Biology subjects

Eijkelkamp, B. A.

Publications and source records attributed to Eijkelkamp, B. A..

3 recordsLinked to original sources

bioRxiv2026

Second-site capsule-locus mutations, not Ade efflux disruption, determine phage susceptibility across an Acinetobacter baumannii transposon mutant panel

Resistance-Nodulation-Division (RND) efflux pumps have been implicated in phage adsorption in several Gram-negative bacteria, suggesting that AdeABC, AdeFGH and AdeIJK, the three characterised RND efflux systems of multidrug-resistant Acinetobacter baumannii, could play a similar role. We tested this hypothesis using five phages (Equilibrator, Taro, AT01, BB02, and AC03) and a panel of 13 A. baumannii strains, including nine AB5075 transposon mutants affecting AdeABC, AdeFGH, or AdeIJK. Host-range testing, efficiency-of-plating assays, capsule-associated density measurements, antimicrobial susceptibility testing, and whole-genome sequencing were performed to assess the relationship between genotype and phage infection. Overall, the data did not support a role for the Ade components as receptors. Phages Equilibrator, Taro and AT01 formed plaques on every strain, and the restricted host ranges of BB02 and AC03 did not correspond to disruption of a particular efflux system. Sequencing instead identified second-site mutations in the KL25 capsule locus in six of the ten AB5075 strains. These included a 1,998-bp deletion affecting wzc, substitutions in mnaA and mnaB, an ISAba13 insertion in a putative glycosyltransferase and a subpopulation-associated frameshift in wzx. AC03 formed plaques on all six strains with capsule-locus changes but on none of the five strains without them. Capsule dependence differed among the other phages: relative to the parental AB5075, infection by these phages, Equilibrator, Taro and BB02, was restricted on the capsule-deficient wzc::T26 strain, whereas AT01 efficiency was only slightly reduced. Insertion-site mapping also distinguished a near-terminal adeK insertion that retained the parental antimicrobial phenotype from an early adeK insertion associated with loss of AdeIJK function. Together, these findings identify capsule-locus variation as the strongest correlation with phage susceptibility in this panel and demonstrate the importance of verifying mutant genomes before assigning phenotypes to their annotated insertions.

microbiology↗

bioRxiv2021

To make or take: bacterial lipid homeostasis during infection

Bacterial fatty acids are critical components of the cellular membrane. A shift in environmental conditions or in the bacteriums lifestyle may result in the requirement for a distinct pool of fatty acids with unique biophysical properties. This can be achieved by the modification of existing fatty acids or via de novo synthesis. Furthermore, bacteria have evolved efficient means to acquire these energy-rich molecules from their environment. However, the balance between de novo fatty acid synthesis and exogenous acquisition during pathogenesis is poorly understood. Here we studied the mouse fatty acid landscape prior and post infection with Acinetobacter baumannii, a Gram-negative, opportunistic human pathogen. The lipid fluxes observed following infection revealed fatty acid- and niche-specific changes. Lipidomic profiling of A. baumannii isolated from the pleural cavity of mice identified novel A. baumannii membrane phospholipid species and an overall increased abundance of unsaturated fatty acid species. Importantly, we found that A. baumannii relies largely upon fatty acid acquisition in all but one of the studied niches, the blood, where the pathogen biosynthesises its own fatty acids. This work is the first to reveal the significance of balancing the making and taking of fatty acids in a Gram-negative bacterium during infection, which provides new insights into the validity of targeting fatty acid synthesis as a treatment strategy. ImportanceAcinetobacter baumannii is one of the worlds most problematic superbugs, and is associated with significance morbidity and mortally in the hospital environment. The critical need for new antimicrobial strategies is recognised, but our understanding of its behaviour and adaptation to a changing environment during infection is limited. Here, we investigated the role of fatty acids at the host-pathogen interface using a mouse model of disease. We provide comprehensive insights into the bacterial membrane composition when they colonise the pleural cavity. Further, we show that A. baumannii heavily relies upon making its fatty acids when residing in the blood, whereas the bacterium favours fatty acid acquisition in most other host niches. Our new knowledge aids in understanding the importance of host fatty acids in infectious diseases. Further, fatty acid synthesis is an attractive target for the development of new antimicrobial strategies, but our work emphasizes the critical need to understand the microbial lipid homeostasis before this can be deemed suitable.

microbiology↗

bioRxiv2020

The molecular basis of Acinetobacter baumannii cadmium toxicity and resistance

Acinetobacter species are ubiquitous Gram-negative bacteria that can be found in water, soil and as commensals of the human skin. The successful inhabitation of Acinetobacter species in diverse environments is primarily attributable to the expression of an arsenal of stress resistance determinants, which includes an extensive repertoire of metal ion efflux systems. Although metal ion homeostasis in the hospital pathogen Acinetobacter baumannii is known to contribute to pathogenesis, insights into its metal ion transporters for environmental persistence are lacking. Here, we studied the impact of cadmium stress on A. baumannii. Our functional genomics and independent mutant analyses revealed a primary role for CzcE, a member of the cation diffusion facilitator (CDF) superfamily, in resisting cadmium stress. Further, we show that the CzcCBA heavy metal efflux system also contributes to cadmium efflux. Analysis of the A. baumannii metallome under cadmium stress showed zinc depletion and copper enrichment, which are likely to influence cellular fitness. Overall, this work expands our understanding of the role of membrane transporters in A. baumannii metal ion homeostasis. IMPORTANCECadmium toxicity is a widespread problem, yet the interaction of this heavy metal with biological systems is poorly understood. Some microbes have evolved traits to proactively counteract cadmium toxicity, which includes Acinetobacter baumannii. Here we show that A. baumannii utilises a dedicated cadmium efflux protein in concert with a system that is primarily attuned to zinc efflux, to efficiently overcome cadmium stress. The molecular characterization of A. baumannii under cadmium stress revealed how active cadmium efflux plays a key role in preventing the dysregulation of bacterial metal ion homeostasis, which appeared to be the primary means by which cadmium exerts toxicity upon the bacterium.

microbiology↗