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Miami University
Dr. Luis A. Actis

Professor
Department of Microbiology
Phone: 513-529-5424
Fax: 513-529-2431
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Dr. Luis A. Actis
Dr. Luis A. Actis "Our laboratory is interested in understanding the mechanisms by which bacteria form biofilms on surfaces and obtain nutrients, particularly iron, in natural and medical environments. We are also interested in exploring the effects nanoparticles have in the physiology of bacteria isolated from soil and clinical samples. These studies should provide a better comprehension of the interactions of bacterial cells with the extracellular milieu."


Description of Research
Nanoparticles are more reactive and often possess novel properties that differ from that of the bulk material due, in large part, to a relatively higher surface-to-mass ratio. As interest in nanoparticles has increased, so have concerns that these structures may exert toxic effects on living systems.

Concerns over tissue penetration have been a dominating topic in the studies of the effects of nanoparticles in humans. A decrease in mitochondrial activity was found in cells exposed to a low concentration of Ag nanoparticles. Similarly, studies have reported bactericidal effects of MgO, ZnO, and CaO nanoparticles on Escherichia coli, Staphylococcus aureus, and various Bacillus species. However, the toxicity of nanoparticles seems to depend on the their size and the method used for their preparation. It was also shown that Al2O3 and SiO2 nanoparticles affixed to glass enhance bacterial biofilm formation. While the specific interactions of nanoparticles with living systems is not known, it is clear that the problem of studying nanoparticle effects on cells is complex.

Our laboratory is exploring the interactions of magnetite and ferrihydrite nanoparticles with two species of Acinetobacter, ubiquitous bacteria that grow on a diverse range of carbon and energy sources. FOr this work we chose Acinetobacter baumannii 19606, which represents clinical isolates that cause severe human infections, and Acinetobacter ADP1, a naturally transformable soil isolate that could be used for bioremediation. These studies should provide novel insights on the interactions of nanoparticles and their effects on living systems using tractable and relevant experimental models.

Undergraduate researcher's roles in your lab
Undergraduate students work together with graduate students on research projects they use to earn credit for Independent Study. This is an excellent opportunity for undergraduate students to experience hands-on research and participate in meeting presentations and the preparation of scientific publications.

Graduate student's role in your lab
Graduate students develop their master or doctoral dissertations based on research projects that will most likely make significant contributions to the field of microbiology. Graduate students work together with undergraduate students and postdoctoral fellows. These interaction foster collaborations and fulfill the commitment of our graduate program to provide education and training in microbiology at the undergraduate and graduate levels.

Presentations

Funding
$100.000 Grant from the State of Ohio
Nanomaterials in our Environment

$100.000 Grant from the State of Ohio
Nanomaterials in our Environment
Publications

Tomaras, A. P., C. W. Dorsey, R. E. Edelmann, and L. A. Actis. Attachment to and biofilm formation on abiotic surfaces by Acinetobacter baumannii: involvement of a novel chaperone-usher pili assembly system. Microbiology, 149, 3461-3484, 2003.

Actis, L. A, E. Rhodes, and A. Tomaras. Genetic and molecular characterization of a dental pathogen using genome-wide approaches. Advances in Dental Research, 17, 95-99, 2003.

Dorsey, C. W., A. P, Tomaras, P. L. Connerly, M. E. Tolmasky, J. H. Crosa, and L. A. Actis. The siderophore-mediated iron acquisition systems of Acinetobacter baumannii ATCC 19606 and Vibrio anguillarum 775 are structurally and functionally related. Microbilogy, 150, 3657-3667, 2004.

McGillivary, G., A. P. Tomaras, E. R. Rhodes, and L. A. Actis. Cloning and sequencing of a genomic island found in the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius. Infect. Immun. 73, 1927-1938, 2005.

Rhodes, E. R., A. P. Tomaras, G. McGillivary, P. L. Connerly, and L. A. Actis. Genetic and functional analysis of the Actinobacillus actinomycetemcomitans AfeABCD siderophore independent iron-acquisition system. Infect. Immun. 73, 3758-3763, 2005.

McGillivary, G., L. M. Smoot, and L. A. Actis. Characterization of the IgA1 protease from the Brazilian purpuric fever strain F3031 of Haemophilus influenzae biogroup aegyptius. FEMS Microbiol. Lett. 250, 229-236, 2005.

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