Document Detail

Actin polymerization drives septation of Listeria monocytogenes namA hydrolase mutants, demonstrating host correction of a bacterial defect.
MedLine Citation:
PMID:  21263016     Owner:  NLM     Status:  MEDLINE    
The Gram-positive bacterial cell wall presents a structural barrier that requires modification for protein secretion and large-molecule transport as well as for bacterial growth and cell division. The Gram-positive bacterium Listeria monocytogenes adjusts cell wall architecture to promote its survival in diverse environments that include soil and the cytosol of mammalian cells. Here we provide evidence for the enzymatic flexibility of the murein hydrolase NamA and demonstrate that bacterial septation defects associated with a loss of NamA are functionally complemented by physical forces associated with actin polymerization within the host cell cytosol. L. monocytogenes ΔnamA mutants formed long bacterial chains during exponential growth in broth culture; however, normal septation could be restored if mutant cells were cocultured with wild-type L. monocytogenes bacteria or by the addition of exogenous NamA. Surprisingly, ΔnamA mutants were not significantly attenuated for virulence in mice despite the pronounced exponential growth septation defect. The physical force of L. monocytogenes-mediated actin polymerization within the cytosol was sufficient to sever ΔnamA mutant intracellular chains and thereby enable the process of bacterial cell-to-cell spread so critical for L. monocytogenes virulence. The inhibition of actin polymerization by cytochalasin D resulted in extended intracellular bacterial chains for which septation was restored following drug removal. Thus, despite the requirement for NamA for the normal septation of exponentially growing L. monocytogenes cells, the hydrolase is essentially dispensable once L. monocytogenes gains access to the host cell cytosol. This phenomenon represents a notable example of eukaryotic host cell complementation of a bacterial defect.
Francis Alonzo; P David McMullen; Nancy E Freitag
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2011-01-24
Journal Detail:
Title:  Infection and immunity     Volume:  79     ISSN:  1098-5522     ISO Abbreviation:  Infect. Immun.     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-03-22     Completed Date:  2011-05-23     Revised Date:  2013-06-30    
Medline Journal Info:
Nlm Unique ID:  0246127     Medline TA:  Infect Immun     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1458-70     Citation Subset:  IM    
Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, USA.
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MeSH Terms
Actins / genetics,  metabolism*
Blotting, Western
Cell Wall
Host-Parasite Interactions / physiology*
Listeria monocytogenes / pathogenicity*,  physiology*
Listeriosis / genetics,  metabolism
N-Acetylmuramoyl-L-alanine Amidase / genetics,  metabolism*
Polymerase Chain Reaction
Virulence / genetics
Virulence Factors / genetics,  metabolism
Grant Support
Reg. No./Substance:
0/Actins; 0/Virulence Factors; EC Amidase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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