Serum-starvation-induced changes in protein synthesis and morphology of Borrelia burgdorferi

It has been demonstrated previously that motile Borrelia burgdorferi cells transform into non-motile cyst-forms when incubated for several weeks in BS KII (a complex medium) lacking rabbit serum. B. burgdorferi cells cannot sy nthesize fatty acids de novo and serum is thought to provide a source of fa tty acids and lipids. When B. burgdorferi cells were serum-starved in defin ed RPMI medium, similar to 90% of the cells formed spherical cysts within 4 8 h. Cyst formation was inhibited by tetracycline. Cyst opening and recover y of vegetative cells was rapidly induced by the addition of either BSKII o r rabbit serum. The percentage of viable cells recovered from cysts ranged from 2.9 % to 52.5 %, Viability was inversely proportional to cyst age. Pro tein synthesis by B. burgdorferi during serum starvation was examined by la belling cells with Tran(35)S-Label and analysing the labelled proteins by t wo-dimensional gel electrophoresis and fluorography. The synthesis of over 20 proteins was induced during serum starvation. Western blots of proteins from vegetative cells and cysts probed with sera from either B. burgdorferi -infected humans or monkeys revealed that several cyst proteins were antige nic. These data suggest that cells of B. burgdorferi, although possessing a small genome and extremely limited biosynthetic capabilities, rapidly resp ond to conditions of serum starvation by inducing changes in protein synthe sis and cell morphology, This study may help explain how cells of B. burgdo rferi can survive periods of nutrient deprivation in different hosts and ho st tissues.