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Wu ML, Gengenbacher M, Dick T. Mild Nutrient Starvation Triggers the Development of a Small-Cell Survival Morphotype in Mycobacteria. Front Microbiol 2016; 7:947. [PMID: 27379076 PMCID: PMC4909757 DOI: 10.3389/fmicb.2016.00947] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/01/2016] [Indexed: 11/13/2022] Open
Abstract
Mycobacteria, generally believed to be non-sporulating, are well known to survive shock starvation in saline for extended periods of time in a non-replicating state without any apparent morphological changes. Here, we uncover that mycobacteria can undergo cellular differentiation by exposing Mycobacterium smegmatis to mild starvation conditions. Traces of various carbon sources in saline triggered the development of a novel small resting cell (SMRC) morphotype. Development of SMRCs could also be observed for other mycobacteria, suggesting evolutionary conservation of this differentiation pathway. Fluorescence microscopic analyses showed that development of SMRCs progresses via septated, multi-nucleoided cell intermediates, which divide to generate mono-nucleoided SMRCs. Intriguingly, saline shock-starved large resting cells (LARCs), which did not show cell size or surface changes when observed by scanning electron microscopy, remodeled their internal structure to septated, multi-nucleoided cells, similar to the intermediates seen during differentiation to SMRCs. Our results suggest that mycobacteria harbor a starvation-induced differentiation program in which at first septated, multi-nucleoided cells are generated. Under zero-nutrient conditions bacteria terminate development at this stage as LARCs. In the presence of traces of a carbon source, these multi-nucleoided cells continue differentiation into mono-nucleoided SMRCs. Both SMRCs and LARCs exhibited extreme antibiotic tolerance. SMRCs showed increased long-term starvation survival, which was associated with the presence of lipid inclusion bodies.
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Affiliation(s)
- Mu-Lu Wu
- Antibacterial Drug Discovery Laboratory, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore
| | - Martin Gengenbacher
- Tuberculosis Research Laboratory, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore
| | - Thomas Dick
- Antibacterial Drug Discovery Laboratory, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore Singapore, Singapore
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Chopra S, Matsuyama K, Tran T, Malerich JP, Wan B, Franzblau SG, Lun S, Guo H, Maiga MC, Bishai WR, Madrid PB. Evaluation of gyrase B as a drug target in Mycobacterium tuberculosis. J Antimicrob Chemother 2012; 67:415-21. [PMID: 22052686 PMCID: PMC3254195 DOI: 10.1093/jac/dkr449] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 09/28/2011] [Accepted: 10/03/2011] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES New classes of drugs are needed to treat tuberculosis (TB) in order to combat the emergence of resistance to existing agents and shorten the duration of therapy. Targeting DNA gyrase is a clinically validated therapeutic approach using fluoroquinolone antibiotics to target the gyrase subunit A (GyrA) of the heterotetramer. Increasing resistance to fluoroquinolones has driven interest in targeting the gyrase subunit B (GyrB), which has not been targeted for TB. The biological activities of two potent small-molecule inhibitors of GyrB have been characterized to validate its targeting as a therapeutic strategy for treating TB. MATERIALS AND METHODS Novobiocin and aminobenzimidazole 1 (AB-1) were tested for their activity against Mycobacterium tuberculosis (Mtb) H37Rv and other mycobacteria. AB-1 and novobiocin were also evaluated for their interaction with rifampicin and isoniazid as well as their potential for cytotoxicity. Finally, AB-1 was tested for in vivo efficacy in a murine model of TB. RESULTS Novobiocin and AB-1 have both been shown to be active against Mtb with MIC values of 4 and 1 mg/L, respectively. Only AB-1 exhibited time-dependent bactericidal activity against drug-susceptible and drug-resistant mycobacteria, including a fluoroquinolone-resistant strain. AB-1 had potent activity in the low oxygen recovery assay model for non-replicating persistent Mtb. Additionally, AB-1 has no interaction with isoniazid and rifampicin, and has no cross-resistance with fluoroquinolones. In a murine model of TB, AB-1 significantly reduced lung cfu counts in a dose-dependent manner. CONCLUSIONS Aminobenzimidazole inhibitors of GyrB exhibit many of the characteristics required for their consideration as a potential front-line antimycobacterial therapeutic.
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Affiliation(s)
- Sidharth Chopra
- Center for Infectious Disease and Biodefense Research, Bioscience Division, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493, USA
| | - Karen Matsuyama
- Center for Infectious Disease and Biodefense Research, Bioscience Division, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493, USA
| | - Tran Tran
- Center for Infectious Disease and Biodefense Research, Bioscience Division, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493, USA
| | - Jeremiah P. Malerich
- Center for Infectious Disease and Biodefense Research, Bioscience Division, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493, USA
| | - Baojie Wan
- Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, IL, USA
| | - Scott G. Franzblau
- Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, IL, USA
| | - Shichun Lun
- Center for Tuberculosis Research, Johns Hopkins School of Medicine, 1550 Orleans St., Baltimore, MD, USA
| | - Haidan Guo
- Center for Tuberculosis Research, Johns Hopkins School of Medicine, 1550 Orleans St., Baltimore, MD, USA
| | - Mariama C. Maiga
- Center for Tuberculosis Research, Johns Hopkins School of Medicine, 1550 Orleans St., Baltimore, MD, USA
| | - William R. Bishai
- Center for Tuberculosis Research, Johns Hopkins School of Medicine, 1550 Orleans St., Baltimore, MD, USA
- KwaZulu-Natal Research Institute for Tuberculosis and HIV (K-RITH), Suite Z310 Doris Duke Building, 719 Umbilo Road, Durban, 4001, Republic of South Africa
- Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA
| | - Peter B. Madrid
- Center for Infectious Disease and Biodefense Research, Bioscience Division, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493, USA
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