Genome mining to identify valuable secondary metabolites and their regulation in Actinobacteria from different niches.

Actinobacteria are the largest bacteria group with 18 significant lineages, which are ubiquitously distributed in all the possible terrains. They are known to produce more than 10,000 medically relevant compounds. Despite their ability to make critical secondary metabolites and genome sequences' availability, these two have not been linked with certainty. With this intent, our study aims at understanding the biosynthetic capacity in terms of secondary metabolite production in 528 Actinobacteria species from five different habitats, viz., soil, water, plants, animals, and humans. In our analysis of 9,646 clusters of 59 different classes, we have documented 64,000 SMs, of which more than 74% were of unique type, while 19% were partially conserved and 7% were conserved compounds. In the case of conserved compounds, we found the highest distribution in soil, 79.12%. We found alternate sources of antibiotics, such as viomycin, vancomycin, teicoplanin, fosfomycin, ficellomycin and patulin, and antitumour compounds, such as doxorubicin and tacrolimus in the soil. Also our study reported alternate sources for the toxin cyanobactin in water and plant isolates. We further analysed the clusters to determine their regulatory pathways and reported the prominent presence of the two component system of TetR/AcrR family, as well as other partial domains like CitB superfamily and HTH superfamily, and discussed their role in secondary metabolite production. This information will be helpful in exploring Actinobacteria from other environments and in discovering new chemical moieties of clinical significance.

Potentiating the intracellular killing of Staphylococcus aureus by dihydroquinazoline analogues as NorA efflux pump inhibitor.

Staphylococcus aureus is an emerging human pathogen that has become difficult to treat due to its high resistance against wide range of drugs. Emergence of drug resistant isolates has further convoluted the treatment process. Among different resistance mechanisms, efflux pump proteins play a central role and has made itself a direct approach for therapeutic exploration. To demarcate the role of dihydroquinazoline analogues as NorA efflux pump inhibitor in S. aureus1199B (NorA over producing) strain total seventeen analogues were synthesized and tested for their modulatory effects on norfloxacin and Etbr resistance. Further accumulation assays, bacterial time kill kinetics, cytotoxicity assay were also carried out. The intracellular killing ability of analogues, as EPI was determined using THP-1 monocytes. The binding interaction of analogues with NorA was also predicted. Dihydroquinazoline analogues notably reduced the MIC of norfloxacin and Etbr in S. aureus1199B. In addition to their very low toxicity, they showed high Etbr and norfloxacin accumulation respectively. Further effective over time log reduction in bacterial kill kinetics in presence of these analogues confirmed their role as NorA efflux pump inhibitor. FESEM analysis clearly depicted their effect on the cell surface morphology owing to its lyses. The most significant finding of this study was the ability of analogues to significantly reduce the intracellular S. aureus1199B in human THP-1 monocytes in presence of norfloxacin. Our study has shown for the first time the possibility of developing the dihydroquinazoline analogues as NorA efflux pump inhibitors for S. aureus and control its infection.

Alterations in molecular response of Mycobacterium tuberculosis against anti-tuberculosis drugs.

BACKGROUND: Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis, has plagued humans since the early middle-ages. More than one million deaths are recorded annually due to TB, even in present times. These deaths are primarily attributed to the constant appearance of resistant TB strains. Even with the advent of new therapeutics and diagnostics techniques, tuberculosis remains challenging to control due to resistant M. tuberculosis strains. Aided by various molecular changes, these strains adapt to stress created by anti-tuberculosis drugs. MATERIALS AND METHODS: The review thus is an overview of ongoing research in the genome and transcriptome of antibiotic-resistant TB. It explores omics-based research to identify mutation and utilization of differential gene expression. CONCLUSIONS: This study shows several mutations distinctive in the first- and second-line drug-resistant M. tuberculosis strains. It also explores the expressional differences of genes involved in the fundamental process of the cells and how they help in drug resistance. With the development of transcriptomics-based studies, a new insight has developed to inquire about gene expression changes in drug resistance. This information on expressional pattern changes can be utilized to design the basic platform of anti-TB treatments and therapeutic approaches. These novel insights can be instrumental in disease diagnosis and global containment of resistant TB.

Efflux pump inhibition by 11H-pyrido[2,1-b]quinazolin-11-one analogues in mycobacteria.

Mycobacterium tuberculosis infection causes 1.8 million deaths worldwide, of which half a million has been diagnosed with resistant tuberculosis (TB). Emergence of multi drug resistant and extensive drug resistant strains has made all the existing anti-TB therapy futile. The major involvement of efflux pump in drug resistance has made it a direct approach for therapeutic exploration against resistant M. tuberculosis. This study demarcates the role of 11H-pyrido[2,1-b]quinazolin-11-one (quinazolinone) analogues as efflux pump inhibitor in Mycobacterium smegmatis. Sixteen quinazolinone analogues were synthesized by treating 2-aminopyridine and 2-fluorobenzonitrile with KtOBu. Analogues were tested, and 3a, 3b, 3c, 3g, 3j, 3l, 3m, and 3p were found to modulate EtBr MIC by >4 whereas 3a, 3g, 3i and 3o showed >4 modulation on norfloxacin MIC. 3l and 3o in addition to their very low toxicity they showed high EtBr and norfloxacin accumulation respectively. Time kill curve showed effective log reduction in colony forming unit in presence of these analogues, thus confirming their role as efflux pump inhibitor. Through docking and alignment studies, we have also shown that the LfrA amino acid residues that the analogues are interacting with are present in Rv2333c and Rv2846c of M. tuberculosis. This study have shown for the first time the possibility of developing the 11H-pyrido[2,1-b]quinazolin-11-one analogues as efflux pump inhibitors for M. smegmatis and hence unbolts the scope to advance this study against resistant M. tuberculosis as well.