الفهرس 
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Abstract
This study was focused on isolation and characterization of bacteriocin producing by lactic acid bacteria (LAB) from traditional food products such as raw milk, yoghurt, domiati cheese, fermented milk, mixed pickles and sourdough. Antimicrobial effects of these LAB (171) isolates were determined by the agar spot test and agar well diffusion assay method. Only 8 isolates were selected out of 112 tested ones, which showed the best results for antimicrobial activity when agar spot and agar well diffusion assay adopted. These isolates were identified up to the species level as: Pediococcus acidilactici, Streptococcus uberis, Strept. thermophilus, Lactobacillus delbrueckii subsp bulgaricus, Lb. delbrueckii subsp lactis, Lb. brevis, Lb. rhamnosus and Bifidobacterium bifidium. RAPD fingerprinting using the primers A-04, A- 05, B-O5, B-06,O-O3 and O-12 of 7 LAB species, results clearly showed the existence of wide range of genetic variations between them. The crude bacteriocin – supernatant fluid (CBSF) was active against the gram-postive bacteria Staphylococcus aureus and some gram negative bacteria belong to Enterobacteriaceae i.e., E. coli and Klebsiella pneumoniae. Again, Strept. uberis, Lb. delbrueckii subsp lactis, Strept. thermophilus and Lb. delbrueckii subsp bulgaricus were more effective against Staph. aureus while other species such as Bifid. bifidium, Ped. acidilactici and Lb. delbrueckii subsp bulgaricus were effective against E. coli. Also Bifid. bifidium showed their antimicrobial activity against E. coli and K. pneumoniae. The importance of three major parameters (temperature, pH, antibiotics) on bacterial life and their CBSF secretion were tested. Highest antimicrobial activity was found at 30◦C and pH 2.0 to 6.5. Eight of LAB species were totally susceptible to all antibiotics tested and multiple resistance was observed. Most of the species were resistant to Cefoxitin, Ampicilin, Cefotax, Piperacillin and Fosbac plus T-bedson.