Biology subjects

Lear, L.

Publications and source records attributed to Lear, L..

3 recordsLinked to original sources

bioRxiv2022

The effect of metal remediation on the virulence and antimicrobial resistance of the opportunistic pathogen Pseudomonas aeruginosa

Metal contamination poses both a direct threat to human health as well as an indirect threat through its potential to affect bacterial pathogens. Metals can not only co-select for antibiotic resistance, but also might affect pathogen virulence via increased siderophore production. Siderophores are extracellular compounds released to increase ferric iron uptake -- a common limiting factor for pathogen growth within hosts - making them an important virulence factor. However, siderophores can also be positively selected for to detoxify non-ferrous metals, and consequently metal stress can potentially increase bacterial virulence. Anthropogenic methods to remediate environmental metal contamination commonly involve amendment with lime-containing materials, but whether this reduces in situ co-selection for antibiotic resistance and virulence remains unknown. Here, using microcosms containing metal-contaminated river water and sediment, we experimentally test whether metal remediation by liming reduces co-selection for these traits in the opportunistic pathogen Pseudomonas aeruginosa embedded within a natural microbial community. To test for the effects of environmental structure, which can impact siderophore production, microcosms were incubated under either static or shaking conditions. Evolved P. aeruginosa populations had greater fitness in the presence of toxic concentrations of copper than the ancestral strain, but this effect was reduced in the limed treatments. Evolved P. aeruginosa populations showed increased resistance to the clinically-relevant antibiotics apramycin, cefotaxime, and trimethoprim, regardless of lime addition or environmental structure. Although we found virulence to be significantly associated with siderophore production, neither virulence nor siderophore production significantly differed between the four treatments. We therefore demonstrate that although remediation via liming reduced the strength of selection for metal resistance mechanisms, it did not mitigate metal-imposed selection for antibiotic resistance or virulence in P. aeruginosa. Consequently, metal-contaminated environments may select for antibiotic resistance and virulence traits even when treated with lime. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/508257v2_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@2f396corg.highwire.dtl.DTLVardef@62e7b3org.highwire.dtl.DTLVardef@159d269org.highwire.dtl.DTLVardef@52395_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2021

Bacterial colonisation dynamics of household plastics in a coastal environment

Accumulation of plastics in the marine environment has widespread detrimental consequences for ecosystems and wildlife. Marine plastics are rapidly colonised by a wide diversity of bacteria, including human pathogens, posing potential risks to human health. Here, we investigate the effect of polymer type, residence time and estuarine location on bacterial colonisation of common household plastics, including pathogenic bacteria. To do so, we submerged five main household plastic types: low-density PE (LDPE), high-density PE (HDPE), polypropylene (PP), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) at an estuarine site in Cornwall (U.K.) and tracked bacterial colonisation dynamics. Using both culture-dependent and culture-independent approaches, we found that bacteria rapidly colonised plastics irrespective of polymer type. While biofilm community composition changed with colonisation time, no difference was observed between polymer types. Likewise, the presence of pathogenic bacteria, quantified using the insect model Galleria mellonella, increased over a five-week period, with no consistent differences observed between polymer types. Pathogens isolated from plastic biofilms using Galleria enrichment included Serratia and Enterococcus species and harboured a wide range of antimicrobial resistance genes. Our findings show that plastics in coastal waters are rapidly colonised by a wide diversity of bacteria, including known human pathogens, independent of polymer type.

ecology↗

bioRxiv2021

Copper selects for siderophore-mediated virulence in Pseudomonas aeruginosa

Iron is essential for almost all bacterial pathogens and consequently it is actively withheld by their hosts. However, the production of extracellular siderophores enables iron sequestration by pathogens, increasing their virulence. Another function of siderophores is extracellular detoxification of non-ferrous metals. Here, we experimentally link the detoxification and virulence roles of siderophores by testing whether the opportunistic pathogen Pseudomonas aeruginosa displays greater virulence after exposure to copper. To do this, we incubated P. aeruginosa under different environmentally relevant copper regimes for either two or twelve days. Subsequent growth in a copper-free environment removed phenotypic effects, before we quantified pyoverdine production (the primary siderophore produced by P. aeruginosa), and virulence using the Galleria mellonella infection model. Copper selected for increased pyoverdine production, which was positively correlated with virulence. This effect increased with time, such that populations incubated with high copper for twelve days were the most virulent. Replication of the experiment with a non-pyoverdine producing strain of P. aeruginosa demonstrated that pyoverdine production was largely responsible for the change in virulence. Therefore we here show a direct link between metal stress and bacterial virulence, highlighting another dimension of the detrimental effects of metal pollution on human health.

ecology↗