RESUMEN
ObjectiveTo investigate the effects of using the polysaccharides from two Chinese medicine compound prescriptions as the carbon source on the growth of Bacteroides fragilis and to decipher the mechanism from the perspective of differential expression of polysaccharide utilization loci （PULs） based on transcriptomics. MethodThe media with different carbon sources ［20% polysaccharides of Lizhongtang， polysaccharides of Shenling Baizhusan， glucose， and brain heart infusion （BHI） Broth］ were used for the anaerobic culture of B. fragile ATCC25285. The effects of different carbon sources on the growth of B. fragilis ATCC25285 were determined by continuous sampling and spectrophotometry. Then， transcriptome sequencing was performed for the cultures obtained with different carbon sources to study the mechanism of different carbon sources in regulating bacterial growth. ResultThe concentration of bacteria with the polysaccharide of Lizhongtang， polysaccharide of Shenling Baizhusan， BHI Broth， and glucose as the carbon sources peaked at 26， 32， 26， 38 h， respectively， and the bacteria in all the four groups achieved robust growth. Gene ontology （GO） enrichment indicated that the differentially expressed genes in the Lizhongtang polysaccharide group and Shenling Baizhusan polysaccharide group were concentrated in the transport and transmembrane transport of dicarboxylic acid. The Shenling Baizhusan polysaccharide and BHI Broth groups showed high expression of PUL 4 and 27， glycoside hydrolase 13 （GH13）， and glycosyl transferases 5 （GT5）. PUL9 was highly expressed in Shenling Baizhusan polysaccharide group， and PUL 17， 19， and 20， GH3， and GH144 in the BHI Broth group. PUL27 and GT5 were highly expressed in Shenling Baizhusan polysaccharide and glucose groups. PUL 4 and 9 and GH13 were only highly expressed in Shenling Baizhusan polysaccharide group， and PUL 2， 17， and 19 and GH2 in the glucose group. Both Lizhongtang polysaccharide group and BHI group highly expressed PUL 4， 17， 19， 20， and 27， GH3， and GH144. PUL 2， 8， 23， and 27， GH2， and GH57 were highly expressed in Lizhongtang polysaccharide group， while GH13 showed high expression in the BHI group. Both the glucose and Lizhongtang polysacharride groups showed high expression of PUL 4 and 27 and GH2. PUL 4， 8， 20， and 23， GH3， and GH144 were highly expressed in Lizhongtang polysaccharide group， while PUL30 was highly expressed in the glucose group. ConclusionThe in vitro experiments and transcriptome sequencing results confirmed that the expression of PULs and GH may provide benefits or costs to the adaptive growth of Bacteroides fragilis ATCC25285 cultured with different carbon sources， which may be one of the mechanisms by which polysaccharides from Chinese medicine compound prescriptions regulate the growth of B. fragilis ATCC25285. The findings can provide a reference for further research on the relationship between B. fragilis metabolic pathway and polysaccharides of Chinese medicine compound prescriptions.
RESUMEN
Polysaccharide utilization loci (PULs) are a group of gene clusters related to polysaccharides catabolism and located in specific areas, including starch utilization system(SusC), SusD, encoding outer membrane glycoprotein binding proteins, and carbohydrate active enzymes. The wide existence of PULs in Bacteroides, and the extraordinary ability of utilizing polysaccharide is its survival strategy to adapt to the intestinal tract. On one hand, Bacteroides feature a high abundance and variety, making it the most important bacterial target group regulated by traditional Chinese medicine(TCM). On the other hand, polysaccharide is an important effective constituent among TCM chemicals, with a high content, and can also be used as a competitive carbon source for intestinal bacteria. Therefore, what is the mechanism of regulating the intestinal flora based on the carbon source of polysaccharide is an important part of the pharmacological research of TCM. According to the latest literatures, this paper introduces the gene and protein composition of PULs, reviews the latest developments in PULs research, and analyzes the structure of PULs in the genomes of Bacteroides fragilis and Bacteroides thetaiotaomicron. Furthermore, we also put forward a prospect for the pharmacological micro-ecological mechanism of TCM based on PULs based on our carbon source experiments, which focuses the effects of Bacteroides by TCM polysaccharides in vitro. This research is not only the new content of bacterial PULs researches, but also the important part of researches of "human-drug-bacteria" holistic view and TCM spleen-tonifying concept.