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The Caenorhabditis elegans assay: a tool to evaluate the pathogenic potential of bacterial biocontrol agents

European Journal of Plant Pathology (Impact Factor: 1.71). 11/2009; 125(3):367-376. DOI: 10.1007/s10658-009-9486-3

ABSTRACT Bacterial biocontrol agents (BCAs) open up the possibility of controlling plant pathogens in an environmentally friendly way.
Although they are naturally occurring microbes, some of them can cause diseases in humans. For successful registration it
is necessary to test potentially adverse effects on the human health of at-risk candidates. Existing pathogenicity assays
are cost-intensive, time-consuming and furthermore they are often inappropriate for facultative pathogens. We developed a
new, fast and inexpensive bioassay on the basis of the nematode Caenorhabditis elegans, which is a well-accepted model organism to study bacterial pathogenicity. A selection of eight strains from clinical and
environmental origin as well as potential and commercial BCAs from the genera Bacillus, Pseudomonas, Serratia and Stenotrophomonas were screened for their potential to kill the nematode in an in vitro agar plate assay. Furthermore, the motility and reproductive behaviour of nematodes exposed to strains were tested in comparison
with those fed by the human pathogen Pseudomonas aeruginosa QC14-3-8 (positive control) and the negative control Escherichia coli OP50. Commercial as well as potential biocontrol strains did not display any adverse effects in all tests. In contrast, the
C. elegans assay showed slight effects for clinical and environmental Stenotrophomonas strains. Results showed that the nematode C. elegans provides a model system to indicate the pathogenic potential of BCAs in a very early stage of product development.

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    • "The use of C. elegans is becoming increasingly popular in invertebrate animal testing of substances used in pharmaceutical or cosmetic applications (Leung et al. 2008). It is a widely accepted model organisms to test bacteria pathogenicity and has hence been proposed to test the newly emerging group of bacterial plant protection agents (Zachow et al. 2012). As well as testing undesirable side effects, C. elegans can be used to test desirable effects of pharmaceutic substances , since it can easily be genetically transformed to display typical elements of human diseases. "
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    ABSTRACT: While nematodes are most commonly known for their negative impact on plants, animals, and humans, there are a number of species which are commercially explored. This review highlights some of the most important success stories for the application of nematodes. They are used as bioindicators in ecological and toxicity studies, as model organisms for elucidating fundamental biological questions and for high throughput screening of drugs. Besides these indirect uses, direct applications include the use of Beddingia siricidicola against a major forest pest and the commercialization of Steinernema, Heterorhabditis, and Phasmarhabditis as biological pest control products. New directions for the commercialization of nematodes are the use as living food, specifically loaded with essential nutrients for various fish and shrimp larvae. Even human parasites or closely related species have been successfully used for curing autoimmune disorders and are currently in the process of being developed as drugs. With the striving development of life sciences, we are likely to see more applications for nematodes in the future. A prerequisite is that we continue to explore the vast number of yet undiscovered nematode species.
    Applied Microbiology and Biotechnology 06/2013; DOI:10.1007/s00253-013-4941-7 · 3.81 Impact Factor
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    • "In addition, strains able to grow at 37 • C, the temperature of the human body, should be rejected from further development as well (Fravel et al., 1999). Finally, the use of a bioassay with the nematode Caenorhabditis elegans can be a helpful tool for the evaluation of pathogenicity of the candidate strains (Zachow et al., 2009). It should be noted that the three methods described above provide a good impression of the safety of strains used in the development of a product. "
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    ABSTRACT: The development of microbial inoculants for specific crops is a multistage process with participation of scientific researchers and industry. The process starts with isolation/selection of potential strains with desired properties such as plant growth stimulation, enhancement of availability of vitally important nutrients and therefore improvement of plant nutrition, amelioration of biotic and abiotic stress, degradation of pollutants, and biological control of phytopathogenic microbes. Subsequent assessment of the potentially promising strains for safety, the development of industrial production protocols and suitable formulations, registration and marketing are the most costly and time consuming steps in product development. Elucidation of dominant properties of the strain will help to choose correct strategy for positioning of the product on the market of microbial inoculants. The evaluation of examples of selected products based on Trichoderma harzianum T22, Bacillus subtilis FZB24, Bacillus amyloliquefaciens FZB42 and Pseudomonas chlororaphis MA342 provides important insights of successful transfer of academically gained knowledge in commercially successful microbial products used worldwide. Major challenges in development, registration and marketing of microbial inoculants are discussed.
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    • "The four PGPR strains selected have different origins: Pseudomonas putida 1T1 was isolated from mosses (Opelt & Berg, 2004), P. trivialis 3Re27 from the endosphere of potato (Berg et al., 2005), P. extremorientalis TSAU20 from the wheat rhizozsphere (Egamberdieva & Kucharova, 2009) and Stenotrophomonas rhizophila ep-17 from the caulosphere of potato, (Lottmann et al., 1999). They all are known for their safe use in biotechnology (Faltin et al., 2004; Scherwinski et al., 2008; Zachow et al., 2009). "
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    ABSTRACT: Saline conditions are known to suppress the growth of crops. One possibility to circumvent this problem is to use root colonizing, salt tolerant bacterial inoculants, which can alleviate salt stress in plants. To evaluate the effect of different plant growth promoting rhizobacteria (PGPR) under salt stress conditions, the four strains Pseudomonas putida 1T1, Pseudomonas trivialis 3Re27, Pseudomonas extremorientalis TSAU20 and Stenotrophomonas rhizophila ep-17 were analysed on cucumber and tomato in pot experiments. Four salinity levels (2.5, 5.0, 7.5 and 10.0 dSm–1) were maintained in potting soil amended with NaCl. Results showed that PGPR inoculation, even at higher salinities (7.5 dSm–1), significantly increased dry weight of cucumber and tomato by on average 68% compared with noninoculated plants. All bacterial strains were salt tolerant, growing well with 3% NaCl in the growth medium, and survived in the rhizosphere , the numbers of Cfu being equal at salinity levels 0 – 7.5, All strains produced IAA under salt conditions in vitro. Due to the our results we recommend using of PGPRs as a seed dressing in the greenhouse and fields in order to improve the growth of cucumber and tomato in farmlands with a high soil salinity.
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