Severity: Warning
Message: file_get_contents(https://...@pubfacts.com&api_key=b8daa3ad693db53b1410957c26c9a51b4908&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 176
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 176
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 250
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3122
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
Line: 575
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 489
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Peptidoglycan (PG) is an essential, envelope-fortifying macromolecule of eubacterial cell walls. It is a large polymer with multiple glycan strands interconnected by short peptide chains forming a sac-like structure around cytoplasmic membrane. In most bacteria, the composition of the peptide chain is well-conserved and distinctive; in E. coli, the peptide chain length varies from two to five amino acids with a tetrapeptide consisting of L-alanine - D-glutamic acid - meso-diaminopimelic acid - D-alanine. However, it is not known how bacteria conserve the composition and sequence of peptide chains of PG. Here, we find that a conserved open reading frame of unknown function, YfiH (renamed PgeF) contributes to the maintenance of peptide composition in E. coli. Using genetic, biochemical and mass spectrometrical analyses we demonstrate that absence of yfiH results in incorporation of non-canonical amino acids, L-serine or glycine in place of L-alanine in PG sacculi leading to β-lactam - sensitivity, lethality in mutants defective in PG remodelling or recycling pathways, altered cell morphology and reduced PG synthesis. yfiH orthologs from other Gram-positive genera were able to compensate the absence of yfiH in E. coli indicating a conserved pathway in bacterial kingdom. Our results suggest editing/quality control mechanisms exist to maintain composition and integrity of bacterial peptidoglycan.
Download full-text PDF |
Source |
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http://dx.doi.org/10.1111/mmi.13730 | DOI Listing |
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