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Abnormal microbiota composition in the ileocolonic mucosa of Crohn's disease patients as revealed by polymerase chain reaction-denaturing gradient gel electrophoresis.

BACKGROUND: Bacteria might play a role in the pathogenesis of Crohn's disease (CD), and patients harbor a different type and density of gut microbiota compared with normal healthy subjects. Thus, the aim of this study was to compare the microbiota adhered to the mucosa of CD patients with that of healthy subjects. METHODS: Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene fragments was used to identify the dominant bacterial species present in fresh biopsy samples obtained from the mucosa of 15 healthy and 19 CD subjects. Two patients suffering from ulcerative colitis and 1 suffering from ischemic colitis also were included. RESULTS: Individuals were clustered in 2 groups according to their molecular fingerprint, which differentiated the majority of CD specimens (88.2%) from the majority of healthy/ulcerative colitis/ischemic colitis specimens (82.3%). In addition, the patient-to-patient variability in microbiota was greater within the CD cluster than in the healthy/ulcerative colitis cluster (P = 0.000). One hundred forty-one sequences were obtained from the PCR-DGGE bands that were grouped into 58 different phylotypes, 8 of which were novel. BLAST analysis revealed that 74.5% of the sequences were similar to those of bacteria that have never been cultivated. In CD samples, prevalence values for Clostridium spp Ruminococcus torques and Escherichia coli were significantly higher, whereas Faecalibacterium was more frequently found in healthy specimens. Opportunistic pathogenic gamma-proteobacteria were found occasionally, only in CD mucosal microbiota. CONCLUSIONS: Microbiota attached to the ileocolonic mucosa of CD patients is distinguishable from that of healthy subjects. We postulate that individuals who are predisposed to CD are less able to regulate the microbial makeup of their intestines, which leads to an unstable microbial population.

Adult↗

Evidence for the placement of the gram-negative Catonella morbi (Moore and Moore) and Johnsonella ignava (Moore and Moore) within the Clostridium subphylum of the gram-positive bacteria on the basis of 16S rRNA sequences.

Comparative 16S rRNA analysis was used to determine the phylogenetic positions of Catonella morbi and Johnsonella ignava, which are members of two monospecific genera of gram-negative anaerobic bacilli isolated from human gingival crevices. Both of these genera were found to belong to cluster XIVa (M. D. Collins, P. A. Lawson, A. Willems, J. J. Cordoba, J. Fernandez-Garayzabal, P. Garcia, J. Cai, H. Hippe, and J. A. E. Farrow, Int. J. Syst. Bacteriol. 44:812-826, 1994) of the Clostridium subphylum of gram-positive bacteria. Within this cluster, which contains several Clostridium, Coprococcus, Eubacterium, and Ruminococcus species, C. morbi and J. ignava formed two distinct lines that were separate from all other taxa. Our findings support the separate generic status of the genera Catonella and Johnsonella and show that these genera do not belong to the family Bacteroidaceae but instead belong to the gram-positive Clostridium subphylum.

Base Sequence↗

Phylogenetic analysis of Butyrivibrio strains reveals three distinct groups of species within the Clostridium subphylum of the gram-positive bacteria.

The phylogenetic positions of 40 Butyrivibrio strains were determined by performing a comparative sequence analysis of the 16S rRNA genes of these organisms. We found that all of the strains which we studied belong to cluster XIVa (M. D. Collins, P. A. Lawson, A. Willems, J. J. Cordoba, J. Fernandez=Garayzabal, P. Garcia, J. Cai, H. Hippe, and J. A. E. Farrow, Int. J. Syst. Bacteriol. 44:812-826, 1994) of the Clostridium subphylum of the gram-positive bacteria, which also includes several Clostridium, Coprococcus, Eubacterium, and Ruminococcus species. We also found that the Butyrivibrio strains which we examined were genotypically heterogeneous and exhibited 12 distinct rRNA sequence types. The 12 rRNA sequence types formed three distinct lineages in cluster XIVa, which were separate from each other and from all other species belonging to this cluster. One lineage consisted of strains which exhibited a single rRNA type and corresponded to the species Butyrivibrio crossotus. The second lineage consisted of 12 strains designated Butyrivibrio fibrisolvens which exhibited seven distinct rRNA sequence types. The type strain of B. fibrisolvens was a member of this lineage, but its position was peripheral. The third lineage comprised 26 B. fibrisolvens strains which exhibited four distinct rRNA sequence types. Tree topology and sequence divergence considerations indicated that the three lineages correspond to three separate genera and that the genus Butyrivibrio should be restricted to the group that contains the type strain of B. fibrisolvens.

Base Sequence↗

A survey of peptidase activity in rumen bacteria.

Twenty-nine strains of 14 species of rumen bacteria were screened for their ability to hydrolyse Ala2, Ala5, GlyArg-4-methoxy-2-naphthylamide (GlyArg-MNA) and Leu-MNA. Several species, notably Megasphaera elsdenii, were active against Ala2, and a smaller number, including Bacteroides ruminicola, Butyrivibrio fibrisolvens, Ruminococcus flavefaciens, Lachnospira multipara and Ruminobacter amylophilus, broke down Ala5. Streptococcus bovis had an exceptionally high leucine arylamidase activity. However, only Ba. ruminicola hydrolysed GlyArg-MNA. Further investigation revealed that only Ba. ruminicola and Bu. fibrisolvens hydrolysed Ala5 to Ala3 and Ala2, with little ALa4 being produced, in a manner similar to rumen fluid. The activity of Ba. ruminicola against synthetic peptidase substrates, including GlyArg-MNA, LysAla-MNA, ArgArg-MNA, GlyPro-MNA, LeuVal-MNA, and Ala3-p-nitroanilide, was similar to that of rumen fluid, whereas the activity of Bu. fibrisolvens was quite different. Since the main mechanism by which peptides are broken down in the rumen is similar to dipeptidyl aminopeptidase type I, for which GlyArg-MNA is a diagnostic substrate, it was concluded that Ba. ruminicola was the most important single species in peptide breakdown in the rumen.

Alanine↗

Three Neocallimastix patriciarum esterases associated with the degradation of complex polysaccharides are members of a new family of hydrolases.

Acetylesterase and cinnamoyl ester hydrolase activities were demonstrated in culture supernatant of the anaerobic ruminal fungus Neocallimastix patriciarum. A cDNA expression library from N. patriciarum was screened for esterases using beta-naphthyl acetate and a model cinnamoyl ester compound. cDNA clones representing four different esterase genes (bnaA-D) were isolated. None of the enzymes had cinnamoyl ester hydrolase activity, but two of the enzymes (BnaA and BnaC) had acetylxylan esterase activity, bnaA, bnaB and bnaC encode proteins with several distinct domains. Carboxy-terminal repeats in BnaA and BnaC are homologous to protein-docking domains in other enzymes from Neocallimastix species and another anaerobic fungus, a Piromyces sp. The catalytic domains of BnaB and BnaC are members of a recently described family of Ser/His active site hydrolases [Upton, C. & Buckley, J.T. (1995). Trends Biochem Sci 20, 178-179]. BnaB exhibits 40% amino acid identity to a domain of unknown function in the CelE cellulase from Clostridium thermocellum and BnaC exhibits 52% amino acid identity to a domain of unknown function in the XynB xylanase from Ruminococcus flavefaciens. BnaA, whilst exhibiting less than 10% overall amino acid identity to BnaB or BnaC, or to any other known protein, appears to be a member of the same family of hydrolases, having the three universally conserved amino acid sequence motifs. Several other previously described esterases are also shown to be members of this family, including a rhamnogalacturonan acetylesterase from Aspergillus aculeatus. However, none of the other previously described enzymes with acetylxylan esterase activity are members of this family of hydrolases.

Amino Acid Sequence↗

The hydrogenation of unsaturated fatty acids by five bacterial isolates from the sheep rumen, including a new species.

Five strictly anaerobic bacteria able to hydrogenate unsaturated fatty acids were isolated from sheep rumen. One was characterized as Ruminococcus albus, two as Eubacterium spp. and two as Fusocillus spp., one of which is named as a new species. The Fusocillus organisms were able to hydrogenate oleic acid and linoleic acid to stearic acid, and linolenic acid to cis-octadec-15-enoic acid. The R. albus and the two Eubacteria did not hydrogenate oleic acid but converted linoleic and linolenic acids to a mixture of octadecenoic acids; trans-octadec-II-enoic acid predominated but several isomeric cis and trans octadecenoic acids were produced together with isomers of non-conjugated octadecadienoic acids. The intermediate and final products of hydrogenation by each organism were compatible with the results from mixed rumen bacteria.

Anaerobiosis↗

Molecular analysis of fecal microbiota in elderly individuals using 16S rDNA library and T-RFLP.

Fecal microbiota in six elderly individuals were characterized by the 16S rDNA libraries and terminal restriction fragment length polymorphism (T-RFLP) analysis. Random clones of 16S rRNA gene sequences were isolated after PCR amplification with universal primer sets from total genomic DNA extracted from feces of three elderly individuals. These clones were partially sequenced (about 500 bp). T-RFLP analysis was performed using 16S rDNA amplified from six subjects. The lengths of the terminal restriction fragment (T-RF) were analyzed after digestion by HhaI and MspI. Among 240 clones obtained, approximately 46% belonged to 27 known species. About 54% of the other clones were 56 novel "phylotypes" (at least 98% homology of clone sequence). These libraries included 83 species or phylotypes. In addition, about 13% (30 phylotypes) of these phylotypes were newly discovered in these libraries. A large number of species that are not yet known exist in the feces of elderly individuals. 16S rDNA libraries and T-RFLP analysis revealed that the majority of bacteria were Bacteroides and relatives, Clostridium rRNA cluster IV, IX, Clostridium rRNA subcluster XIVa, and "Gammaproteobacteria". The proportion of Clostridium rRNA subcluster XIVa was lower than in healthy adults. In addition, although Ruminococcus obeum and its closely related phylotypes were detected in high frequency in healthy young subjects, hardly any were detected in our elderly individuals. "Gammaproteobacteria" were detected at high frequency.

Aged↗

Clostridium glycyrrhizinilyticum sp. nov., a glycyrrhizin-hydrolysing bacterium isolated from human faeces.

Screening of faecal bacteria for glycyrrhetic acid (GA) production by hydrolysing of glycyrrhizin (GL) resulted in the isolation of two strains, designated ZM35T and ZM38. Strains ZM35T and ZM38 were Gram-positive, obligate anaerobic, non-spore-forming and rod-shaped bacteria. Analysis of the 16S rRNA gene sequences indicated that strains ZM35T and ZM38 belonged to cluster XIVa of the genus Clostridium. The 16S rRNA gene sequences of strains ZM35T and ZM38 were identical. Strain ZM35T exhibited approximately 94% to 95% identity with the validly described species, Clostridium oroticum(94.5%), Eubacterium contortum(93.8%), Ruminococcus gnavus(94.5%) and R. torques(95.1%). In an experiment of DNA-DNA hybridization, it was confirmed that strains ZM35T and ZM38 were the same species. The guanine-plus-cytosine (G+C) content of strain ZM35T is 45.7 mol%. Based on the phylogenetic and phenotypic findings, we propose that strains ZM35T and ZM38 be assigned to a novel species named Clostridium glycyrrhizinilyticum. The type strain is ZM35T (=JCM 13368T=DSM 17593T).

Clostridium↗

The effect of ammonia treatment on the solubilization of straw and the growth of cellulolytic rumen bacteria.

Pre-treatment of straw with anhydrous ammonia increased its susceptibility to solubilization by the predominant cellulolytic bacteria from the rumen, Bacteroides succinogenes, Ruminococcus albus and R. flavefaciens. Ammonia treatment also increased the production of microbial protein and fermentation products by all three species. Scanning electron microscope observations of straw during digestion suggested that the attack of straw by these bacteria was accompanied by the formation of substantial numbers of adherent microcolonies.

Ammonia↗

Binding and degradation of lectins by components of rumen liquor.

The binding of 15 different plant lectins to feed particles and microbes in rumen liquor, and their degradation were studied in vitro. The rate of degradation assessed from the label released when radioactive iodine-labelled lectins were incubated with rumen liquor conflicted with the rates calculated from measurements of the survival of the antigenic structure (immuno-rocket electrophoresis) or the biological function (haemagglutination) of the lectins. Thus solubilization of the radioactive label indicated that Concanavalin A (Con A), but not the soyabean agglutinin, SBA, or kidney bean phytohaemagglutinin, PHA-E3L, was stable to rumen proteolysis. In contrast, both SBA and PHA-E3L were shown by immuno-rocket electrophoresis or haemagglutination tests to be highly resistant to breakdown, while the degradation of Con A proceeded at a constant slow rate under the same conditions. This was in accord with the previously established general stability of lectins in the gut of single-stomach animals. Of the 15 lectins, SBA, favin (Vicia faba lectin) and Con A were bound by hay and the particle fraction of rumen liquor. This was, in part, specific and reversible in the presence of appropriate sugars. Most pure bacterial strains preferentially bound lectins with specificity for glucose/mannose (favin and Con A), while rumen fungi reacted with SBA. The level of binding was low with other lectins. However, inter-strain differences of lectin-binding were found in Selenomonas ruminantium and Ruminococcus flavefaciens. Clearly, as some lectins were not fully degraded in the rumen, they could be expected to depress the utilization of the diet not only in single-stomach animals but, possibly, also in ruminants.

Animals↗

Interactions between rumen bacterial strains during the degradation and utilization of the monosaccharides of barley straw cell-walls.

Pure cultures and pair-combinations of strains representative of the rumen cellulolytic species Ruminococcus flavefaciens, Fibrobacter succinogenes and Butyrivibrio fibrisolvens were grown on cell-wall materials from barley straw. Of the pure cultures, R. flavefaciens solubilized straw most rapidly. The presence of B. fibrisolvens, which was unable to degrade straw extensively in pure culture, increased the solubilization of dry matter by R. flavefaciens and the solubilization of cell-wall carbohydrates by both R. flavefaciens and F. succinogenes. During fermentation, both R. flavefaciens and F. succinogenes released bound glucose and free and bound arabinose and xylose into solution. The accumulation of these sugars, especially arabinose and xylose, was greatly reduced in co-cultures containing B. fibrisolvens, suggesting that significant interspecies cross feeding of the products of hemicellulose hydrolysis (particularly soluble bound xylose released by F. succinogenes) occurs during straw degradation by mixed cultures containing this species.

Animal Feed↗

Degradation and utilization of forage hemicellulose by rumen bacteria, singly in coculture or added sequentially.

Procedures for sequential addition experiments were developed to study the mechanisms involved in the synergistic and inhibitory interactions observed in forage hemicellulose digestion by rumen bacterial cocultures. One organism was allowed to ferment a forage substrate, the culture tube was sterilized and then inoculated with a second organism. No differences were found in the extent of degradation or utilization between fermentations sterilized by oxidation or heat, and based on ease of handling, heat was used in all subsequent experiments. Studies were conducted with Fibrobacter succinogenes A3c, Ruminococcus flavefaciens B34b and Prevotella ruminicola H2b, singly and in all possible combinations. Results from the sequential addition studies substantiated earlier suggestions that the increase observed in hemicellulose utilization results from initial solubilization of the hemicellulose from the forage by the non-utilizer and subsequent utilization of subsequent utilization of this solubilized polysaccharide by the utilizing, but non-degrading organism.

Animal Feed↗

Molecular characterization of the bacteria adherent to human colorectal mucosa.

AIMS: To study large intestinal mucosal bacterial communities by Denaturing Gradient Gel Electrophoresis (DGGE) profiling and sequencing of 16S rRNA gene polymerase chain reaction (PCR) products amplified from DNA extracted from colorectal biopsies taken from healthy individuals. The specific aims were to determine how similar the mucosa-associated bacterial communities are within and between individuals and also to characterize the phylogenetic origin of isolated DGGE bands. METHODS AND RESULTS: Human colorectal biopsies were taken at routine colonoscopy from 33 patients with normal looking mucosa. The DNA was extracted directly from single biopsies and the bacterial 16S rDNA PCR amplified. The PCR products were profiled using DGGE to generate a fingerprint of the dominant members of the bacterial community associated with the biopsy. The reproducibility of this method was high (>98%). Washed and unwashed biopsies gave similar DGGE banding patterns (Median Similarity Coefficient - MSC 96%, InterQuartile Range - IQR 3.0%, n = 5). Adjacent biopsies sampled from the same patient using different forceps gave similar DGGE profiles (MSC 94%, n = 2). Two colorectal biopsies sampled at locations 2-5 cm apart, from each of 18 patients, resulted in very similar profiles (MSC 100%, IQR 2.8%). Biopsies sampled from different locations within the large intestine of the same patient also gave similar DGGE profiles (MSC 98% IQR 3.3%n = 6). Although all patients (n = 33) gave different DGGE profiles, some similarity (c. 34%) was observed between profiles obtained from 15 patients arbitrarily selected. 35 DGGE bands were excised and sequenced. Many were found to be most closely related to uncultured bacterial sequence entries in the Genbank database. Others belonged to typical gut bacterial genera including Bacteroides, Ruminococcus, Faecalibacterium and Clostridium. CONCLUSIONS: Bacterial communities adherent to colorectal mucosa within a normal patient show little variation; in contrast, mucosal bacterial communities sampled from different patients with normal colorectal mucosa show a high degree of variation. SIGNIFICANCE AND IMPACT OF THE STUDY: This research demonstrates that DGGE profiling of 16S rRNA gene PCR products amplified from DNA extracted directly from mucosal samples offers fresh insight into the bacterial communities that are adherent to colorectal mucosa. These findings are important with respect to further studies on the gastrointestinal tract in health and disease.

Adenomatous Polyposis Coli↗

Homologous catalytic domains in a rumen fungal xylanase: evidence for gene duplication and prokaryotic origin.

A cDNA (xynA), encoding xylanase A (XYLA), was isolated from a cDNA library, derived from mRNA extracted from the rumen anaerobic fungus, Neocallimastix patriciarum. Recombinant XYLA, purified from Escherichia coli harbouring xynA, had a M(r) of 53,000 and hydrolysed oat-spelt xylan to xylobiose and xylose. The enzyme did not hydrolyse any cellulosic substrates. The nucleotide sequence of xynA revealed a single open reading frame of 1821 bp coding for a protein of M(r) 66,192. The predicted primary structure of XYLA comprised an N-terminal signal peptide followed by a 225-amino-acid repeated sequence, which was separated from a tandem 40-residue C-terminal repeat by a threonine/proline linker sequence. The large N-terminal reiterated regions consisted of distinct catalytic domains which displayed similar substrate specificities to the full-length enzyme. The reiterated structure of XYLA suggests that the enzyme was derived from an ancestral gene which underwent two discrete duplications. Sequence comparison analysis revealed significant homology between XYLA and bacterial xylanases belonging to cellulase/xylanase family G. One of these homologous enzymes is derived from the rumen bacterium Ruminococcus flavefaciens. The homology observed between XYLA and a rumen prokaryote xylanase could be a consequence of the horizontal transfer of genes between rumen prokaryotes and lower eukaryotes, either when the organisms were resident in the rumen, or prior to their colonization of the ruminant. It should also be noted that Neocallimastix XYLA is the first example of a xylanase which consists of reiterated sequences. It remains to be established whether this is a common phenomenon in other rumen fungal plant cell wall hydrolases.

Amino Acid Sequence↗

Design and validation of 16S rRNA probes to enumerate members of the Clostridium leptum subgroup in human faecal microbiota.

Among human faecal bacteria, many members of the Clostridium leptum subgroup are fibrolytic and butyrate producing microorganisms thereby contributing to processes important to colonic health. Yet this phylogenetic subgroup remains poorly described to date. To improve detection and description of members of the C. leptum subgroup, the Clep 866 group probe was developed. Its association with probes targeting the Clostridium viride cluster (Cvir 1414) and Eubacterium desmolans species (Edes 635) allowed for the first time the detection of all members found in this phylogenetic group in human faecal microbiota. A species-specific probe was also designed to detect members of the Ruminococcus callidus species (Rcal 733). The design of signature regions was based on alignment of 16S rRNA sequences isolated from faeces of five healthy adults. Furthermore, an oligonucleotide competitor strategy was developed in order to improve the specificity of the probes formerly validated or designed in this study. The oligonucleotide probes were tested using a collection of target and non-target strains using FISH combined with flow cytometry. These new probes were added to a panel of 18 phylogenetic probes selected to describe faecal microbiota composition in 21 human faeces of healthy adults. Clostridium leptum subgroup represented 22% of the total faecal bacteria and codominated with members of Clostridium coccoides group. The cluster Faecalibacterium prausnitzii was the dominant component of the C. leptum subgroup and 20% of the latter subgroup remained unidentified at the species level.

Adult↗

The effect of rumen chitinolytic bacteria on cellulolytic anaerobic fungi.

The polycentric anaerobic fungus Orpinomyces joyonii A4 was cultivated on microcrystalline cellulose alone and in association with the rumen chitinolytic bacterium Clostridium sp. strain ChK5, which shows strong phenotypic similarity to Clostridium tertium. The presence of strain ChK5 significantly depressed the solubilization of microcrystalline cellulose, the production of short-chain fatty acids (SCFA) and the release of endoglucanase by the fungus. Co-culture of the monocentric anaerobic fungus Neocallimastix frontalis strain RE1, Neocallimastix sp. strain G-1 and Caecomyces sp. strain SC2 with strain ChK5 also resulted in depressed fungal cellulolysis. Cell-free supernatant fluids from strain ChK5 inhibited the release of reducing sugars from carboxymethylcellulose by cell-free supernatant fluids from O. joyonii strain A4. Strain 007 of the cellulolytic anaerobe Ruminococcus flavefaciens was also shown to produce small amounts of soluble products upon incubation with colloidal chitin. Mixtures of culture supernates from this bacterium and from O. joyonii strain A4 showed cellulase activity that was less than that of the component cultures. It is suggested that the ability of some rumen bacteria to hydrolyse or transform chitin may be an important factor in the interactions between bacteria and fungi in the rumen.

Anaerobiosis↗

A longitudinal study of infant faecal microbiota during weaning.

For infants, the introduction of food other than breast milk is a high risk period due to diarrheal diseases, and may be corroborated with a shift in the faecal microbiota. This longitudinal study was the first undertaken to understand the effect of the supplementation on the infant's faecal microbiota and particularly the bifidobacteria. Eleven infants were enrolled. Their faecal microbiota were analysed using temporal temperature gradient gel electrophoresis (TTGE) with bacterial and bifidobacterial primers. In parallel, bifidobacterial counts were followed using competitive PCR. Three periods were distinguished: exclusive breastfeeding (Bf period), weaning (i.e. formula-milk addition, W period) and postweaning (i.e. breastfeeding cessation, Pw period). The bifidobacterial counts were not modified, reaching 10.5 (Log10 cells g(-1) wet weight). In the TTGE profiles, the main identified bands corresponded to Escherichia coli, Ruminococcus sp. and Bifidobacterium sp., more precisely Bifidobacterium longum, Bifidobacterium infantis and Bifidobacterium breve. For both TTGE profiles, the analysis of the distance suggested a maturation of the faecal microbiota but no correlation could be established with the diet. Despite a high interindividual variability, composition of the faecal microbiota appeared more homogenous after weaning and this point may be correlated with the cessation of breastfeeding.

Bacteria↗

Development of a real-time PCR assay for monitoring anaerobic fungal and cellulolytic bacterial populations within the rumen.

Traditional methods for enumerating and identifying microbial populations within the rumen can be time consuming and cumbersome. Methods that involve culturing and microscopy can also be inconclusive, particularly when studying anaerobic rumen fungi. A real-time PCR SYBR Green assay, using PCR primers to target total rumen fungi and the cellulolytic bacteria Ruminococcus flavefaciens and Fibrobacter succinogenes, is described, including design and validation. The DNA and crude protein contents with respect to the fungal biomass of both polycentric and monocentric fungal isolates were investigated across the fungal growth stages to aid in standard curve generation. The primer sets used were found to be target specific with no detectable cross-reactivity. Subsequently, the real-time PCR assay was employed in a study to detect these populations within cattle rumen. The anaerobic fungal target was observed to increase 3.6-fold from 0 to 12 h after feeding. The results also indicated a 5.4-fold increase in F. succinogenes target between 0 and 12 h after feeding, whereas R. flavefaciens was observed to maintain more or less consistent levels. This is the first report of a real-time PCR assay to estimate the rumen anaerobic fungal population.

Anaerobiosis↗