Proteomic Analysis of Thermophilic Starter Streptococcus thermophilus NCDC74 on Low Temperature

Low temperature adaptation of a thermophilic starter Streptococcus thermophilus NCDC74 (St74) (routinely used for production of ‘Dahi’ (yoghurt) in Indian Dairy Industries) was analysed by physiology and proteomic approach. Cold shock at 20?C for 2, 4 and 6h to St74 demonstrated a factorial increase in freeze-thaw survival of 80%, 800% and 250% respectively, compared to the control (42?C). Proteomic analysis of cold-induced cells at 20?C for 6h revealed 23 spots, which were differentially expressed. Of the differentially expressed proteins, 14 and 9 were of low (< 10 kDa) and high molecular weight (> 10 kDa) respectively. Peptide mass finger printing (PMF) analysis revealed that spot1 (MW ~7.2 kDa) matched with cold shock protein A (cspA) fragment of Lactobacillus casei (Mowsescore: 164) and spot3 (MW ~7.2 kDa) matched with csp fragment of Leuconostoc mesenteroides, thus suggesting their strong role in cryoprotection. General stress proteins induced during cold shock include lp_0704 (MW 8 kDa) from L. plantarum, dnaA from L. monocytogenes and acetolactate synthases of B. cereus. Two repressed spots (5 and 6) include chorismate synthase of S. epidermidis, t1pA from C. tetani (spot5), and ABC transporter from C. perfringens respectively (spot6). Cold inducible proteins identified in high MW include glyceraldehyde-3-phosphate dehydrogenase, parvulin-like peptidyl-prolyl isomerase, (PrsA), PTS (phosphotransferase) system and cIp protease, cIpB, UTP-glucose-1-phosphate uridylyltransferase among the repressed spots. Results revealed increased freeze thaw survival capacity after adaptation to low temperature as well as identification of several proteins that include csps, general stress proteins and repressed proteins in St74.