الفهرس 
Studies on Antibiotic Producing Microorganisms Isolated from Extreme Environments
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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.