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The plant-associated Bacillus amyloliquefaciens subsp. plantarum strain B9601-Y2, isolated from wheat rhizosphere, is a powerful plant growth-promoting rhizobacterium. Its relative large genome size of 4.24Mbp, exceeding that of other representatives of the B. amyloliquefaciens subsp. plantarum taxon, is mainly due to the presence of 18 DNA-islands containing remnants of phages, a unique restriction modification system, a gene cluster for mersacidin synthesis, and an orphan gene cluster devoted to non-ribosomal synthesis of an unidentified peptide. Like other members of the taxon, the Y2 genome contains giant gene clusters for non-ribosomal synthesis of the polyketides macrolactin, difficidin, and bacillaene, the antifungal lipopeptides bacillomycin D, and fengycin, the siderophore bacillibactin, and the dipeptide bacilysin. A gene cluster encoding enzymes for a degradative pathway with 2-keto-3-deoxygluconate and 2-keto-3-deoxy-phosphogluconate as intermediates was explored by genome mining and found as being a unique feature for representatives of the plantarum subspecies. A survey of the Y2 genome against other B. amyloliquefaciens genomes revealed 130 genes only occurring in subsp. plantarum but not in subsp. amyloliquefaciens. Notably, the surfactin gene cluster is not functional due to a large deletion removing parts of the Srf synthetases B and C. Expression of polyketides, lipopeptides, mersacidin, and of the growth hormone indole-3-acetic acid in Y2 was demonstrated by matrix-assisted laser desorption ionization-time of flight mass spectroscopy and high-performance liquid chromatography, respectively., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A single copy of the gfp gene linked with the P(spac) promoter and flanked by the terminal FZB42 amyE sequences was stably integrated into the chromosome of plant growth promoting bacterium Bacillus amyloliquefaciens FZB42 via homologous recombination. A spontaneous mutant, FB01mut, emitting bright fluorescence was detected among the transformants and found suitable for colonization experiments performed with Zea mays, Arabidopsis thaliana and Lemna minor. Real-time RT-PCR revealed that FB01mut expressed 2.5 times more of the gfp transcript than the original GFP-labeled strain. Confocal laser scanning microscopy of plant roots infected with gfp+ tagged FZB42 revealed that the bacterium behaves different in colonizing surfaces of plant roots of different species. In contrast to maize, FZB42 colonized preferentially root tips when colonizing Arabidopsis. FZB42 colonized heavily Lemna fronds and roots by forming biofilms consisting of extracellular matrix and cells with altered morphology. Surfactin, but no other lipopeptide or polyketide synthesized by FZB42 under laboratory conditions, was detected in extracts of Lemna plantlets colonized by FZB42. Due to its stable and long-lasting emission of bright fluorescence without antibiotic pressure FB01mut is an excellent tool for studying plant colonization under competitive, environmental conditions., (Copyright © 2011 Elsevier B.V. All rights reserved.)