Journal
MARINE DRUGS
Volume 19, Issue 1, Pages -Publisher
MDPI
DOI: 10.3390/md19010007
Keywords
Streptomyces bacillaris; lactoquinomycins; methicillin-resistant Staphylococcus aureus; dual-reporter system; DNA intercalation
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Funding
- Basic Science Research Program through the National Research Foundation of Korea - Ministry of Education, Science, and Technology [NRF-2018R1D1A1B07043375]
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This study isolated a series of compounds from marine actinomycetes with potent antibacterial activity against Gram-positive bacteria, particularly exhibiting significant inhibition against methicillin-resistant Staphylococcus aureus (MRSA). LQM-A was found to induce DNA damage rather than inhibit protein synthesis, suggesting its mechanism of action involves intercalating into double-stranded DNA and damaging DNA repair processes.
This study aims to isolate and identify the structure of antibacterial compounds having potent activity on methicillin-resistant Staphylococcus aureus (MRSA) from marine actinomycetes, and also to identify their mode of action. Lactoquinomycin A (LQM-A) (compound 1) and its derivatives (2-4) were isolated from marine-derived Streptomyces bacillaris strain MBTC38, and their structures were determined using extensive spectroscopic methods. These compounds showed potent antibacterial activities against Gram-positive bacteria, with MIC values of 0.06-4 mu g/mL. However, the tested compounds exhibited weak inhibitory activity against Gram-negative bacteria, although they were effective against Salmonella enterica (MIC = 0.03-1 mu g/mL). LQM-A exhibited the most significant inhibitory activity against methicillin-resistant Staphylococcus aureus (MRSA) (MIC = 0.25-0.5 mu g/mL), with a low incidence of resistance. An in vivo dual-reporter assay designed to distinguish between compounds that inhibit translation and those that induce DNA damage was employed to assess the mode of action of LQM-A. LQM-A-induced DNA damage and did not inhibit protein synthesis. The gel mobility shift assay showed that LQM-A switched plasmid DNA from the supercoiled to relaxed form in a time- and concentration-dependent manner. These data suggest that LQM-A intercalated into double-stranded DNA and damaged DNA repair.
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