotovorum.

BACKGROUND AND OBJECTIVE: Pectobacterium carotovorum subsp. carotovorum is a plant-pathogenic bacterium. It is a post-harvest pathogen and causes soft rot diseases in infected plants. Different virulent bacteriophages have been isolated from different regions in the world. These bacteriophages were tolerant to high concentrations of calcium chloride and magnesium chloride. Whereas, the high concentrations of zinc chloride and aluminum chloride decreased the activity and stability of phages. Therefore, the present research aimed to study the biology of P. carotovorum phage (Pc1) by using a one-step growth experiment, its stability to different concentrations of some chemicals and molecular characteristics of this phage isolate. MATERIALS AND METHODS: One step growth experiment, chemical stability, and molecular characteristics by using RAPD-PCR of P. carotovorum phage (Pc1) were studied. RESULTS: The P. carotovorum phage (Pc1) isolate was found to have a latent period of 20 min and its burst size is about 92 pfu cell-1. Calcium chloride, magnesium chloride, and copper sulphate (from 0.1-0.5 mM) increased the infectivity of Pc1 phage, while, zinc chloride in the same concentrations reduced its infectivity. RAPD-PCR amplification was indicated that the total amplified products were 32 bands with size ranged from 0.179-2.365 Kbp. CONCLUSION: Since, zinc chloride (at concentrations of 0.1-0.5 mM) reduced infectivity of Pc1 phage isolate, therefore, any chemical compounds containing zinc must be avoided in designing biocontrol strategy by using phages against soft rot bacterium (P. carotovorum) in potatoes.

Characterization and comparative genomic analysis of virulent and temperate Bacillus megaterium bacteriophages.

Next-Generation Sequencing (NGS) technologies provide unique possibilities for the comprehensive assessment of the environmental diversity of bacteriophages. Several Bacillus bacteriophages have been isolated, but very few Bacillus megaterium bacteriophages have been characterized. In this study, we describe the biological characteristics, whole genome sequences, and annotations for two new isolates of the B. megaterium bacteriophages (BM5 and BM10), which were isolated from Egyptian soil samples. Growth analyses indicated that the phages BM5 and BM10 have a shorter latent period (25 and 30 min, respectively) and a smaller burst size (103 and 117 PFU, respectively), in comparison to what is typical for Bacillus phages. The genome sizes of the phages BM5 and BM10 were 165,031 bp and 165,213 bp, respectively, with modular organization. Bioinformatic analyses of these genomes enabled the assignment of putative functions to 97 and 65 putative ORFs, respectively. Comparative analysis of the BM5 and BM10 genome structures, in conjunction with other B. megaterium bacteriophages, revealed relatively high levels of sequence and organizational identity. Both genomic comparisons and phylogenetic analyses support the conclusion that the sequenced phages (BM5 and BM10) belong to different sub-clusters (L5 and L7, respectively), within the L-cluster, and display different lifestyles (lysogenic and lytic, respectively). Moreover, sequenced phages encode proteins associated with Bacillus pathogenesis. In addition, BM5 does not contain any tRNA sequences, whereas BM10 genome codes for 17 tRNAs.