Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2014
Publication Date: 9/3/2014
Citation: Rogers, E.E., Backus, E.A. 2014. Anterior foregut microbiota of the glassy-winged sharpshooter explored using deep 16S rRNA gene sequencing from individual insects. PLoS One. 9(9):e106215. Interpretive Summary: Xylella fastidiosa (Xf) is a bacterium that causes a number of different leaf-scorching diseases of horticulturally important plants, including Pierce’s disease of grapevine, almond leaf scorch, and citrus variegated chlorosis. The Xf bacterium is transmitted from one plant to another by sharpshooter leafhoppers. If sharpshooters ingest fluid from an infected plant, bacteria also will be taken up and can attach to surfaces of the oral cavity and multiply. Any sharpshooter already containing Xf can deposit bacterial cells into a previously healthy plant during feeding, thereby spreading Xf and increasing disease incidence. Very little is known about the details of how Xf cells stick to the sharpshooter oral cavity. It is possible that other bacteria, that do not cause disease in plants, also are present in the oral cavity and may either help Xf cells stick or prevent Xf cells from sticking. A DNA-sequence based method was used to inventory all bacterial species present in and around the oral cavity of individual sharpshooters. Ninety-six individual insects, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a 10-year old laboratory colony), were examined. No significant differences in bacterial populations were found among the four locations. A large number of bacterial species previously known to be associated with insects, plants, and/or soils were detected; Xf was detected in all 96 individuals. This work is the necessary first step before testing for positive and negative interactions of sharpshooter-associated bacteria with Xf. Such interactions are ideal targets for limiting Xf spread to grapevines.
Technical Abstract: The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce’s disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-six individual GWSS, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a laboratory colony), were characterized for bacteria in dissected sharpshooter cibarium and precibarium by amplification and sequencing of a portion of the 16S rDNA gene. An average of approximately 150,000 sequence reads were obtained per insect. The most common genus detected was Wolbachia; further sequencing of the Wolbachia ftsZ gene placed this strain in group B, one of two Wolbachia groups associated with arthropods. X. fastidiosa was detected in all 96 individuals examined. By multilocus sequence typing, both X. fastidiosa subspecies fastidiosa and subspecies sandyi were present in GWSS from California and the colony; only subspecies fastidiosa was detected in GWSS from Florida. In addition to Wolbachia and X. fastidiosa, 23 other bacterial genera were detected at or above an average incidence of 0.1%; these included plant-associated microbes (Methylobacterium, Sphingomonas, Agrobacterium, and Ralstonia) and soil- or water-associated microbes (Anoxybacillus, Novosphingobium, Caulobacter, and Luteimonas). Sequences belonging to species of the family Enterobacteriaceae also were detected but it was not possible to assign these to individual genera. In an unexpected finding for a strictly xylem-ingesting insect, chloroplast 16S rDNA also was amplified from dissected sharpshooter cibarium and precibarium.