Bright luminescence of Vibrio fischeri aconitase mutants reveals a connection between citrate and the Gac/Csr regulatory system.
The Gac/Csr regulatory system is conserved throughout the γ-proteobacteria and controls key pathways in central carbon metabolism, quorum sensing, biofilm formation and virulence in important plant and animal pathogens. Here we show that elevated intracellular citrate levels in a Vibrio fischeri aconitase mutant correlate with activation of the Gac/Csr cascade and induction of bright luminescence. Spontaneous or directed mutations in the gene that encodes citrate synthase reversed the bright luminescence of aconitase mutants, eliminated their citrate accumulation and reversed their elevated expression of CsrB. Our data elucidate a correlative link between central metabolic and regulatory pathways, and they suggest that the Gac system senses a blockage at the aconitase step of the tricarboxylic acid cycle, either through elevated citrate levels or a secondary metabolic effect of citrate accumulation, and responds by modulating carbon flow and various functions associated with host colonization, including bioluminescence.
Department of Microbiology, University of Georgia, 120 Cedar Street, Athens, GA, 30602, USA.
Alecia N
AN
Septer
Jeffrey L
JL
Bose
Anna
A
Lipzen
Joel
J
Martin
Cheryl
C
Whistler
Eric V
EV
Stabb
D000154:Aconitate Hydratase / Q000235:genetics* / Q000378:metabolism*; D048908:Aliivibrio fischeri / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000235:genetics / Q000378:metabolism; D019343:Citric Acid / Q000378:metabolism*; D002952:Citric Acid Cycle; D015964:Gene Expression Regulation, Bacterial; D005838:Genotype; D049449:Luminescence; D009154:Mutation; D013489:Suppression, Genetic
D001426:Bacterial Proteins; D019343:Citric Acid; D002950:Citrate (si)-Synthase; D000154:Aconitate Hydratase