title: Heterogeneity of heat-resistant proteases from milk Pseudomonas species.
abstract: Pseudomonas fragi, Pseudomonas lundensis and members of the Pseudomonas fluorescens group may spoil Ultra High Temperature (UHT) treated milk and dairy products, due to the production of heat-stable proteases in the cold chain of raw milk. Since the aprX gene codes for a heat-resistant protease in P. fluorescens, the presence of this gene has also been investigated in other members of the genus. For this purpose an aprX-screening PCR test has been developed. Twenty-nine representatives of important milk Pseudomonas species and thirty-five reference strains were screened. In 42 out of 55 investigated Pseudomonas strains, the aprX gene was detected, which proves the potential of the aprX-PCR test as a screening tool for potentially proteolytic Pseudomonas strains in milk samples. An extensive study of the obtained aprX-sequences on the DNA and the amino acid level, however, revealed a large heterogeneity within the investigated milk isolates. Although this heterogeneity sets limitations to a general detection method for all proteolytic Pseudomonas strains in milk, it offers a great potential for the development of a multiplex PCR screening test targeting individual aprX-genes. Furthermore, our data illustrated the potential use of the aprX gene as a taxonomic marker, which may help in resolving the current taxonomic deadlock in the P. fluorescens group.
authors.affiliation: Institute for Agricultural and Fisheries Research, Melle, Belgium. sophie.marchand@ilvo.vlaanderen.be
authors.forename: Sophie
authors.initials: S
authors.lastname: Marchand
authors.forename: Gonzalez
authors.initials: G
authors.lastname: Vandriesche
authors.forename: An
authors.initials: A
authors.lastname: Coorevits
authors.forename: Katleen
authors.initials: K
authors.lastname: Coudijzer
authors.forename: Valerie
authors.initials: V
authors.lastname: De Jonghe
authors.forename: Koen
authors.initials: K
authors.lastname: Dewettinck
authors.forename: Paul
authors.initials: P
authors.lastname: De Vos
authors.forename: Bart
authors.initials: B
authors.lastname: Devreese
authors.forename: Marc
authors.initials: M
authors.lastname: Heyndrickx
authors.forename: Jan
authors.initials: J
authors.lastname: De Block
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002417:Cattle; D003080:Cold Temperature; D004269:DNA, Bacterial; D005516:Food Microbiology; D005798:Genes, Bacterial; D014644:Genetic Variation; D006358:Hot Temperature; D006801:Humans; D008892:Milk / Q000382:microbiology*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011549:Pseudomonas / Q000235:genetics* / Q000302:isolation & purification; D012034:Refrigeration; D012697:Serine Endopeptidases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C402704:AprX protein, bacteria; D012697:Serine Endopeptidases