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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.
摘要：
半乳糖寡糖（GOS）是有据可查的益生元化合物，但是对乳酸菌利用GOS的代谢和调节机制的了解仍然有限。在这里，我们使用转录组和生理分析来研究植物乳杆菌和植物乳杆菌ΔccpA代谢GOS或葡萄糖作为碳水化合物的唯一来源的对数生长期的差异。总的来说,在葡萄糖和GOS上生长的野生型植物乳杆菌中差异转录了489个基因（16％），由于ccpA的丢失，该值降低至7％。当在GOS上比较野生型和ccpA突变体时，只有6％的基因差异表达。转录组数据显示，碳源显著影响几个基因的表达，一些基因是由CpA介导的。特别是,lac和gal基因簇类似于嗜酸乳杆菌NCFM中参与GOS代谢的相应簇，表明这些集群可能参与了GOS的利用。此外，逆转录-PCR分析显示GOS相关基因簇组织在五个独立的多顺反子单元中。此外,在植物乳杆菌中发现低聚果糖和GOS代谢之间存在许多共性，包括参与寡糖代谢的差异表达基因，代谢物的转化，和脂肪酸生物合成的变化。总的来说,我们的发现提供了有关基因转录和与GOS利用相关的代谢机制的新信息，并证实CpA在植物乳杆菌的碳代谢调控中起重要作用。
