Biology subjects

Wakeman, C. A.

Publications and source records attributed to Wakeman, C. A..

4 recordsLinked to original sources

bioRxiv2026

Temperature-dependent reprogramming of virulence traits during Pseudomonas aeruginosa biofilm formation

Pseudomonas aeruginosa is an opportunistic pathogen that occupies diverse ecological niches, including soil, water, and the human host. Environmental cues encountered across these habitats trigger adaptive responses that promote survival and persistence through regulation of virulence-associated traits, including secreted factors, siderophores, and biofilm exopolysaccharides (EPS). One major change experienced during the transition from environmental reservoirs to the host is an increase in temperature. Although temperature is a key signal encountered during host transition, its global impact on P. aeruginosa physiology remains poorly understood. We therefore investigated the effects of temperature on planktonic and biofilm-populations, comparing both growth states at 23{degrees}C and 30{degrees}C, representing environmental temperatures, and at 37{degrees}C and 40{degrees}C, representing normal and febrile host temperatures. Transcriptomic and phenotypic analyses revealed extensive temperature-dependent regulation of virulence determinants in both growth states. Expression of the type VI secretion system was elevated at environmental temperatures, whereas pyoverdine biosynthesis and the type III secretion system were upregulated at host temperatures. Building on our previous finding that biofilms formed at environmental and host temperatures differ in architecture, biomass, and EPS composition, we next examined how these structural differences influence stress tolerance. Biofilms grown at 23{degrees}C and 30{degrees}C exhibited substantially greater tolerance to antibiotic stress than biofilms grown at 37{degrees}C and 40{degrees}C. Growth temperature therefore establishes biofilm properties that subsequently influence the stress-tolerance profile of the population. Collectively, our findings identify temperature as a major environmental cue that reprograms P. aeruginosa physiology in ways likely to support persistence across distinct ecological niches.

microbiology↗

bioRxiv2026

Interspecies synergism and antagonism induce differential and potentially exploitable susceptibility to various classes of antibiotics in a wound-like polymicrobial community

Chronic wounds are persistent and difficult to treat. Often this is because they are colonized by polymicrobial communities which contribute to changes in antimicrobial susceptibilities, making these infections harder to effectively clear. We explored the role a community can play in individual members survival when challenged by antibiotics, specifically looking at a community consisting of Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, and Acinetobacter baumannii. Our data shows that communities can contribute to both increases and decreases in susceptibilities depending on the species and the antibiotic. The changes in susceptibilities can be due to interspecies cooperation or competition, with identifiable mechanisms. We also demonstrated that current antimicrobial susceptibility testing (AST) methods used in hospitals, which focus on determining the minimum inhibitory concentration (MIC) via determination of visible turbidity breakpoints, are not able to truly indicate the clearance of bacteria, as species can persist in higher antibiotic concentrations after visible turbidity is gone. To combat decreases in antibiotic susceptibilities contributed to by the community, we used our data from individual antibiotics to determine a potentially effective antibiotic combination, similar to combinatorial therapy used in hospitals to treat recalcitrant infections. Our data proved useful, as the combination of gentamicin and cephalexin was able to overcome polymicrobial synergism and clear the desired bacteria. This demonstrates that it is possible to determine effective antibiotic treatments for polymicrobial infections, whether they be combinatorial in nature or not. One simply must account for the role of the community in order to prescribe the most effective treatment.

microbiology↗

bioRxiv2024

Global stress response in Pseudomonas aeruginosa upon malonate utilization

Versatility in carbon source utilization assists Pseudomonas aeruginosa in its adaptation to various niches. Recently, we characterized the role of malonate, an understudied carbon source, in quorum sensing regulation, antibiotic resistance, and virulence factor production in P. aeruginosa. These results indicate that global responses to malonate metabolism remain to be uncovered. We leveraged a publicly available metabolomic dataset on human airway and found malonate to be as abundant as glycerol, a common airway metabolite and carbon source for P. aeruginosa. Here, we explored and compared adaptations of P. aeruginosa UCBPP-PA14 (PA14) in response to malonate or glycerol as a sole carbon source using transcriptomics and phenotypic assays. Malonate utilization activated glyoxylate and methylcitrate cycles and induced several stress responses, including oxidative, anaerobic, and metal stress responses associated with increases in intracellular aluminum and strontium. Some induced genes were required for optimal growth of P. aeruginosa in malonate. To assess the conservation of malonate-associated responses among P. aeruginosa strains, we compared our findings in strain PA14 with other lab strains and cystic fibrosis isolates of P. aeruginosa. Most strains grew on malonate as a sole carbon source as efficiently as or better than glycerol. While not all responses to malonate were conserved among strains, formation of biomineralized biofilm-like aggregates, increased tolerance to kanamycin, and increased susceptibility to norfloxacin were the most frequently observed phenotypes. Our findings reveal global remodeling of P. aeruginosa gene expression during its growth on malonate as a sole carbon source that is accompanied by several important phenotypic changes. These findings add to accumulating literature highlighting the role of different carbon sources in the physiology of P. aeruginosa and its niche adaptation. ImportancePseudomonas aeruginosa is a notorious pathogen that causes local and systemic infections in immunocompromised individuals. Different carbon sources can uniquely modulate metabolic and virulence pathways in P. aeruginosa, highlighting the importance of the environment that the pathogen occupies. In this work, we used a combination of transcriptomic analysis and phenotypic assays to determine how malonate utilization impacts P. aeruginosa, as recent evidence indicates this carbon source may be relevant to certain niches associated within the human host. We found that malonate utilization can induce global stress responses, alter metabolic circuits, and influence various phenotypes of P. aeruginosa that could influence host colonization. Investigating the metabolism of malonate provides insight into P. aeruginosa adaptations to specific niches where this substrate is abundant, and how it can be leveraged in the development of much-needed antimicrobial agents or identification of new therapeutic targets of this difficult-to-eradicate pathogen.

microbiology↗

bioRxiv2022

Development of a polymicrobial checkerboard assay as a tool for determining combinatorial antibiotic effectiveness in polymicrobial communities

AIMSTo establish a methodology for identifying the effects of combinatorial antibiotic treatment on individual members of a polymicrobial community. METHODS AND RESULTSBoth gentamicin and ceftazidime were diluted to concentrations ranging from 0.06 g ml-1 to 128 g ml-1. An equal ratio polymicrobial community of Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, and Acinetobacter baumannii was inoculated into the combined antibiotics in the checkerboard and incubated for 18 hours in static conditions. After incubation, visible turbidity of the overall community was recorded, and bacteria from the wells were diluted to 10-3 and then spot plated on selective and differential media. After 24 hours, colony-forming unit (CFU) counts were obtained for each species. CONCLUSIONSVisible turbidity is not truly indicative of cell viability, and the polymicrobial community can decrease the antibiotic susceptibility of P. aeruginosa, rendering the clinically-established beneficial combination of gentamicin and ceftazidime ineffective. SIGNIFICANCEPrevious checkerboard methodology which focuses on using visible turbidity to determine monomicrobial antibiotic susceptibility fails to account for polymicrobial cooperation that has been shown to reduce antibiotic efficacy. Our new methodology could be implemented in clinical microbiology laboratories with minimal impact on the overall time for diagnosis.

microbiology↗