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Neufahrn bei Freising, Germany

Dorn-In S.,WZW | Bassitta R.,WZW | Bauer J.,WZW | Holzel C.S.,WZW
Journal of Microbiological Methods | Year: 2015

Universal primers targeting the bacterial 16S-rRNA-gene allow quantification of the total bacterial load in variable sample types by qPCR. However, many universal primer pairs also amplify DNA of plants or even of archaea and other eukaryotic cells. By using these primers, the total bacterial load might be misevaluated, whenever samples contain high amounts of non-target DNA. Thus, this study aimed to provide primer pairs which are suitable for quantification and identification of bacterial DNA in samples such as feed, spices and sample material from digesters. For 42 primers, mismatches to the sequence of chloroplasts and mitochondria of plants were evaluated. Six primer pairs were further analyzed with regard to the question whether they anneal to DNA of archaea, animal tissue and fungi. Subsequently they were tested with sample matrix such as plants, feed, feces, soil and environmental samples. To this purpose, the target DNA in the samples was quantified by qPCR. The PCR products of plant and feed samples were further processed for the Single Strand Conformation Polymorphism method followed by sequence analysis. The sequencing results revealed that primer pair 335F/769R amplified only bacterial DNA in samples such as plants and animal feed, in which the DNA of plants prevailed. © 2015 Elsevier B.V. Source


Dorn-In S.,WZW | Holzel C.S.,WZW | Janke T.,WZW | Schwaiger K.,WZW | And 2 more authors.
International Journal of Food Microbiology | Year: 2013

Food processing of spoiled meat is prohibited by law, since it is a deception and does not comply with food safety aspects. In general, spoilage of meat is mostly caused by bacteria. However, a high contamination level of fungi could be also found in some meat or meat products with certain preserving conditions. In case that unhygienic meat is used to produce heat processed products, the microorganisms will be deactivated by heat, so that they cannot be detected by a standard cultivation method. Therefore, this study aimed to develop and apply a molecular biological method-polymerase chain reaction and single strand conformation polymorphism (PCR-SSCP)-to reconstruct the original fungal flora of heat processed meat. Twenty primer pairs were tested for their specificity for fungal DNA. Since none of them fully complied with all study criteria (such as high specificity and sensitivity for fungal DNA; suitability of the products for PCR-SSCP) in the matrix "meat", we designed a new reverse primer, ITS5.8R. The primer pair ITS1/ITS5.8R amplified DNA from all tested fungal species, but not DNA from meat-producing animals or from ingredients of plant origin (spices). For the final test, 32 DNA bands in acrylamide gel from 15 meat products and 1 soy sauce were sequenced-all originating from fungal species, which were, in other studies, reported to contaminate meat e.g. Alternaria alternata, Aureobasidium pullulans, Candida rugosa, C. tropicalis, C. zeylanoides, Eurotium amstelodami and Pichia membranifaciens, and/or spices such as Botrytis aclada, Guignardia mangiferae, Itersonilia perplexans, Lasiodiplodia theobromae, Lewia infectoria, Neofusicoccum parvum and Pleospora herbarum. This confirms the suitability of PCR-SSCP to specifically detect fungal DNA in heat processed meat products, and thus provides an overview of fungal species contaminating raw material such as meat and spices. © 2013 Elsevier B.V. Source

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