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Abstract:
Bacteria were isolated from necrotic apple and pear tree tissue and from dead wood in Germany andAustria as well as from pear tree exudate in China. They were selected for growth at 37◦C, screenedfor levan production and then characterized as Gram-negative, facultatively anaerobic rods. Nucleotidesequences from 16S rRNA genes, the housekeeping genes dnaJ, gyrB, recA and rpoB alignments, BLASTsearches and phenotypic data confirmed by MALDI-TOF analysis showed that these bacteria belong to thegenus Gibbsiella and resembled strains isolated from diseased oaks in Britain and Spain. Gibbsiella-specificPCR primers were designed from the proline isomerase and the levansucrase genes. Acid secretion wasinvestigated by screening for halo formation on calcium carbonate agar and the compound identified byNMR as acetic acid. Its production by Gibbsiella spp. strains was also determined in culture supernatantsby GC/MS analysis after derivatization with pentafluorobenzyl bromide. Some strains were differentiatedby the PFGE patterns of SpeI digests and by sequence analyses of the lsc and the ppiD genes, and the ChineseGibbsiella strain was most divergent. The newly investigated bacteria as well as Gibbsiella querinecans,Gibbsiella dentisursi and Gibbsiella papilionis, isolated in Britain, Spain, Korea and Japan, are taxonomicallyrelated Enterobacteriaceae, tolerate and secrete acetic acid. We therefore propose to unify them in thespecies Gibbsiella acetica sp. nov.
