Abstract
BackgroundIn the present study, adaptive laboratory evolution was used to stimulate antibiotic production in a Streptomyces strain JB140 (wild-type) exhibiting very little antimicrobial activity against bacterial pathogens. The seven different competition experiments utilized three serial passages (3 cycles of adaptation-selection of 15 days each) in which Streptomyces strain (wild-type) was challenged repeatedly to one (bi-culture) or two (tri-culture) or three (quadri-culture) target pathogens. The study demonstrates a simple laboratory model to study the adaptive potential of evolved phenotypes and genotypes in Streptomyces to induce antibiotic production. ResultsCompetition experiments resulted in the evolution of the wild-type Streptomyces strain JB140 into the seven unique mutant phenotypes that acquired the ability to constitutively exhibit increased antimicrobial activity against three bacterial pathogens Salmonella Typhi (NCIM 2051), Staphylococcus aureus (NCIM 2079), and Proteus vulgaris (NCIM 2027). The mutant phenotypes not only effectively inhibited the growth of the tested pathogens but were also observed to exhibit improved antimicrobial responses against one clinical multidrug-resistant (MDR) uropathogenic Escherichia coli (UPEC 1021) isolate. In contrast to the adaptively evolved mutants, only a weak antimicrobial activity was detected in the wild-type parental strain. To get molecular evidence of evolution, RAPD profiles of the wild-type Streptomyces and its evolved mutants were compared which revealed significant polymorphism among them. ConclusionThe competition-based adaptive laboratory evolution method can constitute a platform for evolutionary engineering to select improved phenotypes (mutants) with increased antibacterial profiles against targeted pathogens.
Highlights
In the present study, adaptive laboratory evolution was used to stimulate antibiotic production in a Streptomyces strain JB140 exhibiting very little antimicrobial activity against bacterial pathogens
The co-culture experiments involve the cultivation of two microbes in the same closed and restricted environment for a certain period. The supernatant from these mixed cultures and mono-culture is analyzed for their bio-activity or no bioactivity. In contrast to this approach, in the laboratory evolution experiments described in the present study, the wild-type Streptomyces strain JB140 is co-cultured with different bacterial pathogens in the bi, tri, and quadriculture assays
Isolation and characterization of JB140 Based on characteristic colonial morphology, notably the ability to form aerial hypha and substrate mycelia, earthy smell and chalky appearance of the mature colony, darker in the center and lighter farther, irregular, fuzzy edge, pigmented, strongly adhered and leathery texture, the isolate was putatively identified as actinobacteria
Summary
Adaptive laboratory evolution was used to stimulate antibiotic production in a Streptomyces strain JB140 (wild-type) exhibiting very little antimicrobial activity against bacterial pathogens. Co-cultures of two different organisms have been observed to improve the production of antimicrobial molecules [13,14,15,16,17] These experiments have not used adaptive-selection cycles as these used in the present study. The supernatant from these mixed cultures and mono-culture (control) is analyzed for their bio-activity or no bioactivity In contrast to this approach, in the laboratory evolution experiments described in the present study, the wild-type Streptomyces strain JB140 is co-cultured with different bacterial pathogens in the bi-, tri-, and quadriculture assays. After isolation and purification of the Streptomyces phenotypes from the first cycle, these phenotypes were repeatedly exposed (three successive cycles of adaptation-selection of 15 days each) to the bacterial pathogens until the bio-activity was detected
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
