Kurz, M. | bioRxiv Science

bioRxiv2021

Genomic and chemical decryption of the Bacteroidetes phylum for its potential to biosynthesize natural products

With progress in genome sequencing and data sharing, 1000s of bacterial genomes are publicly available. Genome mining - using bioinformatics tools in terms of biosynthetic gene cluster (BGC) identification, analysis and rating - has become a key technology to explore the capabilities for natural product (NP) biosynthesis. Comprehensively, analyzing the genetic potential of the phylum Bacteroidetes revealed Chitinophaga as the most talented genus in terms of BGC abundance and diversity. Guided by the computational predictions, we conducted a metabolomics and bioactivity driven NP discovery program on 25 Chitinophaga strains. High numbers of peerless strain-specific metabolite buckets confirmed the upfront predicted biosynthetic potential and revealed a tremendous uncharted chemical space. Sourcing this dataset, we isolated the new iron chelating nonribosomally-synthesized cyclic tetradeca- and pentadecalipodepsipeptide antibiotics chitinopeptins with activity against Candida, produced by C. eiseniae DSM 22224 and C. flava KCTC 62435, respectively. TeaserCombination of omics-technologies revealed taxonomical hotspots for specialized metabolites within Bacteroidetes.

microbiology↗

bioRxiv2020

A KCNQ2 variant causing Early Onset Epileptic Encephalopathy increases spontaneous network-driven activity and excitability of pyramidal cells in the layer II/III and V of the motor cortex during a limited period of development

De novo missense variants in the KCNQ2 gene encoding the Kv7.2 subunit of the voltage-gated potassium Kv7/M channel are the main cause of Developmental and Epileptic Encephalopathy (DEE). KCNQ2 related-DEE is characterized by pharmaco-resistant neonatal seizures associated with a developmental delay. While seizures usually resolve some weeks or months after birth, cognitive/behavioral deficits persist. To better understand the cellular mechanisms underlying KCNQ2-associated network dysfunction and their progression over time, we investigated in vivo, using local field potential recordings of freely moving animals, and ex-vivo in layers II/III and V of motor cortical slices, using patch-clamp recordings, the electrophysiological properties of pyramidal cells from a heterozygous knock-in (KI) mouse model carrying the p.T274M pathogenic variant during neonatal, post-weaning and juvenile developmental stages. We found that KI mice displayed spontaneous seizures preferentially at post-weaning rather than at juvenile stages. At the cellular level, the variant led to a reduction in M current density/chord conductance and to an increase in neuronal excitability. These alterations were observed already during the neonatal period in pyramidal cells of layers II / III and during post-weaning stage in pyramidal cells of layer V. Moreover there was an increase in the frequency of spontaneous network driven events mediated by GABA receptors in the layers II/III suggesting that the excitability of some interneurons was also increased. However, all these alterations were time limited and no more observed in layers II/III and V of juvenile mice. At this stage, M-current density and neuronal excitability were not different from the measurements made in juvenile wild-type mice. Thus our data indicate that the action of the variant on neuronal activity is developmentally regulated and that some cellular mechanisms leading to the recovery of Kv7/M channels function took place during brain maturation of KI mice. These results raise the possibility that the age related seizure remission observed in KCNQ2-related DEE patient results also from a time limited alteration of Kv7 channels activity and neuronal excitability.

neuroscience↗