Expression of Bacillus stearothermophilus LV cadmium resistance genes in Escherichia coli causes hypersensitivity to cadmium chloride

Determination of the nucleotide sequence of a 4.5-kb chromosomal DNA fragment of Bacillus stearothermophilus LV revealed two open reading frames (ORFs) of 121 and 727 amino acids (aa) that exhibit a high degree of similarity with the cadC and cadA cadmium resistance genes of a number of microorganisms. Transfer and expression of the B. stearothermophilus LV cadA or cadC/cadA genes in E. coli caused increased cadmium chloride susceptibility in the bacterial host. Transfer of cadC alone did not result in any detectable phenotypic change in E. coli. Received: 26 November 2001 / Accepted: 21 December 2001     

Rhizoctonia spp. Causing Root and Hypocotyl Rot in Phaseolus vulgaris in Cuba

Sixty isolates of Rhizoctonia spp. were obtained from Cuban bean fields during the period 2004–2007. Isolates were characterized with different techniques, including nuclei staining, pectic zymogram, PCR–RFLP analysis of the rDNA–ITS region and sequencing of the rDNA–ITS region. The majority of the isolates were identified as multinucleate Rhizoctonia solani isolates, representing two different anastomosis groups (AGs), AG 2‐2 WB and AG 4 HGI; the remaining isolates were binucleate Rhizoctonia isolates and belonged to AG F and AG A. AG 4 HGI isolates were equally distributed in all soil types; AG 2‐2 isolates were more frequently isolated from cambisols, whereas AG F isolates were related to calcisols. Pathogenicity experiments in vitro and in the greenhouse, revealed that binucleate isolates only caused root rot, whereas R. solani isolates were able to cause root rot and hypocotyl rot. Furthermore, differences in virulence level were observed between R. solani and binucleate isolates and among different AGs. Isolates of R. solani AG 4 HGI and R. solani AG 2‐2 WB were the most aggressive, binucleate isolates of AG F were intermediate aggressive, whereas a binucleate isolate of AG A was weakly aggressive. In contrast with other reports about R. solani in bean, web blight symptoms were never observed during this study.