BATON ROUGE, La. – Juan J. Martinez, PhD, associate professor in the Department of Pathobiological Sciences (PBS), has been accepted for publication in Infection and Immunity. The work is entitled “Non-selective Persistence of a Rickettsia conorii Extrachromosomal Plasmid during Mammalian Infection,” and is scheduled to be published in the March 2016 issue. Dr. Martinez and his lab are interested in understanding the molecular basis by which certain obligate intracellular bacteria of the Spotted Fever Group (SFG) Rickettsiae, cause severe and often fatal disease in humans and companion animals.
Infection and Immunity is a research journal that reports on key discoveries in the fields of molecular pathogenesis, cellular microbiology, microbiome relating to host-pathoigen interactions and bacterial infection, among other research topics.
In this current work, Dr. Martinez and senior author, Sean P. Riley, MS, PhD, assistant professor (research) in PBS, have demonstrated that introduction of an extrachromosomal DNA element called a plasmid into a pathogenic species of rickettsiae, Rickettsia conorii, does not lead to any defects in fitness in vitro nor in fatal outcomes in a murine model of disseminated rickettsial disease. The group’s findings indicate that under non-selective antibiotic pressures, bacteria harboring this piece of DNA maintain the plasmid both in cell culture and when the bacteria are introduced into an animal. Plasmid is defined as a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan.
“Genetics in rickettsial species is really in its’ infancy,” said Dr. Martinez. “By demonstrating that the introduction of a plasmid does not have any negative impacts on the pathogenic potential of the bacterium, we will be able to use this as a genetic tool to introduce wild-type or normal genes on the plasmid so as to complement strains that have natural or generated mutations in genes of interest.”
This work was a collaborative effort with several investigators in PBS and was funded by a research grant from the National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIH/NIAID) to Dr. Martinez’ group and by a pilot grant from the LSU-SVM Center for Experimental Research in Infectious Disease Research (CEIDR) to Dr. Riley.