Access Type

Open Access Dissertation

Date of Award


Degree Type


Degree Name



Biological Sciences

First Advisor

Dr. L.S. Luckinbill

Second Advisor

Dr. J. W. Wireman


Many researchers have observed that bacteria can enter into a viable but nonculturable state. In order to study this phenomenon in Legionella pneumophila, a model hot water system was constructed to serve as a source of planktonic and biofilm cells. Both planktonic and biofilm L. pneumophila existed primarily as nonculturable cells. A portion of these nonculturable cells were shown to be viable using the tetrazolium salt, INT, which is an indicator of respiratory activity. The nonLegionella bacteria which coexisted with L. pneumophila in the water system had no effect on its culturability. Inoculation of embryonated chicken eggs indicated that a mixture of planktonic cells (L. pneumophila and nonLegionella) from the water system were more virulent than a mixture of biofilm cells. However, embryo deaths were due primarily to the nonLegionella, and L. pneumophila had little or no impact. Published reports of studies where embryonated eggs are inoculated with environmental samples and the virulence of the mixture attributed to the L. pneumophila in the sample should be reevaluated.