Article

Distinct penicillin binding proteins involved in the division, elongation, and shape of Escherichia coli K12.

Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 09/1975; 72(8):2999-3003. DOI: 10.1073/pnas.72.8.2999
Source: PubMed

ABSTRACT The varied effects of beta-lactam antibiotics on cell division, cell elongation, and cell shape in E. coli are shown to be due to the presence of three essential penicillin binding proteins with distinct roles in these three processes. (A) Cell shape: beta-Lactams that specifically result in the production of ovoid cells bind to penicillin binding protein 2 (molecular weight 66,000). A mutant has been isolated that fails to bind beta-lactams to protein 2, and that grows as round cells. (B) Cell division: beta-Lactams that specifically inhibit cell division bind preferentially to penicillin binding protein 3 (molecular weight 60,000). A temperature-sensitive cell division mutant has been shown to have a thermolabile protein 3. (C) Cell elongation: One beta-lactam that preferentially inhibits cell elongation and causes cell lysis binds preferentially to binding protein 1 (molecular weight 91,000). Evidence is presented that penicillin bulge formation is due to the inhibition of proteins 2 and 3 in the absence of inhibition of protein 1.

0 Followers
 · 
75 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The biological roles of low molecular weight penicillin-binding proteins (LMW PBP) have been difficult to discern in Gram-negative organisms. In E. coli, mutants lacking these proteins often have no phenotype, and cells lacking all 7 LMW PBPs remain viable. In contrast, we report here that Vibrio cholerae lacking DacA-1, a PBP5 homolog, displays slow growth, aberrant morphology, and altered peptidoglycan (PG) homeostasis in LB medium, as well as a profound plating defect. DacA-1 alone among V. cholerae's LMW PBPs is critical for bacterial growth; mutants lacking the related protein DacA-2 and/or homologs of PBP4 or PBP7 displayed normal growth and morphology. Remarkably, the growth and morphology of the dacA-1 mutant were unimpaired in LB media containing reduced concentrations of NaCl (100 mM or less), and also within suckling mice, a model host for the study of cholera pathogenesis. PG from the dacA-1 mutant contained elevated pentapeptide levels in standard and low salt media, and comparative analyses suggest that DacA-1 is V. cholerae's principal DD-carboxypeptidase. The basis for the dacA-1 mutant's halosensitivity is unknown; nonetheless, the mutant's survival in biochemically uncharacterized environments (such as the suckling mouse intestine) can be used as a reporter of low Na+ content.
    Environmental Microbiology 01/2015; 17(2). DOI:10.1111/1462-2920.12779 · 6.24 Impact Factor
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Symbiotic associations between animals and microbes are ubiquitous in nature, with an estimated 15% of all insect species harboring intracellular bacterial symbionts. Most bacterial symbionts share many genomic features including small genomes, nucleotide composition bias, high coding density and a paucity of mobile DNA, consistent with long-term host association.In the current study, we focus on the early stages of genome degeneration in a recently derived insect-bacterial mutualistic intracellular association. We present the complete genome sequence and annotation of Sitophilus oryzae primary endosymbiont (SOPE). We also present the finished genome sequence and annotation of strain HS, a close free-living relative of SOPE and other insect symbionts of the Sodalis-allied clade, whose gene inventory is expected to closely resemble the putative ancestor of this group.Structural, functional and evolutionary analyses indicate that SOPE has undergone extensive adaptation towards an insect-associated lifestyle in a very short time period. The genome of SOPE is large in size when compared to many ancient bacterial symbionts; however, almost half of the protein-coding genes in SOPE are pseudogenes. There is also evidence for relaxed selection on the remaining intact protein-coding genes. Comparative analyses of the whole genome sequence of strain HS and SOPE highlight numerous genomic rearrangements, duplications and deletions facilitated by a recent expansion of insertions sequence (IS) elements, some of which appear to have catalyzed adaptive changes. Functional metabolic predictions suggest that SOPE has lost the ability to synthesize several essential amino acids and vitamins. Analyses of the bacterial cell envelope and genes encoding secretion systems suggest that these structures and elements have become simplified in the transition to a mutualistic association.
    Genome Biology and Evolution 01/2014; 6(1):76-93. DOI:10.1093/gbe/evt210 · 4.53 Impact Factor

Preview

Download
0 Downloads
Available from