Comparative analysis of acholeplasmataceae genomes highlights the particular genetic repertoire of Candidatus Phytoplasma strains

Introduction Acholeplasmataceae comprises the genera Acholeplasma and ‘Ca. Phytoplasma’. Acholeplasmas are described as saprophytic bacteria in general, while phytoplasma strains are characterized as obligate intracellular parasites of the plant phloem associated to diseases in >1,000 plant species. Genome research enables the identification of effector proteins and the reconstruction of the metabolism. The complete genomes of 5 phytoplasma strains and 4 Acholeplasma spp. have been analysed (1,2). Objectives Comparative genome analyses provide insights into the evolutionary split of these two genera and the obligate parasitism of phytoplasmas in comparison to the acholeplasmas. Methods Different technologies ranging from clone-based Sanger sequencing, pyro-sequencing, sequencing by synthesis and single molecule real time sequencing were applied. Annotation included functional reconstruction and comparative analyses accomplished by gene expression studies. Results The conserved gene core of phytoplasmas is also encoded by the analysed 4 acholeplasmas in majority. Phytoplasmas are separated by a particular carboxylic acid metabolism, membrane proteins involved in host interaction and virulence factors. Conclusion. Particularities of the phytoplasmas such as the symporter for the uptake of carboxylic acids and their conversion to pyruvate should be interpreted with respect to the Gram+ origin in contrast to genes encoding effectors, which may be derived from horizontal gene transfers.