Crystal L Schmerk

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The Francisella pathogenicity island (FPI) is a cluster of 16-19 genes, which is found duplicated in most of the Francisella genomes that have been sequenced. Although 16 FPI genes are highly conserved there are 2-3 putative genes that are absent or interrupted by stop codons in some strains. Francisella strains with experimentally induced mutations in FPI(More)
The Francisella pathogenicity island (FPI) encodes proteins thought to compose a type VI secretion system (T6SS) that is required for the intracellular growth of Francisella novicida. In this work we used deletion mutagenesis and genetic complementation to determine that the intracellular growth of F. novicida was dependent on 14 of the 18 genes in the FPI.(More)
Burkholderia cenocepacia is a Gram-negative aerobic bacterium that belongs to a group of opportunistic pathogens displaying diverse environmental and pathogenic lifestyles. B. cenocepacia is known for its ability to cause lung infections in people with cystic fibrosis and it possesses a large 8 Mb multireplicon genome encoding a wide array of pathogenicity(More)
Francisella tularensis is a highly infectious, facultative intracellular bacterial pathogen that is the causative agent of tularemia. Nearly a century ago, researchers observed that tularemia was often fatal in North America but almost never fatal in Europe and Asia. The chromosomes of F. tularensis strains carry two identical copies of the Francisella(More)
Francisella tularensis is a highly virulent, intracellular pathogen that causes the disease tularaemia. A research surrogate for F. tularensis is Francisella novicida, which causes a tularaemia-like disease in mice, grows similarly in macrophages, and yet is unable to cause disease in humans. Both Francisella species contain a cluster of genes referred to(More)
Several genes contained in the Francisella pathogenicity island (FPI) encode proteins needed for intracellular growth and virulence of Francisella tularensis. The pdpA gene is the first cistron in the larger of the two operons found in the FPI. In this work we studied the intracellular growth phenotype of a Francisella novicida mutant in the pdpA gene. The(More)
Hopanoids are pentacyclic triterpenoids that are thought to be bacterial surrogates for eukaryotic sterols, such as cholesterol, acting to stabilize membranes and to regulate their fluidity and permeability. To date, very few studies have evaluated the role of hopanoids in bacterial physiology. The synthesis of hopanoids depends on the enzyme(More)
All bacteria share a set of evolutionarily conserved essential genes that encode products that are required for viability. The great diversity of environments that bacteria inhabit, including environments at extreme temperatures, place adaptive pressure on essential genes. We sought to use this evolutionary diversity of essential genes to engineer bacterial(More)
Hopanoids are bacterial surrogates of eukaryotic membrane sterols and among earth's most abundant natural products. Their molecular fossils remain in sediments spanning more than a billion years. However, hopanoid metabolism and function are not fully understood. Burkholderia species are environmental opportunistic pathogens that produce hopanoids and also(More)
Previous results suggest that mutations in most genes in the Francisella pathogenicity island (FPI) attenuate the bacterium. Using a mouse model, here we determined the impact of mutations in pdpA, pdpC, and pdpD in Francisella novicida on in vitro replication in macrophages, and in vivo immunogenicity. In contrast to most FPI genes, deletion of pdpC(More)