Transcriptional and functional analysis of galactooligosaccharide uptake bylacSinLactobacillus acidophilus

Abstract

Probiotic microbes rely on their ability to survive in the gastrointestinal tract, adhere to mucosal surfaces, and metabolize available energy sources from dietary compounds, including prebiotics. Genome sequencing projects have proposed models for understanding prebiotic catabolism, but mechanisms remain to be elucidated for many prebiotic substrates. Although β-galactooligosaccharides (GOS) are documented prebiotic compounds, little is known about their utilization by lactobacilli. This study aimed to identify genetic loci in Lactobacillus acidophilus NCFM responsible for the transport and catabolism of GOS. Whole-genome oligonucleotide microarrays were used to survey the differential global transcriptome during logarithmic growth of L. acidophilus NCFM using GOS or glucose as a sole source of carbohydrate. Within the 16.6-kbp gal-lac gene cluster, lacS, a galactoside-pentose-hexuronide permease-encoding gene, was up-regulated 5.1-fold in the presence of GOS. In addition, two β-galactosidases, LacA and LacLM, and enzymes in the Leloir pathway were also encoded by genes within this locus and up-regulated by GOS stimulation. Generation of a lacS-deficient mutant enabled phenotypic confirmation of the functional LacS permease not only for the utilization of lactose and GOS but also lactitol, suggesting a prominent role of LacS in the metabolism of a broad range of prebiotic β-galactosides, known to selectively modulate the beneficial gut microbiota.lactose permease | catabolite repression element

Impact of short-chain galactooligosaccharides on the gut microbiome of lactose-intolerant individuals

“…ANOVA analysis and Tukey tests were performed to identify statistically significant differences in relative abundance between time points. *P < 0.05. glycolytic enzyme essential for GOS metabolism that typically is genetically linked with a LacS permease responsible for transport and internalization of GOS (6). B. dentium has been less thoroughly characterized, is mostly associated with the oral cavity, and recently was shown to be increased in the stools of 100-to 108-y-old centenarians living in Bama, Guangxi (China) as compared with younger (80-to 99-y-old) elderly persons (19).…”

Diverse galactooligosaccharides consumption by bifidobacteria: implications of β-galactosidase—LacS operon

“…26,35) It seems plausible that GOS-induced bifidobacteria utilize this system for GOS uptake, because it does not require ATP for substrate import and thus allows energy-efficient and rapid adaptive transport. Recently, Andersen et al clearly demonstrated by generating a lacS-deficient mutant of Lactobacillus acidophilus that LacS is indispensable for GOS uptake by bacteria; this also supports the strong link between LacS and …”

“…[26][27][28][29] Accordingly, we embarked on a search for a "GOS operon" in bifidobacteria. We chose B. adolescentis YIT 4011 T as a model bacterium, because (as indicated above) it exhibited highly adaptable use of GOS.…”

Development of an integration mutagenesis system inLactobacillus gasseri

“…Genes successfully deleted using this gene replacement strategy in L. acidophilus NCFM include surfacelayer (S-layer) protein X, (LBA0512), aggregation promoting factor (LBA0493), myosin cross-reactive antigen (LBA0649), and lactose permease (LBA1463). 15,[20][21][22] Establishing this system in L. gasseri provides numerous advantages, notably the ability to positively select for excision recombinants yielding gene deletions or replacements. In concurrent efforts, this system was used to successfully and efficiently delete the sortase A gene (srtA) from L. gasseri (Call et al, submitted).…”