The Blackledge lab is interested in understanding and manipulating bacterial behavior and pathogenesis using small molecules and peptides. Specifically, we are interested in identifying novel small molecules that combat bacterial biofilm formation, antibiotic resistance, and bacterial persistence. We use a wide variety of techniques from organic synthesis to microbiology and biochemistry to answer these questions. Currently, there are three main projects in the Blackledge lab:

Eukaryotic-like serine/threonine kinases (eSTK) were first described in bacteria approximately 27 years ago. The penicillin-binding protein and serine/threonine associated (PASTA) kinases are a subset of eSTKs found in numerous gram-positive pathogens and mycobacteria that feature a single transmembrane region linking the cytoplasmic kinase domain to extracellular penicillin-binding protein domain. The extracellular penicillin binding domain is hypothesized to bind cell wall precursor muropeptides as a monitor of cell wall homeostasis. Pathogenic bacteria have co-opted this sensing mechanism to respond to antibiotics, such as b-lactams, that also bind in the extracellular domain of PASTA kinases.

Because of their role in homeostasis and virulence regulation, this family of kinases has been identified as an attractive drug target for novel therapeutics that address bacterial virulence and antibiotic resistance. The Blackledge lab has identified several small molecules that inhibit Stk1. We are utilizing these molecules as chemical probes to elucidate novel regulatory functions of Stk1 and develop a more comprehensive model for resistance and virulence gene regulation in S. aureus.

We are now living in a post-antibiotic era. Bacteria are developing resistance to our current therapeutic arsenal at a rate that far outpaces our ability to create new treatments. The Review on Antimicrobial Resistance estimates that by 2050 antibiotic resistant infections will kill someone every three seconds. Compounding the problem of antibiotic resistance is the propensity of pathogenic bacteria to form biofilms, which provide a persistent reservoir of infection in patients. Antibiotic treatments alone are inefficient at eradicating or fully preventing bacterial biofilms and can contribute to the enrichment of resistant strains of bacteria. Compounds that disarm bacterial biofilm formation and resistance mechanisms have potential as novel therapeutics.

In an effort to identify such compounds, we turned to FDA-approved drugs as a rich source of well-studied molecules with known safety and bioavailability profiles. We hypothesize that this drug repurposing approach will provide us with lead compounds for development and could even identify approved compounds that could rapidly be deployed in the clinic. To date we have identified four FDA-approved drugs capable of potentiating antibiotics and inhibiting biofilm formation in resistant strains of Staphylococci.

We are currently investigating bacterial toxin-antitoxin systems as novel targets for antibiotics and antibiotic adjuvants. Toxin-antitoxin systems are two or more closely related genes that encode a protein “toxin” and a corresponding “antitoxin”. When the toxin and antitoxin are bound together, the bacterial cells proceed normally through growth and colony formation. However, under certain stress conditions, the antitoxin will be destroyed and the toxin initiates activity that ultimately results in death of the bacterial cell.

Our lab is seeking to more fully understand the molecular basis of interactions between specific toxins and antitoxins by using small peptide mimics of the antitoxin. By understanding these molecular interactions, we can design and synthesize novel molecules with the potential to act as antibiotics or as protective antibiotic adjuvants, additives to an already available antibiotic that can protect “good” bacteria from being eliminated during antibiotic treatment.