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HrtBA and menaquinones control haem homeostasis in L actococcus lactis
Author(s) -
Joubert Laetitia,
DerréBobillot Aurélie,
Gaudu Philippe,
Gruss Alexandra,
Lechardeur Delphine
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12705
Subject(s) - lactococcus lactis , biology , intracellular , biochemistry , operon , permease , efflux , extracellular , antiporter , bacteria , microbiology and biotechnology , membrane , transporter , gene , escherichia coli , genetics , lactic acid
Summary L actococcus lactis is a fermenting G ram‐positive bacterium widely used for production of dairy products. Lacking haem biosynthesis genes, L . lactis can still shift to an energetically favourable respiratory metabolism by activating a terminal cytochrome bd oxidase when haem is added to an aerated culture. Haem intracellular homeostasis is mediated by the hrtRBA operon encoding the conserved membrane HrtBA haem efflux permease and the unique intracellular haem sensor and regulator, HrtR . Here we report that membrane‐associated menaquinones ( MK ) favour the accumulation of reduced haem in membranes. An oxidative environment, provided by oxygen, prevents and reverses haemin reduction by MK and thus limits haem accumulation in membranes. HrtBA counteracts MK ‐dependent membrane retention of excess haem in membrane, suggesting direct efflux from this compartment. Moreover, both HrtBA and MK ‐mediated reduction have a strong impact on haem intracellular pools, as determined via HrtR haem sensor induction, suggesting that intracellular haem acquisition is controlled at the membrane level without the need for dedicated import systems. Our conclusions lead to a new hypothesis of haem acquisition and regulation in which HrtBA and the bacterial membrane have central roles in L . lactis .