Remodeling of Lipid A in Pseudomonas syringae pv. phaseolicola In Vitro

Abstract

Pseudomonas species infect a variety of organisms, including mammals and plants. Mammalian pathogens of the Pseudomonas family modify their lipid A during host entry to evade immune responses and to create an effective barrier against different environments, for example by removal of primary acyl chains, addition of phosphoethanolamine (P-EtN) to primary phosphates, and hydroxylation of secondary acyl chains. For Pseudomonas syringae pv. phaseolicola (Pph) 1448A, an economically important pathogen of beans, we observed similar lipid A modifications by mass spectrometric analysis. Therefore, we investigated predicted proteomes of various plant-associated Pseudomonas spp. for putative lipid A-modifying proteins using the well-studied mammalian pathogen Pseudomonas aeruginosa as a reference. We generated isogenic mutant strains of candidate genes and analyzed their lipid A. We show that the function of PagL, LpxO, and EptA is generally conserved in Pph 1448A. PagL-mediated de-acylation occurs at the distal glucosamine, whereas LpxO hydroxylates the secondary acyl chain on the distal glucosamine. The addition of P-EtN catalyzed by EptA occurs at both phosphates of lipid A. Our study characterizes lipid A modifications in vitro and provides a useful set of mutant strains relevant for further functional studies on lipid A modifications in Pph 1448A.

Cross-family transfer of the Arabidopsis cell-surface immune receptor LORE to tomato confers sensing of 3-hydroxylated fatty acids and enhanced disease resistance

“…Additionally, different bacteria use mc-3-OH-FAs as building blocks in various other compounds, such as lipopeptides (Souza et al ., 2003; Raaijmakers et al ., 2006), HAAs and rhamnolipids (Abdel-Mawgoud et al ., 2010), N-acyl-homoserine lactone-type quorum sensing molecules (Williams, 2007; Thiel et al ., 2009), or polyhydroxyalkanoates (Raza et al ., 2018; Paduvari et al ., 2024). While most of these compounds do not activate LORE-mediated immunity directly (Kutschera et al ., 2019), mc-3-OH-FAs could be released from these compounds or the ACP/CoA-bound precursors (Zheng, Z. et al ., 2004; Zheng, Zhong et al ., 2004; Geurtsen et al ., 2005; Ernst et al ., 2006; Kutschera et al ., 2019; Gerster et al ., 2022). Free 3-OH-C10:0 FAs are, for example, prevalent in the secretome of Pseudomonas spp.…”

In-depth biological characterization of two black soldier fly anti- Pseudomonas peptides reveals LPS-binding and immunomodulating effects

“…In contrast to some other cystic fibrosis isolates, RP73 does not contain LPS mutations that typically confer increased resistance to AMPs, such as the addition of aminoarabinose to the free phosphate groups of the glucosamine backbone ( 62 , 63 ). However, the under-acylation of LPS molecules has in the past also been linked to increased AMP and polymyxin resistance in various Gram-negative bacteria ( 64 – 67 ). For P. aeruginosa specifically, strains with penta-acylated LPS structures are less susceptible to polymyxin B due to decreased hydrophobic interactions ( 67 ).…”

A Single Residue within the MCR-1 Protein Confers Anticipatory Resilience

“…Details on the lipid A molecular species can be found in Table S2. MS 2 experiments for further detailed analysis of the lipid A structure were performed as described previously ( 61 ). All samples of the NBD-glycerol-PEA TLC-based assay were diluted 20-fold in the spray solution comprising water–propan-2-ol–7 M triethylamine–acetic acid (50:50:0.06:0.02 [vol/vol/vol/vol]) and then centrifuged briefly at 16,000 × g at room temperature.…”