MurJ and a novel lipid II flippase are required for cell wall biogenesis in Bacillus subtilis.
Bacterial surface polysaccharides are synthesized from lipid-linked precursors at the inner surface of the cytoplasmic membrane before being translocated across the bilayer for envelope assembly. Transport of the cell wall precursor lipid II in Escherichia coli requires the broadly conserved and essential multidrug/oligosaccharidyl-lipid/polysaccharide (MOP) exporter superfamily member MurJ. Here, we show that Bacillus subtilis cells lacking all 10 MOP superfamily members are viable with only minor morphological defects, arguing for the existence of an alternate lipid II flippase. To identify this factor, we screened for synthetic lethal partners of MOP family members using transposon sequencing. We discovered that an uncharacterized gene amj (alternate to MurJ; ydaH) and B. subtilis MurJ (murJBs; formerly ytgP) are a synthetic lethal pair. Cells defective for both Amj and MurJBs exhibit cell shape defects and lyse. Furthermore, expression of Amj or MurJBs in E. coli supports lipid II flipping and viability in the absence of E. coli MurJ. Amj is present in a subset of gram-negative and gram-positive bacteria and is the founding member of a novel family of flippases. Finally, we show that Amj is expressed under the control of the cell envelope stress-response transcription factor σ(M) and cells lacking MurJBs increase amj transcription. These findings raise the possibility that antagonists of the canonical MurJ flippase trigger expression of an alternate translocase that can resist inhibition.
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115; and.
Alexander J
AJ
Meeske
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115; and.
Lok-To
LT
Sham
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115; and.
Harvey
H
Kimsey
Department of Microbiology and Immunology, University of California, San Francisco, CA 94158.
Byoung-Mo
BM
Koo
Department of Microbiology and Immunology, University of California, San Francisco, CA 94158.
Carol A
CA
Gross
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115; and.
Thomas G
TG
Bernhardt
Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115; and rudner@hms.harvard.edu.
David Z
DZ
Rudner
D001412:Bacillus subtilis / Q000201:enzymology* / Q000254:growth & development*; D001426:Bacterial Proteins / Q000378:metabolism*; D002473:Cell Wall / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D008856:Microscopy, Fluorescence; D009024:Morphogenesis / Q000502:physiology*; D049294:Phospholipid Transfer Proteins / Q000378:metabolism*; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000031:analogs & derivatives / Q000378:metabolism
D001426:Bacterial Proteins; D049294:Phospholipid Transfer Proteins; D014538:Uridine Diphosphate N-Acetylmuramic Acid; C069249:muramyl-NAc-(pentapeptide)pyrophosphoryl-undecaprenol
MurJ; flippase; lipid II; peptidoglycan; sigM