Comparative genomic analysis of clinical Candida glabrata isolates identifies multiple polymorphic loci that can improve existing multilocus sequence typing strategy

Candida glabrata is the second leading cause of candidemia in many countries and is one of the most concerning yeast species of nosocomial importance due to its increasing rate of antifungal drug resistance and emerging multidrug-resistant isolates. Application of multilocus sequence typing (MLST) to clinical C. glabrata isolates revealed an association of certain sequence types (STs) with drug resistance and mortality. The current C. glabrata MLST scheme is based on single nucleotide polymorphisms (SNPs) at six loci and is therefore relatively laborious and costly. Furthermore, only a few high-quality C. glabrata reference genomes are available, limiting rapid analysis of clinical isolates by whole genome sequencing. In this study we provide long-read based assemblies for seven additional clinical strains belonging to three different STs and use this information to simplify the C. glabrata MLST scheme. Specifically, a comparison of these genomes identified highly polymorphic loci (HPL) defined by frequent insertions and deletions (indels), two of which proved to be highly resolutive for ST. When challenged with 53 additional isolates, a combination of TRP1 (a component of the current MLST scheme) with either of the two HPL fully recapitulated ST identification. Therefore, our comparative genomic analysis identified a new typing approach combining SNPs and indels and based on only two loci, thus significantly simplifying ST identification in C. glabrata. Because typing tools are instrumental in addressing numerous clinical and biological questions, our new MLST scheme can be used for high throughput typing of C. glabrata in clinical and research settings.

The pea aphid phylome: a complete catalogue of evolutionary histories and arthropod orthology and paralogy relationships for Acyrthosiphon pisum genes

Phylogenetic analyses serve many purposes, including the establishment of orthology relationships, the prediction of protein function and the detection of important evolutionary events. Within the context of the sequencing of the genome of the pea aphid, Acyrthosiphon pisum, we undertook a phylogenetic analysis for every protein of this species. The resulting phylome includes the evolutionary relationships of all predicted aphid proteins and their homologues among 13 other fully-sequenced arthropods and three out-group species. Subsequent analyses have revealed multiple gene expansions that are specific to aphids and have served to transfer functional annotations to 4058 pea aphid genes that display one-to-one orthology relationships with Drosophila melanogaster annotated genes. All phylogenies and alignments are accessible through the PhylomeDB database. Here we provide a description of this dataset and provide some examples on how can it be exploited.