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At least 19 recordsLinked to original sources
PubMed2026

Population Genomics Approaches Identify a Cryptic, Emerging Generalist Pest Complex.

Information about biological traits essential for pest management, such as species identity, diet and movement often require laborious and time-intensive studies on pest natural history, in both laboratory and field settings. However, new agricultural pest threats are continually emerging, often requiring prompt responses with limited information. Using a combination of molecular gut content analysis and RAD-seq, we examined the species identities, plant diet composition, and population genetic structure of an emerging and important agricultural pest in the US, the peanut burrower bug, Pangaeus bilineatus Say (Hemiptera, Cydnidae). We found that two, morphologically similar, burrowing bug species (including P. bilineatus) were commonly caught in light traps near peanut fields, one of which (Dallasiellus lugubris) was not previously considered a pest of peanut. Molecular gut content analysis revealed a wide, but somewhat distinct, variety of plants among the diets of both bug species. Surprisingly, peanut was a rare part of the diet of either species. RAD-seq analysis revealed evidence consistent with weak isolation-by-distance and modest spatial genetic differentiation for both species. Together, these results suggest a potential pest complex where previously only one species was in focus. Moreover, their broad diets and spatially restricted population dispersal patterns may also explain the sporadic nature of damage that has been recorded for this potential pest complex. Responses to emerging pest challenges can benefit from insights generated by population genomics techniques, opening up new avenues for research and supporting efforts to quickly tailor management strategies for novel pests.

burrower bug↗
PubMed1998

Effects of preservation methods, parasites, and gut contents of black flies (Diptera: Simuliidae) on polymerase chain reaction products.

Molecular analysis of biological specimens usually requires extraction of high-molecular weight DNA free of foreign DNA contaminants. DNA was extracted from black flies at different life stages that had been preserved by 4 methods: larvae and adults in ethanol, larvae in Carnoy's solution, adults on card-points, and adults hand-swatted and sun-dried. Using specific primers for the mitochondrial ND4 gene, a 257-bp amplicon was obtained from specimens preserved by ethanol, card-point mounting, and sun-drying. Successful amplification often required DNA dilutions > or = 1:20 (< 1-10 ng). DNA from specimens preserved in Carnoy's solution (ethanol: acetic acid, 3:1) yielded degraded DNA, resulting in fewer successful amplications. Parasitic nematodes and, to a lesser extent, gut contents resulted in extra products when amplified with randomly amplified polymorphic DNA (RAPD) primers. Sufficient DNA was extracted from the head of a larva for a successful polymerase chain reaction (PCR), eliminating the need to remove the contaminating gut and parasites.

Animals↗
PubMed2005

Molecular analysis of jejunal, ileal, caecal and recto-sigmoidal human colonic microbiota using 16S rRNA gene libraries and terminal restriction fragment length polymorphism.

Microbiota in gut contents of jejunum, ileum, caecum and recto-sigmoid colon obtained from three elderly individuals at autopsy were compared using 16S rRNA gene libraries and terminal restriction fragment length polymorphism (T-RFLP). Random clones of 16S rRNA gene sequences were isolated after PCR amplification with universal primer sets of total genomic DNA extracted from each sample of gut contents. An average of 90 randomly selected clones were partially sequenced (about 500 bp). T-RFLP analysis was performed using the 16S rRNA gene amplified from each sample. The lengths of the terminal restriction fragments were analysed after digestion with HhaI and MspI. The jejunal and ileal microbiota consisted of simple microbial communities of streptococci, lactobacilli, 'Gammaproteobacteria', the Enterococcus group and the Bacteroides group. Most of the species were facultative anaerobes or aerobes. The Clostridium coccoides group and the Clostridium leptum subgroup, which are the most predominant groups in human faeces, were not detected in samples from the upper gastrointestinal tract. The caecal microbiota was more complex than the jejunal and ileal microbiota. The C. coccoides group, the C. leptum subgroup and the Bacteroides group were detected in the caecum. The recto-sigmoidal colonic microbiota consisted of complex microbial communities, with numerous species that belonged to the C. coccoides group, the C. leptum subgroup, the Bacteroides group, 'Gammaproteobacteria', the Bifidobacterium group, streptococci and lactobacilli, and included more than 26 operational taxonomic units. The results showed marked individual differences in the composition of microbiota in each region.

Aged↗
PubMed2005

Molecular analysis of the anaerobic rumen fungus Orpinomyces - insights into an AT-rich genome.

The anaerobic gut fungi occupy a unique niche in the intestinal tract of large herbivorous animals and are thought to act as primary colonizers of plant material during digestion. They are the only known obligately anaerobic fungi but molecular analysis of this group has been hampered by difficulties in their culture and manipulation, and by their extremely high A+T nucleotide content. This study begins to answer some of the fundamental questions about the structure and organization of the anaerobic gut fungal genome. Directed plasmid libraries using genomic DNA digested with highly or moderately rich AT-specific restriction enzymes (VspI and EcoRI) were prepared from a polycentric Orpinomyces isolate. Clones were sequenced from these libraries and the breadth of genomic inserts, both genic and intergenic, was characterized. Genes encoding numerous functions not previously characterized for these fungi were identified, including cytoskeletal, secretory pathway and transporter genes. A peptidase gene with no introns and having sequence similarity to a gene encoding a bacterial peptidase was also identified, extending the range of metabolic enzymes resulting from apparent trans-kingdom transfer from bacteria to fungi, as previously characterized largely for genes encoding plant-degrading enzymes. This paper presents the first thorough analysis of the genic, intergenic and rDNA regions of a variety of genomic segments from an anaerobic gut fungus and provides observations on rules governing intron boundaries, the codon biases observed with different types of genes, and the sequence of only the second anaerobic gut fungal promoter reported. Large numbers of retrotransposon sequences of different types were found and the authors speculate on the possible consequences of any such transposon activity in the genome. The coding sequences identified included several orphan gene sequences, including one with regions strongly suggestive of structural proteins such as collagens and lampirin. This gene was present as a single copy in Orpinomyces, was expressed during vegetative growth and was also detected in genomes from another gut fungal genus, Neocallimastix.

AT Rich Sequence↗
PubMed1975

Immunoglobulin E (IgE) and IgE-containing cells in human gastrointestinal fluids and tissues.

Human gastric, small intestinal, colonic and rectal mucosae were examined for IgE-containing cells by single- and double-antibody immunofluorescence techniques, and IgE in intesinal fluids was measured by a double-antibody radioimmunoassay. IgE-containing cells were identified in all tissue specimens and comprised about 2% of all immunoglobulin-containing cells. Although less numerous than cells containing IgA, IgM or IgG, they were remarkably numerous in relation to the concentration of IgE in serum (about 0-001% of total immunoglobulin). IgE immunocytes were significantly more numerous in stomach and proximal small bowel than in colon and rectum, and were very numerous at bases of gastric and duodenal peptic ulcers. Measurable IgE was found in seventy-eight of eighty-five (92%) intestinal fluids. Sucrose gradient ultracentrifugation analysis of four of the fluids revealed that the immunologically reactive IgE was largely in fractions corresponding to molecules of lower molecular weight than that of albumin, which suggests that IgE in gut contents is degraded by proteolytic enzymes. The presence of IgE-forming cells in gastrointestinal tissues, and IgE or a fragment of IgE in intestinal fluids, suggests that IgE antibodies are available for participation in local reaginic-type reactions in the gut.

Adult↗
PubMed2004

Infiltration by alien predators into invertebrate food webs in Hawaii: a molecular approach.

Abstract Alien invertebrate predators have been introduced to Hawaii to control pests, particularly in lowland areas where most crops are grown. We developed techniques for assessing the impact of these predators on native food webs in relatively pristine upland areas where, it was hypothesized, few lowland predators might be found. Predator densities were assessed along transects within the Alakaii Swamp on Kaua'i. The most numerous alien biocontrol agents found were Halmus chalybeus (Coccinellidae), a species known to feed on Lepidoptera eggs. Laboratory experiments were conducted using two genera of endemic Lepidoptera, Scotorythra and Eupithecia (Geometridae), that are of considerable conservation value, the former because of its recent speciation across Hawaii, the latter for its unique predatory larvae. Techniques were developed for detecting Lepidoptera DNA within the guts of alien predators using prey-specific PCR primers. General primers amplified fragments of the mitochondrial cytochrome oxidase I gene from beetles and Lepidoptera. The sequences were aligned and used successfully to design target-specific primers for general detection of the remains of Geometridae and for particular species, including Scotorythra rara and Eupithecia monticolans. DNA fragments amplified were short [140-170 base pairs (bp)], optimizing detection periods following prey ingestion. Trials using the introduced biocontrol agent Curinus coeruleus (Coccinellidae) demonstrated detection of Lepidoptera DNA fragments = 151 bp in 85-100% of beetles after 24 h digestion of an early instar larva. This study provides a framework for future use of molecular gut analysis in arthropod conservation ecology and food web research with considerable potential for quantifying threats to endemic species in Hawaii and elsewhere.

Amino Acid Sequence↗
PubMed1990

Biochemical characterization of porcine enteric calicivirus: analysis of structural and nonstructural viral proteins.

In this report, the molecular weight and antigenicity of the proteins of a porcine enteric calicivirus (PEC) were characterized. The PEC virions were purified from intestinal contents of infected pigs and from infected cell culture lysates. The average buoyant density of the purified virus was 1.37 gm/cm3 in cesium chloride. One major structural protein with a molecular weight of approximately 58 k was found in the gut and cell culture-passaged PEC using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Using immunoblotting techniques only one immunoreactive protein (58 k) ws identified. The PEC and a prototype calicivirus, feline calicivirus (FCV) were propagated in pig kidney and feline kidney (Crandell) cell lines, respectively and intrinsically labeled using [35S]methionine at various times post-inoculation (PI). SDS-PAGE of the radiolabeled proteins indicated the presence of the major structural protein (58 k) and one probable nonstructural protein (28 k) synthesized in the PEC-infected cell lysates by 12 h PI. Other minor protein bands were also evident by 24 h PI (32 k and 82 k). Only the 58 k major protein was detected by radioimmunoprecipitation (RIP) analysis using hyperimmune anti-PEC serum. SDS-PAGE and RIP analysis of FCV-infected cell lysates using hyperimmune anti-FCV serum identified a single major protein of approximately 64 k. No antigenic relationship between PEC and FCV proteins was detected by RIP analysis. The single major structural protein of PEC, the morphological appearance and size of the virus, and its average density of 1.37 gm/cm3 in cesium chloride are consistent with properties of other members of the family Caliciviridae.

Animals↗
PubMed2006

Dietary carbohydrate source influences molecular fingerprints of the rat faecal microbiota.

BACKGROUND: A study was designed to elucidate effects of selected carbohydrates on composition and activity of the intestinal microbiota. Five groups of eight rats were fed a western type diet containing cornstarch (reference group), sucrose, potato starch, inulin (a long- chained fructan) or oligofructose (a short-chained fructan). Fructans are, opposite sucrose and starches, not digestible by mammalian gut enzymes, but are known to be fermentable by specific bacteria in the large intestine. RESULTS: Animals fed with diets containing potato starch, or either of the fructans had a significantly (p < 0.05) higher caecal weight and lower caecal pH when compared to the reference group, indicating increased fermentation. Selective cultivation from faeces revealed a higher amount of lactic acid bacteria cultivable on Rogosa agar in these animals. Additionally, the fructan groups had a lower amount of coliform bacteria in faeces. In the inulin and oligofructose groups, higher levels of butyrate and propionate, respectively, were measured.Principal Component Analysis of profiles of the faecal microbiota obtained by Denaturing Gradient Gel Electrophoresis (DGGE) of PCR amplified bacterial 16S rRNA genes as well as of Reverse Transcriptase-PCR amplified bacterial 16S rRNA resulted in different phylogenetic profiles for each of the five animal groups as revealed by Principal Component Analysis (PCA) of band patterns. CONCLUSION: Even though sucrose and cornstarch are both easily digestible and are not expected to reach the large intestine, the DGGE band patterns obtained indicated that these carbohydrates indeed affected the composition of bacteria in the large gut. Also the two fructans resulted in completely different molecular fingerprints of the faecal microbiota, indicating that even though they are chemically similar, different intestinal bacteria ferment them. Comparison of DNA-based and RNA-based profiles suggested that two species within the phylum Bacteroidetes were not abundant in numbers but had a particularly high ribosome content in the animals fed with inulin.

Animals↗
PubMed1995

Characterization of a cDNA encoding a cytosolic peptidylprolyl cis-trans-isomerase from Blattella germanica.

Cyclophilins are an abundant and ubiquitous class of proteins first identified by their high affinity for the immunosuppressive drug cyclosporin A. Cyclophilins have peptidylprolyl cis/trans-isomerase activity in vitro, and thus may be involved in protein folding and trafficking in vivo. In this study, we report the cloning and characterization of a Blattella germanica cyclophilin cDNA. Analysis of this 846-bp cDNA reveals an open reading frame coding for a polypeptide of 164 amino acid residues with a molecular mass of 17934 Da. This B. germanica cyclophilin shares a central peptidylprolyl cis/trans-isomerase and a cyclosporin-A-binding domain with other cyclophilin sequences. The B. germanica cyclophilin amino acid sequence shares 83% identity with the cytosolic cyclophilin isoform from Drosophila melanogaster (Cyp-1). This identity suggests that B. germanica cyclophilin is a member of the cytosolic cyclophilin A (CyPA) family. From the alignment of cyclophilin sequences, we have found that 62 residues (positional identity of 40%) have remained invariant in eukaryotes for more than 1 billion years of divergence. We calculated a unit evolutionary period of 30.9 million years for the cytosolic isoform. Northern-blot analyses show that B. germanica CyPA mRNA is abundant, and present in all insect organs tested. The highest values for B. germanica cyclophilin mRNA tissue content were found in 6-day-old ovary, followed by brain, testis, and gut (15-30% the content of ovary). The muscle, fat body, and colleterial gland contained the lowest cyclophilin mRNA level (1-5% the content of ovary). There is a developmental pattern of gene expression affecting the embryo stages. These results suggest that this ubiquitously expressed B. germanica cyclophilin is subject to a differential regulation in tissues and during development. Southern-blot analysis of B. germanica DNA shows that only one copy of the CyPA gene is present per genome, whereas at least 20 genes or pseudogenes were detected in the mammalian genome.

Amino Acid Isomerases↗
PubMed2005

Molecular phylogenetic diversity of the bacterial community in the gut of the termite Coptotermes formosanus.

The phylogenetic diversity of the bacterial community in the gut of the termite Coptotermes formosanus was investigated using a 16S rRNA gene clone library constructed by PCR. After screening by restriction fragment length polymorphism (RFLP) analysis, 49 out of 261 clones with unique RFLP patterns were sequenced and phylogenetically analyzed. Many of the clones (94%) were derived from Bacteroidales, Spirochaetes, and low G + C content gram-positive bacteria consisting of Clostridiales, Mycoplasmatales, Bacillales, and Lactobacillales. In addition, a few clones derived from Actinobacteria, Proteobacteria, Planctomycetes, Verrucomicrobia, and the candidate phylum "Synergistes" were also found. The most frequently identified RFLP type, BCf1-03, was assigned to the order Bacteroideales, and it constituted about 70% of the analyzed clones. The phylogenetic analysis revealed that the representative clones found in this study tended to form some clusters with the sequences cloned from the termite gut in several other studies, suggesting the existence of termite-specific bacterial lineages.

Animals↗
PubMed2003

Microorganisms in the gut of beetles: evidence from molecular cloning.

We have regularly cultured yeasts from the gut of certain beetles in our ongoing research. In this study cloned PCR products amplified from the gut contents of certain mushroom-feeding and wood-ingesting beetles in four families (Erotylidae, Tenebrionidae, Ciidae, and Passalidae) were sequenced and compared with culture results. Cultural techniques detected some yeasts present in the gut of the beetles, including a Pichia stipitis-like yeast associated with wood-ingesting passalid beetles. Clone sequences similar to several ascomycete yeasts and Malassezia restricta, a fastidious basidiomycetous yeast requiring special growth media, however, were not detected by culturing. Unexpectedly, phylogenetic analysis of additional clone sequences discovered from passalid beetles showed similarity to members of the Parabasalia, protists known from other wood-ingesting insects, termites, and wood roaches. Examination of all gut regions of living passalids, however, failed to reveal parabasalids, and it is possible that they were parasites in the gut tissue present in low numbers.

Animals↗
PubMed1981

Goblet cell glycoprotein: an organ-specific antigen for gut. Isolation, tissue localization and immune response.

We report, for the first time, immune responses within two lines of inbred rats to a purified Lewis rat glycoprotein antigen which is organ-specific for intestine. The antigen was prepared by solubilization of gut epithelial cell-associated macromolecules, fractionation in ethanol, and molecular sieve chromatography over Sepharose 2B. Homogeneity of the end product (RGCG-PK1) was supported by results of both double diffusion in agar and SDS polyacrylamide gel electrophoresis. Amino acid analysis and specific sugar determination proved that RGCG-PK1 was not a classical mucin because of its comparatively high tyrosine and low galactosamine + glucosamine content, and the absence of glycosidic linkages to serine and threonine. Organ-specificity was shown by the ability of RGCG (but not liver homogenate) to inhibit precipitation and haemagglutination by heterologous specific sera. Organ-specificity was confirmed by the demonstration of RGCG-PK1-specific immunofluorescence staining of rat small and large intestine, but not esophagus, stomach or liver. RGCG-PK1 determinants within rat and human small bowel were found to be confined to goblet cells and intestinal glycocalyx. Anti-RCGC-PK1 serum showed no reactivity with highly purified xenogeneic mucins nor with syngeneic small bowel mucin. Specific antibody (as well as antibody-dependent cellular cytotoxicity) to RGCG was elicited and detected for up to 10 days in two lines of inbred rats, including the one (Lewis) from which the antigen was isolated. The duration and peak of the humoral immune response were abbreviated compared with that of a xenogeneic control glycoprotein studied in parallel, probably due to immunoregulatory mechanisms operative for self antigens.

Amino Acids↗
PubMed1988

Occupational allergy to locusts: an investigation of the sources of the allergen.

Allergic symptoms occur commonly in subjects working closely with locusts and are associated with specific IgE antibody. Extracts of intact locusts (Schistocerca gregaria and Locusta migratoria) were used to identify specific IgE antibody, to define the major allergens of the locust and their sources, and to estimate aeroallergen concentration in the working environment. With questionnaire, skin prick tests, and specific IgE measurements, 35 individuals, working in a research center, were surveyed. Of the 15 currently exposed individuals, contact with locusts provoked asthma, rhinitis, and contact urticaria in five, rhinitis and urticaria in three, and rhinitis alone in one individual. Symptoms provoked by locusts and skin test reactions to locust extracts were associated with specific IgE antibody in the serum. The "immunoblot" technique demonstrated the presence of multiple allergens in the locust extracts of approximately 68, 66, 54, 43, 37, 29, and 18 K daltons molecular weight. Locust antigen was identified in the atmosphere by means of an immunochemical method involving elution of high-volume air-sampler filters exposed in the locust breeding room and analysis of eluate allergen content by RAST-inhibition assays. Logit transformation of RAST-inhibition lines demonstrated that the filter extract shared a common slope with the locust extract and with an extract of locust gut. This gut extract also shared a common slope with extracts of locust feces and peritrophic membrane. The major source of allergen appears to be the peritrophic membrane that is present in the gut and is excreted surrounding the feces.

Allergens↗
PubMed2000

Molecular characterization and pathogenesis of transmissible gastroenteritis coronavirus (TGEV) and porcine respiratory coronavirus (PRCV) field isolates co-circulating in a swine herd.

TGEV replicates in intestinal enterocytes and causes diarrhea in young pigs. PRCV, a spike (S) gene deletion mutant of TGEV with an altered respiratory tissue tropism, causes mild or subclinical respiratory infections. Comparisons of TGEV and PRCV strains suggest that tropism and pathogenicity are influenced by the S gene and ORF3, respectively. Recently, outbreaks of TGE of reduced virulence were reported in the field. We investigated a similar suspect TGEV outbreak of reduced virulence in nursery pigs from a swine herd in the Midwest. A TGEV strain (BW021898B) was isolated in swine testicular cells from gut contents of a diarrheic pig and three PRCV strains (BW126, BW154, BW155) were isolated from nasal swabs from normal TGEV-seronegative sentinel pigs in contact with the diarrheic pigs. Sequence analysis of the TGEV isolate in the partial S gene and ORF3/3a and ORF3-1/3b revealed high homology with enteropathogenic TGEV strains. Gnotobiotic pig inoculation and histopathological results revealed that this TGEV isolate retained virulence even though in the field outbreak the diarrheal disease was of reduced severity. Sequence analysis of the S gene deletion region of the three PRCV isolates revealed identical deletions between nt 105-752, which differ from deletions previously reported among PRCV strains. The three PRCV isolates had variable sequence changes in ORF 3/3a and ORF 3-1/3b, affecting the ORF size and amino acid sequence. Thus, sequence analysis and pathogenicity studies indicate that this TGEV isolate resembles other enteropathogenic TGEV strains. Therefore, the reduced severity of TGE observed in this herd may be due to the ongoing PRCV infections, which induce antibodies cross-reactive with TGEV and result in decreased disease severity. The results outlined in this study highlight the need to monitor the molecular epidemiology of TGEV/PRCV strains with sensitive differential diagnostic assays, followed by sequence analysis of the critical regions to identify changes and pathogenicity studies to confirm the disease potential of the TGEV isolates.

Amino Acid Sequence↗
PubMed2004

Microflora ecology of the chicken intestine using 16S ribosomal DNA primers.

The microflora in the gastrointestinal tract of broiler chickens influences digestion, health, and wellbeing. Analysis of chicken gut microflora has been mainly by culture-based methods. Studies using these techniques have been useful for identification and analysis of specific groups of bacteria, however, the use of enrichment medium precludes even relative quantitation of bacterial species. Recent advances in ribosomal DNA-based molecular techniques make it possible to identify different bacterial populations in environmental samples without cultivation. In this study, the intestinal microflora was examined using 16S ribosomal DNA (rDNA) targeted probes from bacterial DNA isolated from intestinal and cecal contents of chickens at 4, 14, and 25 d of age. The ribosomal gene sequence was amplified using PCR with universal primers to determine total bacterial DNA and specific primers directed at 6 bacterial species: Lactobacillus, Bifidobacterium, Salmonella, Campylobacter, Escherichia coli, and Clostridium. The use of universal primers extends these methods to allow determination of relative proportions of different bacterial species. The results indicated that in young chicks the major species present in the small intestines and ceca was Lactobacilli, with a Bifidobacteria population becoming more dominant in the ceca at older age. Clostridium was detected in some segments of the small intestine in young chicks. In older chickens, Salmonella, Campylobacter, and E. coli species were found in the ceca. This study has demonstrated the use of molecular techniques for determining relative proportions of bacterial species and monitoring pathogens in the chick gastrointestinal tract.

Aging↗
PubMed2006

Response of the digestive system of Helicoverpa zea to ingestion of potato carboxypeptidase inhibitor and characterization of an uninhibited carboxypeptidase B.

Carboxypeptidase activity participates in the protein digestion process in the gut of lepidopteran insects, supplying free amino-acids to developing larvae. To study the role of different carboxypeptidases in lepidopteran protein digestion, the effect of potato carboxypeptidase inhibitor (PCI) on the digestive system of larvae of the pest insect Helicoverpa zea was investigated, and compared to that of Soybean Kunitz Trypsin Inhibitor. Analysis of carboxypeptidase activity in the guts showed that ingested PCI remained active in the gut, and completely inhibited the activity of carboxypeptidases A and O. Interestingly, carboxypeptidase B activity was not affected by PCI. All previously described enzymes from the same family, both from insect or mammalian origin, have been found to be very sensitive to PCI. Analysis of several lepidopteran species showed the presence of carboxypeptidase B activity resistant to PCI in most of them. The H. zea carboxypeptidase B enzyme (CPBHz) was purified from gut content by affinity chromatography. N-terminal sequence information was used to isolate its corresponding full-length cDNA, and recombinant expression of the zymogen of CPBHz in Pichia pastoris was achieved. The substrate specificity of recombinant CPBHz was tested using peptides. Unlike other CPB enzymes, the enzyme appeared to be highly selective for C-terminal lysine residues. Inhibition by PCI appeared to be pH-dependent.

Amino Acid Sequence↗
PubMed2005

Ontogenetic development of the gastrointestinal microbiota in the marine herbivorous fish Kyphosus sydneyanus.

Molecular techniques were used to investigate the composition and ontogenetic development of the intestinal bacterial community in the marine herbivorous fish Kyphosus sydneyanus from the north eastern coast of New Zealand. Previous work showed that K. sydneyanus maintains an exclusively algivorous diet throughout post-settlement life and passes through an ontogenetic diet shift from a juvenile diet which is readily digestible to an adult diet high in refractory algal metabolites. Terminal restriction fragment length polymorphism (T-RFLP) analysis was used to investigate the relationship between bacterial community structure and fish size. Bacterial diversity was higher in posterior gut sections than anterior gut sections, and in larger fish than in smaller fish. Partial sequencing of bacterial 16S rDNA genes PCR amplified and cloned from intestine content samples was used to identify the phylogenetic affiliation of dominant gastrointestinal bacteria. Phylogenetic analysis of clones showed that most formed a clade within the genus Clostridium, with one clone associated with the parasitic mycoplasmas. No bacteria were specific to a particular intestinal section or size class of host, though some appeared more dominant than others and were established in smaller fishes. Clones closely related to C. lituseburense were particularly dominant in most intestine content samples. All bacteria identified in the intestinal samples were phylogenetically related to those possessing fermentative type metabolism. Short-chain fatty acids in intestinal fluid samples increased from 15.6 +/- 2.1 mM in fish <100 mm to 51.6 +/- 5.5 mM in fish >300 mm. The findings of this study support the hypothesis that the ontogenetic diet shift of K. sydneyanus is accompanied by an increase in the diversity of intestinal microbial symbionts capable of degrading refractory algal metabolites into short-chain fatty acids, which can then be assimilated by the host.

Age Factors↗
PubMed2003

Collembola as alternative prey sustaining spiders in arable ecosystems: prey detection within predators using molecular markers.

Collembola comprise a major source of alternative prey to linyphiid spiders in arable fields, helping to sustain and retain these predators as aphid control agents within the crop. Polymerase chain reaction primers were developed for the amplification, from spider gut samples, of DNA from three of the most abundant species of Collembola in wheat crops in Europe, namely Isotoma anglicana, Lepidocyrtus cyaneus and Entomobrya multifasciata. The primers amplified fragments of the mitochondrial cytochrome oxidase subunit I (COI) gene and were designed following alignment of comparable sequences for a range of predator and prey species. Each of the primer pairs proved to be species-specific to a Collembola species, amplifying DNA fragments from 211 to 276 base pairs in length. Following consumption of a single collembolan, prey DNA was detectable in 100% of spiders after 24 h of digestion. We report the first use of DNA-based techniques to detect predation by arthropods on natural populations of prey in the field. All three species of Collembola were consumed by the spiders. By comparing the ratios of the Collembola species in the field with the numbers of spiders that gave positive results for each of those species, it was possible to demonstrate that the spiders were exercising prey choice. Overall, a single target species of Collembola was eaten by 48% of spiders while a further 16% of spiders contained DNA from two different species of Collembola. Preference was particularly evident for I. anglicana, the species most frequently found in spider guts yet the least numerous of the three target species in the field.

Animals↗