Novel Aconitase: Targeting Phenotypic Adaptation for Antimicrobial Development


    Worldwide, bacterial pathogens pose an alarming public health threat due to their resistance to current antimicrobial drugs. While antibiotics have been widely used to prevent bacterial infections over the last 50-60 years, all major bacterial pathogens now are showing resistance to currently prescribed antibiotics worldwide. Increasing drug resistance is extremely concerning because bacterial diseases are globally widespread and can move easily between countries, culminating in the current global public health crisis. Antimicrobial drug-resistant infections become life-threatening in hospitals and seriously complicate medical practices, including cancer treatments and biomedical devices. Furthermore, existing strategies for developing new antimicrobial drugs are not effective because they mainly focus on previously-exploited modes of action or derivatives of existing drug compounds that pathogens have already gained resistance to. Thus, the need for new antimicrobial products to control invasive bacterial pathogens is greater now than it has ever been. We present a novel target for the development of antimicrobial compounds which involves a critically-important metabolic process that is unique to bacteria & effectively diminishes the phenotypic resistance of bacterial pathogens.



    Virulence and resistance of bacterial pathogens during infection involve phenotypic adaptation in which pathogens modulate their metabolic activity in response to changing environment and nutrient availability in the host. This phenotypic adaptation is a survival strategy and allows pathogens to persist under severely-limited nutritional environments and utilize molecules acquired from the host during infection. Mucoid (resembling mucus) phenotype is the most well-known adaptive phenotype. Several species of bacterial pathogens exhibit mucoid phenotype by secreting exopolysaccharides and form multicellular conglomerates known as biofilms. Biofilms represent a typical structured adaptation environment in which secreted exopolysaccharides facilitate adherence to surfaces, and provide a mechanism for colonization and resistance during infection. Bacteria in biofilms remain protected from administered antibiotics and become refractory to the immune system defenses.

    Mucoid bacteria are among the most clinically-challenging pathogens. Mucoid phenotype is observed in highly virulent subpopulations of pathogens and is responsible for the onset and progression of disease as well as antimicrobial resistance. It also plays a critical role in the establishment of chronic infections. One particularly important example, Pseudomonas aeruginosa, generally inhabits humans but is notorious for impairing pulmonary function and damaging the lung and digestive tissues in cystic-fibrosis (CF) patients. In CF, bacterial exopolysaccharides clog the lungs and digestive system of the patients, preventing clearance and resulting in chronic infection and inflammation. Because P. aeruginosa produces biofilm in the lungs and digestive systems of CF patients, whom are unable to clear this biofilm, P. aeruginosa infection is a major cause of death among such individuals. Serious, life-threatening Pseudomonas infections can also occur in hospitalized patients, especially those on breathing machines, those with devices such as catheters, burn victims, and patients with surgical wounds.

    Many additional bacteria switch to a mucoid phenotype as a response to their growth environment. In fact, under unfavorable growth conditions, many bacteria switch to an exopolysaccharide-producing mucoid phenotype and form biofilm to resist the environmental stress and adapt to unfavorable conditions. Exopolysaccharides produced by bacteria also have industrial importance as they can spoil/impair processes in paper, food, and health industries.



    We present the discovery of a “Novel Aconitase,” also referred to as aconitase C, or AcnC, as a new and unique target for developing antimicrobial products. AcnC is required for bacteria to detoxify propionic acid, a compound that is commonly generated as an intermediary metabolite in the form of propionyl CoA or propionate. If not cleared by metabolism, propionic acid/propionate/propionyl CoA becomes a toxic metabolite and inhibits the growth of bacteria, including those exhibiting the mucoid phenotype. During infection, invading pathogens need to metabolize propionic acid/propionate/propionyl CoA arising from utilization of carbon sources like cholesterol, odd chain fatty acid, and certain amino acids as well as fermentation of various sugars under limited glucose availability in host. Effective inhibition of the production or the activity of AcnC abolishes propionic acid metabolism in bacteria, resulting in significant reduction in bacterial growth and virulence expression, including biofilm production. Most bacteria have AcnC homologs (reported under the gene name acnD, and AcnD protein designation). However, there is no mammalian homolog for AcnC (or AcnD). Thus, this innovation prioritizes AcnC protein and acnC gene as unique microbial molecular targets for identifying novel and robust compounds for antimicrobial drug development. Accordingly, chemicals that inhibit either the production or activity of the AcnC protein will be useful in making bacterial pathogens more susceptible to propionic acid toxicity and to agents which generate propionic acid. Disruption of the activity or production of AcnC along with the administration of propionic acid, compounds which generate propionic acid, or of probiotic organisms that increase propionic acid levels have a deleterious and inhibitory effect on pathogenic bacteria. Inhibition of AcnC also potentiates the action of existing antibiotic drugs to inhibit the growth of bacterial pathogens.


Technical Description:

    Bacterial resistance to antibiotics is usually associated with acquisition of resistance genes or due to mutations in elements relevant for the activity of the antibiotic. However, during infections, bacterial resistance to drugs typically involves non-genetic phenotypic attributes related to metabolic adaptation. Propionic acid catabolism is a critically-important metabolic process required for pathogenic bacteria to adapt, survive, and grow in the host environment. Effective inhibition of production or activity of AcnC is a novel anti-infective strategy that diminishes the phenotypic resistance of bacterial pathogens and enhances the killing action of existing antibiotic drugs.

    The prioritized target, novel aconitase, is a metabolic enzyme with classifiable substrate and catalytic function. This ascertains that information about target biochemistry is available to design iterative screening strategies and to make predictions on potential antimicrobial compound chemistry at the front end of the drug discovery process. As enzyme inhibition is a major strategy for most of the drug design, identification of assayable inhibitors that act on specific site on AcnC, or related metabolic activity, is a highly promising approach for discovery of new antimicrobial drugs.


Value Proposition:

    The presented antimicrobial target, novel aconitase (also referred to as AcnC protein and acnC gene) - involved in propionic acid catabolism, metabolic adaptation, and bacterial virulence - provides a new opportunity for the potential design and development of new anti-microbial, anti-infective, and anti-bacterial compounds as well as biofilm control agents.



Inhibitors of “Novel Aconitase” (a.k.a. acnC) production or activity will serve as agents for:

  • Antimicrobial products – Control of bacteria and biofilm production
  • Anti-Infectives – Reduction of bacterial virulence
  • Antibiotic Adjuvants – Enhancing or potentiating the action of antibiotics
  • Crop Disease Management – Regulation of bacterial diseases in crop plants
  • Industrial Contamination Prevention – Inhibition of bacterial contamination in industrial processes


Key Benefits:

  • New Antimicrobial Target – Provides a novel target for inhibiting growth and resistance of bacteria during infection, including inhibition of biofilm production, allowing for treatment of antibiotic-resistant bacteria.
  • Desired Druggability Features – A metabolic enzyme target with properties desirable for antimicrobial drug development - AcnC protein, acnC gene, and RNA transcript of the corresponding gene are exclusive to bacterial pathogens; information about target biochemistry is available, facilitating predictions on potential antimicrobial compound chemistry, and making inhibitor selection, iterative design and assays affordable.
  • Antibiotic Adjuvant – Inhibition of production or activity of AcnC may be used to potentiate the effects of current antimicrobials and inhibit growth of bacterial pathogens, facilitating or accelerating infection clearance.
  • Vast Application Potential – Antimicrobial agents targeting AcnC have application potential to control bacteria that have significance in medicine, agriculture, veterinary medicine, and industrial processes.



Candas M. Novel aconitase. United States Patent Application Publication U.S. 2004/0248276 A1. Pub. Date: December 9, 2004.

IP Status: US patent 7,183,100 issued.

Licensing Opportunity: This technology is available for exclusive or non-exclusive licensing.

ID Number: 09-026



Related Publications:

Catenazzi MC, Jones H, Wallace I, Clifton J, Chong JP, Jackson MA, Macdonald S, Edwards J, Moir JW. A large genomic island allows Neisseria meningitidis to utilize propionic acid, with implications for colonization of the human nasopharynx. Mol Microbiol. 2014 Jul;93(2):346-55.

Folkesson A, Jelsbak L, Yang L, Johansen HK, Ciofu O, Høiby N, Molin S. Adaptation of Pseudomonas aeruginosa to the cystic fibrosis airway: an evolutionary perspective. Nat Rev Microbiol. 2012 Dec;10(12):841-51.

McKenna M. Antibiotic resistance: The last resort. Nature. 2013 Jul 25;499(7459):394-6.

Janis C. Kelly. Antibiotic Shortages Worsening in United States Medscape Medical News. (

Yael Waknine. Hospital Infections Cost Billions. Medscape Medical News. (

Mark Woolhouse, Catriona Waugh, Meghan Rose Perry, and Harish Nair. Global disease burden due to antibiotic resistance – state of the evidence. J Glob Health. 2016 Jun; 6(1): 010306.

Colvin KM, Gordon VD, Murakami K, Borlee BR, Wozniak DJ, Wong GC, Parsek MR. The pel polysaccharide can serve a structural and protective role in the biofilm matrix of Pseudomonas aeruginosa. PLoS Pathog. 2011 Jan 27;7(1): e1001264.

Grimek TL, Escalante-Semerena JC. The acnD genes of Shewenella oneidensis and Vibrio cholerae encode a new Fe/S-dependent 2-methylcitrate dehydratase enzyme that requires prpF function in vivo.  J Bacteriol. 2004 Jan;186(2):454-62.

Xin Fang, Anders Wallqvist, and Jaques Reifman. A systems biology framework for modeling metabolic enzyme inhibition of Mycobacterium tuberculosis. BMC Syst Biol. 2009; 3: 92.

Maria Chiara E Catenazzi, Helen Jones, Iain Wallace, Jacqueline Clifton, James P J Chong, Matthew A Jackson, Sandy Macdonald, James Edwards, James W B Moir. A large genomic island allows Neisseria meningitidis to utilize propionic acid, with implications for colonization of the human nasopharynx.

Mol Microbiol. 2014 Jul; 93(2): 346–355.

Hyungjin Eoh, Kyu Y. Rhee. Methylcitrate cycle defines the bactericidal essentiality of isocitrate lyase for survival of Mycobacterium tuberculosis on fatty acids. Proc Natl Acad Sci U S A. 2014 Apr 1; 111(13): 4976–4981.

Stephen K. Dolan, Andre Wijaya, Stephen M. Geddis, David R. Spring, Rafael Silva-Rocha, Martin Welch. Loving the poison: the methylcitrate cycle and bacterial pathogenesis. Microbiology 164: 251-259.

Paweł Masiewicz, Anna Brzostek, Marcin Wolański, Jarosław Dziadek, Jolanta Zakrzewska-Czerwińska. A Novel Role of the PrpR as a Transcription Factor Involved in the Regulation of Methylcitrate Pathway in Mycobacterium tuberculosis. PLoS One. 2012; 7(8): e43651.

Wagley S, Newcombe J, Laing E, Yusuf E, Sambles CM, Studholme DJ, La Ragione RM, Titball RW, Champion OL. Differences in carbon source utilisation distinguish Campylobacter jejuni from Campylobacter coli. BMC Microbiol. 2014 Oct 28;14:262. doi: 10.1186/s12866-014-0262-y.

VanderVen BC, Fahey RJ, Lee W, Liu Y, Abramovitch RB, Memmott C, Crowe AM, Eltis LD, Perola E, Deininger DD, Wang T, Locher CP, Russell DG. Novel inhibitors of cholesterol degradation in Mycobacterium tuberculosis reveal how the bacterium's metabolism is constrained by the intracellular environment. PLoS Pathog. 2015 Feb 12;11(2):e1004679.

Upton AM, McKinney JD. Role of the methylcitrate cycle in propionate metabolism and detoxification in Mycobacterium smegmatis. Microbiology. 2007 Dec;153(Pt 12):3973-82.

Fang X, Wallqvist A, Reifman J. A systems biology framework for modeling metabolic enzyme inhibition of Mycobacterium tuberculosis. BMC Syst Biol. 2009 Sep 15;3:92.

Chin CY, Tipton KA, Farokhyfar M, Burd EM, Weiss DS, Rather PN. A high-frequency phenotypic switch links bacterial virulence and environmental survival in Acinetobacter baumannii. Nat Microbiol. 2018 May;3(5):563-569.

Suvorova IA, Ravcheev DA, Gelfand MS. Regulation and evolution of malonate and propionate catabolism in proteobacteria. J Bacteriol. 2012 Jun;194(12):3234-40.

Thomas Dandekar and Wolfgang Eisenreich.  Host-adapted metabolism and its regulation in bacterial pathogens. Front Cell Infect Microbiol. 2015; 5: 28.

Ryall B, Carrara M, Zlosnik JE, Behrends V, Lee X, Wong Z, Lougheed KE, Williams HD. The mucoid switch in Pseudomonas aeruginosa represses quorum sensing systems and leads to complex changes to stationary phase virulence factor regulation. PLoS One. 2014 May 22;9(5):e96166.

Riquelme SA, Ahn D, Prince A. Pseudomonas aeruginosa and Klebsiella pneumoniae Adaptation to Innate Immune Clearance Mechanisms in the Lung. J Innate Immun. 2018 Apr 4.

Sanders DB. Phenotypes that matter: Pseudomonas aeruginosa and progression of cystic fibrosis lung disease. Am J Respir Crit Care Med. 2014 Aug 1;190(3):245-6.

Terry JM, Piña SE, Mattingly SJ. Role of energy metabolism in conversion of nonmucoid Pseudomonas aeruginosa to the mucoid phenotype. Infect Immun. 1992 Apr;60(4):1329-35.

Jacobson A, Lam L, Rajendram M, Tamburini F, Honeycutt J, Pham T, Van Treuren W, Pruss K, Stabler SR, Lugo K, Bouley DM, Vilches-Moure JG, Smith M, Sonnenburg JL, Bhatt AS, Huang KC, Monack D. A Gut Commensal-Produced Metabolite Mediates Colonization Resistance to Salmonella Infection. Cell Host Microbe. 2018 Aug 8;24(2):296-307.e7.


Patent Information:
Research Tools
For Information, Contact:
OTC Licensing
Mehmet Candas
Lee Bulla
Life Sciences
Molecular Biology
© 2024. All Rights Reserved. Powered by Inteum