Abstract
Sixty (60) strains of Streptococcus thermophilus isolated from dairy traditional Egyption yoghurt samples were characterized. The yoghurt samples were collected from the local markets in Egypt. The results showed that few phages can attack S. thermophilus strains isolated from traditional Egyptian yoghurt (Zabady) samples, only three temperate phages were isolated. The isolated phages attacking samples were induced with mitomycin C (0.05 or 0.1 μg/ml, final concentration) and characterized by SDS-polyacrylamide gel electrophoresis, PCR and electron microscope. The characterization of phages showed that the bacteriophages belonged to the family Siphoviridae and they had an isometric head and long non contractile tail. SDS polyacrylamide gels and PCR amplification showed that all isolated phages belongs to pac phage. The PCR described in this worak can detect and differentiate S. thermophilus phages in a short time, it is very sensitive and reveals a high limit of detection. Key words: Streptococcus thermophilus, bacteriophage, SDS-polyacrylamide gel electrophoresis, PCR amplification.
Highlights
The results showed that few phages can attack S. thermophilus strains isolated from traditional Egyptian yoghurt (Zabady) samples, only three temperate phages were isolated
Streptococcus thermophilus is one of the most economically important lactic acid bacteria (LAB), it is a component of dairy starter cultures and used in a large amount for the manufacture of dairy products
A rapid and reliable multiplex-Polymerase chain reaction (PCR) method is described allowing the simultaneous detection of S. thermophilus phages and their differentiation into the two well known pac- and cos-type subgroups
Summary
Streptococcus thermophilus is one of the most economically important lactic acid bacteria (LAB), it is a component of dairy starter cultures and used in a large amount for the manufacture of dairy products (annual market of about 40 billion USD). It is usually used in combination with Lactobacillus delbrueckii subsp. Thermophilus is used alone or in combination with lactobacilli for the production of mozzarella and cheddar cheeses (Duplessis et al, 2006; Binetti et al, 2005; Hols et al, 2005)
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