Abstract:
Laban jameed is a dried salty dairy product obtained by fermentation of milk using a complex population of lactic acid
bacteria. Jameed is considered a traditional food product in most eastern Mediterranean countries and is usually made
from sheep or cow milk. The aim of this study was to assess phage contamination of jameed dairy product. Two phages
were isolated: one from sheep milk jameed (PPUDV) and the other from cow milk jameed (PPURV). Each of the two
bacteriophages was partially characterized. The PPUDV phage was identified as a single stranded DNA virus with an
approximately 20 kb genome that was resistant to RNase, whereas PPURV phage possessed a double stranded RNA
genome of approximately 20 kb and was resistant to DNase. The phage bacterial strain hosts were identified as Lactobacillus
helveticus and Bacillus amyloliquefaciens for PPUDV and PPURV, respectively. One step growth curve using
a double layer plaque assay test was carried out to monitor the phage life cycle after host infection. PPUDV showed a
latent period of about 36 h, burst period of 70 h and a burst size of about 600 Plaque Forming Units (PFU) per infected
cell. PPURV phage showed a latent period of about 24 h, burst period of 47 h and a burst size of about 700 PFU per
infected cell. SDS-PAGE analysis of total viral proteins showed at least three major bands (27, 40, and 45 kDa) for
PPUDV. This is the first study to report the isolation of both DNA and RNA bacteriophages from laban jameed. This
study adds new insights into the complexity of dairy contamination and fermentation microbiology of the jameed revealing
the existence of two viral genomes in this highly dried and salty dairy product.
