Open AccessRequirement for Phosphoglucomutase in Exopolysaccharide Biosynthesis in Glucose- and Lactose-Utilizing Streptococcus thermophilus
Author(s) -
Fredrik Levander,
Peter Rådström
Publication year - 2001
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.67.6.2734-2738.2001
Subject(s) - streptococcus thermophilus , phosphoglucomutase , lactose , mutant , biochemistry , galactose , biology , escherichia coli , thermus thermophilus , operon , microbiology and biotechnology , gene , enzyme , fermentation , lactobacillus
To study the influence of phosphoglucomutase (PGM) activity on exopolysaccharide (EPS) synthesis in glucose- and lactose-growing Streptococcus thermophilus, a knockout PGM mutant and a strain with elevated PGM activity were constructed. The pgmA gene, encoding PGM in S. thermophilus LY03, was identified and cloned. The gene was functional in Escherichia coli and was shown to be expressed from its own promoter. The pgmA-deficient mutant was unable to grow on glucose, while the mutation did not affect growth on lactose. Overexpression of pgmA had no significant effect on EPS production in glucose-growing cells. Neither deletion nor overexpression of pgmA changed the growth or EPS production on lactose. Thus, the EPS precursors in lactose-utilizing S. thermophilus are most probably formed from the galactose moiety of lactose via the Leloir pathway, which circumvents the need for a functional PGM.