Transcriptional analysis of galactomannooligosaccharides utilization by Lactobacillus plantarum WCFS1

Plant derived galactomannooligosaccharides (GMOS) are an emerging class of prebiotics, but no information is available on their utilization in lactobacilli at the molecular level. The current study aimed at identifying the genetic loci involved in the transport and catabolism of locust bean gum derived GMOS in Lactobacillus plantarum WCFS1. Substrate depletion study showed that L. plantarum WCFS1 can metabolize only short chain GMOS (degree of polymerization; DP ≤ 3). Global transcriptome microarray profiling of L. plantarum WCFS1 revealed differential expression when GMOS or control sugars (glucose, galactose, and mannose) were used as a sole carbohydrate source. Two genetic loci involved in cellobiose (~3.2 kb) and oligo-sucrose (~7.3 kb) utilization in L. plantarum WCFS1 were highly up-regulated up to 8.3 and up to 6.7-fold, respectively by GMOS utilization. qRT-PCR studies of the selected gene clusters showed correlation with microarray data. Altogether, transcriptome and qRT-PCR studies of L. plantarum WCFS1 suggested that un-substituted mannobiose (DP₂) might be metabolized by proteins encoded by the cellobiose operon while, substituted DP₂ (galactomannose) and DP₃ (galactomannobiose) were most likely transported and catabolized by the oligo-sucrose utilization loci encoded proteins.