Abstract
Bottromycin is a ribosomally synthesized and post-translationally modified peptide (RiPP) produced by several streptomycetes, including the plant pathogen Streptomyces scabies. There is significant interest in this molecule as it possesses strong antibacterial activity against clinically relevant multidrug resistant pathogens and is structurally distinct from all other antibiotics. However, studies into its efficacy are hampered by poor yields. An understanding of how bottromycin biosynthesis is regulated could aid the development of strategies to increase titres. Here, we use 5′-tag-RNA-seq to identify the transcriptional organization of the gene cluster, which includes an internal transcriptional start site that precedes btmD, the gene that encodes the bottromycin precursor peptide. We show that the gene cluster does not encode a master regulator that controls pathway expression and instead encodes a regulatory gene, btmL, which functions as a modulator that specifically affects the expression of btmD but not genes up- or downstream of btmD. In order to identify non-cluster associated proteins involved in regulation, proteins were identified that bind to the main promoter of the pathway, which precedes btmC. This study provides insights into how this deceptively complex pathway is regulated in the absence of a pathway specific master regulator, and how it might coordinate with the central metabolism of the cell.
Highlights
Infectious diseases are responsible for one-fifth of deaths worldwide, and antimicrobial resistance is becoming an increasingly serious threat to global public health, which makes the development of new antibiotics a pressing need (Laxminarayan et al, 2016; Martens and Demain, 2017)
The btm gene cluster in S. scabies encodes a single putative regulator, BtmL, a 20.5 kDa protein that contains a C-terminal domain of unknown function (DUF2087 or PF09860), which has been associated with putative transcriptional regulators and is proposed to bind nucleic acids (Rigden, 2011)
No canonical winged helix-turn-helix (wHTH) domain was detected by sequence analysis and the protein appears to lack the conserved residues characteristically involved in ArsR-family metal binding (Osman and Cavet, 2010; Crone et al, 2012)
Summary
Infectious diseases are responsible for one-fifth of deaths worldwide, and antimicrobial resistance is becoming an increasingly serious threat to global public health, which makes the development of new antibiotics a pressing need (Laxminarayan et al, 2016; Martens and Demain, 2017). Bottromycin was first isolated in 1957 from cultures of Streptomyces bottropensis (Waisvisz et al, 1957), and more recently as a product of Regulation of Bottromycin Biosynthesis the plant pathogen Streptomyces scabies (Crone et al, 2012) and other Streptomyces species (Gomez-Escribano et al, 2012; Hou et al, 2012; Huo et al, 2012). A precursor peptide (BtmD) undergoes a complex and unprecedented series of modifications catalyzed by enzymes encoded in the bottromycin (btm) gene cluster (Figure 1) (Crone et al, 2012, 2016; Gomez-Escribano et al, 2012; Huo et al, 2012; Franz et al, 2017; Schwalen et al, 2017; Sikandar et al, 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
