This study was aimed to alter the ability of Pseudomonas aeruginosa H3 in alginate production by using some physical and chemical mutagens. Physical mutagenesis were UV radiation and laser mutagens. Chemical mutagenes were N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and Mitomycin C.
Physical mutagenesis was performed by subjection the cell suspension of P. aeruginosa H3 to different doses of UV radiation (2, 4, 6, 8 and 10 J/m2) and laser for (30, 60, 90 and 120 sec.), then, cell suspension was spread on LB agar plates and incubated at 37 ˚C for 24hrs. After that, random selection of thirty colonies that arose from the cells subjection to the effect of different doses of UV radiation and laser were made (90% of the suspended cells were killed and were tested for their alginate production). Results showed that the mutagenesis by UV radiation caused an increase in the ability of P. aeruginosa H3 in alginate production. Over-producer mutant, H3R1, was obtained from this treatment. The productivity of this mutant was 170mg/L in comparison with the productivity of wild type (70mg/L). On the other hand, results also showed that mutagenesis using laser radiation caused an increase in the ability of P. aeruginosa H3 in alginate production. Over-producer mutant, H3R42, was obtained from this treatment characterized by its high ability in alginate production was 130mg/L in comparison with the productivity of wild type (70mg/L).
Chemical mutagenesis was achieved by incubation P. aeruginosa H3 with 30µg/ml of MNNG and 10µg/ml of mitomycin C separately for 60 minutes, then cell suspension was spread on LB agar plates and incubated at 37 ˚C for 24 hrs. After that, random selection of thirty colonies that arose from the cells incubation with the chemical mutagens for the period that caused killing of 90% of the cells was made, and the alginate production of P. aeruginosa H3 was examined. Results showed that mutagenesis by MNNG caused an increase of P. aeruginosa H3 alginate production. Over-producer mutant H3R78 was obtained, the productivity of this mutant was 160mg/L. Results also showed that mutagenesis by mitomycin C caused an increase of P. aeruginosa H3 alginate production. Over-producer mutant H3R97, was obtained, the productivity of this mutant was 160mg/L compared with the productivity of the wild type.
In order to analyze the chemical structure of alginate produced by P. aeruginosa H3 (wild type) and the over producer mutants, Fourier Transform- Infrared was performed. Results showed that there are no differences in the chemical structure of alginate produced by the wild type and over producer mutants.
