Project description:We exposed Salmonella TA100 cells to 3 concentrations of MX that produced a linear concentration-response for mutagenesis with little cell killing. We measured mutagenesis, survival, and global gene expression. We used custom-spotted glass slides as our microarray platform and identified genes whose expressions were altered by MX treatment using three methods: (1) a Bayesian t-test, (2) an operon analysis that assumes if one gene in an operon is differentially expressed then all genes in that operon are differentially expressed, and (3) a monotonic-expression response to increasing doses of MX. The resulting list of genes was analyzed for functional and KEGG pathway representation. Keywords: dose response
Project description:Vibrio cholerae uses multiple strategies to resist predation by heterotrophic protozoa. For example, V. cholerae releases toxic compounds such as ammonium and pyomelanin, that can kill protists such as Tetrahymena pyriformis. V. cholerae also survives intracellularly and escapes as viable cells inside protozoan expelled food vacuoles (EFVs). We previously reported that V. cholerae encased in EFVs are hyperinfectious, establishing an important link between anti-protozoal strategies and bacterial virulence. Although the intracellular resistance and escape of V. cholerae in EFVs has been reported, the molecular mechanisms behind this remain poorly understood. Here, we used single cell transcriptomics of V. cholerae exposed to T. pyriformis and captured a total of 5,344 bacterial cells with heterogeneous gene expression. Cells with the same pattern of gene expression were grouped, resulting in eleven clusters of cells with a unique gene expression profile. Genes encoding outer membrane proteins, F1F0-Na+/H+ ATPase, metabolites and toxins showed differential expression among the clusters. Furthermore, the motility-associated killing factor (Mak) toxins (makA, makB and makC) were differentially expressed. Individual V. cholerae ΔmakA, ΔmakB, and ΔmakE strains were not capable of killing T. pyriformis and ΔmakA and ΔmakE showed reduced survival inside EFVs compared to the wild type. Our findings reveal new insights into the grazing resistance mechanisms of V. cholerae, identify factors associated with the survival of V. cholerae within EFVs and more broadly, highlight the connection between antiprotozoal and virulence factors displayed by pathogenic bacteria.
Project description:Paratrimastix pyriformis is a free-living flagellate thriving in low-oxygen freshwater sediments. It belongs to the group Metamonada along with human parasites, such as Giardia and Trichomonas. Like other metamonads, P. pyriformis has a mitochondrion-related organelle (MRO) which in this protist is primarily involved in one-carbon folate metabolism. The MRO contains four members of the solute carrier family 25 (SLC25) responsible for the exchange of metabolites across the mitochondrial inner membrane. Here, we characterise the function of the adenine nucleotide carrier PpMC1 by thermostability shift and transport assays. We show that it transports ATP, ADP and, to a lesser extent, AMP, but not phosphate. The carrier is distinct in function and origin from both ADP/ATP carriers and ATP-Mg/phosphate carriers, and it most likely represents a distinct class of adenine nucleotide carriers.