Lipidomic discovery of deoxysiderophores reveals a revised mycobactin biosynthesis pathway in Mycobacterium tuberculosis.
To measure molecular changes underlying pathogen adaptation, we generated a searchable dataset of more than 12,000 mass spectrometry events, corresponding to lipids and small molecules that constitute a lipidome for Mycobacterium tuberculosis. Iron is essential for M. tuberculosis survival, and the organism imports this metal using mycobactin and carboxymycobactin siderophores. Detection of an unexpected siderophore variant and deletions of genes for iron scavenging has led to a revised mycobactin biosynthesis model. An organism-wide search of the M. tuberculosis database for hypothetical compounds predicted by this model led to the discovery of two families of previously unknown lipids, designated monodeoxymycobactins and monodeoxycarboxymycobactins. These molecules suggest a revised biosynthetic model that alters the substrates and order of action of enzymes through the mycobactin biosynthetic pathway. We tested this model genetically by solving M. tuberculosis lipidomes after deletion of the iron-dependent regulator (ideR), mycobactin synthase B (mbtB), or mycobactin synthase G (mbtG). These studies show that deoxymycobactins are actively regulated during iron starvation, and also define essential roles of MbtG in converting deoxymycobactins to mycobactin and in promoting M. tuberculosis growth. Thus, lipidomics is an efficient discovery tool that informs genetic relationships, leading to a revised general model for the biosynthesis of these virulence-conferring siderophores.
Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Cressida A
CA
Madigan
Tan-Yun
TY
Cheng
Emilie
E
Layre
David C
DC
Young
Matthew J
MJ
McConnell
C Anthony
CA
Debono
Jeffrey P
JP
Murry
Jun-Rong
JR
Wei
Clifton E
CE
Barry
G Marcela
GM
Rodriguez
Isamu
I
Matsunaga
Eric J
EJ
Rubin
D Branch
DB
Moody
D053898:Biosynthetic Pathways / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D017931:DNA Primers / Q000235:genetics; D016208:Databases, Factual; D007501:Iron / Q000378:metabolism; D008055:Lipids / Q000737:chemistry*; D013058:Mass Spectrometry; D008954:Models, Biological; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D010080:Oxazoles / Q000378:metabolism*; D017262:Siderophores / Q000378:metabolism*
D017931:DNA Primers; D008055:Lipids; D010080:Oxazoles; D017262:Siderophores; C018608:mycobactins; D007501:Iron