Publications - Faculty - Recently Submitted Faculty Publications 2008
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Davis - Plant Disease
Cocultivation of Candidatus Liberibacter asiaticus with Actinobacteria from Citrus with Huanglongbing
Michael J. Davis, Sachindra N. Mondal, Huiqin Chen, Michael E. Rogers, and Ronald H. Brlansky
Abstract. Huanglongbing (HLB), also known as citrus greening disease, is a devastating disease of citrus caused by phloem-limited bacteria that have not been grown in culture. Three species, Candidtatus Liberibacter asiaticus, L. africanus, and L. americanus, are known. Candidatus L. asiaticus and its insect vector, the psyllid Diaphorina citri, have been recently introduced into Florida. We attempted to isolate Candidatus L. asiaticus using media formulations developed in response to the growth of another bacterium that appears to be related to the liberibacters based on 16S rRNA gene homologies. Cultures were obtained that were PCR positive for Candidatus L. asiaticus. However, transmission electron microscope examination of the culture, PCR using generic primers, and sequencing of the PCR products revealed the presence of other bacteria in the cultures. These were actinobacteria related to Propionibacterium acnes based on 16S rRNA homologies. The cocultures remained after attempts to purify the cultures by single colony isolation suggesting that the bacteria might be mutually beneficial to each other in culture. The cocultures have survived more than 10 weekly passages to fresh medium. PCR using P. acnes specific primers indicated that actinobacteria are common inhabitants of citrus and psyllids, whether or not Candidatus L. asiaticus is present.
