16S rRNA gene-based analysis of mucosa-associated bacterial community and phylogeny in the chicken gastrointestinal tracts: from crops to ceca

Mucosa-associated microbiota from different regions of the gastrointestinal (GI) tract of adult broilers was studied by analysis of 16S rRNA gene sequences. The microbiota mainly comprised Gram-positive bacteria along the GI tract. Fifty-one operational taxonomic units (OTUs) (from 98 clones) were detected in the ceca, as compared with 13 OTUs (from 49 clones) in the crops, 11 OTUs (from 51 clones) in the gizzard, 14 OTUs (from 52 clones) in the duodenum, 12 OTUs (from 50 clones) in the jejunum and nine OTUs (from 50 clones) in the ileum. Ceca were dominantly occupied by clostridia-related sequences (40%) with other abundant sequences being related to Faecalibacterium prausnitzii (14%), Escherichia coli (11%), lactobacilli (7%) and Ruminococcus (6%). Lactobacilli were predominant in the upper GI tract and had the highest diversity in the crop. Both Lactobacillus aviarius and Lactobacillus salivarius were the predominant species among lactobacilli. Candidatus division Arthromitus was also abundant in the jejunum and ileum.     

Bacterial Community Mapping of the Mouse Gastrointestinal Tract

Keeping mammalian gastrointestinal (GI) tract communities in balance is crucial for host health maintenance. However, our understanding of microbial communities in the GI tract is still very limited. In this study, samples taken from the GI tracts of C57BL/6 mice were subjected to 16S rRNA gene sequence-based analysis to examine the characteristic bacterial communities along the mouse GI tract, including those present in the stomach, duodenum, jejunum, ileum, cecum, colon and feces. Further analyses of the 283,234 valid sequences obtained from pyrosequencing revealed that the gastric, duodenal, large intestinal and fecal samples had higher phylogenetic diversity than the jejunum and ileum samples did. The microbial communities found in the small intestine and stomach were different from those seen in the large intestine and fecal samples. A greater proportion of Lactobacillaceae were found in the stomach and small intestine, while a larger proportion of anaerobes such as Bacteroidaceae, Prevotellaceae, Rikenellaceae, Lachnospiraceae, and Ruminococcaceae were found in the large intestine and feces. In addition, inter-mouse variations of microbiota were observed between the large intestinal and fecal samples, which were much smaller than those between the gastric and small intestinal samples. As far as we can ascertain, ours is the first study to systematically characterize bacterial communities from the GI tracts of C57BL/6 mice.     

Comparison of bacterial diversity along the human intestinal tract by direct cloning and sequencing of 16S rRNA genes

Bacterial diversity of the mucosal biopsies from human jejunum, distal ileum, ascending colon and rectum were compared by analysis of PCR-amplified 16S rDNA clone libraries. A total of 347 clones from the mucosal biopsies were partially sequenced and assigned to six phylogenetic phyla of the domain Bacteria: Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, Verrucomicrobia, and Actinobacteria. The jejunum sample had least microbial diversity compared to the other samples and a trend towards highest diversity in ascending colon was observed. The clone libraries of distal ileum, ascending colon and rectum were not significantly different from each other (P>0.0043), but they differed significantly from the jejunum library (P=0.001). The population of sequences retrieved from jejunal biopsies was dominated by sequences closely related to Streptococcus (67%), while the population of sequences derived from distal ileum, ascending colon and rectum were dominated by sequences affiliated with Bacteroidetes (27-49%), and Clostridium clusters XIVa (20-34%) and IV (7-13%). The results indicate that the microbial community in jejunum is different from those in distal ileum, ascending colon and rectum, and that the major phylogenetic groups are similar from distal ileum to rectum.     

Fecal microbial diversity in a strict vegetarian as determined by molecular analysis and cultivation

Fecal microbial diversity in a strictly vegetarian woman was determined by the 16S rDNA library method, terminal restriction fragment length polymorphism (T-RFLP) analysis and a culture-based method. The 16S rDNA library was generated from extracted fecal DNA, using bacteria-specific primers. Randomly selected clones were partially sequenced. T-RFLP analysis was performed using amplified 16S rDNA. The lengths of T-RF were analyzed after digestion by HhaI and MspI. The cultivated bacterial isolates were used for partial sequencing of 16S rDNA. Among 183 clones obtained, approximately 29% of the clones belonged to 13 known species. About 71% of the remaining clones were novel "phylotypes" (at least 98% similarity of clone sequence). A total of 55 species or phylotypes were identified among the 16S rDNA library, while the cultivated isolates included 22 species or phylotypes. In addition, many new phylotypes were detected from the 16S rDNA library. The 16S rDNA library and isolates commonly included the Bacteroides group, Bifidobacterium group, and Clostridium rRNA clusters IV, XIVa, XVI and XVIII. T-RFLP analysis revealed the major composition of the vegetarian gut microbiota were Clostridium rRNA subcluster XIVa and Clostridium rRNA cluster XVIII. The dominant feature of this strictly vegetarian gut microbiota was the detection of many Clostridium rRNA subcluster XIVa and C. ramosum (Clostridium rRNA cluster XVIII).     

Quantification of Hyphomicrobium populations in activated sludge from an industrial wastewater treatment system as determined by 16S rRNA analysis

The bacterial community structure of the activated sludge from a 25 million-gal-per-day industrial wastewater treatment plant was investigated using rRNA analysis. 16S ribosomal DNA (rDNA) libraries were created from three sludge samples taken on different dates. Partial rRNA gene sequences were obtained for 46 rDNA clones, and nearly complete 16S rRNA sequences were obtained for 18 clones. Seventeen of these clones were members of the beta subdivision, and their sequences showed high homology to sequences of known bacterial species as well as published 16S rDNA sequences from other activated sludge sources. Sixteen clones belonged to the alpha subdivision, 7 of which showed similarity to Hyphomicrobium species. This cluster was chosen for further studies due to earlier work on Hyphomicrobium sp. strain M3 isolated from this treatment plant. A nearly full-length 16S rDNA sequence was obtained from Hyphomicrobium sp. strain M3. Phylogenetic analysis revealed that Hyphomicrobium sp. strain M3 was 99% similar to Hyphomicrobium denitrificans DSM 1869(T) in Hyphomicrobium cluster II. Three of the cloned sequences from the activated sludge samples also grouped with those of Hyphomicrobium cluster II, with a 96% sequence similarity to that of Hyphomicrobium sp. strain M3. The other four cloned sequences from the activated sludge sample were more closely related to those of the Hyphomicrobium cluster I organisms (95 to 97% similarity). Whole-cell fluorescence hybridization of microorganisms in the activated sludge with genus-specific Hyphomicrobium probe S-G-Hypho-1241-a-A-19 enhanced the visualization of Hyphomicrobium and revealed that Hyphomicrobium appears to be abundant both on the outside of flocs and within the floc structure. Dot blot hybridization of activated sludge samples from 1995 with probes designed for Hyphomicrobium cluster I and Hyphomicrobium cluster II indicated that Hyphomicrobium cluster II-positive 16S rRNA dominated over Hyphomicrobium cluster I-positive 16S rRNA by 3- to 12-fold. Hyphomicrobium 16S rRNA comprised approximately 5% of the 16S rRNA in the activated sludge.     

PCR/DGGE and 16S rRNA gene library analysis of the colonic microbiota of HLA-B27/beta2-microglobulin transgenic rats

AIMS: To determine the phylogenetic composition of the colonic microbiota of transgenic (TG) HLA-B27 rats using 16S ribosomal RNA (rRNA) gene sequences obtained from denaturing gradient gel electrophoresis (DGGE) gels and sequences from a 16S rRNA gene library. METHODS AND RESULTS: Colonic microbiota of TG and nontransgenic (NT) rats harboured by 10-week-old and 6-month-old animals was screened using PCR/DGGE. Six months old TG rats had marked inflammation of the colon compared with 10-week-old TG and NT rats. The DGGE profiles of rats with inflamed colon were similar from rat to rat (Dice's Similarity Coefficient proximal colon 73%, distal colon 83%) whereas profiles from animals without inflammation were dissimilar (52-64%). Identifications of bacterial origins of 16S rRNA gene sequences obtained from DGGE gels (200 bp) and from 16S rRNA clones (450 bp) of the colonic microbiota of diseased rats gave sequences most closely phylogenetically affiliated with uncultured or unknown bacteria. CONCLUSIONS: PCR/DGGE was shown to be an effective method to compare the colonic microbiota composition of TG and NT rats relative to the progression of inflammatory disease. Sequencing of 16S rRNA gene fragments from DGGE gels or 16S rRNA gene clones from a random library showed that uncultured or unknown bacteria were most commonly detected by both methods. It can be concluded that it would be better in future studies to search for the antigens produced by the gut microbiota against which the dysfunctional immune system reacts rather than seek phylogenetic associations. SIGNIFICANCE AND IMPACT OF THE STUDY: PCR/DGGE can be used as a rapid initial screening method to compare the composition of bacterial communities of initially unknown composition that are associated with the development of intestinal disease.     

Diversity of microbes associated with the marine sponge, Haliclona simulans, isolated from Irish waters and identification of polyketide synthase genes from the sponge metagenome

Samples of the sponge Haliclona simulans were collected from Irish waters and subjected to a culture-independent analysis to determine the microbial, polyketide synthase (PKS) and non-ribosomal peptide synthase (NRPS) diversity. 16S rRNA gene libraries were prepared from total sponge, bacterial enriched sponge and seawater samples. Eight phyla from the Bacteria were detected in the sponge by phylogenetic analyses of the 16S rRNA gene libraries. The most abundant phylum in the total sponge library was the Proteobacteria (86%), with the majority of these clones being from the γ- Proteobacteria (77%); two groups of clones were dominant and together made up 69% of the total. Both of these groups were related to other sponge-derived microbes and comprised novel genera. Within the other bacterial phyla groups of clones representing novel candidate genera within the phyla Verrucomicrobia and Lentisphaerae were also found. Selective enrichment of the bacterial component of the sponge prior to 16S rRNA gene analysis resulted in a 16S rRNA gene library dominated by a novel genus of δ- Proteobacteria , most closely related to the Bdellovibrio . The potential for the sponge microbiota to produce secondary metabolites was also analysed by polymerase chain reaction amplification of PKS and NRPS genes. While no NRPS sequences were isolated seven ketosynthase (KS) sequences were obtained from the sponge metagenome. Analyses of these clones revealed a diverse collection of PKS sequences which were most closely affiliated with PKS from members of the Cyanobacteria , Myxobacteria and Dinoflagellata .     

Molecular characterization of the microbial species that colonize human ileal and colonic mucosa by using 16S rDNA sequence analysis

AIM: The aim of this study was to characterize the bacterial community adhering to the mucosa of the terminal ileum, and proximal and distal colon of the human digestive tract. METHODS AND RESULTS: Pinch samples of the terminal ileum, proximal and distal colon were taken from a healthy 35-year-old, and a 68-year-old subject with mild diverticulosis. The 16S rDNA genes were amplified using a low number of PCR cycles, cloned, and sequenced. In total, 361 sequences were obtained comprising 70 operational taxonomic units (OTU), with a calculated coverage of 82.6%. Twenty-three per cent of OTU were common to the terminal ileum, proximal colon and distal colon, but 14% OTU were only found in the terminal ileum, and 43% were only associated with the proximal or distal colon. The most frequently represented clones were from the Clostridium group XIVa (24.7%), and the Bacteroidetes (Cytophaga-Flavobacteria-Bacteroides) cluster (27.7%). CONCLUSION: Comparison of 16S rDNA clone libraries of the hindgut across mammalian species confirms that the distribution of phylogenetic groups is similar irrespective of the host species. Lesser site-related differences within groups or clusters of organisms, are probable. SIGNIFICANCE AND IMPACT: This study provides further evidence of the distribution of the bacteria on the mucosal surfaces of the human hindgut. Data contribute to the benchmarking of the microbial composition of the human digestive tract.     

免培养法研究野生川金丝猴肠道内生细菌多样性

【目的】了解野生川金丝猴(Rhinopithecus roxellana)肠道内生细菌的组成及其多样性。【方法】提取川金丝猴肠道内生细菌总DNA,选用细菌通用引物799F和1492R对总DNA进行16S rRNA基因特异性扩增,构建川金丝猴肠道内生细菌16S rRNA基因克隆文库,对阳性克隆进行限制性内切酶片段长度多态性(PCR-RFLP)分析,并对HaeⅢ酶切带谱菌株进行测序,构建系统发育树。【结果】根据酶切带谱分析和测序结果,将随机挑取的157个阳性克隆归为27个不同的可操作分类单元(OTUs)。系统发育分析表明这些克隆序列有62.10%属于厚壁菌门(Firmicutes),其中包括梭菌属(Clostridium)、Cellulosilyticum属、Robinsoniella属、Anaerofustis属、Blautia属和Anaerovorax属,有37.90%属于未培养细菌。【结论】川金丝猴肠道内生细菌多样性丰富,并且可能存在新的分类单元。     

Antibiotics conspicuously affect community profiles and richness, but not the density of bacterial cells associated with mucosa in the large and small intestines of mice

The influence of three antibiotics (bacitracin, enrofloxacin, and neomycin sulfate) on the mucosa-associated enteric microbiota and the intestines of mice was examined. Antibiotics caused conspicuous enlargement of ceca and an increase in overall length of the intestine. However, there were no pathologic changes associated with increased cecal size or length of the intestine. Conspicuous reductions in the richness of mucosa-associated bacteria and changes to community profiles within the small (duodenum, proximal jejunum, middle jejunum, distal jejunum, and ileum) and large (cecum, ascending colon, and descending colon) intestine occurred in mice administered antibiotics. Communities in antibiotic-treated mice were dominated by a limited number of Clostridium-like (i.e. clostridial cluster XIVa) and Bacteroides species. The richness of mucosa-associated communities within the small and large intestine increased during the 14-day recovery period. However, community profiles within the large intestine did not return to baseline (i.e. relative to the control). Although antibiotic administration greatly reduced bacterial richness, densities of mucosa-associated bacteria were not reduced correspondingly. These data showed that the antibiotics, bacitracin, enrofloxacin, and neomycin sulfate, administered for 21 days to mice did not sterilize the intestine, but did impart a tremendous and prolonged impact on mucosa-associated bacterial communities throughout the small and large intestine.     

Diversity and abundance of uncultured cytophaga-like bacteria in the Delaware estuary

The Cytophaga-Flavobacterium group is known to be abundant in aquatic ecosystems and to have a potentially unique role in the utilization of organic material. However, relatively little is known about the diversity and abundance of uncultured members of this bacterial group, in part because they are underrepresented in clone libraries of 16S rRNA genes. To circumvent a suspected bias in PCR, a primer set was designed to amplify 16S rRNA genes from the Cytophaga-Flavobacterium group and was used to construct a library of these genes from the Delaware Estuary. This library had several novel Cytophaga-like 16S rRNA genes, of which about 40% could be grouped together into two clusters (DE clusters 1 and 2) defined by sequences initially observed only in the Delaware library; the other 16S rRNA genes were classified into an additional four clades containing sequences from other environments. An oligonucleotide probe was designed for the cluster with the most clones (DE cluster 2) and was used in fluorescence in situ hybridization assays. Bacteria in DE cluster 2 accounted for about 10% of the total prokaryotic abundance in the Delaware Estuary and in a depth profile of the Chukchi Sea (Arctic Ocean). The presence of DE cluster 2 in the Arctic Ocean was confirmed by results from 16S rRNA clone libraries. The contribution of this cluster to the total bacterial biomass is probably larger than is indicated by the abundance of its members, because the average cell volume of bacteria in DE cluster 2 was larger than those of other bacteria and prokaryotes in the Delaware Estuary and Chukchi Sea. DE cluster 2 may be one of the more abundant bacterial groups in the Delaware Estuary and possibly other marine environments.     

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.     

Microbial diversity of active layer and permafrost in an acidic wetland from the Canadian High Arctic

The abundance and structure of archaeal and bacterial communities from the active layer and the associated permafrost of a moderately acidic (pH < 5.0) High Arctic wetland (Axel Heiberg Island, Nunavut, Canada) were investigated using culture- and molecular-based methods. Aerobic viable cell counts from the active layer were ～100-fold greater than those from the permafrost (2.5 × 10(5) CFU·(g soil dry mass)(-1)); however, a greater diversity of isolates were cultured from permafrost, as determined by 16S rRNA gene sequencing. Isolates from both layers demonstrated growth characteristics of a psychrotolerant, halotolerant, and acidotolerant community. Archaea constituted 0.1% of the total 16S rRNA gene copy number and, in the 16S rRNA gene clone library, predominantly (71% and 95%) consisted of Crenarchaeota related to Group I. 1b. In contrast, bacterial communities were diverse (Shannon's diversity index, H = ～4), with Acidobacteria constituting the largest division of active layer clones (30%) and Actinobacteria most abundant in permafrost (28%). Direct comparisons of 16S rRNA gene sequence data highlighted significant differences between the bacterial communities of each layer, with the greatest differences occurring within Actinobacteria. Comparisons of 16S rRNA gene sequences with those from other Arctic permafrost and cold-temperature wetlands revealed commonly occurring taxa within the phyla Chloroflexi, Acidobacteria, and Actinobacteria (families Intrasporangiaceae and Rubrobacteraceae).     

Quantification of Hyphomicrobium Populations in Activated Sludge from an Industrial Wastewater Treatment System as Determined by 16S rRNA Analysis

The bacterial community structure of the activated sludge from a 25 million-gal-per-day industrial wastewater treatment plant was investigated using rRNA analysis. 16S ribosomal DNA (rDNA) libraries were created from three sludge samples taken on different dates. Partial rRNA gene sequences were obtained for 46 rDNA clones, and nearly complete 16S rRNA sequences were obtained for 18 clones. Seventeen of these clones were members of the beta subdivision, and their sequences showed high homology to sequences of known bacterial species as well as published 16S rDNA sequences from other activated sludge sources. Sixteen clones belonged to the alpha subdivision, 7 of which showed similarity to Hyphomicrobium species. This cluster was chosen for further studies due to earlier work on Hyphomicrobium sp. strain M3 isolated from this treatment plant. A nearly full-length 16S rDNA sequence was obtained from Hyphomicrobium sp. strain M3. Phylogenetic analysis revealed that Hyphomicrobium sp. strain M3 was 99% similar to Hyphomicrobium denitrificans DSM 1869^T in Hyphomicrobium cluster II. Three of the cloned sequences from the activated sludge samples also grouped with those of Hyphomicrobium cluster II, with a 96% sequence similarity to that of Hyphomicrobium sp. strain M3. The other four cloned sequences from the activated sludge sample were more closely related to those of the Hyphomicrobium cluster I organisms (95 to 97% similarity). Whole-cell fluorescence hybridization of microorganisms in the activated sludge with genus-specific Hyphomicrobium probe S-G-Hypho-1241-a-A-19 enhanced the visualization of Hyphomicrobium and revealed that Hyphomicrobium appears to be abundant both on the outside of flocs and within the floc structure. Dot blot hybridization of activated sludge samples from 1995 with probes designed for Hyphomicrobium cluster I and Hyphomicrobium cluster II indicated that Hyphomicrobium cluster II-positive 16S rRNA dominated over Hyphomicrobium cluster I-positive 16S rRNA by 3- to 12-fold. Hyphomicrobium 16S rRNA comprised approximately 5% of the 16S rRNA in the activated sludge.     

The microbial ecology of anaerobic cellulose degradation in municipal waste landfill sites: evidence of a role for fibrobacters

Cellulose is reputedly the most abundant organic polymer in the biosphere, yet despite the fundamental role of cellulolytic microorganisms in global carbon cycling and as potential sources of novel enzymes for biotechnology, their identity and ecology is not well established. Cellulose is a major component of landfill waste and its degradation is therefore a key feature of the anaerobic microbial decomposition process. Here, we targeted a number of taxa containing known cellulolytic anaerobes (members of the bacterial genus Fibrobacter, lineages of Clostridium clusters I, III, IV and XIV, and anaerobic fungi of the Neocallimastigales) in landfill leachate and colonized cellulose 'baits' via PCR and quantitative PCR (qPCR). Fibrobacter spp. and Clostridium clusters III, IV and XIV were detected in almost all leachate samples and cluster III and XIV clostridia were the most abundant (1-6% and 1-17% of total bacterial 16S rRNA gene copies respectively). Two landfill leachate microcosms were constructed to specifically assess those microbial communities that colonize and degrade cellulose substrates in situ. Scanning electron microscopy (SEM) of colonized cotton revealed extensive cellulose degradation in one microcosm, and Fibrobacter spp. and Clostridium cluster III represented 29% and 17%, respectively, of total bacterial 16S rRNA gene copies in the biofilm. Visible cellulose degradation was not observed in the second microcosm, and this correlated with negligible relative abundances of Clostridium cluster III and Fibrobacter spp. (≤ 0.1%), providing the first evidence that the novel fibrobacters recently detected in landfill sites and other non-gut environments colonize and degrade cellulose substrates in situ.     

Enumeration of anaerobic bacterial microflora of the equine gastrointestinal tract.

Samples from the duodenum, jejunum, and ileum, as well as from the cecum and colon, were obtained from 11 mature grass-fed horses. Viable counts of total culturable and proteolytic bacteria were made on habitat-simulating media containing 40% clarified ruminal fluid. The mean pHs in the duodenum, jejunum, and ileum were 6.32, 7.10, and 7.47, respectively; the mean pH decreased to 6.7 in the hindgut. The acetate concentration increased along the length of the small intestine and was the only volatile fatty acid present in this gut segment. Molar proportions of acetate, propionate, and butyrate in the hindgut were 85:10:3. Differences in bacterial counts on habitat-simulating media containing equine cecal fluid or clarified ruminal fluid were negligible. Bacterial counts showed a substantial population in the duodenum (ca. 2.9 x 10(6) per g [wet weight] of sample), and this increased to 29.0 x 10(6) in the jejunum and 38.4 x 10(6) in the ileum. Proteolytic bacteria formed a high proportion of the total culturable bacteria, especially in duodenal samples. Counts of proteolytic bacteria per gram (wet weight) of sample were 3.0 x 10(6), 15.6 x 10(6), and 22.0 x 10(6) in the duodenum, jejunum, and ileum, respectively. There was a close relationship between lumenal and mucosal bacterial counts, although actual values were lower in mucosal samples. The mucosal bacterial population in the duodenum was high relative to the lumenal population. Although the comparison of bacterial populations in the hindgut of the horse and white rhino was limited to a single animal, the results were of interest. Counts were higher in the cecum than in the colon for both the horse and the white rhino.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enumeration of anaerobic bacterial microflora of the equine gastrointestinal tract

Samples from the duodenum, jejunum, and ileum, as well as from the cecum and colon, were obtained from 11 mature grass-fed horses. Viable counts of total culturable and proteolytic bacteria were made on habitat-simulating media containing 40% clarified ruminal fluid. The mean pHs in the duodenum, jejunum, and ileum were 6.32, 7.10, and 7.47, respectively; the mean pH decreased to 6.7 in the hindgut. The acetate concentration increased along the length of the small intestine and was the only volatile fatty acid present in this gut segment. Molar proportions of acetate, propionate, and butyrate in the hindgut were 85:10:3. Differences in bacterial counts on habitat-simulating media containing equine cecal fluid or clarified ruminal fluid were negligible. Bacterial counts showed a substantial population in the duodenum (ca. 2.9 x 10(6) per g [wet weight] of sample), and this increased to 29.0 x 10(6) in the jejunum and 38.4 x 10(6) in the ileum. Proteolytic bacteria formed a high proportion of the total culturable bacteria, especially in duodenal samples. Counts of proteolytic bacteria per gram (wet weight) of sample were 3.0 x 10(6), 15.6 x 10(6), and 22.0 x 10(6) in the duodenum, jejunum, and ileum, respectively. There was a close relationship between lumenal and mucosal bacterial counts, although actual values were lower in mucosal samples. The mucosal bacterial population in the duodenum was high relative to the lumenal population. Although the comparison of bacterial populations in the hindgut of the horse and white rhino was limited to a single animal, the results were of interest. Counts were higher in the cecum than in the colon for both the horse and the white rhino.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of the rates of testosterone metabolism to various products and of glutathione transferase and sulfotransferase activities in rat intestine and comparison to the corresponding hepatic and renal drug-metabolizing enzymes

Metabolism of testosterone to various products (catalyzed by several different CYP isozymes) and the activities of phenol sulfotransferase (pST) and glutathione transferase (GST) in S9 fractions prepared from the mucosa of the duodenum, jejunum, ileum, caecum and upper and lower colon of male Sprague-Dawley rats were determined and compared to the corresponding hepatic and renal activities. Incubation of the S9 fraction prepared from the jejunum with testosterone and NADPH resulted in the formation of 2alpha-, 6alpha-, 6beta- and 16alpha-hydroxytestosterone and androstenedione at rates that were 1.6, 24, 1.3, 0.6 and 1.3%, respectively, of the corresponding hepatic values. The production of 2alpha-hydroxytestosterone was catalyzed only by the preparations from the duodenum and jejunum; whereas 6alpha-, 6beta- and 16alpha-hydroxytestosterone and androstenedione were produced in all regions of the intestine. In the case of the rat kidney, the rates of formation of the different testosterone metabolites were between 0.6 and 35% of the corresponding liver activity. The activity of glutathione transferase was approximately 12-26% of the corresponding hepatic activity throughout the intestine. The highest activity of phenol sulfotransferase was observed in the lower colon (almost 6% of the liver activity) and the lowest activity in the duodenum (1%). The renal activities of GST and pST were 70 and 1%, respectively, of the corresponding liver values. In summary, the metabolism of testosterone and the activities of GST and pST in rat intestine are generally low to very low in comparison to the corresponding activities in rat liver. In most cases, these activities are present throughout the entire intestine and not restricted to a particular portion(s) of this organ.     

南美白对虾肠道微生物群落的分子分析

采用分子生物学手段16S rDNA克隆文库方法对实验室养殖条件下的南美白对虾肠道细菌进行了多样性研究。用限制性片段长度多态性(RFLP)方法从文库中筛选出可能不同细菌来源的克隆子12个,测定其16S rDNA片段核甘酸序列,将所获得的序列与GenBank数据库进行BLAST比对,结果表明:南美白对虾肠道的16S rDNA克隆文库中126个克隆子分属2个不同的细菌类群:变形细菌(Proteobacteria)和厚壁细菌(Firmicutes),其中厚壁细菌为优势菌群占到75.4%,且与最相似序列同源性均低于94%;变形细菌占到24.6%,与最相似序列同源性均高于98%,分别为希瓦氏菌属(Shewanella),泛菌属(Pantoea),Aranicola属,假单胞菌属(Pseudomonas)和弧菌属(Vibrio)。