Dataset Information

Phylogenomics picks out the par excellence markers for species phylogeny in the genus Staphylococcus.

ABSTRACT: Although genome sequencing has become a very promising approach to conduct microbial taxonomy, few labs have the resources to afford this especially when dealing with data sets of hundreds to thousands of isolates. The goal of this study was to identify the most adequate loci for inferring the phylogeny of the species within the genus Staphylococcus; with the idea that those who cannot afford whole genome sequencing can use these loci to carry out species assignation confidently. We retrieved 177 orthologous groups (OGs) by using a genome-based phylogeny and an average nucleotide identity analysis. The top 26 OGs showed topologies similar to the species tree and the concatenation of them yielded a topology almost identical to that of the species tree. Furthermore, a phylogeny of just the top seven OGs could be used for species assignment. We sequenced four staphylococcus isolates to test the 26 OGs and found that these OGs were far superior to commonly used markers for this genus. On the whole, our procedure allowed identification of the most adequate markers for inferring the phylogeny within the genus Staphylococcus. We anticipate that this approach will be employed for the identification of the most suitable markers for other bacterial genera and can be very helpful to sort out poorly classified genera.

SUBMITTER: Grana-Miraglia L

PROVIDER: S-EPMC6203942 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Phylogenomics picks out the par excellence markers for species phylogeny in the genus <i>Staphylococcus</i>.

Graña-Miraglia Lucia L Arreguín-Pérez César C López-Leal Gamaliel G Muñoz Alan A Pérez-Oseguera Angeles A Miranda-Miranda Estefan E Cossío-Bayúgar Raquel R Castillo-Ramírez Santiago S

PeerJ 20181024

Although genome sequencing has become a very promising approach to conduct microbial taxonomy, few labs have the resources to afford this especially when dealing with data sets of hundreds to thousands of isolates. The goal of this study was to identify the most adequate loci for inferring the phylogeny of the species within the genus <i>Staphylococcus</i>; with the idea that those who cannot afford whole genome sequencing can use these loci to carry out species assignation confidently. We retri ...[more]

PMID: 30386709

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Project description:BACKGROUND:Multilocus phylogenies can be used to infer the species tree of a group of closely related species. In species trees, the nodes represent the actual separation between species, thus providing essential information about their evolutionary history. In addition, multilocus phylogenies can help in analyses of species delimitation, gene flow and genetic differentiation within species. However, few adequate markers are available for such studies. RESULTS:In order to develop nuclear markers that can be useful in multilocus studies of mammals, we analyzed the mammalian genomes of human, chimpanzee, macaque, dog and cow. Rodents were excluded due to their unusual genomic features. Introns were extracted from the mammalian genomes because of their greater genetic variability and ease of amplification from the flanking exons. To an initial set of more than 10,000 one-to-one orthologous introns we applied several filters to select introns that belong to single-copy genes, show neutral evolutionary rates and have an adequate length for their amplification. This analysis led to a final list of 224 intron markers randomly distributed along the genome. To experimentally test their validity, we amplified twelve of these introns in a panel of six mammalian species. The result was that seven of these introns gave rise to a PCR band of the expected size in all species. In addition, we sequenced these bands and analyzed the accumulation of substitutions in these introns in five pairs of closely related species. The results showed that the estimated genetic distances in the five species pairs was quite variable among introns and that this divergence cannot be directly predicted from the overall intron divergence in mammals. CONCLUSIONS:We have designed a new set of 224 nuclear introns with optimal features for the phylogeny of closely related mammalian species. A large proportion of the introns tested experimentally showed a perfect amplification and enough variability in most species, indicating that this marker set can be very helpful in multilocus phylogenetics of mammals. Due to the lower variability and stronger stochasticity of nuclear markers with respect to mitochondrial genes, studies should be designed to make use of several markers like the ones designed here.

Project description:Staphylococcus aureus is a prominent nosocomial pathogen that causes several life-threatening diseases, such as pneumonia and bacteremia. S. aureus modulates the expression of its arsenal of virulence factors through sensing and integrating responses to environmental signals. The agr (accessory gene regulator) quorum sensing (QS) system is a major regulator of virulence phenotypes in S. aureus. There are four agr specificity groups each with a different autoinducer peptide sequence encoded by the agrD gene. Although agr is critical for the expression of many toxins, paradoxically, S. aureus strains often have nonfunctional agr activity due to loss-of-function mutations in the four-gene agr operon. To understand patterns in agr variability across S. aureus, we undertook a species-wide genomic investigation. We developed a software tool (AgrVATE; https://github.com/VishnuRaghuram94/AgrVATE) for typing and detecting frameshift mutations in the agr operon. In an analysis of over 40,000 S. aureus genomes, we showed a close association between agr type and S. aureus clonal complex. We also found a strong linkage between agrBDC alleles (encoding the peptidase, autoinducing peptide itself, and peptide sensor, respectively) but not agrA (encoding the response regulator). More than 5% of the genomes were found to have frameshift mutations in the agr operon. While 52% of these frameshifts occurred only once in the entire species, we observed cases where the recurring mutations evolved convergently across different clonal lineages with no evidence of long-term phylogenetic transmission, suggesting that strains with agr frameshifts were evolutionarily short-lived. Overall, genomic analysis of agr operon suggests evolution through multiple processes with functional consequences that are not fully understood. IMPORTANCE Staphylococcus aureus is a globally pervasive pathogen that produces a plethora of toxic molecules that can harm host immune cells. Production of these toxins is mainly controlled by an active agr quorum-sensing system, which senses and responds to bacterial cell density. However, there are many reports of S. aureus strains with genetic changes leading to impaired agr activity that are often found during chronic bloodstream infections and may be associated with increased disease severity. We developed an open-source software called AgrVATE to type agr systems and identify mutations. We used AgrVATE for a species-wide genomic survey of S. aureus, finding that more than 5% of strains in the public database had nonfunctional agr systems. We also provided new insights into the evolution of these genetic mutations in the agr system. Overall, this study contributes to our understanding of a common but relatively understudied means of virulence regulation in S. aureus.

Dataset Information

Phylogenomics picks out the par excellence markers for species phylogeny in the genus Staphylococcus.

Publications

Phylogenomics picks out the par excellence markers for species phylogeny in the genus <i>Staphylococcus</i>.

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