Microbiology & Immunology - Research Publications
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ItemIntraspecies Variation in Tetrahymena rostrata(MDPI, 2021-10)Two distinct isolates of the facultative parasite, Tetrahymena rostrata were compared, identifying and utilising markers that are useful for studying clonal variation within the species were identified and utilised. The sequences of mitochondrial genomes and several nuclear genes were determined using Illumina short read sequencing. The two T. rostrata isolates had similar morphology. The linear mitogenomes had the gene content and organisation typical of the Tetrahymena genus, comprising 8 tRNA genes, 6 ribosomal RNA genes and 45 protein coding sequences (CDS), twenty-two of which had known function. The two isolates had nucleotide identity within common nuclear markers encoded within the histone H3 and H4 and small subunit ribosomal RNA genes and differed by only 2-4 nucleotides in a region of the characterised actin genes. Variation was observed in several mitochondrial genes and was used to determine intraspecies variation and may reflect the natural history of T. rostrata from different hosts or the geographic origins of the isolates.
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ItemInfection of Slugs with Theronts of the Ciliate Protozoan, Tetrahymena rostrata(MDPI, 2021-09)Tetrahymena rostrata is a free-living ciliated protozoan and is a facultative parasite of some species of terrestrial mollusks. It is a potential biopesticide of pest slugs, such as the grey field slug, which cause considerable damage to crops. T. rostrata has several developmental forms. Homogeneous preparations of the feeding stage cells (trophonts) and excysted stage cells (theronts) were compared for their ability to infect and kill Deroceras reticulatum slugs. Theronts were more effective and remained viable and infective, even after prolonged starvation.
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ItemThe mitochondrial genome of Tetrahymena rostrata(TAYLOR & FRANCIS LTD, 2020)Tetrahymena rostrata is a ciliated protist which can parasitize the gray field slug, Deroceras reticulatum. Here, we report the sequence of the mitochondrial genome (mt genome) of a strain of T. rostrata that was isolated from the egg of D. reticulatum. Whole cell genomic DNA was sequenced using Illumina® MiSeq and the mitochondrial DNA sequence reads were extracted and assembled. The resulting 47,235 bp assembly contained rRNAs, tRNAs, and 45 protein coding DNA sequences of which 21 encoded proteins of unknown function. Phylogenetic analysis showed T. rostrata clustered with Tetrahymena thermophila, Tetrahymena pigmentosa, Tetrahymena pyriformis, Tetrahymena paravorax, and Tetrahymena malaccensis.
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ItemMolecular characterization of isoniazid-resistant Mycobacterium tuberculosis isolates collected in Australia(AMER SOC MICROBIOLOGY, 2005-10)Elucidation of the molecular basis of isoniazid (INH) resistance in Mycobacterium tuberculosis has led to the development of different genotypic approaches for the rapid detection of INH resistance in clinical isolates. Mutations in katG, in particular the S315T substitution, are responsible for INH resistance in a large proportion of tuberculosis cases. However, the frequency of the katG S315T substitution varies with population samples. In this study, 52 epidemiologically unrelated clinical INH-resistant M. tuberculosis isolates collected in Australia were screened for mutations at katG codon 315 and the fabG1-inhA regulatory region. Importantly, 52 INH-sensitive isolates, selected to reflect the geographic and genotypic diversity of the isolates, were also included for comparison. The katG S315T substitution and fabG1-inhA -15 C-to-T mutation were identified in 34 and 13 of the 52 INH-resistant isolates, respectively, and none of the INH-sensitive isolates. Three novel katG mutations, D117A, M257I, and G491C, were identified in three INH-resistant strains with a wild-type katG codon 315, fabG1-inhA regulatory region, and inhA structural gene. When analyzed for possible associations between resistance mechanisms, resistance phenotype, and genotypic groups, it was found that neither the katG S315T nor fabG1-inhA -15 C-to-T mutation clustered with any one genotypic group, but that the -15 C-to-T substitution was associated with isolates with intermediate INH resistance and isolates coresistant to ethionamide. In total, 90.4% of unrelated INH-resistant isolates could be identified by analysis of just two loci: katG315 and the fabG1-inhA regulatory region.