Selective colonization of insoluble substrates by human faecal bacteria

Insoluble plant polysaccharides and endogenous mucin are important energy sources for human colonic microorganisms. The object of this study was to determine whether or not specific communities colonize these substrates. Using faecal samples from four individuals as inocula for an anaerobic in vitro continuous flow system, the colonization of wheat bran, high amylose starch and porcine gastric mucin was examined. Recovered substrates were extensively washed and the remaining tightly attached bacterial communities were identified using polymerase chain reaction-amplified 16S rRNA gene sequences and fluorescent in situ hybridization. The substrate had a major influence on the species of attached bacteria detected. Sequences retrieved from bran were dominated by clostridial cluster XIVa bacteria, including uncultured relatives of Clostridium hathewayi, Eubacterium rectale and Roseburia species. Bacteroides species were also detected. The most abundant sequences recovered from starch were related to the cultured species Ruminococcus bromii, Bifidobacterium adolescentis, Bifidobacterium breve and E. rectale. The most commonly recovered sequences from mucin were from Bifidobacterium bifidum and uncultured bacteria related to Ruminococcus lactaris. This study suggests that a specific subset of bacteria is likely to be the primary colonizers of particular insoluble colonic substrates. For a given substrate, however, the primary colonizing species may vary between host individuals.     

Lactate-utilizing bacteria, isolated from human feces, that produce butyrate as a major fermentation product

The microbial community of the human colon contains many bacteria that produce lactic acid, but lactate is normally detected only at low concentrations (<5 mM) in feces from healthy individuals. It is not clear, however, which bacteria are mainly responsible for lactate utilization in the human colon. Here, bacteria able to utilize lactate and produce butyrate were identified among isolates obtained from 10(-8) dilutions of fecal samples from five different subjects. Out of nine such strains identified, four were found to be related to Eubacterium hallii and two to Anaerostipes caccae, while the remaining three represent a new species within clostridial cluster XIVa based on their 16S rRNA sequences. Significant ability to utilize lactate was not detected in the butyrate-producing species Roseburia intestinalis, Eubacterium rectale, or Faecalibacterium prausnitzii. Whereas E. hallii and A. caccae strains used both D- and L-lactate, the remaining strains used only the d form. Addition of glucose to batch cultures prevented lactate utilization until the glucose became exhausted. However, when two E. hallii strains and one A. caccae strain were grown in separate cocultures with a starch-utilizing Bifidobacterium adolescentis isolate, with starch as the carbohydrate energy source, the L-lactate produced by B. adolescentis became undetectable and butyrate was formed. Such cross-feeding may help to explain the reported butyrogenic effect of certain dietary substrates, including resistant starch. The abundance of E. hallii in particular in the colonic ecosystem suggests that these bacteria play important roles in preventing lactate accumulation.     

Two routes of metabolic cross-feeding between Bifidobacterium adolescentis and butyrate-producing anaerobes from the human gut

Dietary carbohydrates have the potential to influence diverse functional groups of bacteria within the human large intestine. Of 12 Bifidobacterium strains of human gut origin from seven species tested, four grew in pure culture on starch and nine on fructo-oligosaccharides. The potential for metabolic cross-feeding between Bifidobacterium adolescentis and lactate-utilizing, butyrate-producing Firmicute bacteria related to Eubacterium hallii and Anaerostipes caccae was investigated in vitro. E. hallii L2-7 and A. caccae L1-92 failed to grow on starch in pure culture, but in coculture with B. adolescentis L2-32 butyrate was formed, indicating cross-feeding of metabolites to the lactate utilizers. Studies with [(13)C]lactate confirmed carbon flow from lactate, via acetyl coenzyme A, to butyrate both in pure cultures of E. hallii and in cocultures with B. adolescentis. Similar results were obtained in cocultures involving B. adolescentis DSM 20083 with fructo-oligosaccharides as the substrate. Butyrate formation was also stimulated, however, in cocultures of B. adolescentis L2-32 grown on starch or fructo-oligosaccharides with Roseburia sp. strain A2-183, which produces butyrate but does not utilize lactate. This is probably a consequence of the release by B. adolescentis of oligosaccharides that are available to Roseburia sp. strain A2-183. We conclude that two distinct mechanisms of metabolic cross-feeding between B. adolescentis and butyrate-forming bacteria may operate in gut ecosystems, one due to consumption of fermentation end products (lactate and acetate) and the other due to cross-feeding of partial breakdown products from complex substrates.     

Genetic Diversity of Viable, Injured, and Dead Fecal Bacteria Assessed by Fluorescence-Activated Cell Sorting and 16S rRNA Gene Analysis

A novel approach combining a flow cytometric in situ viability assay with 16S rRNA gene analysis was used to study the relationship between diversity and activity of the fecal microbiota. Simultaneous staining with propidium iodide (PI) and SYTO BC provided clear discrimination between intact cells (49%), injured or damaged cells (19%), and dead cells (32%). The three subpopulations were sorted and characterized by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene amplicons obtained from the total and bifidobacterial communities. This analysis revealed that not only the total community but also the distinct subpopulations are characteristic for each individual. Cloning and sequencing of the dominant bands of the DGGE patterns showed that most of clones retrieved from the live, injured, and dead fractions belonged to Clostridium coccoides, Clostridium leptum, and Bacteroides. We found that some of the butyrate-producing related bacteria, such as Eubacterium rectale and Eubacterium hallii, were obviously viable at the time of sampling. However, amplicons affiliated with Bacteroides and Ruminococcus obeum- and Eubacterium biforme-like bacteria, as well as Butyrivibrio crossotus, were obtained especially from the dead population. Furthermore, some bacterial clones were recovered from all sorted fractions, and this was especially noticeable for the Clostridium leptum cluster. The bifidobacterial phylotypes identified in total samples and sorted fractions were assigned to Bifidobacterium adolescentis, Bifidobacterium longum, Bifidobacterium infantis, Bifidobacterium pseudocatenulatum, and Bifidobacterium bifidum. Phylogenetic analysis of the live, dead, and injured cells revealed a remarkable physiological heterogeneity within these bacterial populations; B. longum and B. infantis were retrieved from all sorted fractions, while B. adolescentis was recovered mostly from the sorted dead fraction.     

慢性乙型肝炎患者肠道菌群与肝脏生化指标的相关性

乙型肝炎病毒感染引起的慢性乙型肝炎(Chronic hepatitis B,CHB)是一种全球性流行疾病,严重时可引起肝功能衰竭,甚至发展成肝硬化和肝癌.也已发现CHB的发生和发展与肠道菌群的组成和结构的变化密切相关.为进一步探究肠道菌群结构与肝脏生化指标之间的联系,文中随机纳入14名CHB患者和11名健康对照者(Co...     

Ruminococcus bromii, identification and isolation as a dominant community member in the rumen of cattle fed a barley diet

AIMS: To identify dominant bacteria in grain (barley)-fed cattle for isolation and future use to increase the efficiency of starch utilization in these cattle. METHODS AND RESULTS: Total DNA was extracted from samples of the rumen contents from eight steers fed a barley diet for 9 and 14 days. Bacterial profiles were obtained using denaturing gradient gel electrophoresis (DGGE) of the PCR-amplified V2/V3 region of the 16S rRNA genes from total bacterial DNA. Apparently dominant bands were excised and cloned, and the clone insert sequence was determined. One of the most common and dominant bacteria present was identified as Ruminococcus bromii. This species was subsequently isolated using traditional culture-based techniques and its dominance in the grain-fed cattle was confirmed using a real-time Taq nuclease assay (TNA) designed for this purpose. In some animals, the population of R. bromii reached densities above 10(10)R. bromii cell equivalents per ml or approximately 10% of the total bacterial population. CONCLUSIONS: Ruminococcus bromii is a dominant bacterial population in the rumen of cattle fed a barley-based diet. SIGNIFICANCE AND IMPACT OF THE STUDY: Ruminococcus bromii YE282 may be useful as a probiotic inoculant to increase the efficiency of starch utilization in barley-fed cattle. The combination of DGGE and real-time TNA has been an effective process for identifying and targeting for isolation, dominant bacteria in a complex ecosystem.     

Phylotypes related to Ruminococcus bromii are abundant in the large bowel of humans and increase in response to a diet high in resistant starch

To further understand how diets containing high levels of fibre protect against colorectal cancer, we examined the effects of diets high in nonstarch polysaccharides (NSP) or high in NSP plus resistant starch (RS) on the composition of the faecal microbial community in 46 healthy adults in a randomized crossover intervention study. Changes in bacterial populations were examined using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. Bacterial profiles demonstrated changes in response to the consumption of both RS and NSP diets [analysis of similarities (ANOSIM): R=0.341-0.507, P<0.01]. A number of different DGGE bands with increased intensity in response to dietary intervention were attributed to as-yet uncultivated bacteria closely related to Ruminococcus bromii. A real-time PCR assay specific to the R. bromii group was applied to faecal samples from the dietary study and this group was found to comprise a significant proportion of the total community when individuals consumed their normal diets (4.4+/-2.6% of total 16S rRNA gene abundance) and numbers increased significantly (+/-67%, P<0.05) with the RS, but not the NSP, dietary intervention. This study indicates that R. bromii-related bacteria are abundant in humans and may be significant in the fermentation of complex carbohydrates in the large bowel.     

In vitro determination of prebiotic properties of oligosaccharides derived from an orange juice manufacturing by-product stream

Fermentation properties of oligosaccharides derived from orange peel pectin were assessed in mixed fecal bacterial culture. The orange peel oligosaccharide fraction contained glucose in addition to rhamnogalacturonan and xylogalacturonan pectic oligosaccharides. Twenty-four-hour, temperature- and pH-controlled, stirred anaerobic fecal batch cultures were used to determine the effects that oligosaccharides derived from orange products had on the composition of the fecal microbiota. The effects were measured through fluorescent in situ hybridization to determine changes in bacterial populations, fermentation end products were analyzed by high-performance liquid chromatography to assess short-chain fatty acid concentrations, and subsequently, a prebiotic index (PI) was determined. Pectic oligosaccharides (POS) were able to increase the bifidobacterial and Eubacterium rectale numbers, albeit resulting in a lower prebiotic index than that from fructo-oligosaccharide metabolism. Orange albedo maintained the growth of most bacterial populations and gave a PI similar to that of soluble starch. Fermentation of POS resulted in an increase in the Eubacterium rectale numbers and concomitantly increased butyrate production. In conclusion, this study has shown that POS can have a beneficial effect on the fecal microflora; however, a classical prebiotic effect was not found. An increase in the Eubacterium rectale population was found, and butyrate levels increased, which is of potential benefit to the host.     

Effects of alternative dietary substrates on competition between human colonic bacteria in an anaerobic fermentor system

Duplicate anaerobic fermentor systems were used to examine changes in a community of human fecal bacteria supplied with different carbohydrate energy sources. A panel of group-specific fluorescent in situ hybridization probes targeting 16S rRNA sequences revealed that the fermentors supported growth of a greater proportion of Bacteroides and a lower proportion of gram-positive anaerobes related to Faecalibacterium prausnitzii, Ruminococcus flavefaciens-Ruminococcus bromii, Eubacterium rectale-Clostridium coccoides, and Eubacterium cylindroides than the proportions in the starting fecal inoculum. Nevertheless, certain substrates, such as dahlia inulin, caused a pronounced increase in the number of bacteria related to R. flavefaciens-R. bromii and E. cylindroides. The ability of three strictly anaerobic, gram-positive bacteria to compete with the complete human fecal flora was tested in the same experiment by using selective plating to enumerate the introduced strains. The Roseburia-related strain A2-183(F) was able to grow on all substrates despite the fact that it was unable to utilize complex carbohydrates in pure culture, and it was assumed that this organism survived by cross-feeding. In contrast, Roseburia intestinalis L1-82(R) and Eubacterium sp. strain A2-194(R) survived less well despite the fact that they were able to utilize polysaccharides in pure culture, except that A2-194(R) was stimulated 100-fold by inulin. These results suggest that many low-G+C-content gram-positive obligate anaerobes may be selected against during in vitro incubation, although several groups were stimulated by inulin. Thus, considerable caution is necessary when workers attempt to predict the in vivo effects of probiotics and prebiotics from their effects in vitro.     

Dominance of <Emphasis Type="Italic">Prevotella</Emphasis> and low abundance of classical ruminal bacterial species in the bovine rumen revealed by relative quantification real-time PCR

Relative quantification real-time PCR was used to quantify several bacterial species in ruminal samples from two lactating cows, each sampled 3 h after feeding on two successive days. Abundance of each target taxon was calculated as a fraction of the total 16S rRNA gene copies in the samples, using taxon-specific and eubacterial domain-level primers. Bacterial populations showed a clear predominance of members of the genus Prevotella, which comprised 42% to 60% of the bacterial rRNA gene copies in the samples. However, only 2% to 4% of the bacterial rRNA gene copies were represented by the classical ruminal Prevotella species Prevotella bryantii, Prevotella ruminicola and Prevotella brevis. The proportion of rRNA gene copies attributable to Fibrobacter succinogenes, Ruminococcus flavefaciens, Selenomonas ruminantium and Succinivibrio dextrinosolvens were each generally in the 0.5% to 1% range. Proportions for Ruminobacter amylophilus and Eubacterium ruminantium were lower (0.1% to 0.2%), while Butyrivibrio fibrisolvens, Streptococcus bovis, Ruminococcus albus and Megasphaera elsdenii were even less abundant, each comprising <0.03% of the bacterial rRNA gene copies. The data suggest that the aggregate abundance of the most intensively studied ruminal bacterial species is relatively low and that a large fraction of the uncultured population represents a single bacterial genus.     

Analysis of intestinal flora of a patient with congenital absence of the portal vein

Abstract A 14-year-old female patient, admitted for a closer examination of liver tumour (hepatocellular adenoma), was diagnosed as having a congenital absence of the portal vein. The blood ammonia level (approximately 120 μg dl⁻¹) in the superior mesenteric vein was markedly low compared to the normal value of 300–350 μg dl⁻¹ in the portal vein. The decreased ammonia concentration and urease activity of the patient's faeces were demonstrated. The dominant intestinal flora in the faeces of the patient, before operation, was Bifidobacterium sp., Bifidobacterium breve, Bifidobacterium lonqum, Lactobacillus plantarum , and after the operation Bacteroides vulgatus, Veillonella parvula, Peptococcus magnus Bifidobacterium longum . In contrast, Bifidobacterium bifidum, Bacteroides ureolyticus, Bacteroides ovatus and Bacteroides distasonis, B. ovatus, Bifidobacterium adolescentis were dominant flora in the faeces of two healthy volunteers, respectively. Among microorganisms isolated from the patient, Morganella morganii, Candida sp., Eubacterium aerofacience and Eubacterium rectale were strongly positive in urease activity in vitro; Streptococcus mitior, Staphylococcus intermedius, Micrococcus kristinae, Selenomonas ruminantum, Bacteroides ureolyticus and Lactobacillus casei ss. pseudoplantarum from the healthy volunteers. These results imply the homeostatic regulation system of faecal ammonia concentration by urease-producing microorganisms in the patient.     

Evaluation of three different forward primers by terminal restriction fragment length polymorphism analysis for determination of fecal bifidobacterium spp. in healthy subjects

The 27F forward primer is frequently used in 16S rRNA gene libraries and T-RFLP analysis. However, Bifidobacterium spp. were barely detected with this primer in human fecal samples. In this study, fecal microbiota were analyzed using the T-RFLP method with three different forward primers (27F, 35F, and 529F) in conjunction with one reverse primer (1492R). T-RFLP analysis of fecal microbiota using 35F and 529F detected higher proportions of the terminal restriction fragment (T-RF) corresponding to Bifidobacterium spp. than that using 27F. 27F is in imperfect agreement while 35F and 529F are in good concordance with the 16S rRNA gene sequences of Bifidobacterium spp., and the latter primers allowed for the detection of T-RFs of Bifidobacterium spp. in fecal samples from five healthy subjects. The T-RFs presumed to be Bifidobacterium spp. were cloned and sequenced, and found to match the 16S rRNA gene sequences of Bifidobacterium spp. Among the five fecal samples, two samples with low frequencies of T-RFs of Bifidobacterium spp. were detected using these forward primers. This probably reflects a low prevalence of Bifidobacterium spp. in these two samples. Our study emphasizes the importance of selecting a suitable forward primer for detection of Bifidobacterium spp.     

Arabinoxylans and inulin differentially modulate the mucosal and luminal gut microbiota and mucin-degradation in humanized rats

The endogenous gut microbiota affects the host in many ways. Prebiotics should favour beneficial intestinal microbes and thus improve host health. In this study, we investigated how a novel class of potential prebiotic long-chain arabinoxylans (LC-AX) and the well-established prebiotic inulin (IN) modulate the gut microbiota of humanized rats. Six weeks after axenic rats were inoculated with a human faecal microbiota, their colonic microbiota was similar to this inoculum (～ 70%), whereas their caecal microbiota was enriched with Verrucomicrobia and Firmicutes concomitant with lower abundance of Bacteroidetes. Moreover, different Bifidobacterium species colonized the lumen (B. adolescentis) and mucus (B. longum and B. bifidum). Both LC-AX and IN increased SCFA levels and induced a shift from acetate towards health-promoting propionate and butyrate respectively. By applying a high-resolution phylogenetic micro-array (HITChip) at the site of fermentation (caecum), IN and LC-AX were shown to stimulate bacterial groups with known butyrate-producers (Roseburia intestinalis, Eubacterium rectale, Anaerostipes caccae) and bifidobacteria (B. longum) respectively. Prebiotic administration also resulted in lower caecal abundances of the mucin-degrading Akkermansia muciniphila and potentially more mucin production by the host. Both factors might explain the increased caecal mucin levels for LC-AX (threefold) and IN (sixfold). These mucins were degraded along the colon, resulting in high faecal abundances of Akkermansia muciniphila for LC-AX and especially IN-treated rats. Finally, the microbial changes caused an adaptation period for the host with less weight gain, after which the host fine-tuned the interaction with this altered microbiota. Our results demonstrate that next to IN, LC-AX are promising prebiotic compounds by stimulating production of health-promoting metabolites by specific microbes in the proximal regions. Further, prebiotic supplementation shifted mucin degradation to distal regions, where mucin-degraders may produce beneficial metabolites (e.g. propionate by Akkermansia muciniphila), so that prebiotics may potentially improve gut health along the entire length of the intestine.     

Fecal microbiome composition and stability in 4- to 8-year old children is associated with dietary patterns and nutrient intake

How long-term dietary intake shapes microbiota composition and stability in young children is poorly understood. Herein, the temporal variability in stool microbiota composition in relation to habitual dietary patterns of 4- to 8-year-old children (n=22) was investigated. Fecal samples were collected at baseline, 6 weeks and 6 months. Bacterial composition and volatile fatty acids were assessed by 16S rRNA sequencing and gas-chromatography, respectively. Nutrient intake was assessed using 3-day food diaries and dietary patterns were empirically derived from a food frequency questionnaire. Using a factor loading of >0.45 for a food group to be a major contributor to the overall dietary pattern, two dietary patterns were found to be associated with distinct microbiome composition. Dietary Pattern 1 (DP1), characterized by intake of fish, protein foods, refined carbohydrates, vegetables, fruit, juice and sweetened beverages, kid’s meals and snacks and sweets, was associated with higher relative abundance of Bacteroidetes, Bacteroides and Ruminococcus and lower abundance of Bifidobacterium, Prevotella, Blautia and Roseburia. Dietary Pattern 2 (DP2), characterized by intake of grains, dairy and legumes, nuts and seeds, was associated with higher relative abundance of Cyanobacteria and Phascolarctobacterium and lower abundance of Dorea and Eubacterium. Fruit and starchy foods were present in both patterns, but were more associated with DP1 and DP2, respectively. Temporal stability of microbiota over a 6-month period was associated with baseline dietary patterns. Understanding how dietary intake contributes to microbiota composition and stability in early life in important for dietary recommendations and designing clinical interventions for microbiota-associated diseases.     

Quantitative real-time PCR assays to identify and quantify fecal Bifidobacterium species in infants receiving a prebiotic infant formula

A healthy intestinal microbiota is considered to be important for priming of the infants' mucosal and systemic immunity. Breast-fed infants typically have an intestinal microbiota dominated by different Bifidobacterium species. It has been described that allergic infants have different levels of specific Bifidobacterium species than healthy infants. For the accurate quantification of Bifidobacterium adolescentis, Bifidobacterium angulatum, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium catenulatum, Bifidobacterium dentium, Bifidobacterium infantis, and Bifidobacterium longum in fecal samples, duplex 5' nuclease assays were developed. The assays, targeting rRNA gene intergenic spacer regions, were validated and compared with conventional PCR and fluorescent in situ hybridization methods. The 5' nuclease assays were subsequently used to determine the relative amounts of different Bifidobacterium species in fecal samples from infants receiving a standard formula or a standard formula supplemented with galacto- and fructo-oligosaccharides (OSF). A breast-fed group was studied in parallel as a reference. The results showed a significant increase in the total amount of fecal bifidobacteria (54.8% +/- 9.8% to 73.4% +/- 4.0%) in infants receiving the prebiotic formula (OSF), with a diversity of Bifidobacterium species similar to breast-fed infants. The intestinal microbiota of infants who received a standard formula seems to resemble a more adult-like distribution of bifidobacteria and contains relatively more B. catenulatum and B. adolescentis (2.71% +/- 1.92% and 8.11% +/- 4.12%, respectively, versus 0.15% +/- 0.11% and 1.38% +/- 0.98% for the OSF group). In conclusion, the specific prebiotic infant formula used induces a fecal microbiota that closely resembles the microbiota of breast-fed infants also at the level of the different Bifidobacterium species.     

Fermentation of mucins and plant polysaccharides by anaerobic bacteria from the human colon

A total of 154 strains from 22 species of Bifidobacterium, Peptostreptococcus, Lactobacillus, Ruminococcus, Coprococcus, Eubacterium, and Fusobacterium, which are present in high concentrations in the human colon, were surveyed for their ability to ferment 21 different complex carbohydrates. Plant polysaccharides, including amylose, amylopectin, pectin, polygalacturonate, xylan, laminarin, guar gum, locust bean gum, gum ghatti, gum arabic, and gum tragacanth, were fermented by some strains from Bifidobacterium, Peptostreptococcus, Ruminococcus, and Eubacterium species. Porcine gastric mucin, which was fermented by some strains of Ruminococcus torques and Bifidobacterium bifidum, was the only mucin utilized by any of the strains tested.     

Molecular analyses of the intestinal microbiota of chimpanzees in the wild and in captivity

Little information is available regarding the intestinal bacteria of chimpanzees in the wild, due to the technical difficulties of studying intestinal bacteria in the field. In this study, molecular-based bacterial analyses were performed to overcome this difficulty because polymerase chain reaction (PCR)-based methods, such as temperature gradient gel electrophoresis (TGGE) and amplified ribosomal DNA restriction analysis (ARDRA), of the bacterial 16S rRNA gene can be applied to ethanol-fixed fecal samples. The common presence of bacteria belonging to the Clostridium rRNA sub-group XIVa, such as Ruminococcus obeum and Eubacterium sp., was indicated for Bossou wild chimpanzees by ARDRA. TGGE on partial 16S rDNA followed by hierarchical clustering analysis showed a systematic difference in the composition of intestinal microbiota between wild and captive chimpanzees. However, several TGGE bands commonly shared by wild and captured chimpanzees were excised, and their sequences were obtained. They were suggested to be the Clostridium leptum subgroup bacteria, Lactobacillus gasseri-like bacterium, and Bifidobacterium pseudocatenulatum- or B. catenulatum-like bacterium. These may be considered as common intestinal bacteria for chimpanzees, and may be transmitted vertically over generations.     

Species-specific oligonucleotide probes for five Bifidobacterium species detected in human intestinal microflora.

Portions of the 16S rRNA from closely related species of the genus Bifidobacterium that are found in the human intestinal microflora were sequenced in order to design species-specific oligonucleotide probes. Five oligonucleotide probes ranging from 16 to 19 bases in length and complementary to 16S rRNA sequences from Bifidobacterium adolescentis, B. bifidum, B. breve, B. infantis, and B. longum were synthesized. With crude high-molecular-weight RNA preparations as targets, these probes showed the desired species specificity, even down to a 1-nucleotide difference. For the practical evaluation of these probes, their specificity and sensitivity were tested against seven strains of the same species and 54 strains of heterologous bacteria with fixed whole cells as targets. The probes for B. adolescentis, B. breve, and B. longum showed efficient and specific hybridization. Although the probes for B. bifidum and B. infantis cross-reacted with a few bacterial strains not isolated from humans, these probes showed species specificity for human intestinal bacteria. These 16S rRNA probes should prove valuable for the identification and detection of human intestinal Bifidobacterium species.     

Species-specific oligonucleotide probes for five Bifidobacterium species detected in human intestinal microflora.

Portions of the 16S rRNA from closely related species of the genus Bifidobacterium that are found in the human intestinal microflora were sequenced in order to design species-specific oligonucleotide probes. Five oligonucleotide probes ranging from 16 to 19 bases in length and complementary to 16S rRNA sequences from Bifidobacterium adolescentis, B. bifidum, B. breve, B. infantis, and B. longum were synthesized. With crude high-molecular-weight RNA preparations as targets, these probes showed the desired species specificity, even down to a 1-nucleotide difference. For the practical evaluation of these probes, their specificity and sensitivity were tested against seven strains of the same species and 54 strains of heterologous bacteria with fixed whole cells as targets. The probes for B. adolescentis, B. breve, and B. longum showed efficient and specific hybridization. Although the probes for B. bifidum and B. infantis cross-reacted with a few bacterial strains not isolated from humans, these probes showed species specificity for human intestinal bacteria. These 16S rRNA probes should prove valuable for the identification and detection of human intestinal Bifidobacterium species.     

Fermentation of mucins and plant polysaccharides by anaerobic bacteria from the human colon.

A total of 154 strains from 22 species of Bifidobacterium, Peptostreptococcus, Lactobacillus, Ruminococcus, Coprococcus, Eubacterium, and Fusobacterium, which are present in high concentrations in the human colon, were surveyed for their ability to ferment 21 different complex carbohydrates. Plant polysaccharides, including amylose, amylopectin, pectin, polygalacturonate, xylan, laminarin, guar gum, locust bean gum, gum ghatti, gum arabic, and gum tragacanth, were fermented by some strains from Bifidobacterium, Peptostreptococcus, Ruminococcus, and Eubacterium species. Porcine gastric mucin, which was fermented by some strains of Ruminococcus torques and Bifidobacterium bifidum, was the only mucin utilized by any of the strains tested.