Genome-level homology and phylogeny of Vibrionaceae (Gammaproteobacteria: Vibrionales) with three new complete genome sequences.

BACKGROUND: Phylogenetic hypotheses based on complete genome data are presented for the Gammaproteobacteria family Vibrionaceae. Two taxon samplings are presented: one including all those taxa for which the genome sequences are complete in terms of arrangement (chromosomal location of fragments; 19 taxa) and one for which the genome sequences contain multiple contigs (44 taxa). Analyses are presented under the Maximum Parsimony and Maximum Likelihood optimality criteria for total evidence datasets, the two chromosomes separately, and individual analyses of locally collinear blocks. Three of the genomes included in the 44 taxon dataset, those of Vibrio gazogenes, Salinivibrio costicola, and Aliivibrio logei have been newly sequenced and their genome sequences are documented here. RESULTS: Phylogenetic results for the 19-taxon datasets show similar levels of collinear subset of dataset incongruence as a previous study of 22 taxa from the sister family Shewanellaceae, while also echoing the strong phylogenetic performance of random subsets of data also shown in this study. Phylogenetic results for both the 19-taxon and 44-taxon datasets corroborate previous hypotheses about the placement of Photobacterium and Aliivibrio within Vibrionaceae and also highlight problems with how Photobacterium is delimited and indicate that it likely should be dissolved into Vibrio to produce a phylogenetic taxonomy. The 19-taxon and 44-taxon trees based on the large chromosome are congruent for the majority of taxa that are present in both datasets. Analyses of the 44-taxon sampling based on the second, small chromosome are quite different from those based on the large chromosome, which is not surprising given the dramatically divergent nature of the small chromosome and the difficulty in postulating primary homologies. CONCLUSIONS: The phylogenetic analyses presented here represent the most comprehensive genome-level phylogenetic analyses in terms of taxa and data. Based on the availability of genome data for many bacterial species on GenBank, many other bacterial groups would also be amenable to similar genome-scale phylogenetic analyses even when present in multiple contigs. The result that collinear subsets of data are incongruent with the concatenated dataset and with each other while random data subsets show very little incongruence echoes the result of previous work on Shewanellaceae. The 44-taxon phylogenetic analysis presented here thus represents the future of phylogenomic analyses in scope and complexity.

Complete genome sequences provide a case study for the evaluation of gene-tree thinking.

Complete genome sequences from a genus of Gammaproteobacteria, Shewanella, are used to generate a genome-wide exploration of the gene-tree species-tree dichotomy. A number of datasets were constructed and analyses were attempted. Single genes were chosen from 243 regions of collinear gene homology (128 of these 243 chosen genes are from the core Shewanella genome and 162 of 243 have the complete taxon sampling) from a previous study (Dikow, 2011) and subjected to phylogenetic analysis both individually and concatenated. In addition, three of the 243 sets of collinear genes from the core Shewanella genome were also chosen (comprising 15, 17, and 23 genes each) to be analysed in detail, this time to maximize the expectation of gene concordance. Analysis of these 55 genes in maximum parsimony (MP) and maximum likelihood (ML) produced 164 unique topologies (out of 166 resulting topologies). No genes from within collinear regions were congruent with one another, and none of these 164 topologies matches the result from concatenation. This result is particularly striking given that we chose collinear sets of genes. Analyses in MP and ML of 243 genes distributed across the genome produced 567 unique topologies (out of 571 resulting topologies for those 162 genes with complete taxon sampling). These results are discussed in light of recent works focused on incongruence. The gene as a phylogenetic unit is also discussed. It is our conclusion that molecular systematics has been reliant on the gene as a unit without a critical eye on the distinction between gene homology and character homology.

Venom evolution widespread in fishes: a phylogenetic road map for the bioprospecting of piscine venoms.

Knowledge of evolutionary relationships or phylogeny allows for effective predictions about the unstudied characteristics of species. These include the presence and biological activity of an organism's venoms. To date, most venom bioprospecting has focused on snakes, resulting in six stroke and cancer treatment drugs that are nearing U.S. Food and Drug Administration review. Fishes, however, with thousands of venoms, represent an untapped resource of natural products. The first step involved in the efficient bioprospecting of these compounds is a phylogeny of venomous fishes. Here, we show the results of such an analysis and provide the first explicit suborder-level phylogeny for spiny-rayed fishes. The results, based on approximately 1.1 million aligned base pairs, suggest that, in contrast to previous estimates of 200 venomous fishes, >1,200 fishes in 12 clades should be presumed venomous. This assertion was corroborated by a detailed anatomical study examining potentially venomous structures in >100 species. The results of these studies not only alter our view of the diversity of venomous fishes, now representing >50% of venomous vertebrates, but also provide the predictive phylogeny or "road map" for the efficient search for potential pharmacological agents or physiological tools from the unexplored fish venoms.