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Aggregation of nontuberculous mycobacteria is regulated by carbon:nitrogen balance

DePas, William H. and Bergkessel, Megan and Newman, Dianne K. (2019) Aggregation of nontuberculous mycobacteria is regulated by carbon:nitrogen balance. mBio, 10 (4). Art. No. e01715-19. ISSN 2150-7511. PMCID PMC6692514.

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Nontuberculous mycobacteria (NTM) are emerging opportunistic pathogens that colonize household water systems and cause chronic lung infections in susceptible patients. The ability of NTM to form surface-attached biofilms in the nonhost environment and corded aggregates in vivo is important to their ability to persist in both contexts. Underlying the development of these multicellular structures is the capacity of mycobacterial cells to adhere to one another. Unlike most other bacteria, NTM spontaneously and constitutively aggregate in vitro, hindering our ability to understand the transition between planktonic and aggregated cells. While culturing a model NTM, Mycobacterium smegmatis, in rich medium, we fortuitously discovered that planktonic cells accumulate after ∼3 days of growth. By providing selective pressure for bacteria that disperse earlier, we isolated a strain with two mutations in the oligopeptide permease operon (opp). A mutant lacking the opp operon (Δopp) disperses earlier than wild type (WT) due to a defect in nutrient uptake. Experiments with WT M. smegmatis revealed that growth as aggregates is favored when carbon is replete, but under conditions of low available carbon relative to available nitrogen, M. smegmatis grows as planktonic cells. By adjusting carbon and nitrogen sources in defined medium, we tuned the cellular C/N ratio such that M. smegmatis grows either as aggregates or as planktonic cells. C/N-mediated aggregation regulation is widespread among NTM with the possible exception of rough-colony Mycobacterium abscessus isolates. Altogether, we show that NTM aggregation is a controlled process that is governed by the relative availability of carbon and nitrogen for metabolism.

Item Type:Article
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URLURL TypeDescription Paper CentralArticle
DePas, William H.0000-0001-8532-2567
Bergkessel, Megan0000-0002-4530-1224
Newman, Dianne K.0000-0003-1647-1918
Alternate Title:Aggregation regulation in nontuberculous mycobacteria
Additional Information:© 2019 DePas et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Received 28 June 2019; Accepted 22 July 2019; Published 13 August 2019. We thank the Cystic Fibrosis Foundation (grants DEPAS17F0 to W.H.D. and BERGKE16F0 to M.B.) and the NIH (grant 1R01AI127850-01A1 to D.K.N.) for supporting our research. A portion of the imaging was performed in the Caltech Biological Imaging Facility, with the support of the Caltech Beckman Institute and the Arnold and Mabel Beckman Foundation. Lindsay Caverly (CS Mott Children’s Hospital, University of Michigan, Ann Arbor, MI, USA) graciously provided M. abscessus clinical isolates (NTM0253a, NTM0253b, NTM0711a, and NTM0711b), William Jacobs (Albert Einstein College of Medicine, Bronx, NY, USA) provided WT M. smegmatis MC^2155, and William Bishai (Johns Hopkins University School of Medicine, Baltimore, MD, USA) provided plasmids pJV53 and pMH94. Igor Antoshechkin and the Millard and Muriel Jacobs Genetics and Genomics Laboratory at Caltech assisted with genome sequencing. Alex Sessions and Fenfang Wu (Caltech) helped with C/N measurements and analysis. Ion chromatography instrumentation used for this work is located in the Environmental Analysis Center at Caltech. We acknowledge Nathan F. Dalleska, Lev Tsypin, and Melanie Spero for ion chromatography method support. SEM was performed at the Caltech GPS Division Analytical Facility with the assistance of Chi Ma.
Funding AgencyGrant Number
Cystic Fibrosis FoundationDEPAS17F0
Cystic Fibrosis FoundationBERGKE16F0
Caltech Beckman InstituteUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Subject Keywords:Mycobacterium, biofilms, carbon metabolism, nitrogen metabolism, physiology
Issue or Number:4
PubMed Central ID:PMC6692514
Record Number:CaltechAUTHORS:20190509-154449662
Persistent URL:
Official Citation:Aggregation of Nontuberculous Mycobacteria Is Regulated by Carbon-Nitrogen Balance. William H. DePas, Megan Bergkessel, Dianne K. Newman. mBio Aug 2019, 10 (4) e01715-19; DOI: 10.1128/mBio.01715-19
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95386
Deposited By: Tony Diaz
Deposited On:09 May 2019 22:51
Last Modified:23 Dec 2020 23:53

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