Interdependency of respiratory metabolism and phenazine-associated physiology in Pseudomonas aeruginosa PA14

Abstract

240/250 words) 25 Extracellular electron transfer (EET), the reduction of compounds that shuttle electrons to distal oxidants, can support bacterial survival when preferred oxidants are not directly accessible. EET has been shown to contribute to virulence in some pathogenic organisms and is required for current generation in mediator-based fuel cells. In several species, components of the electron transport chain (ETC) have been implicated in electron shuttle 30 reduction, raising the question of how shuttling-based metabolism is integrated with primary routes of metabolic electron flow. The clinically relevant bacterium Pseudomonas aeruginosa can utilize carbon sources (i.e., electron donors) covering a broad range of reducing potentials and possesses a branched ETC that can be modulated to optimize respiratory efficiency. It also produces electron shuttles called phenazines that facilitate 35 intracellular redox balancing, increasing the complexity of its metabolic potential. In this study, we investigated the reciprocal influence of respiratory metabolism and phenazineassociated physiology in Pseudomonas aeruginosa PA14. We found that phenazine production affects respiratory activity and terminal oxidase gene expression, and that carbon source identity influences the mechanisms enabling phenazine reduction. 40 Furthermore, we found that growth in biofilms, a condition for which phenazine metabolism is critical to normal development and redox balancing, dramatically affects the composition of the P. aeruginosa phenazine pool. Together, these findings can aid interpretation of P. aeruginosa behavior during host infection and provide inroads to understanding the crosstalk between primary metabolism and shuttling-based physiology 45 in the diverse bacteria that carry out EET. 3 IMPORTANCE (147/150 words)Pseudomonas aeruginosa is a major cause of healthcare-associated infections and long-50 term lung infections in people with cystic fibrosis. It can use diverse organic compounds as electron donors and possesses multiple enzymes that can transfer electrons from central metabolism to O2. These pathways support a balanced intracellular redox state and the production of cellular energy. Under hypoxic conditions, P. aeruginosa can reduce phenazines, secondary metabolites that also promote redox homeostasis and that 55 contribute to virulence. We asked how these primary and secondary routes of electron flow influence each other. We found that phenazines affect respiratory function, that the roles of respiratory enzymes in phenazine reduction are highly condition-dependent, and that the complement of phenazines produced is strongly affected by growth in assemblages called biofilms. These results provide a more nuanced understanding of P. 60 aeruginosa redox metabolism and may inform strategies for treating persistent infections caused by this bacterium. 4 Members of the domain Bacteria exhibit a vast variety of pathways and substrates that can be used to generate energy (1). This metabolic diversity allows...

Malonate utilization by Pseudomonas aeruginosa affects quorum‐sensing and virulence and leads to formation of mineralized biofilm‐like structures

“…In its reduced form, pyocyanin, a redox active phenazine metabolite, interferes with electron transport, cellular respiration, and energy metabolism within eukaryotic and prokaryotic cells causing them to generate reactive oxygen species (ROS), especially superoxide and hydrogen peroxide (Hassett et al., 1992; Jo et al., 2020; Rada & Leto, 2013). The diversion of the electron transport flow leads to cell death (Hassett et al., 1992; Rada & Leto, 2013).…”

Light/dark and temperature cycling modulate metabolic electron flow inPseudomonas aeruginosabiofilms

“…In contrast, genes coding for components of cbb 3 -type cytochrome c oxidase complex CcoN1O1Q1P1 ("Cco1") and for the orphan terminal oxidase proteins CcoN4Q4, which form the second group, were downregulated in rings of growth that formed during light intervals and upregulated in those that formed during dark intervals (i.e., the opposite expression profile of the first group) (Figure 7A). While the RNAseq sampling did not allow us to address terminal oxidase distribution across the depth of the biofilm, for which we have previously demonstrated a differential expression pattern (32,60), the expression profiles of terminal oxidase genes observed under light/dark and temperature cycling in biofilms nevertheless suggests that the preferential use of terminal oxidases shifts during cycling. We were intrigued to see that the set of terminal oxidase genes showing the largest change in expression during light/dark and temperature cycling was the cyoABCDE operon, because this locus is not expressed at high levels in typical aerobic or microaerobic planktonic cultures grown in the laboratory (61).…”

Fundamentals, Applications, and Future Directions of Bioelectrocatalysis

“…665 However, the enhancement of the slow extracellular electron transfer rate (EET) from bacteria to anode electrodes is necessary, since EET plays a fundamental role in MFC performance. 683 The two EET mechanisms, discussed in previous sections, are (1) direct electron transfer from inside the cells or (2) indirect mediated electron transfer via exogenous or endogenous electron redox mediators. In direct electron transfer, anodes are in physical contact with redox-active proteins on cellular surfaces, facilitating electron transfer.…”