Muropeptides in Pseudomonas aeruginosa and their Role as Elicitors of β‐Lactam‐Antibiotic Resistance

Abstract

In Abbildung 2B dieser Zuschrift wurden die Produkte der Reaktionen von 2e mit PBP4 und AmpDh3 verwechselt. Die Reaktion von 2e mit PBP4 führt zu 2d,und die Reaktion von 2e mit AmpDh3 zu 2a,w ie in der korrigierten Abbildung 2unten gezeigt. In Haupttext und Abbildungslegende ergeben sich dadurch keine ¾nderungen. Figure 2. A) Chemical structures of detected muropeptides. B) The chemoenzymatic syntheses of six muropeptides.

Cell-Wall Recycling of the Gram-Negative Bacteria and the Nexus to Antibiotic Resistance

“…310,314 The possibility of the pentapeptide stem structure as a feature common to both AmpR repressor structures (UDP-MurNAc-pentapeptide 4, Figure 6) and derepressor structures (such anhMurNAc-pentapeptide, 2c) is discussed cogently in connection with the most recent C. freundii AmpR structural studies. 311,312 These same studies (and others in P. aeruginosa) 73,317 would appear to exclude a role for 1,6-anhMurNAc-tripeptide (2a, Figure 6) in AmpR regulation. Whether AmpR is regulated by the replete structural guise of the pentapeptide, or by a subtler competition in the cytoplasm for effector binding to its effector domain, remains an unsolved question.…”

“…Consequently, the muropeptides returned to the cytoplasm are enriched in pentapeptide stems. 374 Both the composition of the muropeptide pool in P. aeruginosa under β-lactam stress, 73 and direct evaluation of the effector-binding domain of AmpR with muropeptides, 317 support the anhMurNAc-pentapeptide as sufficient structure for binding to AmpR in order to affect ampC expression. 276 Two provisos limit further clarification of this structure (toward specific muropeptide candidate structures).…”

“…Evaluating both the breadth (in terms of structural modification to the disaccharide, and to the stem peptide of the disaccharide) and the relative abundance of the structures in this ensemble is accomplished only with great difficulty. 73 Nonetheless, it is evident that the ensemble of muropeptide structures brought into the periplasm is changed as a result of the presence of cell-wall-acting antibiotics (especially the β-lactams), and that Gram-negative bacteria use this change to initiate defensive and virulence pathways. 5,28,30,31,74 While the structures are not known, and the fullness of (and interconnectedness of) the defensive and virulence response is uncertain, the core substrate structure (the GlcNAc-MurNAc disaccharide with its stem oligopeptide) and core enzyme catalysts that act on this structure to comprise the cytoplasmic pathway for muropeptide recycling, are known.…”

Modulation of Peptidoglycan Synthesis by Recycled Cell Wall Tetrapeptides

“…Sample preparation to determine the level of the different soluble muropeptides was performed following the protocol described previously by Lee et al (2016) with some modifications. Briefly, bacteria were grown until exponential phase (OD 600 $0.7), cooled on ice for 10 min and then, after adjusting the OD 600 of the cultures (to have the same number of bacteria in each sample), normalized volumes of cells were harvested by centrifugation at 4,000 rpm, 4 C for 20 min.…”

Dissecting Metabolism of Leaf Nodules in Ardisia crenata and Psychotria punctata

“…We explored the datasets with respect to common nodule specific features: 13 m/z features, initially annotated as putative aminosugars, were detected in samples from both species and displayed higher relative abundances in nodulated tissues (Figures 4C, 5C). These metabolites ranged from 476 to 993 m/z and based on their MS2 fragmentation patterns (Packiam et al, 2015;Lee et al, 2016) we identified them as anhydromuropeptides (AhMPs) (Figure 6C). Within both species these putative AhMPs are highly characteristic for nodulated tissues (Figures 4, 5).…”