99D-19 |
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L. TU, Food Science, University of Missouri - Columbia, 256 William Stringer Wing, Eckles Hall, University of Missouri, Columbia, MO 65211, F. Du, Genome Sequencing Center, Washington University School of Medicine, 4444 Forest Park Boulevard, St Louis, MO 63108, and A. Mustapha, Department of Food Science, University of Missouri, 256 Eckles Hall - Stringer Wing, Columbia, MO 65211. The enzyme UDP-galactose 4-epimerase (GalE) is involved in one of the major steps of galactose metabolism in bacteria. In humans, epimerase deficiency galactosemia can cause severe health problems. People suffering from galactosemia must restrict their consumption of dairy products. Bifidobacteria are probiotics that are commonly added as adjunct cultures in a multitude of dairy products. However, there is a lack of knowledge, at the molecular level, of their carbohydrate fermentation genes. Investigations into the sequence of the epimerase gene in this important organism will contribute to our understanding and ability to manipulate it for future important commercial application purposes. Our objectives were to clone and sequence the epimerase gene from Bifidobacterium infantis. A genomic DNA library of B. infantis 15702 was constructed in l phage and 5 positive clones were further analyzed. Sequencing was performed by primer walking from both directions of the cloned DNA. Sequence results revealed the presence of two open reading frames (ORF) on the cloned 3816-bp DNA fragment. The first ORF consists of 331 amino acid which has the highest identity, 60.8%, to the GalE proteins of Streptococcus mutans. There were also strong homologies to GalE of Streptococcus thermophilus and Lactococcus lactis subsp. lactis (strain IL1403) (59.6% and 57.9%, respectively). Upstream of this ORF, separated by 105 bp, was the second ORF with 62.5% identity to the b-galactosidase of Leuconostoc lactis (strain NZ6009) plasmid pNZ63. The short intergenic regions between the two genes suggested that these genes might be co-transcribed. This is the first time that the relative location of the two important carbohydrate genes has been described in this organism. The structure of the bifidobacterial epimerase gene will provide the basis for genetic approaches that will lead to potential developments of commercial strains with improved characteristics.
Session 99D, Food Microbiology: General
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