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Biology subjects

Little, R. F.

Publications and source records attributed to Little, R. F..

3 recordsLinked to original sources

DiscERN: An Automated Genome Mining Tool for the Discovery of Evolutionarily Related Natural Products

Targeted genome mining to expand known families of natural products is a powerful strategy for discovering bioactive compounds, yet it remains a significant bioinformatics challenge. While tools exist for de novo biosynthetic gene cluster identification and large-scale unsupervised clustering, dedicated methods for the targeted, hypothesis-driven expansion of user-defined BGC families are lacking. Here, we present DiscERN (Discoverer of Evolutionarily Related Natural products), a userfriendly tool designed to address this gap. DiscERN leverages a multi-modal ensemble method that integrates four complementary algorithms classifying biosynthetic gene clusters based on Pfam content, sequence homology, and predicted product structure. This approach allows users to strategically balance discovery sensitivity with predictive precision to suit diverse research goals. We demonstrate DiscERNs utility by applying it to a large collection of actinomycete genomes and validating its predictive power through the successful isolation of discomycin A, a new calcium-dependent lipopeptide antibiotic, from a silent biosynthetic gene cluster. DiscERN provides a robust and accessible platform that streamlines the path from genomic data to a prioritised list of candidate biosynthetic gene clusters, effectively bridging the gap between in silico prediction and bioactive compound discovery.

bioinformatics↗

A metagenomic library cloning strategy that promotes high-level expression of captured genes to enable efficient functional screening

Functional screening of environmental DNA (eDNA) libraries is a potentially powerful approach to discover enzymatic "unknown unknowns", but is usually heavily biased toward the tiny subset of genes preferentially transcribed and translated by the screening strain. We have overcome this by preparing an eDNA library via partial digest with restriction enzyme Fatl (cuts CATG), causing a substantial proportion of ATG start codons to be precisely aligned with strong plasmid-encoded promoter and ribosome-binding sequences. Whereas we were unable to select nitroreductases from standard metagenome libraries, our Fatl strategy yielded 21 nitroreductases spanning eight different enzyme families, each conferring resistance to the nitro-antibiotic niclosamide and sensitivity to the nitro-prodrug metronidazole. We showed expression could be improved by co-expressing rare tRNAs and encoded proteins purified directly using an embedded Hisg-tag. In a transgenic zebrafish model of metronidazole-mediated targeted cell ablation, our lead MhqN-family nitroreductase proved [~]5- fold more effective than the canonical nitroreductase NfsB.

biochemistry↗

A giant leap in sequence space reveals the intracellular complexities of evolving a new function

Selection for a promiscuous enzyme activity provides substantial opportunity for competition between endogenous and new substrates to influence the evolutionary trajectory, an aspect that has generally been overlooked in laboratory directed evolution studies. We evolved the Escherichia coli nitro/quinone reductase NfsA to detoxify chloramphenicol by randomising eight active site residues simultaneously and interrogating [~]250,000,000 reconfigured NfsA variants. Analysis of every possible evolutionary intermediate of the two best chloramphenicol reductases revealed complex epistatic interactions that restrict each hypothetical trajectory. In both cases, improved chloramphenicol detoxification was only possible after one essential substitution had eliminated activity with endogenous quinone substrates. Unlike the predominantly weak trade-offs seen in previous experimental studies, this substrate incompatibility suggests endogenous metabolites have considerable potential to shape evolutionary outcomes. Unselected prodrug-converting activities were mostly unaffected, which emphasises the importance of negative selection to effect enzyme specialisation, and offers an application for the evolved genes as dual-purpose selectable/counter-selectable markers.

biochemistry↗