title: Inorganic Phosphate Limitation Modulates Capsular Polysaccharide Composition in Mycobacteria.
abstract: Mycobacterium tuberculosis is protected by an unusual and highly impermeable cell envelope that is critically important for the successful colonization of the host. The outermost surface of this cell envelope is formed by capsular polysaccharides that play an important role in modulating the initial interactions once the bacillus enters the body. Although the bioenzymatic steps involved in the production of the capsular polysaccharides are emerging, information regarding the ability of the bacterium to modulate the composition of the capsule is still unknown. Here, we study the mechanisms involved in regulation of mycobacterial capsule biosynthesis using a high throughput screen for gene products involved in capsular α-glucan production. Utilizing this approach we identified a group of mutants that all carried mutations in the ATP-binding cassette phosphate transport locus pst These mutants collectively exhibited a strong overproduction of capsular polysaccharides, including α-glucan and arabinomannan, suggestive of a role for inorganic phosphate (Pi) metabolism in modulating capsular polysaccharide production. These findings were corroborated by the observation that growth under low Pi conditions as well as chemical activation of the stringent response induces capsule production in a number of mycobacterial species. This induction is, in part, dependent on σ factor E. Finally, we show that Mycobacterium marinum, a model organism for M. tuberculosis, encounters Pi stress during infection, which shows the relevance of our findings in vivo.
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands, robertisanti@gmail.com.
authors.forename: Robert
authors.initials: R
authors.lastname: van de Weerd
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Maikel
authors.initials: M
authors.lastname: Boot
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Janneke
authors.initials: J
authors.lastname: Maaskant
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Marion
authors.initials: M
authors.lastname: Sparrius
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Theo
authors.initials: T
authors.lastname: Verboom
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Lisanne M
authors.initials: LM
authors.lastname: van Leeuwen
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Maroeska J
authors.initials: MJ
authors.lastname: Burggraaf
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU University Medical Center, P. O. Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: Nanne J
authors.initials: NJ
authors.lastname: Paauw
authors.affiliation: Department of Molecular Medicine, University of Padova, Via Gabelli 63, 35121 Padova, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Dainese
authors.affiliation: Department of Molecular Medicine, University of Padova, Via Gabelli 63, 35121 Padova, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Manganelli
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands, Department of Molecular Microbiology, VU University Amsterdam, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands, and.
authors.forename: Wilbert
authors.initials: W
authors.lastname: Bitter
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands, bj.appelmelk@vumc.nl.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Appelmelk
authors.affiliation: From the Department of Medical Microbiology and Infection Control, VU University Medical Center, De boelelaan 1108, 1081HZ Amsterdam, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Geurtsen
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000187:drug effects / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D009165:Mycobacterium Infections, Nontuberculous / Q000188:drug therapy* / Q000382:microbiology; D019910:Mycobacterium marinum / Q000187:drug effects*; D010710:Phosphates / Q000494:pharmacology*; D011134:Polysaccharides / Q000378:metabolism*; D015027:Zebrafish
chemical_list: D010710:Phosphates; D011134:Polysaccharides
keywords: Mycobacterium tuberculosis; cell surface; confocal microscopy; electron microscopy (EM); zebrafish