Biology subjects

Toth, I.

Publications and source records attributed to Toth, I..

3 recordsLinked to original sources

bioRxiv2022

Canine saliva is a source of interspecies antimicrobial resistance gene transfer

While the One Health issues of intensive animal farming are commonly discussed, keeping companion animals is less associated with the interspecies headway of antimicrobial resistance. With the constant advance of veterinary standards, antibiotics are regularly applied in companion animal medicine. Due to the close coexsistance of dogs and humans, dog bites and other casual encounters with dog saliva (e.g. licking the owner) are common. According to our metagenome studies based on 26 new generation sequencing canine saliva datasets from 2020 and 2021 reposited in NCBI SRA by The 10,000 Dog Genome Consortium and the Broad Institute within Darwins Ark project, canine saliva is rich in bacteria with predictably transferable antimicrobial resistance genes (ARGs). In the genom of potentially pathogenic Bacteroides, Capnocytophaga, Corynebacterium, Fusobacterium, Pasteurella, Porphyromonas, Staphylococcus and Streptococcus species, that are some of the most relevant bacteria in dog bite infections, ARGs against aminoglycosides, carbapenems, cephalosporins, glycylcyclines, lincosamides, macrolides, oxazolidinone, penams, phenicols, pleuromutilins, streptogramins, sulfonamides and tetracyclines could be identfied. Several ARGs, including ones against amoxicillin-clavulanate, the most commonly applied antibiotic by dog bites, was predicted to be potentially transferable based on their association with mobile genetic elements (e.g. plasmids, phages, integrated mobile genetic elements). According to our findings canine saliva may be a source of transfer of ARG-rich bacteria, that can either colonize the human body or transport ARGs to the host bacteriota and thus can be considered as a risk in the spread of antimicrobial resistance.

genomics↗

bioRxiv2022

Uncertainties of cell number estimation in cyanobacterial colonies and the potential use of sphere packing

Cyanobacteria are notorious bloom formers causing various water quality concerns, such as toxin production, extreme diurnal variation of oxygen, or pH, etc., therefore, their monitoring is essential to protect the ecological status of aquatic systems. Cyanobacterial cell counts and biovolumes are currently being used in water management and water quality alert systems. In this study, we investigated the accuracy of colonial biovolume and cell count estimation approaches used in the everyday practice. Using real like 3-dimensional images of cyanobacterial colonies, we demonstrated that their shape cannot be approximated by ellipsoids. We also showed that despite the significant relationship between overall colony volume and cell biovolumes because of the considerable scatter of cell count data the regressions give biased estimates for cyanobacterial cell counts. We proposed a novel approach to estimate cell counts in colonies that was based on the random close sphere packing method. This method provided good results only in those cases when overall colony volumes could be accurately measured. The visual investigation of colonies done by skilled experts has given precise but lower estimates for cell counts. Estimation results of several experts were surprisingly good which suggest that this capability can be improved, and estimation bias can be reduced to the level acceptable for water quality estimations. HighlightsCyanobacterial colony - cell biovolume relationships provide biased estimates for cellbiovolumes. Sphere packing approach provides good cellcount estimates if colony volumes are accurately measured. Considering cyanobacterial colonies as ellipsoids gives inaccurate volume estimates. Skilled experts slightly underestimate the cellcounts but dispersion of their estimates is low.

ecology↗

bioRxiv2021

The role of L-arabinose metabolism for Escherichia coli O157:H7 in edible plants

Arabinose is a major plant aldopentose in the form of arabinans complexed in cell wall polysaccharides or glycoproteins (AGP), but comparatively rare as a monosaccharide. L-arabinose is an important bacterial metabolite, accessed by pectolytic microorganisms such as Pectobacterium atrosepticum via pectin and hemicellulose degrading enzymes. However, not all plant-associated microbes encode cell wall degrading enzymes, yet can metabolise L-arabinose, raising questions about their use of and access to the glycan in plants. Therefore, we examined L-arabinose metabolism in the food-borne pathogen Escherichia coli O157:H7 (isolate Sakai) during its colonisation of plants. L-arabinose metabolism (araBA) and transport (araF) genes were activated at 18 {degrees}C in vitro by L-arabinose and expressed over prolonged periods in planta. Although deletion of araBAD did not impact the colonisation ability of E. coli O157:H7 (Sakai) on plants, araA was induced on exposure to spinach cell wall polysaccharides. Furthermore, debranched and arabinan oligosaccharides induced ara metabolism gene expression in vitro, and stimulated modest proliferation, while immobilised pectin did not. Thus, E. coli O157:H7 (Sakai) can utilise pectin/AGP- derived L-arabinose as a metabolite, but differs fundamentally in ara gene organisation, transport and regulation from the related pectinolytic species P. atrosepticum, reflective of distinct plant- associated lifestyles.

microbiology↗