Paschalidis, C. | bioRxiv Science

bioRxiv2026

PqqU (PA2289) is responsible for Pyrroloquinoline Quinone Uptake in Pseudomonas aeruginosa

Pseudomonas aeruginosa relies on the redox cofactor pyrroloquinoline quinone (PQQ) for efficient glucose and ethanol metabolism via periplasmic dehydrogenases (Gcd and ExaA). While PQQ biosynthesis is well-characterized, its uptake mechanisms remain unclear. Here, we identify PA2289 (PqqU), a TonB-dependent transporter, as the primary PQQ importer in P. aeruginosa. Growth assays with PQQ-deficient mutants ({Delta}pqqABCDEH) demonstrated that PqqU is essential for exogenous PQQ uptake, rescuing growth on glucose and ethanol. Genomic analysis across 210 P. aeruginosa and 263 Pseudomonas strains revealed high conservation of PQQ biosynthesis and utilization genes, while PqqU showed lower prevalence (47.7%) in the genus. Transcriptional analyses using fluorescent reporters and qRT-PCR demonstrated that PqqU expression remains unchanged in response to PQQ, varying carbon sources, or iron availability, suggesting constitutive regulation. Comparative proteomics between wild-type and {Delta}pqqABCDEH strains, cultured on glucose or ethanol, uncovered extensive proteomic shifts, underscoring P. aeruginosas metabolic adaptability. Additionally, PQQ-dependent metabolic pathways appear to indirectly influence iron homeostasis, most likely through environmental acidification. Together, these results emphasize the critical role of PqqU in PQQ uptake and its broader significance in shaping the metabolic and environmental versatility of Pseudomonas.

microbiology↗

bioRxiv2024

Characterisation of Pseudomonas aeruginosas metal-responsive TonB-dependent transporters

Pseudomonas aeruginosa, a versatile bacterium, relies on several TonB-dependent transporters (TBDTs) for nutrient acquisition (such as iron-siderophore complexes) and adaptation to various environments. While some TBDTs are well characterized, a significant number remain unexplored despite their potential role in pathogenicity. In this study, we developed fluorescent reporter plasmids to investigate TBDT promoter activity. Initially, we characterized their promoter activity in commonly used laboratory conditions, revealing diverse expression patterns among all TBDTs. Subsequently, we classified the TBDTs into distinct metal-responsive groups based on their stress-responsive behaviour, shedding light on their functional roles. Additionally, we show that these reporter constructs can be used as a powerful tool for siderophore detection. Finally, single cell analysis of TBDT promoter activity during coculture with an enterobactin-producing Klebsiella pneumoniae strain shows homogenous expression of key TBDT in P. aeruginosa. Our findings provide valuable insights into the expression profiles and functional diversity of P. aeruginosa TBDTs in complex conditions, reaching from commonly used lab media to complex co-culturing conditions.

microbiology↗