The Growth and Division of Burkholderia cepacia, a Bacterium with Multiple Chromosomes
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Cystic Fibrosis (CF) is an autosomal recessive genetic disorder that affects I in 3200 live births. Among many health problems, genetic mutations in the cystic fibrosis transmembrane regulator (CFTR) cause lung disease. A common bacterial pathogen in CF lung disease, a Burholderia cepacia infection correlates with decreased patient survival. Our research focused on the growth and division of B. cepacia to elucidate mechanisms of division which may help find a target for an antibiotic. We hypothesized that B. cepacia would have abnormal growth and division due to its multiple chromosomes. While B. cepacia exhibits some unique traits in growth and division, for the most part it does not exhibit abnormal growth in comparison with the Bacterial Division Model developed by Cooper and Helmsetter (1969) in bacteria with one chromosome, like E. coli. Two strains identical by simple genotyping methods, AUII07 (an isolate from a CF patient) and HI2424 (an isolate from the environment) were examined. AUII07 grows slower than HI2424,suggesting slight genotypic differences in the stains. Shifting HI2424 from a slow growth rate medium ti a fast growth media yielded a "C+D" period (C for genome replication and D for the time between termination of genome replication and cell division, respectively) of approximately one hour, similar to E. coli. However, the cell size did not increase immediately as with E. coli. DAPI staining of the nucleoid regions of HI2424 and AUII07 found no clear relation ship between chromosome number and number of nucleoids in dividing cells. HI2424 also did not take up radioactive thymidine, indicating genetic modification of a wildtype strand will need to be done to use the membrane elution technique, which requires thymidine uptake.