Rhizosphere microbial communities associated to rose replant disease: links to plant growth and root metabolites.

Growth depression of Rosa plants at sites previously used to cultivate the same or closely related species is a typical symptom of rose replant disease (RRD). Currently, limited information is available on the causes and the etiology of RRD compared to apple replant disease (ARD). Thus, this study aimed at analyzing growth characteristics, root morphology, and root metabolites, as well as microbial communities in the rhizosphere of the susceptible rootstock Rosacorymbifera 'Laxa' grown in RRD-affected soil from two sites (Heidgraben and Sangerhausen), either untreated or disinfected by γ-irradiation. In a greenhouse bioassay, plants developed significantly more biomass in the γ-irradiated than in the untreated soils of both sites. Several plant metabolites detected in R. corymbifera 'Laxa' roots were site- and treatment-dependent. Although aloesin was recorded in significantly higher concentrations in untreated than in γ-irradiated soils from Heidgraben, the concentrations of phenylalanine were significantly lower in roots from untreated soil of both sites. Rhizosphere microbial communities of 8-week-old plants were studied by sequencing of 16S rRNA, ITS, and cox gene fragments amplified from total community DNA. Supported by microscopic observations, sequences affiliated to the bacterial genus Streptomyces and the fungal genus Nectria were identified as potential causal agents of RRD in the soils investigated. The relative abundance of oomycetes belonging to the genus Pythiogeton showed a negative correlation to the growth of the plants. Overall, the RRD symptoms, the effects of soil treatments on the composition of the rhizosphere microbial community revealed striking similarities to findings related to ARD.

Contribution of iron and protein contents from rat brain subcellular fractions to MR phase imaging.

PURPOSE: Investigation of magnetic susceptibility and chemical exchange as sources of MRI phase contrast between gray and white matter resulting from protein and iron content from subcellular fractions. METHODS: This study analyzes the iron and macromolecule content of different subcellular fractions from rat brain and their relation to the water-resonance frequency by NMR spectroscopy. Additionally, the contributions of susceptibility and exchange were determined with different NMR reference substances. RESULTS: Only weak correlations between iron (r = 0.4318, P = 0.76) or protein content (r = 0.4704, P = 0.70) and frequency shift were observed. After membrane depletion, the correlation for iron increased to r = -0.9006 (P = 0.0009), whereas the shift relative to protein content increased much less (r = -0.4982, P = 0.64). Exchange-driven frequency shifts were 1.283 ppb/(mg/ml) for myelin and 0.775 ppb/(mg/ml) for synaptosomes; susceptibility-driven shifts were -1.209 ppb/(mg/ml) for myelin and -0.368 ppb/(mg/ml) for synaptosomes. The ratios between susceptibility and exchange differ significantly from simple protein solutions. CONCLUSIONS: As a result of counteracting susceptibility and exchange and increased relative shifts in membrane-depleted fractions, we conclude that tissue microstructure accounts more for the in vivo phase contrast than in the situation of homogenized tissue. Thus, membranes may generate much of the in vivo MR phase contrast resulting from anisotropy. Magn Reson Med 77:2028-2039, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Root exudation and root development of lettuce (Lactuca sativa L. cv. Tizian) as affected by different soils.

Development and activity of plant roots exhibit high adaptive variability. Although it is well-documented, that physicochemical soil properties can strongly influence root morphology and root exudation, particularly under field conditions, a comparative assessment is complicated by the impact of additional factors, such as climate and cropping history. To overcome these limitations, in this study, field soils originating from an unique experimental plot system with three different soil types, which were stored at the same field site for 10 years and exposed to the same agricultural management practice, were used for an investigation on effects of soil type on root development and root exudation. Lettuce (Lactuca sativa L. cv. Tizian) was grown as a model plant under controlled environmental conditions in a minirhizotrone system equipped with root observation windows (rhizoboxes). Root exudates were collected by placing sorption filters onto the root surface followed by subsequent extraction and GC-MS profiling of the trapped compounds. Surprisingly, even in absence of external stress factors with known impact on root exudation, such as pH extremes, water and nutrient limitations/toxicities or soil structure effects (use of sieved soils), root growth characteristics (root length, fine root development) as well as profiles of root exudates were strongly influenced by the soil type used for plant cultivation. The results coincided well with differences in rhizosphere bacterial communities, detected in field-grown lettuce plants cultivated on the same soils (Schreiter et al., this issue). The findings suggest that the observed differences may be the result of plant interactions with the soil-specific microbiomes.

Tumor cell uptake of 99mTc-labeled 1-thio-ß-D-glucose and 5-thio-D-glucose in comparison with 2-deoxy-2-[18F]fluoro-D-glucose in vitro: kinetics, dependencies, blockage and cell compartment of accumulation.

PURPOSE: This study was conducted to investigate the capacity of (99m)Tc-labeled 1-thio-ß-D-glucose ((99m)Tc-1-TG) and 5-thio-D-glucose ((99m)Tc-5-TG) to act as a marker for glucose metabolism in tumor cells in vitro. PROCEDURES: We investigated the cellular uptake of (99m)Tc-1-TG, (99m)Tc-5-TG, and 2-deoxy-2-[(18)F]fluoro-D-glucose((18)F-FDG) in a human colorectal carcinoma and human lung adenocarcinoma cell line (HCT-116, A549) at different time points and varying glucose/insulin concentrations and under transporter blockage by cytochalasin-B and phloretin. Cell compartment analysis was performed. RESULTS: A significant uptake and time dependency thereof, a significant uptake dependency on glucose and insulin and a significant uptake inhibition by cytochalasin-B for (99m)Tc-1-TG and (99m)Tc-5-TG, was shown. Albeit substantial, the uptake was less pronounced in (99m)Tc-1-TG and (99m)Tc-5-TG compared with (18)F-FDG. (99m)Tc-1-TG and (99m)Tc-5-TG showed a higher accumulation in the cell membranes compared with (18)F-FDG. CONCLUSION: Tc-1-TG and (99m)Tc-5-TG showed an uptake in vitro with glucose analog characteristics but with membranous accumulation. Tumor imaging should be investigated in an animal model.

Detection of Acidovorax valerianellae, the causing agent of bacterial leaf spots in corn salad [Valerianella locusta (L.) Laterr.], in corn salad seeds.

AIM: The black leaf spot disease on corn salad caused by the bacterium Acidovorax valerianellae has been observed in Europe for several years and causes economic losses in corn salad cropping. Contaminated seeds or infested soil are considered as the major infection sources. The use of healthy seed material is the only way to prevent disease outbreaks. Therefore, a sensitive diagnostic method for seed testing should be developed. METHODS AND RESULTS: Using a triple antibody sandwich ELISA with a high-specific monoclonal antibody, a quick and reliable detection method for contamination of seed lots with the pathogen was developed. This method allowed to detect contaminated seed lots as well as contamination with A. valerianellae in single seeds. Furthermore, the occurrence and distribution of the pathogen could be shown in symptomatic corn salad leaves and in naturally infested seeds by transmission electron microscopy and immunogold labelling for the first time. CONCLUSION: Our results confirm the seed transmission of this corn salad disease. Pathogen load and distribution vary between positively tested seed lots. SIGNIFICANCE AND IMPACT OF THE STUDY: With this method, not only routine testing of seed material to eliminate contaminated seed lots from production is possible but also the control of sanitation procedures to reduce contamination.

Inter-laboratory evaluation of the ISO standard 11063 "Soil quality - Method to directly extract DNA from soil samples".

Extracting DNA directly from micro-organisms living in soil is a crucial step for the molecular analysis of soil microbial communities. However, the use of a plethora of different soil DNA extraction protocols, each with its own bias, makes accurate data comparison difficult. To overcome this problem, a method for soil DNA extraction was proposed to the International Organization for Standardization (ISO) in 2006. This method was evaluated by 13 independent European laboratories actively participating in national and international ring tests. The reproducibility of the standardized method for molecular analyses was evaluated by comparing the amount of DNA extracted, as well as the abundance and genetic structure of the total bacterial community in the DNA extracted from 12 different soils by the 13 laboratories. High quality DNA was successfully extracted from all 12 soils, despite different physical and chemical characteristics and a range of origins from arable soils, through forests to industrial sites. Quantification of the 16S rRNA gene abundances by real time PCR and analysis of the total bacterial community structure by automated ribosomal intergenic spacer analysis (A-RISA) showed acceptable to good levels of reproducibility. Based on the results of both ring-tests, the method was unanimously approved by the ISO as an international standard method and the normative protocol will now be disseminated within the scientific community. Standardization of a soil DNA extraction method will improve data comparison, facilitating our understanding of soil microbial diversity and soil quality monitoring.

Effects of Cd- and Zn-enriched sewage sludge on soil bacterial and fungal communities.

The effects of sewage sludge selectively enriched with Cd and Zn, both singly and in combination, on the bacterial, fungal, Alphaproteobacteria and Actinobacteria communities of a soil under arable or grassland management were studied with a PCR-DGGE approach. The effects of Cd and Zn were evaluated after a short time (7 d) when the Cd and Zn solubility were low and the C availability was high, and again after 180 d when the labile sludge C was mineralized and the effects of heavy metals predominated. In the arable soil all treatments induced significant short-term changes in the studied microbial groups, and long-term changes were observed in Actinobacteria and fungal communities. In the grassland soil, all treatments induced significant short-term changes in the studied microbial groups except for Alphaproteobacteria and fungi, and long-term effects on the actinobacteria and fungal communities. It was concluded that incorporation of Cd- and Zn-rich sludge into soils may have both short- and long-term effects on various bacterial phylogenetic groups whereas the metals may be better tolerated by the dominant soil fungi. In this study the impact was greater in arable than in grassland soil.

A comparison of the synaptic proteome in human chronic schizophrenia and rat ketamine psychosis suggest that prohibitin is involved in the synaptic pathology of schizophrenia.

Many studies in recent years suggest that schizophrenia is a synaptic disease that crucially involves a hypofunction of N-methyl-D-aspartate receptor-mediated signaling. However, at present it is unclear how these pathological processes are reflected in the protein content of the synapse. We have employed two-dimensional gel electrophoresis in conjunction with mass spectrometry to characterize and compare the synaptic proteomes of the human left dorsolateral prefrontal cortex in chronic schizophrenia and of the cerebral cortex of rats treated subchronically with ketamine. We found consistent changes in the synaptic proteomes of human schizophrenics and in rats with induced ketamine psychosis compared to controls. However, commonly regulated proteins between both groups were very limited and only prohibitin was found upregulated in both chronic schizophrenia and the rat ketamine model. Prohibitin, however, could be a new potential marker for the synaptic pathology of schizophrenia and might be causally involved in the disease process.

Specific and sensitive detection of Ralstonia solanacearum in soil on the basis of PCR amplification of fliC fragments.

Ralstonia solanacearum is the causative agent of bacterial wilt in many important crops. A specific and sensitive PCR detection method that uses primers targeting the gene coding for the flagella subunit, fliC, was established. Based on the first fliC gene sequence of R. solanacearum strain K60 available at GenBank, the Ral_fliC PCR primer system was designed; this system yielded a single 724-bp product with the DNAs of all of the R. solanacearum strains tested. However, R. pickettii and four environmental Ralstonia isolates also yielded amplicons. The Ral_fliC PCR products obtained with 12 strains (R. solanacearum, R. pickettii, and environmental isolates) were sequenced. By sequence alignment, Rsol_fliC primers specific for R. solanacearum were designed. With this primer system, a specific 400-bp PCR product was obtained from all 82 strains of R. solanacearum tested. Six strains of R. pickettii and several closely related environmental isolates yielded no PCR product; however, a product was obtained with one Pseudomonas syzygii strain. A GC-clamped 400-bp fliC product could be separated in denaturing gradient gels and allowed us to distinguish P. syzygii from R. solanacearum. The Rsol_fliC PCR system was applied to detect R. solanacearum in soil. PCR amplification, followed by Southern blot hybridization, allowed us to detect about one target DNA molecule per PCR, which is equivalent to 10(3) CFU g of bulk soil(-1). The system was applied to survey soils from different geographic origins for the presence of R. solanacearum.

Effects of compost addition and simulated solarisation on the fate of Ralstonia solanacearum biovar 2 and indigenous bacteria in soil.

Abstract The effects of compost addition and simulated solarisation of soil on the survival of Ralstonia solanacearum biovar 2 strain 1609, as well as on the structure of indigenous soil bacterial communities, were analysed. In addition, effects on the invasion of susceptible test plants by strain 1609 were assessed. In untreated soil in microcosms and the field, strain 1609 showed slow progressive declines, from 10(6)-10(7) to roughly 10(4)-10(5) CFU per g dry soil in around 60 days. When these soils were used in suppressiveness tests, a majority of plants developed symptoms of wilting and revealed the presence of the pathogen in their lower stem parts, as evidenced by immunofluorescence colony staining (IFC) and polymerase chain reaction (PCR). Solarisation of unamended soil did not drastically affect R. solanacearum survival or plant invasiveness. However, the addition of household compost resulted in enhanced R. solanacearum population decline rates, as well as reduced numbers of diseased plants in suppressiveness tests. Combined solarisation and compost addition yielded differential results between microcosms and the field. Some healthy-looking plants, primarily from soils treated with compost, revealed the latent presence of strain 1609 in the lower stem parts. The eubacterial and beta-subgroup proteobacterial communities in the differentially treated soil microcosms were rather stable, as evidenced by analysis of PCR-denaturing gradient gel electrophoresis (DGGE) generated molecular profiles. However, compost amendment clearly induced changes in these communities, which were detectable until the end of the experiment; two major bands, affiliated with Variovorax paradoxus and Aquaspirillum psychrophylum, were associated with the compost amendment. The decrease in abundance of R. solanacearum in the compost-amended soils was confirmed by the DGGE profiles.

The neuron-specific Ca2+-binding protein caldendrin: gene structure, splice isoforms, and expression in the rat central nervous system.

Caldendrin is the founder member of a recently discovered family of calmodulin-like proteins, which are highly abundant in brain. In this study we examined the organization of the murine and human caldendrin gene as well as the expression pattern of transcripts for caldendrin and two novel splice variants. In addition the distribution of caldendrin in rat brain has been assessed by immunohistochemistry. Caldendrin is localized to the somatodendritic compartment of a subpopulation of mainly principal neurons in brain regions with a laminar organization and is present only at a subset of mature excitatory synapses. Caldendrin immunoreactivity (IR) is tightly associated with the cortical cytoskeleton, enriched in the postsynaptic density (PSD) fraction, and associates late during development with the synaptic cytomatrix. The expression is highly heterogenous within cortex, with highest levels of caldendrin IR in layer III of the piriform and layer II/III of the somatosensory cortex. The segregated cortical distribution to areas, which represent the most important primary sensory systems of the rodent brain, may reflect different requirements for dendritic Ca2+-signaling in these neurons. The presence of caldendrin in the PSD of distinct synapses may have important implications for Ca2+-modulated processes of synaptic plasticity.

Gentamicin resistance genes in environmental bacteria: prevalence and transfer.

A comprehensive multiphasic survey of the prevalence and transfer of gentamicin resistance (Gm(r)) genes in different non-clinical environments has been performed. We were interested to find out whether Gm(r) genes described from clinical isolates can be detected in different environmental habitats and whether hot spots can be identified. Furthermore, this study aimed to evaluate the impact of selective pressure on the abundance and mobility of resistance genes. The study included samples from soils, rhizospheres, piggery manure, faeces from cattle, laying and broiler chickens, municipal and hospital sewage water, and coastal water. Six clusters of genes coding for Gm-modifying enzymes (aac(3)-I, aac(3)-II/VI, aac(3)-III/IV, aac(6')-II/Ib, ant(2'')-I, aph(2'')-I) were identified based on a database comparison and primer systems for each gene cluster were developed. Gm-resistant bacteria isolated from the different environments had a different taxonomic composition. In only 34 of 207 isolates, mainly originating from sewage, faeces and coastal water polluted with wastewater, were known Gm(r) genes corresponding to five of the six clusters detected. The strains belonged to genera in which the genes had previously been detected (Enterobacteriaceae, Pseudomonas, Acinetobacter) but also to phylogenetically distant bacteria, such as members of the CFB group, alpha- and beta-Proteobacteria. Gm(r) genes located on mobile genetic elements (MGE) could be captured in exogenous isolations into recipients belonging to alpha-, beta- and gamma-Proteobacteria from all environments except for soil. A high proportion of the MGE, conferring Gm resistance isolated from sewage, were identified as IncPbeta plasmids. Molecular detection of Gm(r) genes, and broad host range plasmid-specific sequences (IncP-1, IncN, IncW and IncQ) in environmental DNA indicated a habitat-specific dissemination. A high abundance and diversity of Gm(r) genes could be shown for samples from faeces (broilers, layers, cattle), from sewage, from seawater, collected close to a wastewater outflow, and from piggery manure. In the latter samples all six clusters of Gm(r) genes could be detected. The different kinds of selective pressure studied here seemed to enhance the abundance of MGE, while an effect on Gm(r) genes was not obvious.

Bulk and rhizosphere soil bacterial communities studied by denaturing gradient gel electrophoresis: plant-dependent enrichment and seasonal shifts revealed.

The bacterial rhizosphere communities of three host plants of the pathogenic fungus Verticillium dahliae, field-grown strawberry (Fragaria ananassa Duch.), oilseed rape (Brassica napus L.), and potato (Solanum tuberosum L.), were analyzed. We aimed to determine the degree to which the rhizosphere effect is plant dependent and whether this effect would be increased by growing the same crops in two consecutive years. Rhizosphere or soil samples were taken five times over the vegetation periods. To allow a cultivation-independent analysis, total community DNA was extracted from the microbial pellet recovered from root or soil samples. 16S rDNA fragments amplified by PCR from soil or rhizosphere bacterium DNA were analyzed by denaturing gradient gel electrophoresis (DGGE). The DGGE fingerprints showed plant-dependent shifts in the relative abundance of bacterial populations in the rhizosphere which became more pronounced in the second year. DGGE patterns of oilseed rape and potato rhizosphere communities were more similar to each other than to the strawberry patterns. In both years seasonal shifts in the abundance and composition of the bacterial rhizosphere populations were observed. Independent of the plant species, the patterns of the first sampling times for both years were characterized by the absence of some of the bands which became dominant at the following sampling times. Bacillus megaterium and Arthrobacter sp. were found as predominant populations in bulk soils. Sequencing of dominant bands excised from the rhizosphere patterns revealed that 6 out of 10 bands resembled gram-positive bacteria. Nocardia populations were identified as strawberry-specific bands.

Kainate-induced seizures alter protein composition and N-methyl-D-aspartate receptor function of rat forebrain postsynaptic densities.

The postsynaptic density is a highly dynamic structure, which is reorganized in an activity-dependent manner. An animal model for temporal lobe epilepsy, i.e. kainate-induced limbic seizures in rats, was used to study changes in postsynaptic density composition after extensive synaptic activity. Six hours after kainate injection, the protein content of the postsynaptic density fractions from rats that developed strong seizures was increased three-fold compared to saline-treated controls. Immunoblot analysis revealed that the relative amounts of metabotropic glutamate receptor 1alpha, N-ethylmaleimide-sensitive fusion protein, protein kinases C, Fyn and TrkB, as well as the neuronal nitric oxide synthase, were significantly higher in seizure-developing than in control rats. In contrast, the relative contents of the kainate receptor KA2 subunit, beta-actin, alpha-adducin and the membrane-associated guanylate kinase homolog SAP90/PSD-95 were decreased. The relative amounts of additional postsynaptic density proteins, including alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and N-methyl-D-aspartate receptor subunits, calcium/calmodulin-dependent kinase type II, casein kinase 2, tubulin, microtubule-associated protein 2B, the membrane-associated guanylate kinase homolog SAP102, and proline-rich synapse-associated protein 1/cortactin binding protein 1/Shank2 remained essentially unchanged. To assess possible changes in postsynaptic performance, postsynaptic densities were isolated from control and epileptic rats, incorporated into giant liposomes and N-methyl-D-aspartate receptor currents were recorded. A significant reduction in the mean conductance was observed in patches containing postsynaptic densities from animals with high seizure activity. This was due to the presence of reduced conductance levels in each membrane patch compared to control postsynaptic density preparations. From these data, we suggest that intense synaptic activity associated with seizures modifies the composition of postsynaptic densities and has profound consequences on the function of the N-methyl-D-aspartate receptors present in them. This rearrangement may accompany impairment of synaptic plasticity.

Evaluation of potential biocontrol rhizobacteria from different host plants of Verticillium dahliae Kleb.

AIMS: A screening approach was developed to assess the potential of rhizobacterial strains to control Verticillium wilt caused by Verticillium dahliae Kleb. METHODS AND RESULTS: Sixty randomly chosen antagonistic bacterial strains originally isolated from rhizosphere of three different host plants of V. dahliae--strawberry, potato and oilseed rape--were evaluated for biocontrol and plant growth promotion by analysing in vitro antagonism towards V. dahliae and other plant pathogenic fungi, production of fungal cell wall-degrading enzymes and plant growth-promoting effects on strawberry seedlings. To test the plant growth-promoting effect, a microplate assay with strawberry seedlings was developed. Although the rhizobacterial strains were isolated from different plants they showed effects on the growth of strawberry seedlings. According to the in vitro biocontrol and plant growth-promoting activity, the three best candidates Pseudomonas putida B E2 (strawberry rhizosphere), Ps. chlororaphis K15 (potato rhizosphere) and Serratia plymuthica R12 (oilseed rape rhizosphere) were selected for greenhouse experiments to verify the in vitro screening results. Under greenhouse conditions the isolates selected according to this strategy were as effective, or more effective than commercial biocontrol agents and may therefore possibly be valuable as antagonists of V. dahliae. CONCLUSIONS: In this study, the screening strategy resulted in a selection of three interesting biocontrol candidates against Verticillium: Ps. putida B E2 (strawberry rhizosphere), Ps. chlororaphis K15 (potato rhizosphere) and Ser. plymuthica R12 (oilseed rape rhizosphere). SIGNIFICANCE AND IMPACT OF THE STUDY: A new combination of in vitro screening methods including a microplate assay with strawberry seedlings to test the plant growth promoting effect which allow to more efficiently select potential biological control agents was developed successfully.

Neuroma: a donor-age independent source of human Schwann cells for tissue engineered nerve grafts.

Schwann cells are used in combination with biological matrices as tissue engineered nerve grafts in animal models offering a new therapeutic approach for treatment of lesions of the peripheral nervous system. A high yield of human Schwann cells from adult donors is only achieved by pharmacological stimulation, which should, however, be avoided in clinical therapy. Here, we establish cultures of activated human Schwann cells which were isolated from peripheral nerve neuroma which developed after a median nerve lesion. To allow nerve reconstruction neuroma have to be resected. Such neuroma tissue is virtually predegenerated and shows activation of Schwann cells, implying good adherence and high mitotic activity. This allows, irrespective of donor age, growing within a short time period and without any pharmacological treatment.

Neuronal nicotinic acetylcholine receptors of Drosophila melanogaster: the alpha-subunit dalpha3 and the beta-type subunit ARD co-assemble within the same receptor complex.

Dalpha3 is a functional alpha-subunit of Drosophila melanogaster nicotinic acetylcholine receptors (nAChRs). Here, we produced Dalpha3-specific antibodies to study which other nAChR subunits can co-assemble with Dalpha3 in receptor complexes of the Drosophila nervous system. Immunohistochemical studies revealed that Dalpha3 is co-distributed with the beta-subunit ARD in synaptic neuropil regions of the optic lobe. Both subunits can be co-purified by alpha-bungarotoxin affinity chromatography. Dalpha3 antibodies co-immunoprecipitate Dalpha3 and ARD proteins and, vice versa, anti-ARD antibodies co-precipitate ARD and Dalpha3. These data demonstrate that one type of fly nAChRs includes these two subunits as integral components.

Exogenous isolation of antibiotic resistance plasmids from piggery manure slurries reveals a high prevalence and diversity of IncQ-like plasmids.

Antibiotic resistance plasmids were exogenously isolated in biparental matings with piggery manure bacteria as plasmid donors in Escherichia coli CV601 and Pseudomonas putida UWC1 recipients. Surprisingly, IncQ-like plasmids were detected by dot blot hybridization with an IncQ oriV probe in several P. putida UWC1 transconjugants. The capture of IncQ-like plasmids in biparental matings indicates not only their high prevalence in manure slurries but also the presence of efficiently mobilizing plasmids. In order to elucidate unusual hybridization data (weak or no hybridization with IncQ repB or IncQ oriT probes) four IncQ-like plasmids (pIE1107, pIE1115, pIE1120, and pIE1130), each representing a different EcoRV restriction pattern, were selected for a more thorough plasmid characterization after transfer into E. coli K-12 strain DH5alpha by transformation. The characterization of the IncQ-like plasmids revealed an astonishingly high diversity with regard to phenotypic and genotypic properties. Four different multiple antibiotic resistance patterns were found to be conferred by the IncQ-like plasmids. The plasmids could be mobilized by the RP4 derivative pTH10 into Acinetobacter sp., Ralstonia eutropha, Agrobacterium tumefaciens, and P. putida, but they showed diverse patterns of stability under nonselective growth conditions in different host backgrounds. Incompatibility testing and PCR analysis clearly revealed at least two different types of IncQ-like plasmids. PCR amplification of total DNA extracted directly from different manure samples and other environments indicated the prevalence of both types of IncQ plasmids in manure, sewage, and farm soil. These findings suggest that IncQ plasmids play an important role in disseminating antibiotic resistance genes.

Genotypic and phenotypic differentiation of an antifungal biocontrol strain belonging to Bacillus subtilis.

Physiological and molecular fingerprints of biotechnologically relevant rhizobacteria are necessary for registration, patenting, recognition and quality checking of the strains. To characterize the biological control agent, Bacillus subtilis B2g, the strain was compared with other plant-associated B. subtilis isolates. Phenotypic characterization included biochemical and nutritional properties, in vitro activity and analysis of potential antagonistic mechanisms towards several plant pathogenic fungi. According to the phenotypic characteristics, it was not possible to differentiate the biocontrol agent from the other strains, although the enzymatic fingerprint was unique. Genotypic diversity among the isolates was characterized by molecular fingerprinting methods using REP-PCR (repetitive extragenomic palindromic PCR), and macrorestriction of genomic DNA and electrophoretic separation of DNA fragments by pulsed-field gel electrophoresis (PFGE). A protocol for PFGE analysis using restriction enzyme SfiI for B. subtilis was developed. PFGE typing of B. subtilis B2g resulted in a unique fingerprint. Therefore, it was possible to differentiate B. subtilis B2g, the biocontrol agent of Phytovit, from other antifungal B. subtilis isolates.