Project description:Eight species of heliobacteria have had their genomes sequenced. However, only two of these genomes have been analyzed in detail, those from the thermophilic Heliomicrobium (Hmi.) modesticaldum and the alkaliphilic Heliorestis (Hrs.) convoluta. Here we present analyses of the draft genome sequence of a species of heliobacterium that grows optimally at a moderate temperature and neutral pH. The organism, Heliophilum (Hph.) fasciatum, is phylogenetically unique among cultured heliobacteria and was isolated from rice soil, a common habitat for heliobacteria. The Hph. fasciatum genome contains 3.14 Mbp-similar to that of other reported heliobacteria-but has a G+C base ratio that lies between that of Hmi. modesticaldum and Hrs. convoluta. Many of the genomic features of Hmi. modesticaldum and Hrs. convoluta, such as the absence of genes encoding autotrophic pathways, the presence of a superoperonal cluster of photosynthesis-related genes, and genes encoding endospore-specific proteins, are also characteristic of the Hph. fasciatum genome. However, despite the fact that Hph. fasciatum is diazotrophic, classical nif genes encoding the alpha and beta subunits of dinitrogenase (nifDK) present in other heliobacteria could not be identified. Instead, genes encoding several highly divergent NifDK homologs were present, at least one of which likely encodes a functional dinitrogenase and another a methylthio-alkane reductase (MarDK) for sulfur assimilation. A classical NifH (dinitrogenase reductase) homolog was also absent in Hph. fasciatum, but a related protein was identified that likely carries out this function as well as electron delivery to MarDK. The N2-fixing system of Hph. fasciatum is therefore distinct from that of other heliobacteria and may have unusual properties.
Project description:The complete mitochondrial genome of the zebra shark (Stegostoma fasciatum) was first determined in this study. The total length of this circle DNA was 16 658 bp, consisted of 37 genes with typical gene order in vertebrate mitogenome. Its nucleotide content was 34.1% A, 25.9% C, 12.5% G and 27.5% T. This mitogenome had 23 bp short intergenic spaces located in 10 gene junctions and 54 bp overlaps located in 11 gene junctions. In the protein-coding genes, two start codons (GTG and ATG) and two stop codons (TAG and TAA/T) were found. The 22 tRNA genes ranged from 66 bp (tRNA-Cys) to 75 bp (tRNA-Leu1). The phylogenetic result showed that S. fasciatum was clustered with the whale shark Rhincodon typus.
