Project description:Acididesulfobacillus acetoxydans is an acidophilic sulfate reducer that can dissimilatory reduce nitrate to ammonia (DNRA). However, no known nitrite reductase is encoded. This study was performed to investigate how A. acetoxydans reduces nitrate to nitrite and elucidated a novel DNRA mechanism and potential nitrosative stress resistance mechanisms in acidophiles.
Project description:In this work, we evaluated the genetic stabilization process, of the intra- (Saccharomyces cerevisiae) and interspecific (S. cerevisiae x Saccharomyces kudriavzevii) hybrids obtained by different non-GMO techniques, under fermentative conditions. Large-scale transitions in genome size, detected by measuring total DNA content, and genome reorganizations in both nuclear and mitochondrial DNA, evidenced by changes in molecular markers, were observed during the experiments. Interspecific hybrids seem to need fewer generations to reach genetic stability than intraspecific hybrids. The largest number of molecular patterns among the derived stable colonies was observed for intraspecific hybrids, particularly for those obtained by rare-mating in which the total amount of initial DNA was larger. Finally, a representative intraspecific stable hybrid underwent a normal industrial process to obtain active dry yeast production as an important point at which inducing changes in genome composition was possible. No changes in hybrid genetic composition after this procedure were confirmed by comparative genome hybridization. According to our results, fermentation steps 2 and 5 –comprising between 30 and 50 generations- suffice to obtain genetically stable interspecific and intraspecific hybrids, respectively. This work aimed to develop and validate a fast genetic stabilization method for newly generated Saccharomyces hybrids under selective enological conditions. A comparison of the whole stabilization process in intra- and interspecific hybrids showing different ploidy levels, as a result of using different hybridization methodologies, was also made.
Project description:Genome rearrangements are associated with eukaryotic evolutionary processes ranging from tumorigenesis to speciation. Such rearrangements are especially common following the shock of interspecific hybridization, and some of these could be expected to have strong selective value. To test this expectation we created de novo interspecific yeast hybrids between two diverged but largely syntenic species, Saccharomyces cerevisiae and S. uvarum, then experimentally evolved them under continuous ammonium limitation. We discovered that a characteristic interspecific genome rearrangement arose multiple times in independently evolved populations. We uncovered nine different breakpoints, all occurring in a ~1 kb region of chromosome 14, and all producing an “interspecific fusion junction” within the MEP2 gene coding sequence, such that the 5’ portion derives from S. cerevisiae and the 3’ portion derives from S. uvarum. In most cases the rearrangements altered both chromosomes, resulting in what can be considered to be an introgression of a several-kb region of S. uvarum into an otherwise intact S. cerevisiae chromosome 14, while the S. uvarum chromosome 14 experienced an interspecific reciprocal translocation at the same breakpoint within MEP2, yielding a chimaeric chromosome. The net result is the presence in the cell of two MEP2 fusion genes having identical breakpoints. Given that MEP2 encodes for a high-affinity ammonium permease, that MEP2 fusion genes arise repeatedly under ammonium-limitation, and that three independent evolved isolates carrying MEP2 fusion genes are each more fit than their common ancestor, the novel MEP2 fusion genes are very likely adaptive under ammonium limitation. Our results suggest that when homoploid hybrids form, the admixture of two genomes enables swift and otherwise unlikely evolutionary innovations. Furthermore, the architecture of the MEP2 rearrangement suggests a model for rapid introgression, a phenomenon seen in numerous eukaryotic phyla, that does not invoke repeated backcrossing to one of the parental species. Nomenclature: GSY86 TimeZeroInoculum = ancestral interspecific hybrid used to inoculate ammonium-limited chemostats into 3 replicate vessels A, B, C. 150gen = various single-clone isolates from 150 generations of evolutions from vessels A, B or C. 200gen = various isolates from 200 generations of evolutions from vessels A, B or C.
Project description:Cytosine methylation is a conserved base modification, but explanations for its interspecific variation remain elusive. Only through taxonomic sampling of disparate groups can unifying explanations for interspecific variation be thoroughly tested. Here we leverage phylogenetic resolution of cytosine DNA methyltransferases (DNA MTases) and genome evolution to better understand widespread interspecific variation across 40 diverse fungal species. DNA MTase genotypes have diversified from the ancestral DNMT1+DNMT5 genotype through numerous loss events, and duplications, whereas, DIM-2 and RID-1 are more recently derived in fungi. Methylation is typically enriched at intergenic regions, which includes repeats and transposons. Unlike certain Insecta and Angiosperm species, Fungi lack canonical gene body methylation. Some fungi species possess large clusters of contiguous methylation encompassing many genes, repetitive DNA and transposons, and are not ancient in origin. Broadly, methylation is partially explained by DNA MTase genotype and repetitive DNA content. Basidiomycota on average have the highest level of methylation, and repeat content, compared to other phyla. However, exceptions exist across Fungi. Other traits, including DNA repair mechanisms, might contribute to interspecific methylation variation within Fungi. Our results show mechanism and genome evolution are unifying explanations for interspecific methylation variation across Fungi.
Project description:Using reduced representation bisulfite sequencing (RRBS), we have compared the methylomes of neuronal and non-neuronal cells from three female human and three chimpanzee cortices (Brodmann area 10). Differentially methylated regions (DMRs) with genome-wide significance were enriched in specific chromosomal regions. Intraspecific methylation differences between neuronal and non-neuronal cells were approximately three times more abundant than interspecific methylation differences between human and chimpanzee cell types. The vast majority (>90%) of human intraspecific DMRs (including DMRs with retrotransposons) were hypomethylated in neurons, compared to glia. Intraspecific DMRs were enriched in genes that have been associated with different neuropsychiatric disorders. Interspecific DMRs were enriched in genes showing human-specific brain histone modifications. Methylation differences between human and chimpanzee non-neuronal cells (N=666) were much more frequent than neuronal interspecific DMRs (N=96). More than 95% of interspecific non-neuronal DMRs were hypermethylated in humans.
Project description:Four hybrid yeast strains isolated from a variety of industrial substrates were hybridized to an array-CGH platform containing probes to query the whole genomes of seven different Saccharomyces species. For most of the strains we found evidence of multiple interspecific hybridization events and multiple introgressed regions. The strains queried were GSY205 (isolated from a cider fermentation), GSY505 (a contaminant from a lager beer fermentation), GSY2232 (a commercial wine yeast strain), and GSY312 (a commercial lager beer strain). Additionally, 3 different rare viable spores derived from laboratory-created interspecific S. cerevisiae-S. bayanus (aka S. uvarum) hybrids were queried, before and after evolution in chemostats, via S. cerevisiae-S. bayanus microarrays.