Borrelia burgdorferi, the bacterial agent of Lyme disease, has been shown to vary expression of its outer surface proteins(Osp) during transmission from the tick to mammalian host. This shift in Osp production is believed to be important in the initial invasion and establishment of infection. Shifts in expression can be observed by growing the spirochetes at temperatures that mimic conditions found in the separate hosts. The mutant isolate, RJCL 1, has low to no levels of Osp C production when compared to the parent isolate JMNT. This difference in phenotype has been observed in immunoblots of extracted proteins as well as on blots taken of colonies grown on agar plates. Cultivation of spirochetes on solid BSK medium has also demonstrated variance in morphology of the spirochete colonies. Although growth on agar plates has the disadvantage of a long incubation period (2-3 weeks), the technique is still valuable as it provides a more suitable model of the spirochetes natural environment. Growth on a solid medium simulates the spirochetes' association with host tissues. Spirochetes grown on agar plates that have been incubated at 34ºC grow slower and are smaller than colonies grown at 37ºC. Colonies grown at a lower temperature also express lower levels of Osp C. At 37ºC, even colonies of the non-infectious RJCL1 have shown to produce low levels of Osp C. Cloned isolates, such as RJCL1, also show morphological stability of the colonies through sequential platings. Further research may demonstrate that colony platings on solid medium can be used for isolating out different species of Borrelia from a mix. Analyses of colonies grown on solid medium have provided important molecular and morphological data important for discerning the role that outer surface proteins have in infectivity.
Species 1: Spirochetalis Spirocheteceae Borrelia burgdorferi
Species 2: Acarina Ixodidae Ixodes scapularis (black-legged tick)
Keywords: Lyme disease, colony plating
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA