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  • 1
    ISSN: 1600-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Fluorosis of the primary dentition was determined in 146 children living in a hot, dry African village with a fluoride concentration in the drinking water of 0.98–2.7 ppm. The prevalence of fluorosis was compared using Dean's (8) and Thylstrup & Fejerskov's (14) indices. The prevalence varied according to tooth type, being highest in maxillary second molars (25%) and lowest in mandibular central incisors (4.6%). The two scoring systems produced almost identical prevalences of fluorosis but the severity scores varied. Generally Thylstrup & Fejerskov's index scores were one score higher than Dean's. The Thylstrup & Fejerskov index is recommended for future studies.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The nptII+ gene present in the genome of transgenic potato plants transforms naturally competent cells of the soil bacteria Pseudomonas stutzeri and Acinetobacter BD413 (both harboring a plasmid with an nptII gene containing a small deletion) with the same high efficiency as nptII+ genes on plasmid DNA (3×10−5–1×10−4 transformants per nptII+) despite the presence of a more than 106-fold excess of plant DNA. However, in the absence of homologous sequences in the recipient cells the transformation by nptII+ dropped by at least about 108-fold in P. stutzeri and 109-fold in Acinetobacter resulting in the latter strain in ≤1×10−13 transformants per nptII+. This indicated a very low probability of non-homologous DNA fragments to be integrated by illegitimate recombination events during transformation.
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Acquisition of new genetic information by horizontal gene transfer is a major mechanism of genetic adaptation and evolution in prokaryotes. Naturally transformable cells of Acinetobacter sp. were exposed to plant DNA from leaf and root tissue of transplastomic tobacco. With the aadA gene (resistance against spectinomycin and streptomycin) as anchor se-quence, the transfer of segments of the tobacco plastid DNA to Acinetobacter by homology-facilitated illegitimate recombination occurred at a frequency of 1.2 × 10−7 per cell, which was about 0.1% of the frequency of fully homologous transfers. Without anchor sequence, transfer was not detected (≤1.3 × 10−10). The integrated plastid DNA segments extended up to 2539 nucleotides and often encompassed tobacco genes (trnL, ycf5). Expression of trnL (leucyl-tRNA) in a transformant was shown by reverse transcription polymerase chain reaction. About 44% of integration events occurred at a single hot-spot and 38% at other multiply used sites. All illegitimate recombination sites were GC-rich microhomologies of 3–6 bp often neighboured by further microhomologies. The sites were located in plant DNA at the ends of distinct larger high-GC regions, which suggests a role for GC-aided association of heterologous sequences in illegitimate DNA end joining. The results show that integration of plant DNA into a bacterial genome by natural transformation is possible and is probably stimulated by hot-spots of illegitimate recombination.
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  • 4
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In a field release experiment, rifampicin resistant mutants of two antagonistic plant-associated bacteria were used for seed tuber inoculation of transgenic T4 lysozyme expressing potatoes, transgenic control potatoes and non-transgenic parental potatoes. The T4 lysozyme tolerant Pseudomonas putida QC14-3-8 was originally isolated from the tuber surface (geocaulosphere) of T4 lysozyme producing plants and showed in vitro antibacterial activity to the bacterial pathogen Erwinia carotovora ssp. atroseptica. The T4 lysozyme sensitive Serratia grimesii L16-3-3 was originally isolated from the rhizosphere of parental potatoes and showed in vitro antagonism toward the plant pathogenic fungus Verticillium dahliae. The establishment of the inoculated bacteria in the rhizosphere and geocaulosphere of the different plant lines was monitored over one growing season to assess the effect of T4 lysozyme produced by transgenic potato plants on the survival of both inoculants. Both introduced isolates were able to colonize the rhizo- and geocaulosphere of transgenic plants and non-transgenic parental plants, and established in the rhizosphere at levels of ca. log10 5 colony forming units g−1 fresh weight of root. During flowering of plants, significantly more colony counts of the T4 lysozyme tolerant P. putida were recovered from transgenic T4 lysozyme plants than from the transgenic control and the parental line. At this time, the highest level of T4 lysozyme (% of total soluble protein) was detected. Effects of the inoculants on the indigenous microbial community were monitored by analysis of PCR-amplified fragments of the 16S rRNA genes of the whole bacterial community after separation by denaturing gradient gel electrophoresis (DGGE). At any sampling time, the DGGE pattern of rhizosphere and geocaulosphere communities did not show differences between the inoculated and non-inoculated potatoes. Neither of the introduced strains became a dominant member of the bacterial community. This work was the first approach to assess the establishment of plant growth promoting rhizobacteria and potential biocontrol agents on transgenic plants.
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