Mycobacterium marinum produces distinct mycobactin and carboxymycobactin siderophores to promote growth in broth and phagocytes

Abstract

Mycobacterium marinum is a model organism for pathogenic Mycobacterium species, including Mycobacterium tuberculosis, the causative agent of tuberculosis. These pathogens enter phagocytes and replicate within the Mycobacterium‐containing vacuole, possibly followed by vacuole exit and growth in the host cell cytosol. Mycobacteria release siderophores called mycobactins to scavenge iron, an essential yet poorly soluble and available micronutrient. To investigate the role of M. marinum mycobactins, we purified by organic solvent extraction and identified by mass spectrometry the lipid‐bound mycobactin (MBT) and the water‐soluble variant carboxymycobactin (cMBT). Moreover, we generated by specialised phage transduction a defined M. marinum ΔmbtB deletion mutant predicted to be defective for mycobactin production. The M. marinum ΔmbtB mutant strain showed a severe growth defect in broth and phagocytes, which was partially complemented by supplying the mbtB gene on a plasmid. Furthermore, purified Fe‐MBT or Fe‐cMBT improved the growth of wild type as well as ΔmbtB mutant bacteria on minimal plates, but only Fe‐cMBT promoted the growth of wild‐type M. marinum during phagocyte infection. Finally, the intracellular growth of M. marinum ΔmbtB in Acanthamoeba castellanii amoebae was restored by coinfection with wild‐type bacteria. Our study identifies and characterises the M. marinum MBT and cMBT siderophores and reveals the requirement of mycobactins for extra‐ and intracellular growth of the pathogen.

Zn 2+ Intoxication of Mycobacterium marinum during Dictyostelium discoideum Infection Is Counteracted by Induction of the Pathogen Zn 2+ Exporter CtpC

“…For example, while Fe 21 participates in the defense against Mycobacterium avium or Legionella pneumophila (35,(52)(53)(54), Cu 21 or Zn 21 does not affect the infection by Legionella (35). On the other hand, to access poorly available transition metals such as iron, M. marinum stimulates the synthesis and release of small chelating molecules known as siderophores (55).…”

Leishmaniainfection triggers hepcidin‐mediated proteasomal degradation of Nramp1 to increase phagolysosomal iron availability

“…For this, most of the pathogens have evolved high‐affinity iron‐binding proteins (Skaar, 2010; Zhang et al, 2020). For example, Mycobacterium secretes iron‐harvesting siderophore proteins, such as mycobactins and carboxymycobactins, that help it to acquire ferric iron from its surroundings (Knobloch et al, 2020). Similarly, many pathogens are known to secrete hemophores for uptake of heme‐bound iron from the host (Wandersman & Delepelaire, 2004).…”

Temporal genome-wide fitness analysis ofMycobacterium marinumduring infection reveals genetic requirement for virulence and survival in amoebae and microglial cells

“…For instance, the heparin-binding hemagglutinin, HBHA initially described to play a role in adherence to nonphagocytic cells (Menozzi et al, 1996) and recently described to be involved in the formation of cytosolic lipid inclusion (Raze et al, 2018) was detected only in D. discoideum. In a similar way, genes encoding enzymes involved in mycobactin production, a siderophore produced by the bacteria to scavenge iron, was also found only in D. discoideum (Knobloch et al, 2020;Quadri et al, 1998). On the other hand, some pathways have been identified only in BV2 microglial cells model such as the PhoY2/PhoT twocomponent system involved in response to environmental stress including antibiotic treatment (Namugenyi et al, 2017;C.…”