الفهرس | Only 14 pages are availabe for public view |
Abstract Antibiotic-resistant bacteria represent a serious public health threat. Therefore, it has become necessary to develop new and effective antibiotics to control pathogens. The harsh environments have a unique biodiversity including bacteria that have bioactive compounds. This study aims to search for microorganisms effective in antibiotics production. Fifteen sites covering a wide range of harsh environmental conditions in Egypt were studied to search for antibiotic-producing bacteria. Two hundred and eighty bacterial isolates were obtained. Isolates were tested pathogenic bacteria using the Agar Disk Diffusion technique. Fifty-two (18.6% of the total) antagonized one or more of the tested pathogens. Isolates Nos. 113 and 10 were identified using 16S rRNA technique. The isolate 113 was identified as Bacillus licheniformis and isolate 10 as Brevibacillus borstelensis respectively. The B. licheniformis strain was stronger in antibiotic production against both: S. typhi, M. luteus and P. ariginosa, whereas, Br. borstelensis was more efficient against both: B. cearus, E. coli, and Klebs. sp. Sensitivity of the strains to commercial antibiotics showed that B. licheniformis was highly sensitive to seven commercial antibiotics, whereas, Br. borstelensis was sensitive to 9 antibiotics. The two strains were subjected to EMS mutagenesis to obtain mutants with higher antibiotic production. The total bacterial count was measured after treatment with EMS mutagen and showed significant gradual increase in antimicrobial activity were achieved by shaking in the presence of EMS for 60 minutes. High antimicrobial activities were noted with 17 and 14 mutants from B. licheniformis and Br. borstelensis strains, respectively. Mutant B. licheniformis (M15/Amo) was highly active “then the parent strain” against S. aureus (212.5%), while the mutant Br. Borstelensis (B7/Neo) was highly effective against S. typhi (83.3%). Optimization of antibiotic production by mutant strains using statistical modeling revealed that mutant B. licheniformis (M15/Amo) gave highest antibiotic production in the presence of 3% glucose, 2.5% peptone, 60 hours of incubation period and pH 7.5, whereas mutant Br. borstelensis (B7/Neo) gave significant antibiotic production in the presence of 2.5% glucose, 2% peptone, incubated at 50°C and pH 7. The chromatographic separation of the supernatant extract of strains on the silica gel plates resulted in 10 spots with the mutant B. licheniformis (M15/Amo), 3 of them were effective against tested pathogenic bacteria. While the extract of Br. borstelensis (B7/Neo) gave 12 spots, 2 of them were effective against the pathogenic bacteria. The analysis of the extracts using Liquid chromatography showed the presence of seven compounds which have anti-pathogenic activity in the extract of the mutant strain B. licheniformis (M15/Amo), and eight anti-pathogenic compounds in the extract Br. borstelensis (B7/Neo). The study clearly shows the possibility of obtaining potent antibiotic producing bacteria in hot spring waters and further improving indigenous bacterial capacity to produce antibiotics by using EMS mutagenesis. |