In this study, the gram-negative bacteria Xanthomonas campestris, Xanthomonas maltophilia, and Pseudomonas putida, facultative parasites of plants and animals, were shown to accumulate 2-C-methyl-d-erythritol-2,4-cyclopyrophosphate (MEC) in response to benzyl-viologen-induced oxidative stress. Corynebacterium ammoniagenes mutants capable of accumulating MEC in the absence of an exogenous oxidative stress inducer were obtained. Isoprenoid synthesis and MEC synthesis in these and other bacteria were shown to be alternative processes, while biosynthesis of brominated polyene xanthomonadin (an antioxidant pigment of X. campestris) increased concomitantly with the accumulation of MEC.
The 16S-23S rRNA internal transcribed spacer regions (ITS1) from 14 strains of Pseudomonas syringae and P. fluorescens were sequenced. ITS1 exhibited significant sequence variability among different operons within a single genome. From 1 to 4 types of ITS1 were found in individual genomes of the P. syringae and P. fluorescens strains. A total of eight ITS1 types were identified among strains studied. The ITS1 nucleotide sequences consisted of conserved blocks including, among others, a stem-forming region of box B, tRNAIle and tRNAAla genes and several variable blocks. The differences in the variable regions were mostly due to insertions and/or deletions of nucleotide blocks. The intragenomic heterogeneity of ITS1 was brought about by different combinations of variable blocks, which possibly have resulted from recombination and horizontal transfer.
Bacterial spot of tomato, caused by X. vesicatoria (Group B) and X. gardneri (Group 0) (Jones et al., 2004) has become a very important disease of tomato in the Russian Federation. It was reported previously that this plant can be affected by Xantlwmonas campestris pv. raphani as well (White, 1930). Leaf spots and wilt symptoms were observed in 2006 on tomato fields located in Krasnodar, Stavropol, and Alania-Osetia regions. Forty-tree original strains were cloned and characterized based on colony characteristics and biochemical properties (Jones et al., 2004). Reference strains included XV 153 (group A), NCPPB 4221 (Group B), XV 938 (Group C), XV GA2, XV444 (Group D), and several X. campestris (NCPPB 528T, PHW 231, and NCPPB 1946T)• The genes gyrB, operon Xcc0006-Xcc0007 (genome of Xcc ATCC 33913; da Silva et al. , 2002), and gene cytP450 were amplified and sequenced in the strains. Analysis of the nucleotide sequences revealed a unique group (seven strains) isolated from diseased tomato plants collected in Alania-Osetia (North Caucasus) with symptoms of leaf spots and "black rot-like" wiltin. Those strains were grouped together with X. cainpestris pv. raphani NCPPB 1946 from radish. The strains were amylolytic, pectolytic, and most similar to X. vesicatoria in other biochemical properties. This is the first report of X. campestris pv. rap hani on tomato in Russia.
Bacterial spot of tomato, caused by Xanthomonas euvesicatoria (Group A), X. vesicatoria (Group B), X. perforans (group C) and X. gardneri (Group D) (Jones et al., 2004), formerly known as X. campestris pv. vesicatoria, has become very important in the Russian Federation. Leaf spots and wilt symptoms were observed in 2006 in tomato fields located in southern European part of Russia. Field symptoms were first observed in early July of 2006 and had spread to over 30% of the plants in some fields by late August. Yellow-pigmented Xanthornonas-like bacteria were isolated from plants using yeast extract-CaCO3 agar. Forty-three original strains were cloned and characterized based on morphologic and biochemical properties, by genetic analysis including rep-PCR, AP-PCR and gene sequencing. Reference strains included XV153 (group A), NCPPB 422 1 (Group B), XV 938 (Group C), XV GA2, XV444 (Group D), and 15 strains stored since 1947. Phenotypic and genetic properties of newly isolated and archived Russian strains were similar. Twent y-three strains that were not amylolytic or pectolytic and failed to utilize cis-aconitic acid were identified as X. gardneri and 18 strains that were strongly amylolytic and pectolytic were identified as X. vesicatoria; neither X. euvesicatoria nor X. perforans were found.
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