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Background In 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. Results Competition 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. Conclusion The 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.

In the present study, adaptive laboratory evolution was used to stimulate antibiotic production in a weak antibiotic-producing Streptomyces strain JB140. The seven different competition experiments utilized three serial passages (three cycles of adaptation-selection of 15 days each) of a weak antibiotic-producing Streptomyces strain (wild-type) against one (biculture) or two (triculture) or three (quadriculture) target pathogens. This resulted in the evolution of a weak antibiotic-producing strain into the seven unique mutant phenotypes that acquired the ability to constitutively exhibit increased antimicrobial activity against bacterial pathogens. The mutant not only effectively inhibited the growth of the tested pathogens but also observed to produce antimicrobial against multidrug-resistant (MDR) E. coli. Intriguingly, the highest antimicrobial activity was registered with the Streptomyces mutants that were adaptively evolved against the three pathogens (quadriculture competition). In contrast to the adaptively evolved mutants, a weak antimicrobial activity was detected in the un-evolved, wild-type Streptomyces. To get molecular evidence of evolution, RAPD profiles of the wild-type Streptomyces and its evolved mutants were compared that revealed significant polymorphism among them. These results demonstrated that competition-based adaptive laboratory evolution method can constitute a platform for evolutionary engineering to select improved phenotypes (mutants) with increased production of antibiotics against targeted pathogens.

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Diarrhea caused by E. coli has been recognized as an important health problem among children in developing countries particularly in India and is a research priority of the diarrheal disease control program of the World Health Organization. Despite progress in preventing diarrhea and the spread of medical facilities in India, diarrhea remains the second leading cause of death in children, killing an estimated 321 children every day in 2015. It is the aim of the present research to gather information on current definitions, detection and prevalence, characterization of genetic determinants, virulence mechanisms, antibiotic resistance and epidemiology of the major DEC pathotypes with emphasis on the case studies conducted in the Bikaner region of Rajasthan in India. It has been found that the incidence of diarrheal diseases to be very high during the summer months followed by rainy or winter months in the Bikaner region of Rajasthan. Mode of water transportation, poor handling of water (at the household level), the presence of wastewater and unhygienic conditions predisposed children to diarrhea. In addition, indiscriminate stool disposal by mothers, lack of hand-washing before feeding their children or handwashing without soap has also been observed to be associated with the increased threat of diarrheal infection. The health associated risks of diarrheagenic E. coli in under-five children and the possible solutions to prevent the same are discussed.