Intercontinental spread of promiscuous mercury-resistance transposons in environmental bacteria

We demonstrate that horizontal spread of mer operons similar to worldwide spread of antibiotic-resistance genes in medically important bacteria occurred in bacteria found in ores, soils and waters. The spread was mediated by different transposons and plasmids. Some of the spreading transposons were damaged in different ways but this did not prevent their further spread. Certain transposons are mosaics composed of segments belonging to distinct sequence types. These mosaics arose as a result of homologous and site-specific recombination. Our data suggest that the mercury-resistance operons of Gram-negative environmental bacteria can be considered as a worldwide population composed of a relatively small number of distinct recombining clones shared, at least partially, by environmental and clinical bacteria.     

Expression of cecropin P1 gene increases resistance of Camelina sativa (L.) plants to microbial phytopathogenes

Transgenic plants of camelina (Camelina sativa (L.) Crantz) with the synthetic gene of antimicrobial peptide cecropin P1 (cecP1) were obtained. Agrobacterium-mediated transformation is performed using the binary vector pGA482::cecP1 by vacuum infiltration of flower buds. The presence of the cecP1 gene in the genome of plants was confirmed by PCR. CecP1 gene expression in transgenic plants was shown by Western blot analysis and by antimicrobial activity of plant extracts against the bacterial phytopathogene Erwinia carotovora. The plants of F₀ and F₁ generations had the normal phenotype and retained the ability to form viable seeds in self-pollination. cecP1 plants exhibit enhanced resistance to bacterial and fungal phytopathogens: Erwinia carotovora and Fusarium sporotrichioides. The increased sustainability of cecropin P1-expressing plants against salt stress is shown. The possibility of the integration of the cecP1 gene into the overall protective system of plants against biotic and abiotic stresses is discussed.     

Distribution of transposons Tn<Emphasis Type="Italic">5044</Emphasis> and Tn<Emphasis Type="Italic">5070</Emphasis> with noncanonical <Emphasis Type="Italic">mer</Emphasis> operons in environmental bacterial populations

The distribution of noncanonical mercury resistance transposons, Tn5044 and Tn5070 , was examined. A characteristic feature of Tn5044 is temperature sensitivity of its mercury operon and the presence in the mer operon of the gene homologous to RNA polymerase subunit. Structural organization of mercury operon Tn5070 , containing minimum gene set (merRTPA), differs from mer operons of both Gram-negative and Gram-positive bacteria. None of more than two thousand environmental bacterial strains displaying mercury resistance and isolated from the samples selected from different geographical regions hybridized to Tn5044- and Tn5070-specific probes. A concept on the existence of cosmopolite, endemic, and rare transposons in environmental bacterial populations was formulated.Translated from Genetika, Vol. 40, No. 12, 2004, pp. 1717–1721.Original Russian Text Copyright © 2004 by Gorlenko, Kalyaeva, Bass, Petrova, Mindlin.     

Mercury-Resistant Bacteria from Permafrost Sediments and Prospects for their Use in Comparative Studies of Mercury Resistance Determinants

Mercury-resistant bacteria were isolated from permafrost sediments of Kolyma lowland and Canada existing over five thousand to two million years. Their content was shown to vary within the range 0.001–2.9% and to depend on the amount of mercury in sampling sites (coefficient of correlation 0.75). A collection of mercury-resistant bacterial strains was created. In this collection, various representatives of both Gram-positive bacteria (Bacillus, Exiguobacterium, Micrococcus, Arthrobacter) and Gram-negative bacteria (Pseudomonas, Acinetobacter, Plesiomonas, Myxobacteriales) were identified. Most resistant bacteria were found to contain determinants homologous to mer-operons of contemporary bacteria. The isolated strains of paleobacteria are proposed to be used for a comparative structural study of contemporary and ancient plasmids and transposons carrying mercury resistance determinants.