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  • 1
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The prevalence of selected streptomycin (Sm)-resistance genes, i.e. aph (3″), aph (6)-1d, aph (6)-1c, ant (3″) and ant (6), was assessed in a range of pristine as well as polluted European habitats. These habitats included bulk and rhizosphere soils, manure from farm animals, activated sludge from wastewater treatment plants and seawater. The methods employed included assessments of the prevalence of the genes in habitat-extracted DNA by PCR, followed by hybridisation with specific probes, Sm-resistant culturable bacteria and exogenous isolation of plasmids carrying Sm-resistance determinants. The direct DNA-based analysis showed that aph (6)-1d genes were most prevalent in the habitats examined. The presence of the other four Sm-modifying genes was demonstrated in 58% of the tested habitats. A small fraction of the bacterial isolates (8%) did not possess any of the selected Sm-modifying genes. These isolates were primarily obtained from activated sludge and manure. The presence of Sm-modifying genes in the isolates often coincided with the presence of IncP plasmids. Exogenous isolation demonstrated the presence of plasmids of 40–200 kb in size harbouring Sm-resistance genes from all the environments tested. Most plasmids were shown to carry the ant (3″) gene, often in combination with other Sm-resistance genes, such as aph (3″) and aph (6)-1d. The most commonly found Sm-modifying gene on mobile genetic elements was ant (3″). Multiple Sm-resistance genes on the same genetic elements appeared to be the rule rather than the exception. It is concluded that Sm-resistance genes are widespread in the environmental habitats studied and often occur on mobile genetic elements and ant (3″) was most often encountered.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 68 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The response of eight species of unicellular cyanobacteria to growth under high and low CO2 regimes was measured by RuBisCO activity and the extent of inorganic carbon concentration. No significant increase in RuBisCO activity in CO2-limited batch cultures was observed. The main feature of the data presented is the absence of a bicarbonate concentrating process in the oceanic, phycoerythrin-containing species examined, this is discussed in light of bicarbonate supply in freshwater and ocean environments.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 4 (1978), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Thiobacillus versutus responds to both CO2-limitation and increase in chemostat dilution rate under thiosulphate-limitation by increasing ribulose bisphosphate carboxylase specific activity. It has no high affinity CO2-concentrating mechanism like that shown in Synechococcus, and may depend on diffusional uptake of CO2/HCO3−.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9699
    Keywords: Streptomyces ; ecology ; soil microcosm ; survival ; metabolic activity ; plasmids ; conjugation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth and activity of introduced (S. lividans TK24 pIJ673 and S.lividans TK23) and indigenous (S.griseus CAG17) streptomycete strains in soil was studied, under controlled conditions. The effect of environmental parameters such as temperature, soil water content and nutrient availability on the growth and activity of these strains, was studied using a highly dynamic fed-batch soil microcosm system. Using this new system, repeated cycles of active streptomycete growth were achieved, allowing long-term investigation of metabolic activity, plasmid stability and conjugative plasmid transfer. In long-term experiments, respiration rates and enzyme activity patterns matched the pattern of germination/sporulation cycles of the inoculants. In situ hybridisation, using fluorescently labelled oligonucleotides, also proved the presence of metabolically active streptomycete mycelia in sterile soil. Plasmid stability under varying temperatures and selective pressure was studied using the above system. In both sterile and non sterile amended antibiotic containing soil, no intraspecific transfer of plasmid pIJ673 from S.lividans TK24 to S.griseus CAG17 was detected. The soil microcosm system used, though, permitted detection of intraspecific conjugative transfer of this plasmid from S.lividans TK24 to S.lividans TK23 in soil.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Antonie van Leeuwenhoek 78 (2000), S. 323-329 
    ISSN: 1572-9699
    Keywords: gene transfer ; plasmids ; Streptomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies were made of naturally occurring plasmids hosted in Streptomyces strains isolated from two different terrestrial ecosystems: an agricultural field and a protected forest area. Six out of the 147 screened isolates contained plasmids. The strains containing these plasmids were all isolated from the agricultural soil. Plasmids were not found among the strains isolated from the forest area. Cross hybridization of the six newly isolated plasmids revealed very high similarities between four of them. However, no similarities were found between the six newly isolated plasmids and well studied streptomycete plasmids such as pIJ101 and SCP2*. The host strains of the four similar plasmids belonged to three different species S. anulatus, S. rochei and S. diastaticus. This implies a possible conjugative transfer of these plasmids within the streptomycete population in the agricultural area. The reason for the absence of streptomycete plasmids from the populations derived from the forest area is discussed.
    Type of Medium: Electronic Resource
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