Identifying candidate mutations responsible for antimicrobial peptide resistance in experimentally evolved Pseudomonas fluorescens.

Antimicrobial peptides, or AMPs, are cationic oligopeptides present across a wide range of organisms, from bacteria to mammals, as part of their natural defense against microbes. The diverse functions and structures of AMPs have attracted considerable attention over the past few decades as possible alternatives to conventional antibiotics. However, there have been some concerns over bacterial resistance to AMPs as much is still unknown about the rates and mechanisms of AMP resistance. Here, we sequenced the genomes of several experimentally evolved Pseudomonas fluorescens populations resistant to high concentrations of pexiganan, a synthetically modified AMP, to investigate the genetic pathways involved in AMP resistance. Our analysis of the sequence data revealed very poor alignment of the pexiganan resistant genomes to the ancestral reference genome. In order to identify possible large structural genetic variants that might explain the poor alignment, de novo assembly and multiple alignment of the genomes were conducted with limited success. Visual inspection of the reference alignments revealed a high number of variants and gaps across the genome, prompting us to suspect possible contamination. A metagenomic analysis of our sequences revealed close alignment to the genome of another Pseudomonas strain closely related to the the ancestral genome of our P. fluorescens populations, suggesting either genome convergence or, most likely, contamination during the original selection experiment. Due to the nature of our findings, we suggest an investigation into previous studies that have utilized these Pseudomonas populations in order to identify the source of contamination and a reevaluation of the results reported in these studies

Diversification of division mechanisms in endospore-forming bacteria revealed by analyses of peptidoglycan synthesis in Clostridioides difficile

Abstract The bacterial enzymes FtsW and FtsI, encoded in the highly conserved dcw gene cluster, are considered to be universally essential for the synthesis of septal peptidoglycan (PG) during cell division. Here, we show that the pathogen Clostridioides difficile lacks a canonical FtsW/FtsI pair, and its dcw-encoded PG synthases have undergone a specialization to fulfill sporulation-specific roles, including synthesizing septal PG during the sporulation-specific mode of cell division. Although these enzymes are directly regulated by canonical divisome components during this process, dcw-encoded PG synthases and their divisome regulators are dispensable for cell division during normal growth. Instead, C. difficile uses a bifunctional class A penicillin-binding protein as the core divisome PG synthase, revealing a previously unreported role for this class of enzymes. Our findings support that the emergence of endosporulation in the Firmicutes phylum facilitated the functional repurposing of cell division factors. Moreover, they indicate that C. difficile, and likely other clostridia, assemble a distinct divisome that therefore may represent a unique target for therapeutic interventions

Captures of aquatic insects in polarized light traps at three distances from rivers in New York State

We created traps consisting of illumated oil-filled trays of 5 different colors that variously horizontally polarized light from ~20% to ~100%. These were placed in a row 5, 10 and 15 meters from 5 different rivers in southern New York State. They were exposed for 2 hours before sunset and their location randomized every 20 minutes. The goal of the study was to map the behavioral reaction norms of a diversity of aquatic insects to variation in the degree of polarized light and to understand how those reaction norms shifted as a function of the distance between a high quality natural habitat and the ecological trap habitat the test surfaces represented. Metadata for the variables is provided

Data from: Susceptibility to ecological traps is similar among closely related taxa but sensitive to spatial isolation

Ecological traps are maladaptive behavioural scenarios in which animals prefer to settle in habitats with the lowest survival and/or reproductive success. Aquatic insect species, for example, are attracted to sources of horizontally polarized light associated with natural water bodies, but today they commonly prefer to lay their eggs upon asphalt roads and buildings that reflect an unnaturally high percentage of polarized light. Ecological traps are a rapidly emerging threat to the persistence of animal populations, but the degree to which species vary in their susceptibility to them remains uninvestigated. We designed a field experiment to (1) assess the relative susceptibility of aquatic flies (Diptera) to a single maladaptive behavioural cue: variation in degree of horizontally polarized light (d), and (2) quantify how the isolation of an ecological trap from a high-quality habitat affects its relative attractiveness. We exposed wild dipterans to experimental test surfaces varying in d at three distances from natural streams and mapped behavioural reaction norms of habitat preference as a function of d and distance from high-quality habitat. All seven of the dipteran families were captured most in traps with progressively higher d values, especially those (d = 90–100%) that exceeded that of natural water bodies (30–80%). In most taxa, the height and slope of numerical responses to d were influenced by the distance of an ecological trap from a natural water body. Our results illustrate that dipterans have broadly evolved the use of a habitat selection behaviour that treats more strongly polarized light sources as indicative higher-quality habitats, making them broadly susceptible to ecological traps driven by polarized light pollution. We also found that the spatial isolation of ecological traps from higher-quality, but less attractive, habitats can either increase or reduce species' susceptibility to them