Article pubs.acs.org/JAFC
Metagenomic Insights into the Effects of Fructo-oligosaccharides (FOS) on the Composition of Fecal Microbiota in Mice Bingyong Mao,†,∥ Dongyao Li,†,∥ Jianxin Zhao,† Xiaoming Liu,† Zhennan Gu,†,‡ Yong Q. Chen,†,‡ Hao Zhang,*,†,‡ and Wei Chen*,†,‡ †
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, People’s Republic of China ‡ Synergistic Innovation Center for Food Safety and Nutrition, Wuxi 214122, People’s Republic of China S Supporting Information *
ABSTRACT: Fructo-oligosaccharides (FOS) are usually regarded as a type of prebiotic, favorably stimulating the growth of bifidobacteria and lactobacilli. However, they are not the specific substrates for these target species, and other bacteria, such as Streptococcus, Escherichia, and Clostridium, have been shown to be able to utilize FOS. Previous studies have mainly investigated only a few bacteria groups, and few reports analyzed the global effects of FOS on intestinal microbial communities. In this study the effects of FOS on gut bacteria in mice were investigated through a 16S rRNA metagenomic analysis. In the FOS-low group, the abundance of Actinobacteria significantly increased and that of Bacteroidetes decreased after FOS diet (5%) for 3 weeks. In the FOS-high group, Enterococcus was promoted and levels of Bifidobacterium and Olsenella both notably increased after FOS diet (25%) and the microbiota tended to revert to initial structure 2 weeks after FOS treatment ceased. The most striking observation was that Olsenella became a dominant genus comparable with Bif idobacterium after FOS treatment, and one strain of Olsenella, isolated from mice feces, was confirmed, for the first time, to be capable of using FOS. The results indicated that metagenomic analysis was helpful to reveal the FOS effects on the global composition of gut communities and new target for future studies. KEYWORDS: fructo-oligosaccharides, prebiotic, intestinal microbiota, 16S rRNA metagenomic, Olsenella
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INTRODUCTION The human gastrointestinal tract is home to >1012 organisms.1 Maintaining the balance of the microbial communities is crucial for host health, and perturbation of their composition may induce a range of diseases including obesity, diabetes, and inflammatory bowel disease.2−4 It is well recognized that the composition of gut microbiota is dependent on individual genotype5 and environmental factors,6−8 among which diet is of particular importance. Nondigestible oligosaccharides are able to reach the large intestine and modify the microbial community. Fructooligosaccharides (FOS) are regarded as a prebiotic and have well documented beneficial health effects,9,10 which are achieved by restructuring of the gut microbiota. Although FOS are usually considered to favorably stimulate the growth of bifidobacteria and lactobacilli, there is increasing evidence that FOS are not entirely specific for these bacteria and can also be used by nonbifidobacteria, such as Streptococcus,11 Escherichia,12 and Clostridium.13 Valcheva et al. found that FOS treatment increased the abundance of Clostridium leptum in rats14 and stimulated the growth of Faecalibacterium prausnitzii in humans.15 Shen et al. assessed the effects of FOS on Bifidobacterium, the Clostridium leptum subgroup, and Bacteriodes in human flora-associated piglets and found that the effects varied at different developmental stages.16 In contrast to most expectations, Licht et al. and Bovee-Oudehoven et al. found that dietary FOS increased colonic permeability in rats17,18 and dose-dependently increased the translocation of Salmonella in mice and rats,19−21 indicating the adverse effects of FOS consumption. Moreover, an © XXXX American Chemical Society
overdose of prebiotics can lead to the development of intestinal discomfort,9,22−24 including borborygmi and tympanites, which might be caused by the increase in gas production and osmotic pressure.22−24 Thus, the effects of FOS on gut bacteria are far more complex than the bifidogenic effects. Being limited to the analytical technologies, previous studies mainly focused on the changes of given groups of bacteria during FOS consumption, and there were few reports on the global effects of FOS use on the gut communities.25 Therefore, more detailed and extensive studies are required to investigate the effects of FOS on the composition of gut microbiota using the available advanced analytical technologies. In this study, mice were fed FOS at low and high doses, and the composition of the fecal microbiota was determined using a highthroughput MiSeq sequencing technique to assess the effects of the FOS treatment. 16S rRNA metagenomic analysis was performed on both bifidobacteria and non-bifidobacteria to reveal the relationship between FOS and gut bacteria.
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MATERIALS AND METHODS
Chemicals and Reagents. Fructo-oligosaccharides (Meioligo P, Meiji Seika Kaisha, Ltd., Japan) comprised 6.5% fructosylfructosyl nystose (GF5), 43.4% 1F-β-fructofuranosyl nystose (GF4), 40.9% nystose (GF3), 7.1% 1-kestose (GF2), and 2.1% glucose and fructose.
Received: October 24, 2014 Revised: January 6, 2015 Accepted: January 8, 2015
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Figure 1. Experimental design. Thirty-two mice were randomly and equally divided into four groups (control, FOS-low, FOS-high, and FOS-acute). In the control group, mice were fed the control diet (FOS, 0%), and feces were collected at the 1st and 4th weeks. In the FOS-low group, mice were fed diet supplemented with FOS (5%) for 3 weeks, and feces were collected at the 1st, 4th, and 6th weeks. In the FOS-high group, mice were fed diet with FOS at increasing proportions, 5% for the 2nd week, 15% for the 3rd week, and 25% for the 4th week. Feces were collected at the 1st, 2nd, 3rd, 4th, and 6th weeks. In the FOS-acute group, mice were fed diet with FOS (25%) for 2 days and feces were collected before and after the FOS treatment. Animals and Sample Collection. Six-week-old male C57BL/6J mice were obtained from the Shanghai Laboratory Animal Center (Shanghai, China) and maintained in an IVC rodent caging system. The mice were housed in a temperature- and humidity-controlled room under a strict 12 h light cycle and fed a commercial mouse diet; water was given ad libitum. All of the protocols used in this study were approved by the Ethics Committee of Jiangnan University, China (JN No. 20140306-0910-7), and the procedures were carried out in accordance with the European Community guidelines (Directive 2010/63/EU) for the care and use of experimental animals. The mice were randomly divided into four groups (n = 8 for each group), as shown in Figure 1. The average body weight was 19.6 ± 0.8 g. The mice were adapted to the new environment for 1 week, followed by a 3 week intervention period and a 2 week washout period. The commercial diet was smashed and amended with FOS at different proportions, and pellets were formed. In this study, the dose of FOS was determined according to a pre-experiment. Twenty-four 6-week old male C57BL/6J mice were randomly and equally divided into six groups, which were given diets supplemented with FOS at proportions of 2, 5, 10, 20, 25, and 30%. The diet was weighed daily to calculate the FOS intake, and the FOS proportions corresponded to doses of 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 g of FOS per mouse per day (PMPD), respectively. Feces were daily collected for observation. Diarrhea was diagnosed as poorly formed, looser, and more watery feces than normal. Slight diarrhea was found in the 25 and 30% groups after 1 week. Therefore, the FOS proportion was set at 5% for the FOS-low group and 25% for the FOS-high group. The dose was based on a body weight of 20 g. As shown in Figure 1, the control group was fed the control diet (FOS, 0%) throughout the experiment, and the other three groups were fed the diets supplemented with FOS at different proportions (5, 15, and 25%) during the intervention period. Diet was weighed daily and recorded for calculating the actual FOS intake (Supporting Information, Figure S1), and body weight was recorded every week. At the times indicated in Figure 1, mice were transferred to separate sterilized cages, and feces were collected in individual sterile EP tubes on ice, which were taken to the laboratory within 2 h of collection for further study. After the experiment, the mice were euthanized by intraperitoneal injection of 200 mg/kg sodium pentobarbital euthanasia solution. DNA Extraction, PCR Amplification, Quantification, and Sequencing. Microbial genome DNA was extracted from fecal samples using FastDNA Spin Kit for Soil (MP Biomedicals, catalog no. 6560200) following the manufacturer’s instructions. The V4 region of the 16S rRNA was PCR amplified from microbial genome DNA using the primers (forward primer, 5′-AYTGGGYDTAAAGNG-3′; reverse primer, 5′-TACNVGGGTATCTAATCC-3′) as described previously.26 The PCR procedures were 95 °C for 5 min; 95 °C for 30 s, 50 °C for 30 s, and 72 °C for 30 s, repeat for 30 cycles; and 72 °C for 10 min. The PCR products were excised from a 1.5% agarose gel, purified by GeneClean Turbo (MP Biomedicals, catalog no. 111102400) and quantified by Quant-iT PicoGreen dsDNA Assay Kit (Life Tech-
nologies, catalog no. P7589) according to the instructions. Libraries were prepared using TruSeq DNA LT Sample Preparation Kit (Illumina, catalog no. FC-121-2001) and sequenced for 500+7 cycles on Illumina Miseq using the MiSeq Reagent Kit (500 cycles-PE, catalog no. MS-102-2003). Bioinformatic Analysis. Sequences with an average quality score 0.5%) for the control group; (C) principal coordinate (PCoA) score plots based on unweighted UniFrac metrics at the different periods (each point represents the composition of fecal microbiota of one mouse); relative abundance of main phyla (D) and genera >0.1% (E) at different periods. Sequences that could not be classified into any known group were assigned as “other”. Con, control group; Low, FOS-low group. The number following the abbreviations stands for the mouse number. For example, Con1 and Con2 stand for the first and second mice in the control group. Con-0 stands for the 1st week. The number following “Low-” stands for the period: “0”, before FOS treatment; “1”, intervention period; “2”, washout period. The abundance of main phyla is expressed as the mean ± SEM. Waters SugarPak1 column (6.5 × 300 mm, i.d. = 3.5 μm), and the column temperature was set at 85 °C. The mobile phase was water with the flow rate of 0.4 mL/min, and the injection volume was 10 μL.
community was mostly dominated by Firmicutes and Bacteroidetes, and the average ratio between Firmicutes and Bacteroidetes was 3.04 (ranging from 0.42 to 5.04). At the genus level (Figure 2B), unknown genera belonging to Firmicutes, Porphyromonadaceae, Clostridiales, Lachnospiraceae, Bacteroidetes, Desulfovibrionales, Bacteroidales, and Proteobacteria and Alistipes, Lactobacillus, Olsenella, Bif idobacterium, Helicobacter, Odoribacter, Anaeroplasma, Catenibacterium, Enterorhabdus, and Oscillibacter all comprised >0.5% of the microbiota. The fecal microbiota was profoundly affected after FOS treatment (0.2 g PMPD) for 3 weeks (Figure 2C). The abundance of Firmicutes was maintained at about 60%, whereas that of Bacteroidetes dropped markedly from 29.0 to 3.3% (Figure 2D). Accordingly, the average ratio of Firmicutes and Bacteroidetes
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RESULTS A data set consisting of 1,265,448 high-quality, classifiable 16S rRNA gene sequences was generated from 93 fecal samples through MiSeq sequencing analysis. The average sequence read was 13607 per sample (Supporting Information, Table S1). All of the sequences were clustered with representative sequences, and a 97% sequence identity cutoff was used. The number of OTUs per sample ranged between 334 and 2936 (Table S1). Effect of FOS at Low Dose on the Composition of Fecal Microbiota. At the phylum level (Figure 2A,B), the gut bacteria C
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Figure 3. Effect of FOS with increasing doses on the fecal microbiota. (A) Relative abundance of main phyla at different periods. Sequences that could not be classified into any known group were assigned as “other”. High, FOS-high group. High1, High2, High3, High4, High5, High6, High7, and High8 stand for the first, second, third, fourth, fifth, sixth, seventh, and eighth mice in the FOS-high group. The number following “High-” stands for the period. “0”, before FOS treatment; “1”, intervention period (FOS, 5%); “2”, intervention period (FOS, 15%); “3”, intervention period (FOS, 25%); “4”, washout period. (B) Principal coordinate (PCoA) score plots were based on unweighted UniFrac metrics at the different periods. Each point represents the composition of fecal microbiota of one mouse. (C) Relative abundance of main genera >0.1% at different periods. (D) Changes of the abundance of selected genera at different periods. Mean values ± SEM are plotted. Significant differences (P < 0.05) are indicated with different letters (a, b, c).
Actinobacteria (P < 0.01, Student’s t test) and a decrease in Bacteroidetes were observed at the fourth week (High-3). The data points shift from the left of the score plot (High-2) to the right side of the graph (High-3) at the fourth week, indicating significant changes in the fecal microbiota (Figure 3B). Among the Actinobacteria, Bif idobacterium and Olsenella were the two most abundant genera. During the first 3 weeks, the levels of these genera remained lower. However, they both increased significantly (Figure 3C, P < 0.05, Student’s t test) at the fourth week when the dose reached 0.8 g PMPD. For Lactobacillus, no significant changes were observed during the FOS treatment except for significant increases in two mice at the fourth week. Two weeks after the FOS treatment stopped, the fecal microbiota changed and tended to revert to the original levels before the FOS treatment as indicated by the cluster results between the data points of High-4 and High-0 (Figure 3B). During the first 3 weeks, the level of Enterococcus remained low at 0.1%. However, it significantly increased to 4.0% at the fourth week (Figure 3D). The levels of Streptococcus and Clostridium were also increased at the fourth week, although the increases were not significant and their abundance remained low (Figure 3D). Similarly to Bif idobacterium, the abundance of Olsenella significantly increased, and it was even higher than that of
increased to 34.97 (ranging from 9.97 to 79.89). Moreover, significant increases in Actinobacteria (P < 0.01, Student’s t test) were observed. As expected, the abundance of Bifidobacterium was significantly increased (Figure 2E, P < 0.05), confirming the bifidogenic property of FOS. However, the level of Lactobacillus remained stable during the FOS treatment. In addition, the levels of many non-bifidobacteria increased after the FOS treatment. Interestingly, the level of Olsenella belonging to Actinobacteria increased significantly from 0.7 to 10.7% (P < 0.01, Student’s t test), which was even higher than that of Bif idobacterium. During the washout period, the diet was reverted to the control diet. Slight decreases in Actinobacteria and Proteobacteria were observed (Figure 2D). The abundance of Olsenella was also reduced (Figure 2E). It seems that the effect of FOS on the fecal microbiota did not last long, although the original composition had not fully recovered after 2 weeks. Effects of FOS at High Dose on the Composition of Fecal Microbiota. During the intervention period, the proportion of Actinobacteria continued to increase and reached 44.8% (P < 0.01, Student’s t test), whereas that of Firmicutes declined from 57.1 to 34.2% (Figure 3A, P < 0.01, Student’s t test). As shown in Figure 3A, a significant increase in D
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Figure 4. Effect of one-time consumption of FOS on the fecal microbiota. (A) Principal coordinate (PCoA) score plots based on weighted UniFrac metrics. Each point represents the composition of fecal microbiota of one mouse. Relative abundance of five phyla >1% (B) and main genera of different mice before and after FOS treatment (C). Sequences that could not be classified into any known group were assigned as “other”. Acu, FOS-acute group; Acu-0, before FOS treatment; Acu-1, after FOS treatment. Acu1, Acu2, Acu3, Acu4, Acu5, Acu6, Acu7, and Acu8 stand for the first, second, third, fourth, fifth, sixth, seventh, and eighth mice in the FOS-acute group. The abundance of main phyla is expressed as the mean ± SEM (∗, P < 0.05, Student’s t test).
Table 1. Ratio of Bif idobacterium and Olsenella before and after FOS Treatment mice Bifidobacterium/ Olsenella (B/O)
Acu-0 Acu-1
Acu1
Acu2
Acu3
Acu4
Acu5
Acu6
Acu7
Acu8
0.53 2.65
0.77 0.76
2.61 1.15
0.79 1.42
0.53 2.21
3.30 1.09
0.92 0.64
0.16 0.04
Bifidobacterium in several mice at the fourth week. Therefore, more attention needs to be paid to the non-bifidobacteria, especially Olsenella and Enterococcus, during FOS treatment at high doses. Effects of FOS on the Fecal Microbiota in an Acute Model. An acute model was established to study the effect of one-time consumption of FOS on fecal microbiota. After 2 days of FOS treatment (FOS, 25%), feces were collected and sequenced. A PCoA based on unweighted Unifrac distances was performed using the obtained sequence data (Figure 4A). Points representing the fecal microbiota of mice before (Acu-0)
and after treatment (Acu-1) clustered at the bottom right and top left, respectively. There were significant increases in Actinobacteria (P < 0.001, Student’s t test) and slight decreases in Bacteroidetes and Firmicutes (Figure 4B). The dramatic increase of Actinobacteria was mainly attributable to the significant increases in Bif idobacterium and Olsenella (Figure 4C, P < 0.05, Student’s t test). However, the level of Bif idobacterium was not significantly different from that of Olsenella. Therefore, the FOS were able to selectively stimulate the rapid growth of both Bif idobacterium and Olsenella in the gut. To make clear the effects of initial abundance of bacteria on the final abundance, E
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Journal of Agricultural and Food Chemistry correlation between the initial and final ratios of Bif idobacterium and Olsenella (B/O) was investigated (Table 1). The Pearson correlation coefficient was −0.07, which suggests that the final B/ O was not correlated with the initial B/O. Isolation and Identification of Olsenella from Mouse Feces and Characterization of Its Growth on FOS. After 7 days of enrichment, seven purified isolates from fecal samples were identified by 16S rRNA sequencing, one of which was confirmed as the genus Olsenella (Table 2). The most positive
However, previous studies have mainly focused on specific organisms, such as bifidobacteria, lactobacilli, clostridia, and bacteriodes.16,32−34 In this study, the effects of FOS on intestinal bacterial populations were investigated using 16S rRNA metagenomic analysis, which can cover the genera existing in the gut. The FOS were found to alter the intestinal microbiota. Significant increases in the abundance of Actinobacteria and decreases in Bacteroidetes were observed after FOS treatment (Figures 2D and 3A, High-3), consistent with the results of Rycroft et al.,33 who evaluated the in vitro fermentation properties of prebiotics on fecal slurry. However, no effect or higher Bacteroidetes were observed in mice fed FOS,34,35 which was consistent with the results at lower doses (Figure 3A, High-1, High-2), indicating that the effect of FOS on Bacteroidetes was dependent on dose and time. After 3 weeks, the abundance of Firmicutes remained at 60% for the FOS-low group (Figure 2D), but dropped to 35% for the FOS-high group (Figure 3A), indicating that the effect of FOS on the composition of the intestinal microbiota was dependent on the dose. Moreover, the microbial diversity within each group was quantified at given time points (α diversity) (Figure 6). The Shannon index (SI) was estimated to evaluate the ecological diversity of the microbiota in each fecal sample, with a higher SI indicating greater diversity. Significant decreases in α diversity were detected for High-3 and Acu-1 (P < 0.05). The decrease for Acu-0 occurred after only 2 days on the FOS diet (FOS, 25%), demonstrating that diet rapidly altered the gut bacteria.36 Therefore, FOS treatment at a dose of 0.8 g PMPD had a profound effect on the composition and diversity of the intestinal microbiota. Furthermore, the microbiota reverted to their original structure during the washout period (Figure 6), suggesting that the bacterial populations gradually reverted to their prefeeding structures once the FOS treatment ceased.34,37 During the FOS treatment, the most striking change in the fecal microbiota was the increase in Actinobacteria, of which Bif idobacterium and Olsenella were the two most dominant genera. It is not surprising that the FOS stimulated the growth of Bif idobacterium. However, the abundance of Olsenella was also significantly increased and was even higher than Bifidobacterium in certain mice (Figures 3B and 4C). Olsenella has been described as a member of the oral microbiota38,39 and is considered an
Table 2. Identified Strains Isolated from Mouse Feces no.
strain
most positive match
1
Mou01
2 3
Mou02 Mou03
4 5
Mou04 Mou09
6
Mou12
7
Mou19
Lactobacillus animalis JCM 8697 (AB911535.1) Olsenella sp. F0004 (EU592964.1) Lactobacillus animalis JCM 8697 (AB911535.1) Lactobacillus sp. sy4 (KJ801851.1) Lactobacillus johnsonii strain LB-19 (HM772969.1) Lactobacillus taiwanensis JCM 8687 (AB911525.1) Lactobacillus taiwanensis JCM 8687 (AB911525.1)
Ident (%)
GenBank
99
KM405313
93 99
KM405314 KM405315
99 99
KM405316 KM405318
99
KM405319
99
KM405320
match was Olsenella sp. F0004 (accession no. EU592964.1). However, the “Ident” was only 93%, indicating that this strain may belong to unknown species of the genus Olsenella. In addition, the sequence of the V4 region of 16S rRNA for Olsenella (206 bp) was obtained from the established MiSeq library, which could be found in the sequences of 16S rRNA for mou02 (1373 bp). The strain mou02 grew faster in BHI medium with the addition of FOS (Figure 5A), indicating that FOS could be used by the Olsenella strain mou02, which was confirmed by HPLC analysis (Figure 5B).
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DISCUSSION FOS have long been known to act as a prebiotic that can improve human health by selectively stimulating the growth of beneficial bacteria and reducing the levels of putrefactive bacteria.
Figure 5. (A) Growth of the Olsenella strain mou02 in BHI and BHI-FOS media. The concentration of FOS was 8 g/L. (B) HPLC analysis of the supernatant for the Olsenella strain mou02 in BHI-FOS medium at different times: ―, 0 h; ···, 12 h; - - -, 24 h. Peaks at 7.3, 7.7, 8.5, and 9.9 min were assigned as GF5, GF4, GF3, and GF2, respectively. F
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Bif idobacterium after FOS treatment, especially at high doses, and we proved for the first time that one strain of Olsenella was able to grow on FOS. More attention should be paid to the nonbifidobacteria, such as Olsenella and Enterococcus, in future studies to reveal the interactions between FOS and human gut bacteria.
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ASSOCIATED CONTENT
S Supporting Information *
Table S1 and Figure S1. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Authors
*(H.Z.) Phone: 86-510-85912155. Fax: 86-510-85912155. Email:
[email protected]. *(W.C.) Phone: 86-510-85912155. Fax: 86-510-85912155. Email:
[email protected] Figure 6. Shannon index of fecal samples at different periods (α diversity.). Con, control group; Low, FOS-low group; High, FOS-high group; Acu, FOS-acute group. Low-0, before FOS treatment; Low-1, intervention period; Low-2, washout period; High-0, before FOS treatment; High-1, intervention period (FOS, 5%); High-2, intervention period (FOS, 15%); High-3, intervention period (FOS, 25%); High-4, washout period; Acu-0, before FOS treatment; Acu-1, after FOS treatment. Significant differences (P < 0.05) are indicated with different letters (a, b, c). ∗, P < 0.05.
Author Contributions ∥
B.M. and D.L. contributed equally to this work.
Funding
This work was supported by the key projects in the national science and technology pillar program during the 12th five-year plan period (No. 2012BAD28B07, 2012BAD28B08, 2013BAD18B01, and 2013BAD18B02), the 111 project B07029, the Program for Changjiang Scholars and Innovative Research Team in University (IRT1249), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.
opportunistic pathogen according to Technische Regeln für Biologische Arbeitstoffe (TRBA 466) and the Human Opportunistic Pathogen (HOP) Library (Gifu University, Genetic information Genetic Resource Center of Human Pathogens) that is closely related to endodontic disease.38,39 Olsenella is also part of the normal bacterial flora in the human gut (http://www.hmpdacc.org/resources/data_browser.php). 40 However, little is known about the role that Olsenella plays in the gut, and the genus is seldom mentioned in previous studies on the effects of FOS on intestinal microbiota. Owing to the highthroughput MiSeq sequencing technique used in this study, Olsenella was found to be greatly stimulated by FOS and became the dominant genus comparable with Bifidobacterium after the FOS treatment. Moreover, we extensively explored the changes of all genera in the gut, rather than focusing on only limited and specific bacteria. Therefore, we suspect that the FOS preferentially stimulated the growth of beneficial bacteria such as Bif idobacterium at a low dose but that they also promoted the non-bifidobacteria such as Olsenella and Enterococcus when the dose was sufficiently high. One strain of Olsenella was isolated from the mouse feces and was confirmed to be capable of utilizing FOS (Table 2; Figure 5). This may be the first reported finding on the utilization of FOS by Olsenella. Although not examined in this study, some bacteria in the Enterococcus, Streptococcus, and Clostridium genera may also have the ability to use FOS. In conclusion, 16S rRNA metagenomic analysis was helpful in investigating the global effects of FOS on the composition of intestinal microbiota. The FOS were found to alter the microbiota, stimulating the growth of Bif idobacterium and Olsenella at low doses and promoting the growth of nonbifidobacteria such as Enterococcus at high doses. However, the FOS effects were not permanent and the microbiota gradually reverted to their initial structure after the FOS treatment ceased. Owing to the high-throughput MiSeq sequencing technique, we found that Olsenella became a dominant genus comparable with
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We thank Shunhe Wang for technical assistance with mouse care and treatment. ABBREVIATIONS USED FOS, fructo-oligosaccharides; OTU, operational taxonomic unit; PMPD, per mouse per day; PCoA, principal coordinate analysis; BHI, brain−heart infusion; Acu, acute
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Journal of Agricultural and Food Chemistry
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DOI: 10.1021/jf505156h J. Agric. Food Chem. XXXX, XXX, XXX−XXX
