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Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only Publication Acceptance Date: 11/15/2015 Publication Date: 12/15/2015 Citation: Wallis, C.M., Chen, J. 2015. Characterization of different Californian strains of Xylella fastidiosa by fatty acid methyl ester (FAME) analyses. In: Esser T, Randhawa R, eds. Research Progress Reports: Pierce's disease and other designated pests and diseases of winegrapes, December, 2015. California Department of Food and Agriculture, Sacramento, CA. p. 251. Interpretive Summary: Technical Abstract: Detection and characterization of different subspecies of Xylella fastidiosa are often dependent upon genotyping. However, complementary methods to detect and characterize different X. fastidiosa strains based on phenotype are needed to confirm conclusions. Characterization of the composition of fatty acids that comprise bacterial cell membranes is one phenotyping approach to distinguish bacterial species, subspecies, and strains. Fatty acid composition of cell membranes could determine interactions between bacteria and their hosts as well. Fatty acid profiling is performed by a technique involving extraction of fatty acids, conversion to methyl esters, and analysis by gas chromatography. This study examined cell membrane fatty acid profiles of seven different isolates of X. fastidiosa: Dixon, M12, M23, Mulberry, Olive (the 5A isolate from California), Stag’s Leap (SL), and Temecula. Fatty acids were extracted and analyzed from four different cultures of each isolate. The twelve most abundant fatty acids (accounting for approximately 95% of total cell membrane fatty acids) were selected for further analyses. The percent that each of these twelve compromised the fatty acid profile was then used to group each isolate via cluster analyses (both with furthest neighbor linkage using Pearson’s correlations and nearest neighbor linkage using squared Euclidean distances) and principle component analysis. Results showed that M12 consistently grouped alone, M23 and SL consistently grouped together, Dixon and Olive consistently grouped together, and Mulberry and Temecula consistently grouped together. In terms of defined subspecies, M12, Dixon, and Olive are all considered ssp. multiplex, and grouped together consistently. However, M12 was often on a different branch than the others. The ssp. fastidiosa strains of M23, SL, and Temecula were on the same branch when grouped by furthest neighbor joining and closely grouped by PCA, but were on different branches when grouped by nearest neighbor joining. Mulberry, which was defined as subspecies morus, grouped consistently with Temecula suggesting great similarity in fatty acid profiles. Taken together, these results demonstrate the fatty acid profiling can separate ssp. multiplex from ssp. fastidiosa. Additional strains and replication will be performed to verify and expand results. When completed, fatty acid profiling will provide complementary data to genotype-based studies. Commercial equipment that utilizes FAME for bacterial identification could be used to detect and distinguish subspecies and even certain strains of X. fastidiosa. |
