Important Plant Pathogenic Bacteria Research Articles

Inhibition of fungal and bacterial plant pathogens by synthetic peptides: in vitro growth inhibition, interaction between peptides and inhibition of disease progression.

Four synthetic cationic peptides, pep6, pep7, pep11 and pep20, were tested alone and in combinations for their antimicrobial activities against economically important plant pathogenic fungi (Phytophthora infestans and Alternaria solani) and bacteria (Erwinia carotovora subsp. carotovora and E. carotovora subsp. atroseptica). In in vitro studies, P. infestans and A. solani were inhibited by all four peptides, while E. carotovora subsp. carotovora and E. carotovora subsp. atroseptica were inhibited only by pep11 and pep20. All peptides completely inhibited P. infestans and A. solani on potato leaves and P. infestans on tubers at concentrations comparable to the in vitro IC50 (effective concentration for 50% growth inhibition) values, suggesting that these peptides are more potent in preventing infection than in inhibiting hyphal growth in vitro. Microscopic observations of P. infestans and A. solani when treated with these peptides revealed hyphal anomalies. In tuber-infectivity assays, pep11 and pep20 reduced bacterial softrot symptoms by 50% at 2.0 to 2.30 microM and by 100% at 20 microM. In assays involving two-way combinations of these peptides, growth inhibitions of fungi and bacteria by the combinations were no more than the sum of growth inhibitions by each peptide when used alone, indicating that they act additively. pep11 and pep20 are not phytotoxic to potato plants at 200 microM. With strong and broad-spectrum antimicrobial activities of pep11 and pep20 against fungi and bacteria, and with no antagonistic activities, the expression of these peptides in transgenic potato plants could lead to enhanced disease resistance against these pathogens.

Genome size and macrorestriction map of Xanthomonas campestris pv. glycines YR32 chromosome.

Xanthomonas campestris is an important plant pathogenic bacterium which causes severe diseases in a wide variety of plant species. We have generated a macrorestriction map of the X. campestris (axonopodis) pv. glycines chromosome employing pulsed-field gel electrophoresis (PFGE). Restriction endonucleases PacI (5'-TTAATTAA), PmeI (5'-GTTTAAAC) and SwaI (5'-ATTTAAAT) digested the chromosomal DNA into three, five, and five fragments, respectively. In addition, intron-encoded restriction endonuclease I-CeuI was employed to locate the position of the 23S rRNA genes (rrlA and rrlB). All of the generated restriction fragments were aligned along the chromosome using multiple restriction enzyme digestion and two-dimensional PFGE (2-D PFGE) in conjunction with Southern hybridization analysis. This physical map construction has revealed a single circular chromosome with a size of approximately 5 Mb. Two rRNA genes were localized on the chromosome map. Several genes involved in pathogenesis (xpsD, opsX, and pat) as well as genes involved in the biosynthesis of xanthan gum (xanAB, rfbCDAB) were also localized.

Genome size and macrorestriction map of Xanthomonas campestris pv. glycines YR32 chromosome

Xanthomonas campestris is an important plant pathogenic bacterium which causes severe diseases in a wide variety of plant species. We have generated a macrorestriction map of the X. campestris ( axonopodis) pv. glycines chromosome employing pulsed-field gel electrophoresis (PFGE). Restriction endonucleases PacI (5′-TTAATTAA), PmeI (5′-GTTTAAAC) and SwaI (5′-ATTTAAAT) digested the chromosomal DNA into three, five, and five fragments, respectively. In addition, intron-encoded restriction endonuclease I- CeuI was employed to locate the position of the 23S rRNA genes ( rrlA and rrlB). All of the generated restriction fragments were aligned along the chromosome using multiple restriction enzyme digestion and two-dimensional PFGE (2-D PFGE) in conjunction with Southern hybridization analysis. This physical map construction has revealed a single circular chromosome with a size of approximately 5 Mb. Two rRNA genes were localized on the chromosome map. Several genes involved in pathogenesis ( xpsD, opsX, and pat) as well as genes involved in the biosynthesis of xanthan gum ( xanAB, rfbCDAB) were also localized.