Multiscale Models of Antibiotic Cellbots

Foodborne gastrointestinal infections are significant causes of morbidity and mortality worldwide. Alarmingly, because of the extensive, non-therapeutic use of antibiotics in agriculture, foodborne bacteria are emerging that are resistant to our most potent drugs.

We will discuss a novel approach to reduce the use of antibiotics in food-producing animals and to treat gastrointestinal infections. We engineer lactic acid bacteria (LAB) that express and release antimicrobial peptides (AMPs). LAB are part of the gastrointestinal microflora and can be safely delivered with known benefits to humans and animals. AMPs are proteins that can be readily produced by LAB. One unique aspect of our approach is the use of synthetic promoters that precisely regulate the delivery of AMP molecules.

At the heart of proposed efforts are multiscale models that guide explanations and predictions of the antagonistic activity of recombinant LAB against pathogenic strains. Models are developed to quantify how AMPs kill bacteria at distinct but tied scales. Using atomistic simulations the various interaction steps between peptides and cell membranes are explored. Mesoscopic models are developed to study ion transport and depolarization of membranes treated with AMPs. Stochastic kinetic models are developed to quantify the strength of synthetic promoters and AMPs expression. We will also present a closure scheme for chemical master equations, providing a solution to a problem that has remained open for over seventy years.1

Experimentally, we engineer lactic acid bacteria to inducibly produce antimicrobial peptides. We have built a library of synthetic biological constructs.2,3 We test these modified bacteria against pathogenic bacteria. We will present results against salmonella and enterococcus.4,5

1. Smadbeck P, Kaznessis YN. A closure scheme for chemical master equations. Proc Natl Acad Sci U S
A. 2013 Aug 27;110(35):14261-5. doi: 10.1073/pnas.1306481110.
2. Ramalingam KI, Tomshine JR, Maynard JA, Kaznessis YN. Forward engineering of synthetic bio-logical
AND gates, Biochemical Engineering, 47, 38-47, 2009.
3. Volzing K, Billiouris K, Kaznessis YN. proTeOn and proTeOff, New Protein Devices That Inducibly
Activate Bacterial Gene Expression, ACS Chemical Biology, 6, 1107-1116, 2011.
4. Volzing K, Borrero J, Sadowsky MJ, Kaznessis YN. Antimicrobial Peptides Targeting Gram-negative
Pathogens, Produced and Delivered by Lactic Acid Bacteria. ACS Synth Biol. 2013, 15;2(11):643-50.
doi: 10.1021/sb4000367
5. Borrero J, Chen Y, Dunny GM, Kaznessis YN. Modified Lactic Acid Bacteria Detect and Inhibit
Multiresistant Enterococci.ACS Synth Biol. 2014, In press