ATP-dependent Lon protease plays important roles in different physiological processes, including cellular differentiation of the bacteria and is a part of an important stress response regulon (HspR/HAIR). In Streptomyces, biosynthesis of secondary metabolites starts with cellular differentiation and stress is one of the factor that affect metabolite production. To clarify the effect of Lon protease on secondary metabolite production, we constructed a recombinant strain of Streptomyces coelicolor A3( 2) that has one extra copy of lon gene with its own promoter and transcriptional terminator in its genome. Expression of lon gene in the recombinant strain was determined by quantitative real time (RT-qPCR). Actinorhodin and undecylprodigiosin production of the recombinant cell was measured in liquid R2YE and it was found to produce about 34 times more actinorhodin and 9 times more undecylprodigiosin than the wild-type at 168 h of growth. Development of stable Streptomyces strains capable of producing high amounts of secondary metabolites is valuable for biotechnology industry. One extra copy of lon gene is enough to boost antibiotic production by S. coelicolor A3(2) and this change do not cause any metabolic burden in the cell.

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Aim: Host factors are known to modulate virulence, antibiotic susceptibility and growth of bacteria. In the present study we aimed to investigate the effect of human insulin and glucose on growth and expression of mar regulon (marA, marR, ompF, acrA, acrB and tolC) of E. coli SPC105. Material and Methods: E. coli SPC105 was grown in tryptic soy broth (TSB-control) and TSB containing 20 µU/mL insulin, 200 µU/mL insulin, 0.1% glucose and 200 µU/mL insulin + 0.1% glucose. Growths were determined via turbidimetric method. Quantitative polymerase chain reaction (qPCR) was used to determine the gene expression levels. Statistical analysis were performed via Tukey's post hoc-test. Results: According to absorbance values, it has been shown that 0.1% glucose and 200 µU/mL insulin + 0.1% glucose have led a significant decrease on growth. Expression of acrA gene was shown to be decreased in the presence of 200μIU insulin. Expressions of marR and marA were also decreased in 200μU insulin, 0.1 % glucose+200μU insulin and 0.1% glucose added TSB. Decreasing of marA, marR and acrA expressions were shown to be statistically significant (p<0.05). Conclusion: The results of the present study has shown once more that, host factors may influence the growth of a bacterium as well as gene expressions associated with antibiotic susceptibilities.