Biomedical subjects

J M van der Vossen

Publications and source records attributed to J M van der Vossen.

17 recordsLinked to original sources

PubMed1999

Effect of bacteriocin-producing lactobacilli on the survival of Escherichia coli and Listeria in a dynamic model of the stomach and the small intestine.

The survival of Lactobacillus curvatus LTH 1174 (bac ) and (bac ) in combination with Escherichia coli LTH 1600 or Listeria innocua DSM20649 during transit through a dynamic model of the human stomach and small intestine (GIT model) was studied. Furthermore, we determined the digestion of curvacin A during gastro-intestinal transit and the effect of this bacteriocin on microbial survival. Lb. curvatus is rapidly killed in the gastric compartment at pH < 2.0, and less than 0.01% of the cells delivered to the small intestinal compartments were recovered from the ileal compartment of the model. Meat exerted a protective effect against the lethal action of bile against Lb. curvatus. The sensitivity of E. coli to acid depended on the aeration of the preculture and decreased in the order anaerobic > strongly agitated > agitated. Lactic acid and curvacin A enhanced the lethal effect of low pH on E. coli. Accordingly, cells from strongly agitated cultures were killed faster in the gastric compartment of the GIT model than those from agitated cultures, and inactivation was accelerated in the presence of curvacin A. E. coli tolerated the bile concentrations prevailing in the small intestinal compartments of the model. The survival of Listeria innocua in the GIT model was comparable to that of Lb. curvatus. The curvacin A produced by Lb. curvatus LTH1174 (bac+) killed > 90% of the L. innocua within 10 min after mixing of the cultures. Curvacin A was not degraded in the the gastric compartment, and could be detected in the ileal compartment during the first 180 min upon addition of the meal.

Animals↗

PubMed1996

DNA based typing, identification and detection systems for food spoilage microorganisms: development and implementation.

The rapid identification of spoilage microorganisms is of eminent importance to the food industry. It provides the food industry with the opportunity to reduce economical losses by designing adequate intervention measures. The use of identification systems based on biochemical and physiological characteristics resulted often in disappointing identification results and misidentifications. This will inevitably lead to inappropriate strategies to prevent spoilage. This review discusses the potential of the DNA based identification technology including the polymerase chain reaction (PCR) for the identification and specific detection of microorganisms. Fingerprinting methods based on the DNA-probe technology enable a clear insight in the identity of microorganisms on different levels, varying from genus to strain level depending on the systems used. Discrimination between subspecies and strain level is shown to be helpful for investigating routes and sources of contamination. Differentiation at the species level is demonstrated to be essential in order to design a highly specific detection system enabling to signalize a microorganism that belongs to a particular species. Also indicated in this review is the necessity and the technical approach to detect microorganisms that display a particular undesirable trait.

DNA↗

PubMed1996

Evaluation of molecular typing techniques to assign genetic diversity among Saccharomyces cerevisiae strains.

Discrimination of strains within the species Saccharomyces cerevisiae was demonstrated by the use of four different techniques to type 15 strains isolated from spoiled wine and beer. Random amplified polymorphic DNA with specific oligonucleotides and PCR fingerprinting with the microsatellite oligonucleotide primers (GAC)5 and (GTG)5 enabled discrimination between the strains tested. Additionally, restriction enzyme analysis, with TaqI and MseI, of PCR-amplified fragments from the complete internal transcribed spacer and nontranscribed spacer, both present in the rRNA-encoding gene cluster, proved to be suitable for generating intraspecies-specific patterns. Random amplified polymorphic DNA with primers 24 and OPA-11 and PCR fingerprinting with primer (GTG)5 appeared to generate the highest degree of diversity. However, the results indicated that there was no single PCR-mediated typing technique enabling discrimination on the strain level. Discrimination of each individual strain was nevertheless possible by combining the results obtained with all typing techniques.

Base Sequence↗

PubMed1995

Genetic analysis of acidocin B, a novel bacteriocin produced by Lactobacillus acidophilus.

The genes encoding the production of acidocin B, a bacteriocin produced by Lactobacillus acidophilus strain M46 which is active against Listeria monocytogenes, Clostridium sporogenes, Brochothrix thermosphacta, Lactobacillus fermentum and Lactobacillus delbrueckii subsp. bulgaricus, but inactive against most other Lactobacillus species, were previously localized on a 4 kb XbaI-HindIII fragment of plasmid pCV461. In the present work, DNA sequence analysis revealed the presence of three consecutive ORFs, which potentially code for hydrophobic peptides composed of 60, 91 and 114 amino acids, respectively, and a fourth ORF of opposite polarity which could potentially encode a peptide of 59 amino acids. The middle ORF (ORF-2; acdB) was identified as the gene encoding acidocin B by comparing the amino acid composition of highly purified acidocin B with the deduced amino acid sequence of ORF-2. Our results suggest that acidocin B is synthesized as a precursor which is processed at a site which conforms to the ' -3, -1' rules of von Heijne to yield active acidocin B (59 amino acids). The presence of an immunity-protein-encoding gene on the 4 kb XbaI-BamHI fragment was deduced from the capacity of a plasmid vector harbouring this fragment to confer immunity upon transformation of L. fermentum NCK127. One of the three non-assigned ORFs may encode this immunity protein.

Amino Acid Sequence↗

PubMed1995

Random amplified polymorphic DNA and restriction enzyme analysis of PCR amplified rDNA in taxonomy: two identification techniques for food-borne yeasts.

The random amplified polymorphic DNA (RAPD) assay and the restriction enzyme analysis of PCR amplified rDNA are compared for the identification of the common spoilage yeasts Zygosaccharomyces bailii, Z. rouxii, Saccharomyces cerevisiae, Candida valida and C. lipolytica. Both techniques proved to be adequate tools for yeast identification. Since the RAPD does provide less stable patterns than restriction enzyme analysis of PCR amplified rDNA, and a large amount of data had to be compared without data reduction, Principal Component Analysis (PCA) was applied successfully for clustering the RAPD patterns. The success of PCA is highly influenced by the primer used in RAPD and the amount of reference samples. A large amount of reference samples improves the performance of clustering in PCA. The primer of choice was shown to be important with respect to the discriminatory power of the RAPD method. Some primers used enabled discrimination on the subspecies level. The results collected with both typing methods justify the conclusion that the present typing system can be applied for taxonomical purposes.

Base Sequence↗

PubMed1995

Development of a detection system for histidine decarboxylating lactic acid bacteria based on DNA probes, PCR and activity test.

On the basis of the comparison of the nucleotide sequences of the histidine decarboxylase genes (hdcA) of Lactobacillus 30A and Clostridium perfringens and the amino acid sequences of these histidine decarboxylases and those of Lactobacillus buchneri and Micrococcus, oligonucleotides unique to the hdcA genes were synthesized and used in PCR. All histidine-decarboxylating lactic acid bacteria gave a signal with primer set JV16HC/JV17HC in PCR. In addition to this primer set, CL1/CL2 and CL1/JV17HC were also useful for the detection of histamine-forming Leuconostoc aenos strains in PCR. The 150 base pair amplification product of the decarboxylating Leuc. aenos strain generated with primer set CL1/CL2 was sequenced. Alignment studies showed a high degree of relatedness among the hdcA gene products of Gram-positive bacteria. The amplification products of the hdcA genes from Lac. buchneri and Leuct. aenos were used to serve as a DNA probe in hybridization studies. All histidine-decarboxylating lactic acid bacteria gave a hybridization signal with the DNA probes. In hybridization only one false-positive signal with a Lactobacillus lindneri strain was observed, which was anticipated to contain a truncated hdcA gene. In addition to these DNA probe tests, a simple and reliable activity test is presented, which can be used during starter selection to test strains for histidine decarboxylase activity.

Amino Acid Sequence↗

PubMed1994

RAPD analysis: a rapid technique for differentiation of spoilage yeasts.

Techniques for the identification of the spoilage yeasts Saccharomyces cerevisiae and members of the Zygosaccharomyces genus from food and beverages sources were evaluated. The use of identification systems based on physiological characteristics resulted often in incomplete identification or misidentification. Also the cellular fatty acid analysis failed on differentiating species within the Zygosaccharomyces genus. However, the Random Amplified Polymorphic DNA (RAPD) assay, using selected 10-mer oligonucleotides, allowed discrimination between all species tested. For this RAPD assay, a simple and reproducible method of DNA isolation from spoilage yeast cells is described.

Base Sequence↗

PubMed1994

Antimicrobial activity of lactobacilli: preliminary characterization and optimization of production of acidocin B, a novel bacteriocin produced by Lactobacillus acidophilus M46.

Approximately 1000 lactobacillus strains were isolated and screened for the production of antimicrobial activity, using a target panel of spoilage organisms and pathogens. Only eight positive strains were found; two of these were studied in more detail. Lactobacillus salivarius M7 produces the new broad spectrum bacteriocin salivaricin B which inhibits the growth of Listeria monocytogenes, Bacillus cereus, Brochothrix thermosphacta, Enterococcus faecalis and many lactobacilli. A new atypical bacteriocin produced by Lact. acidophilus M46, acidocin B, combines the inhibition of Clostridium sporogenes with a very narrow activity spectrum within the genus Lactobacillus and was selected for further characterization. Acidocin B is sensitive to trypsin, heat-stable (80 degrees C for 20 min) and can be extracted from the culture supernatant fluid with butanol. Native acidocin B occurs as a large molecular weight complex (100 kDa), while with SDS-PAGE the partly purified activity migrates as a peptide of 2.4 kDa. Optimization of the cultivation conditions resulted in an eightfold increase of the amount of acidocin B produced during growth. Growth is not necessary for acidocin B production; washed producer cells can synthesize the bacteriocin in a chemically defined production medium. The application potential of acidocin B is discussed.

Bacteriocins↗

PubMed1994

Microbes in food processing technology.

There is an increasing understanding that the microbial quality of a certain food is the result of a chain of events. It is clear that the microbial safety of food can only be guaranteed when the overall processing, including the production of raw materials, distribution and handling by the consumer are taken into consideration. Therefore, the microbiological quality assurance of foods is not only a matter of control, but also of a careful design of the total process chain. Food industry has now generally adapted quality assurance systems and is implementing the Hazard Analysis Critical Control Point (HACCP) concept. Rapid microbiological monitoring systems should be used in these cases. There is a need for rapid and simple microbiological tests which can be adapted to the technology and logistics of specific production processes. Traditional microbiological methods generally do not meet these high requirements. This paper discusses the tests, based on molecular biological principles, to detect and identify microbes in food-processing chains. Tests based on DNA technology are discussed, including in vitro DNA amplification like the polymerase chain reaction (PCR) method and identifications based on RFLP, RAPD and DNA fingerprinting analysis. PCR-based methodology can be used for the rapid detection of microbes in food manufacturing environments. In addition, DNA fingerprinting methods are suitable for investigating sources and routes of microbial contamination in the food cycle.

Bacterial Typing Techniques↗

PubMed1992

Characterization of transcription initiation and termination signals of the proteinase genes of Lactococcus lactis Wg2 and enhancement of proteolysis in L. lactis.

The transcription initiation signals of the prtP and prtM genes specifying the proteolytic activity of Lactococcus lactis subsp. cremoris Wg2 were mapped by primer extension. The strength of these promoters was analyzed with promoter-screening vector pGKV410, and they appeared to be weaker than previously isolated promoters of strain Wg2. In addition, a putative transcription terminator downstream of the prtP gene was characterized by using the terminator-screening vector pGKV259. The putative terminator decreased the transcription activity of lactococcal promoter P59 by approximately 70% in both Bacillus subtilis and L. lactis. Deletion of a part of the stem-loop structure of the terminator decreased the negative effect on transcription, indicating that the structure could indeed function as a terminator of transcription. The proteolytic activity of the lactococcal host was enhanced by placing the originally oppositely oriented prt genes in tandem and replacing the relatively weak promoters upstream of the prt genes with the stronger promoter, P32, from the chromosome of L. lactis Wg2.

Bacterial Proteins↗

PubMed1990

Heterologous gene expression in Lactococcus lactis subsp. lactis: synthesis, secretion, and processing of the Bacillus subtilis neutral protease.

The Bacillus subtilis nprE gene lacking its own promoter sequence was inserted in the lactococcal expression vector pMG36e. Upon introduction of the recombinant plasmid into Lactococcus lactis subsp. lactis strain MG1363, neutral protease activity could be visualized by the appearance of large clearing zones around colonies grown on milk agar plates. By measuring the activities of the neutral protease and the intracellular enzyme lactate dehydrogenase in culture supernatants and cell fractions, it was demonstrated that the neutral protease was actively secreted into the growth medium. This was corroborated by using the Western blot (immunoblot) technique, which showed the presence of the mature form of the neutral protease in the culture supernatant. On the basis of these results, it is concluded that the B. subtilis neutral protease gene was expressed in L. lactis and that the gene product was secreted into the growth medium and was apparently correctly processed to produced a biologically active protein. The secretion of this particular enzyme may be helpful in achieving accelerated cheese ripening.

Bacillus subtilis↗

PubMed1989

Construction of a lactococcal expression vector: expression of hen egg white lysozyme in Lactococcus lactis subsp. lactis.

A pair of vectors for expression of heterologous genes in Lactococcus lactis was constructed. In addition to an origin of replication that has a broad host range, these vectors contain a multiple cloning site flanked by gene expression signals originating from L. lactis subsp. cremoris Wg2. The two vectors, about 3.7 kilobase pairs in size, differ only in the type of antibiotic resistance they confer to their hosts. pMG36 carries a kanamycin resistance marker, which was replaced by an erythromycin resistance marker in pMG36e. As an example of the use of these vectors, the hen egg white lysozyme-coding sequence was inserted. A fusion protein of the expected size was detected in a transformed L. lactis subsp. lactis strain by using Western blotting (immunoblotting).

Animals↗

PubMed1988

Effect of Plasmid Incompatibility on DNA Transfer to Streptococcus cremoris.

Several Streptococcus cremoris strains were used in protoplast transformation and interspecific protoplast fusion experiments with Streptococcus lactis and Bacillus subtilis, with pGKV110, pGKV21, and DeltapAMbeta1 as the marker plasmids. DeltapAMbeta1 is a 15.9-kilobase nonconjugative, deletion derivative of pAMbeta1, which is considerably larger than the pGKV plasmids (approximately 4.5 kilobases). In general, DeltapAMbeta1 was transferred more efficiently than the pGKV plasmids. Using electroporation, we were able to demonstrate that failure of efficient transfer for the pGKV plasmids was, except for one case, caused by incompatibility of these plasmids with resident plasmids of the recipient strain.

Journal Article↗

PubMed1987

Isolation and characterization of Streptococcus cremoris Wg2-specific promoters.

By cloning MboI fragments in the promoter selection vector pGKV210, which replicates in Streptococcus lactis, Bacillus subtilis, and Escherichia coli and carries a promoterless chloramphenicol acetyltransferase gene, we obtained a number of fragments endowed with promoter activity, partly by direct selection for chloramphenicol resistance in S. lactis IL1403 and partly by selection in B. subtilis. Five fragments were sequenced, and the promoters were mapped with S1 nuclease. The promoters agreed with the E. coli promoter consensus and the B. subtilis vegetative sigma 43 promoter consensus. The promoters were preceded by an A + T-rich region (ranging from 64 to 78% A + T). S1 nuclease mapping data showed that the transcriptional start point in three of the fragments was at a TAG sequence 5 to 9 nucleotides downstream from the promoter. Three fragments carried an open reading frame preceded by a ribosome-binding site which can be recognized by E. coli, B. subtilis, and S. lactis ribosomes.

Bacillus subtilis↗

PubMed1985

Cloning and expression of a Streptococcus cremoris proteinase in Bacillus subtilis and Streptococcus lactis.

Previously, curing experiments suggested that plasmid pWV05 (17.5 megadaltons [Md]) of Streptococcus cremoris Wg2 specifies proteolytic activity. A restriction enzyme map of pWV05 was constructed, the entire plasmid was subcloned in Escherichia coli with plasmids pBR329 and pACYC184. A 4.3-Md HindIII fragment could not be cloned in an uninterrupted way in E. coli but could be cloned in two parts. Both fragments showed homology with the 9-Md proteinase plasmid of S. cremoris HP. The 4.3-Md HindIII fragment was successfully cloned in Bacillus subtilis on plasmid pGKV2 (3.1 Md). Crossed immunoelectrophoresis of extracts of B. subtilis carrying the recombinant plasmid (pGKV500; 7.4 Md) showed that the fragment specifies two proteins of the proteolytic system of S. cremoris Wg2. PGKV500 was introduced in a proteinase-deficient Streptococcus lactis strain via protoplast transformation. Both proteins were also present in cell-free extracts of S. lactis(pGKV500). In S. lactis, pGKV500 enables the cells to grow normally in milk with rapid acid production, indicating that the 4.3-Md HindIII fragment of plasmid pWV05 specifies the proteolytic activity of S. cremoris Wg2.

Animals↗

PubMed1985

Construction of cloning, promoter-screening, and terminator-screening shuttle vectors for Bacillus subtilis and Streptococcus lactis.

Shuttle vectors have been constructed which are suitable both for the selection of regulatory sequences and for gene cloning in Bacillus subtilis and Streptococcus lactis. The promoter screening vectors contain a promoterless chloramphenicol acetyltransferase gene; the insertion of suitable DNA fragments upstream of the gene restored the enzyme activity. With a related set of vectors, transcription termination signals can be selected.

Acetyltransferases↗

PubMed1984

Construction of plasmid cloning vectors for lactic streptococci which also replicate in Bacillus subtilis and Escherichia coli.

The cryptic Streptococcus cremoris Wg2 plasmid pWV01 (1.5 megadaltons) was genetically marked with the chloramphenicol resistance (Cmr) gene from pC194. The recombinant plasmid (pGK1, 2.4 megadaltons) replicated and expressed Cmr in Bacillus subtilis. From this plasmid an insertion-inactivation vector was constructed by inserting the erythromycin resistance (Emr) gene from pE194 cop-6. This plasmid (pGK12, 2.9 megadaltons) contained a unique BclI site in the Emr gene and unique ClaI and HpaII sites outside both resistance genes. It was stably maintained in B. subtilis at a copy number of approximately 5. pGK12 also transformed Escherichia coli competent cells to Cmr and Emr. The copy number in E. coli was about 60. Moreover, pGK12 transformed protoplasts of Streptococcus lactis. In this host both resistance genes are expressed. pGK12 is stably maintained in S. lactis at a copy number of 3.

Bacillus subtilis↗