Intra-species signaling betweenPseudomonas aeruginosagenotypes increases production of quorum sensing controlled virulence factors

Abstract

1The opportunistic pathogen Pseudomonas aeruginosa damages hosts through the 2 production of diverse secreted products, many of which are regulated by quorum 3 sensing. The lasR gene, which encodes a central quorum-sensing regulator, is 4 frequently mutated, and loss of LasR function impairs the activity of downstream 5 regulators RhlR and PqsR. We found that in diverse models, the presence of P. 6 aeruginosa wild type causes LasR loss-of-function strains to hyperproduce RhlR/I-7 regulated antagonistic factors, and autoinducer production by the wild type is not 8 required for this effect. We uncovered a reciprocal interaction between isogenic wild 9 type and lasR mutant pairs wherein the iron-scavenging siderophore pyochelin, 10 specifically produced by the lasR mutant, induces citrate release and cross-feeding from 11 wild type. Citrate stimulates RhlR signaling and RhlI levels in LasR-but not in LasR+ 12 strains, and the interactions occur in diverse media. Co-culture interactions between 13 strains that differ by the function of a single transcription factor may explain worse 14 outcomes associated with mixtures of LasR+ and LasR loss-of-function strains. More 15 broadly, this report illustrates how interactions within a genotypically diverse population, 16 similar to those that frequently develop in natural settings, can promote net virulence 17 factor production. (19, 20). Further, some LasR-strains exhibit rewired regulation of quorum sensing 35 (QS)-controlled exoproducts (21) and LasR-strains can activate QS signaling in 36 response to products from other species (22) or in specific culture conditions (23, 24). 37LasR-strains are also frequently found among LasR+ P. aeruginosa strains where 38 exoproducts can be shared or signal cross-feeding can occur (13). 39 P. aeruginosa LasR participates in the regulation of QS in conjunction with two 40 transcription factors: RhlR and PqsR (MvfR). Each of these three regulators has one or 41 more autoinducer ligands: 3-oxo-C12-homoserine lactone (3OC12HSL) for LasR, C4-42 homoserine lactone (C4HSL) for RhlR, and hydroxyalkylquinolones (Pseudomonas 43Quinolone Signal (PQS) and hydroxy-heptyl quinolone (HHQ)) for PqsR (25). In the 44 regulatory networks described in the widely-used P. aeruginosa model strains, LasR is 45 an upstream regulator of RhlR and PqsR signaling, and together these regulators 46 control the expression of a suite of genes associated with virulence including redox-47 active small molecule phenazines (26-28), cyanide (29), proteases (30-33), and 48 rhamnolipid surfactants important for surface motility, biofilm dispersal, and host cell 49 damage (34)(35)(36). 50Other traits that are often heterogeneous across P. aeruginosa isolates relate to 51 strategies for iron acquisition. P. aeruginosa procures iron through the use of 52 siderophores, including pyochelin (37-39) and pyoverdine (40), from heme or through a 53 direct iron uptake system (41-43). It is common to encounter P. aeruginosa strains with 54 loss of function mutations in genes encoding ...

Loss of LasR function leads to decreased repression ofPseudomonas aeruginosaPhoB activity at physiological phosphate concentrations

“…However, RhlR and PqsR are capable of inducing QS-controlled genes in the absence of LasR in specific strains and conditions. (36,37,59,82) Thus, we assessed the role of RhlR and PqsR in the repression of PhoB. As shown in Fig.…”

“…(36,(52)(53)(54)(55)(56)(57) LasR-isolates are associated with worse disease progression in pwCF (57) and worse lesions during acute ocular infections. (54) In laboratory evolution experiments, the increased fitness of P. aeruginosa LasR-lineages depends on increased CbrA-CbrB activity (58,59) which leads to growth advantages in complex media. (37,58,60) P. aeruginosa CbrA-CbrB is a two-component system that induces expression of the small RNA crcZ which sequesters Crc.…”