Proteolytic activity of lactococcal strains from water-buffalo Mozzarella starter cultures

1998 ◽  
Vol 65 (1) ◽  
pp. 109-118 ◽  
Author(s):  
GIANLUIGI MAURIELLO ◽  
GIANCARLO MOSCHETTI ◽  
GIUSEPPE BLAIOTTA ◽  
FRANCESCO VILLANI ◽  
SALVATORE COPPOLA
Keyword(s):  
Polymerase Chain Reaction ◽  
Proteolytic Activity ◽  
Polymerase Chain Reaction Amplification ◽  
Skim Milk ◽  
Starter Cultures ◽  
Chain Reaction ◽  
Heat Treated ◽  
Genes Encoding ◽  
Specific Amplification ◽  
Polymerase Chain

Growth and proteolytic activity of Lactococcus lactis strains were investigated in milks subjected to different heat treatments. Only 13·7% of the strains were of proteolytic phenotype. Proteinase-positive (Prt+) strains exhibited a proteolytic activity that increased when the level of heat treatment was reduced and grew to a higher level than proteinase-negative (Prt−) strains in low-heat-treated milk. When grown in autoclaved reconstituted skim milk, both Prt− and Prt+ strains had the same specific growth rate. Total DNA from four Prt+ and eleven Prt− strains was extracted and used for polymerase chain reaction amplification of fragments belonging to genes encoding for cell wall proteinase. Specific amplification products were displayed by all the Prt+ strains, and by the Prt− strain Lc. lactis subsp. lactis NWC 125. Reverse transcriptase-polymerase chain reaction was performed to detect the transcript of the proteinase genes. In addition to the Prt+ strains, the experiment also detected the specific transcript in Lc. lactis subsp. lactis NWC 125, suggesting that other structural or functional deficiencies occurred in this strain.

A 23S rDNA-Targeted Polymerase Chain Reaction–Based System for Detection of Staphylococcus aureus in Meat Starter Cultures and Dairy Products

1999 ◽  
Vol 62 (10) ◽  
pp. 1150-1156 ◽  
Author(s):  
JOACHIM A. STRAUB ◽  
CHRISTIAN HERTEL ◽  
WALTER P. HAMMES
Keyword(s):  
Staphylococcus Aureus ◽  
Polymerase Chain Reaction ◽  
Skim Milk ◽  
Starter Cultures ◽  
23S Rrna ◽  
Rrna Gene ◽  
Chain Reaction ◽  
Nested Polymerase Chain Reaction ◽  
Selective Enrichment ◽  
Polymerase Chain

A polymerase chain reaction–based system for detection of Staphylococcus aureus was developed. The system consisted of the following components: (i) selective enrichment, (ii) DNA isolation, (iii) amplification of DNA with primers targeted against the 23S rRNA gene, and (iv) evaluation of the specificity of the polymerase chain reaction by Southern hybridization and nested polymerase chain reaction. The method achieved a high degree of sensitivity and unambiguity as required for the detection of contaminants in food starter preparations. The method permitted detection of Staphylococcus aureus in preparations of meat starter cultures containing Staphylococcus carnosus either alone or in combination with lactobacilli, pediococci, and/or Kocuria varians. Detection limits were sufficiently low to show within 12 h the presence of 100 CFU of S. aureus in starter preparations containing 1010 CFU of S. carnosus. The system was also applied to dried skim milk and cream. For detection without selective enrichment, a protocol was developed and permitted detection of 120 CFU of S. aureus in 1 ml of cream within 6 h. With nested polymerase chain reaction, the detection limit was decreased by one order of magnitude.

Polymerase chain reaction amplification and typing of rotavirus in environmental samples

1995 ◽  
Vol 31 (5-6) ◽  
pp. 371-374 ◽  
Author(s):  
R. Gajardo ◽  
R. M. Pintó ◽  
A. Bosch
Keyword(s):  
Polymerase Chain Reaction ◽  
Environmental Samples ◽  
Polymerase Chain Reaction Amplification ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Pcr Assay ◽  
Group A ◽  
Reaction Amplification ◽  
Stool Specimens ◽  
Polymerase Chain

A reverse transcription polymerase chain reaction (RT-PCR) assay is described that has been developed for the detection and serotyping of group A rotavirus in stool specimens and concentrated and non-concentrated sewage specimens.

PCR BY THERMAL CONVECTION

2004 ◽  
Vol 18 (16) ◽  
pp. 775-784 ◽  
Author(s):  
DIETER BRAUN
Keyword(s):  
Polymerase Chain Reaction ◽  
Thermal Convection ◽  
Dna Amplification ◽  
Reaction Vessel ◽  
Cold Region ◽  
Chain Reaction ◽  
Heating And Cooling ◽  
Highly Sensitive ◽  
Specific Amplification ◽  
Polymerase Chain

The Polymerase Chain Reaction (PCR) allows for highly sensitive and specific amplification of DNA. It is the backbone of many genetic experiments and tests. Recently, three labs independently uncovered a novel and simple way to perform a PCR reaction. Instead of repetitive heating and cooling, a temperature gradient across the reaction vessel drives thermal convection. By convection, the reaction liquid circulates between hot and cold regions of the chamber. The convection triggers DNA amplification as the DNA melts into two single strands in the hot region and replicates into twice the amount in the cold region. The amplification progresses exponentially as the convection moves on. We review the characteristics of the different approaches and show the benefits and prospects of the method.

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