Assessment of expression of Leloir pathway genes in wild-type galactose-fermenting Streptococcus thermophilus by real-time PCR

作者：Anbukkarasi Kaliyaperumal; Nanda Dhiraj Kumar; UmaMaheswari Thiyagamoorthy; Hemalatha Thiagarajan; Singh Prashant; Singh Rameshwar^*

来源：European Food Research and Technology, 2014, 239(5): 895-903.

DOI：10.1007/s00217-014-2286-9

• Gal operon
• Galactose positive
• Gene expression
• RT-PCR
• S. thermophilus

In this study, four galactose-positive (Gal(+)) Streptococcus thermophilus strains viz. AJM, JM1, KM3 and AUKD8 and one galactose-negative (Gal(-)) S. thermophilus NCDC 218 were used to characterize the organization of Leloir pathway genes using long-range PCR, and expression of these genes were studied using real-time PCR, in presence of different sugars. Long-range PCR results showed that both Gal(+) and Gal(-) isolates, the gal-lac gene order (galRKTEM-lacSZ), are conserved including the size of individual genes. The promoter sequence of the three Gal(+) isolates (AJM, JM1 and KM3) possessed single base pair deletion at -28 region of galR and C to T substitution at -9 box galK region. In contrast, Gal(+) AUKD8 had A to T substitution at preceding -25 region of galR. The expression of galK and galM grown in the presence of galactose was significantly higher in case of AJM (30- and 7.6-fold, respectively), followed by KM3 and JM1. In addition, galR, galT and galE showed higher expression in galactose, than in lactose and glucose medium. This study gives a preliminary idea on Leloir pathway gene expression in wild Gal(+) S. thermophilus, and further studies may throw more light on the role of gal-lac operon in galactose metabolism.

• 出版日期2014-11