Transposon [Tn5] and UV Irradiation as mutagenic agents for improving photorhabdus sp. Sinai 1 [S1], an insect - Pathogenic bacterium

ABSTRACT

A local isolate of symbiotic bacterium, Photorhabdus sp. Sinai 1 [S1] was isolated from Heterorhabditis sp. Sl insect-pathogenic nematodes and its character was detected. Antibacterial/antifungal antibiotic[s] and proteinase productions of Photorhabdus Sl play an important role in killing insects. Photorhabdus sp. [Sl] was treated with UV for different times. Survival percentage of the original strain dropped from 100% at zero time to 11.13%,0.23 and 0.022% after UV treatment for 1, 3 and 5 minutes, respectively. However, 32 mutants were isolated, 18 after 1 minute treatment and 14 after 3 minutes treatment. Wide ranges of proteinase production capacities were detected. Eight of the mutants isolated after UV treatment for 1 minute had lower production than Sl, while 4 mutants had the same productivity as Sl. Six mutants of l minute UV treatment, were higher producers than S1. Fourteen mutants were isolated after UV treatment for 3 minutes. Three of them had the same proteinase production at S1, 3 had lower production, and about 8 proved to be highly producer mutants. Mutant number 20 from UV 3 minutes treatment group proved to be the best producer. It produced 25% over than S1. Suicidal plasmid pSUP2021 was mobilized from Escherichia coli to photorhabdus bytransconjugation and 15 transconjugants were isolated. All of them proved electrophoritically to have the plasmid. Fourteen transconjugants were tested for their proteinase productivity, only two transconjugants [14%] were higher proteinase producers, one of them reached 133.3% in comparison with S1. All transconjugants, except one were higher antibacterial antibiotic producers thanS1. Transconjugant number 7 proved to be the best producer one. It produced about 150% antibacterial and 160% antifungal antibiotics in comparison with S1parental strain. Results also indicated that, Photorhabdus S1 mutations due to transposon Tn5 mutagenesis were more powerful than those induced by UV in proteinase production. Transposon Tn5 mutagenesis is one of the most important tool for antibiotic improvement in Photorhabdus