Hydrolysis of peptidoglycan is modulated by amidation of meso-diaminopimelic acid and Mg2+in Bacillus subtilis.
The ability of excess Mg2+to compensate the absence of cell wall related genes in Bacillus subtilis has been known for a long time, but the mechanism has remained obscure. Here, we show that the rigidity of wild-type cells remains unaffected with excess Mg2+, but the proportion of amidated meso-diaminopimelic (mDAP) acid in their peptidoglycan (PG) is significantly reduced. We identify the amidotransferase AsnB as responsible for mDAP amidation and show that the gene encoding it is essential without added Mg2+. Growth without excess Mg2+causes ΔasnB mutant cells to deform and ultimately lyse. In cell regions with deformations, PG insertion is orderly and indistinguishable from the wild-type. However, PG degradation is unevenly distributed along the sidewalls. Furthermore, ΔasnB mutant cells exhibit increased sensitivity to antibiotics targeting the cell wall. These results suggest that absence of amidated mDAP causes a lethal deregulation of PG hydrolysis that can be inhibited by increased levels of Mg2+. Consistently, we find that Mg2+inhibits autolysis of wild-type cells. We suggest that Mg2+helps to maintain the balance between PG synthesis and hydrolysis in cell wall mutants where this balance is perturbed in favor of increased degradation.
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Alex
http://orcid.org/0000-0002-4003-8519
A
Dajkovic
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Benoit
B
Tesson
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Smita
S
Chauhan
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Pascal
P
Courtin
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Ruth
R
Keary
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Pierre
P
Flores
ISMO, UMR CNRS 8214, Université Paris Sud, Orsay Cedex, 91405, France.
Christian
C
Marlière
Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, 2829-516, Portugal.
Sérgio R
http://orcid.org/0000-0002-4485-832X
SR
Filipe
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Marie-Pierre
MP
Chapot-Chartier
MICALIS, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, 78350, France.
Rut
R
Carballido-Lopez
D001412:Bacillus subtilis / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D003960:Diaminopimelic Acid / Q000378:metabolism*; D006868:Hydrolysis; D008274:Magnesium / Q000378:metabolism; D010457:Peptidoglycan / Q000096:biosynthesis / Q000378:metabolism*
D001426:Bacterial Proteins; D010457:Peptidoglycan; D003960:Diaminopimelic Acid; D008274:Magnesium