Abstract
Galactooligosaccharides (GOS) are documented prebiotic compounds, but knowledge of the metabolic and regulatory mechanisms of GOS utilization by lactic acid bacteria is still limited. Here we used transcriptome and physiological analyses to investigate the differences in the logarithmic growth phase of Lactobacillus plantarum and L. plantarum ΔccpA metabolizing GOS or glucose as the sole source of carbohydrate. In total, 489 genes (16%) were differentially transcribed in the wild-type L. plantarum grown on glucose and GOS and the value is decreased to 7% due to the loss of ccpA. Only 6% genes were differentially expressed when the wild-type and the ccpA mutant were compared on GOS. Transcriptome data revealed that the carbon sources significantly affected the expression of several genes, and some of the genes were mediated by CcpA. In particular, lac and gal gene clusters resembled the corresponding clusters in L. acidophilus NCFM that are involved in GOS metabolism, indicating that these clusters may be participating in GOS utilization. Moreover, reverse transcription-PCR analysis showed that GOS-related gene clusters were organized in five independent polycistronic units. In addition, many commonalities were found between fructooligosaccharides and GOS metabolism in L. plantarum, including differentially expressed genes involved in oligosaccharide metabolism, conversion of metabolites, and changes in fatty acid biosynthesis. Overall, our findings provide new information on gene transcription and the metabolic mechanism associated with GOS utilization, and confirm that CcpA plays an important role in carbon metabolism regulation in L. plantarum.
Highlights
Prebiotics are non-digestible food ingredients that exert beneficial effect on the host’s health by selectively stimulating the growth and activity of health-promoting bacteria in the gastrointestinal tract (GIT) (Andersen et al, 2012; Arnold et al, 2018)
We focused on the following three pair-wise comparisons to analyze GOS metabolism: between wild-type strain grown on glucose and GOS, between ccpA mutant grown on glucose and GOS, and between wild-type and ccpA mutant grown on GOS
Two components, melA (LPST-C2855) and lacS2 (LPST-C2856), which encodes an alpha-galactosidase and a major facilitator superfamily transporter, appeared only in L. plantarum. These results indicate that the clusters in L. plantarum and L. acidophilus NCFM have similar structures with a high degree of homology, suggesting that the lac and gal clusters are involved in GOS transport and utilization in L. plantarum
Summary
Prebiotics are non-digestible food ingredients that exert beneficial effect on the host’s health by selectively stimulating the growth and activity of health-promoting bacteria in the gastrointestinal tract (GIT) (Andersen et al, 2012; Arnold et al, 2018). Due to the nature of the oligomer and the association of β-galactoside linkages, GOS act as prebiotic supplements that promote the growth of lactobacilli and bifidobacteria (Andersen et al, 2011; María et al, 2018). GOS is transported intact by a galactoside-pentose-hexuronide (GPH)-type LacS permease and hydrolyzed by two cytoplasmic β-galactosidases (LacA of the GH42 family and LacLM of the GH2 family) into glucose and galactose. The structures of the lac gene cluster differ markedly among LAB (Yong and Klaenhammer, 2015), both lacS and lacA genes exist in LAB, except in L. delbrueckii subsp. bulgaricus, indicating that LacS and β-galactosidases of the GH42 family coevolved
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
