Efficient Screening Methods for Glucosyltransferase Genes inLactobacillusStrains

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Abstract
Limited information is available about homopolysaccharide synthesis in the genus Lactobacillus . Using efficient screening techniques, extracellular glucosyltransferase (GTF) enzyme activity, resulting in alpha-glucan synthesis from sucrose, was detected in various lactobacilli. PCR with degenerate primers based on homologous boxes of known glucosyltransferase (gtf ) genes of lactic acid bacteria strains allowed cloning of fragments of 10 putative gtf genes from eight different glucan producing Lactobacillus strains (five Lactobacillus reuteri strains, one Lactobacillus fermentum strain , one Lactobacillus sake strain and one Lactobacillus parabuchneri strain) . Sequence analysis revealed that these lactobacilli possess a large variation of (putative) gtf genes, similar to what has been observed for Leuconostoc and Streptococcus strains. Homologs of GTFA of Lb. reuteri 121 (synthesizing reuteran, a unique glucan with alpha-(1-->4) and alpha-(1-->6) glycosidic bonds) ( Kralj et al., 2002 ) were found in three of the four other Lb . reuteri strains tested. The other Lactobacillus GTF fragments showed the highest similarity with GTF enzymes of Leuconostoc spp.