Heterogeneity of heat-resistant proteases from milk Pseudomonas species.
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.
Marchand
Sophie
S
Institute for Agricultural and Fisheries Research, Melle, Belgium. sophie.marchand@ilvo.vlaanderen.be
Vandriesche
Gonzalez
G
Coorevits
An
A
Coudijzer
Katleen
K
De Jonghe
Valerie
V
Dewettinck
Koen
K
De Vos
Paul
P
Devreese
Bart
B
Heyndrickx
Marc
M
De Block
Jan
J
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*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C402704:AprX protein, bacteria; D012697:Serine Endopeptidases