Metabolism of Fructooligosaccharides in Lactobacillus plantarum ST-III via Differential Gene Transcription and Alteration of Cell Membrane Fluidity

Abstract

dAlthough fructooligosaccharides (FOS) can selectively stimulate the growth and activity of probiotics and beneficially modulate the balance of intestinal microbiota, knowledge of the molecular mechanism for FOS metabolism by probiotics is still limited. Here a combined transcriptomic and physiological approach was used to survey the global alterations that occurred during the logarithmic growth of Lactobacillus plantarum ST-III using FOS or glucose as the sole carbon source. A total of 363 genes were differentially transcribed; in particular, two gene clusters were induced by FOS. Gene inactivation revealed that both of the clusters participated in the metabolism of FOS, which were transported across the membrane by two phosphotransferase systems (PTSs) and were subsequently hydrolyzed by a ␤-fructofuranosidase (SacA) in the cytoplasm. Combining the measurements of the transcriptome-and membrane-related features, we discovered that the genes involved in the biosynthesis of fatty acids (FAs) were repressed in cells grown on FOS; as a result, the FA profiles were altered by shortening of the carbon chains, after which membrane fluidity increased in response to FOS transport and utilization. Furthermore, incremental production of acetate was observed in both the transcriptomic and the metabolic experiments. Our results provided new insights into gene transcription, the production of metabolites, and membrane alterations that could explain FOS metabolism in L. plantarum. Prebiotics are defined as nondigestible food ingredients that selectively stimulate the growth and activity of beneficial microbial strains residing in the host gastrointestinal tract (GIT) (1). Among the sugars that are qualified as prebiotics, fructooligosaccharides (FOS) are fructose polymers of diverse lengths that can be either derivatives of simple fructose polymers or fructose moieties attached to a sucrose molecule (2). Because of the linkage configuration, FOS are not digested in the upper GIT and have been shown in vivo to beneficially modulate the composition of the intestinal microbiota by preferentially increasing the numbers of bifidobacteria and lactobacilli (3, 4).Despite considerable commercial and research interest in the beneficial effects of FOS, the molecular basis of FOS metabolism by specific members of the intestinal microbiota has only recently been examined. In order to understand the influence of environmental conditions on genome-wide gene expression levels, wholegenome DNA microarrays have often been used to survey the gene expression patterns of strains in the presence and absence of oligosaccharides (2, 5-8). On the basis of in silico analysis of the Lactobacillus acidophilus NCFM genome sequence, Barrangou et al. (2) identified a multiple-sugar metabolism (msm) operon that was involved in the metabolism of FOS. The msm operon encodes an ATP-dependent binding cassette-type transport system and a cytoplasmic ␤-fructosidase, which mediates FOS uptake and intracellular hydrolysis. Moreover, expression of the operon was i...

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“…The membrane fluidity was measured by fluorescence anisotropy as previously described with a little modification (Chen, Zhao, Chen, & Guo, ; Y. N. Liu et al, ). Briefly, approximately 10 8 conidia of strains were inoculated into 100 ml of liquid MM medium and cultured at 30°C for 13 h at 220 rpm.…”

The local transcriptional regulators SacR1 and SacR2 act as repressors of fructooligosaccharides metabolism in Lactobacillus plantarum

“…As shown in Fig. 5b [11]. Specifically, CcpA, a GalR-LacI family protein, is a vital regulator of FOS metabolism in L. plantarum [12].…”

“…Previously, we demonstrated the upregulation of the sacPTS1 and sacPTS26 clusters in response to FOS (versus glucose) after ccpA inactivation, thus demonstrating that both gene clusters may also be affected by other regulators. Moreover, sacR1 and sacR2, which encode putative repressor proteins, were identified within gene clusters related to FOS metabolism [11]. To determine the functions of SacR1 and SacR2 in FOS utilization, two mutant strains (ΔsacR1 and ΔsacR2) were constructed using the Cre-lox-based mutagenesis system [29].…”

“…Fructooligosaccharides (FOS) are non-digestible food ingredients that can selectively stimulate the growth and activity of beneficial intestinal microbiota and are considered an established type of prebiotic [4,8,9]. Several studies have demonstrated that L. plantarum can effectively utilize FOS [10][11][12].…”

“…Many possible cre sites in the putative promoter regions of these two clusters are predicted to bind to CcpA. In addition, two genes encoding the assumed repressor protein, sacR1 and sacR2, were identified in the gene cluster associated with FOS metabolism and found to exhibit significant similarity to members of the GalR-LacI family of bacterial transcription regulators [11].…”