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Acetate is an important intermediate in the anaerobic degradation of organic matter. It is not only produced by fermentation but also by the reduction of CO2 via the acetyl-CoA pathway (acetogenesis). However, the interplay of this process in methanogenic rice field soils is not fully understood. Chemolithotrophic acetogenesis results in a rather strong depletion of the 13C of acetate. Therefore, we measured the δ13C of acetate, CO2 and CH4 that were produced during methanogenic degradation of organic matter in rice paddy soils from two geographical origins (Philippines and Italy) and used three different strategies to estimate the contribution of acetogenesis to acetate formation: (1) Incubation of soil slurries under elevated concentrations of H2/CO2 to specifically activate the H2-dependent communities; (2) incubation at three different temperatures (15, 30, 50 °C) to shift the conditions for H2 consumption; (3) incubation in the presence of inhibitors presumed to inhibit acetogenesis (KCN) or methanogenesis (BES). Only incubations under elevated H2/CO2 resulted in13C-depleted acetate (δ13C of −68 to −65‰) compared to the control (δ13C of −25‰). Temperature and presence of inhibitors also affected the δ13C of acetate, CO2 and/or CH4, but δ13C of acetate was never as low as after addition H2/CO2. A significant 13C enrichment of acetate at 15 °C in presence of BES and KCN indicated that H2-dependent acetogenesis is a favoured process at low temperature. Copy numbers in the Philippine soil of the fhs gene coding for the formyl-tetrahydrofolate synthetase of the acetyl-CoA pathway were on a similar order of magnitude (106 per gram dry soil) irrespectively of the different incubation conditions. Our results indicate that chemolithotrophic acetogenesis was operative in methanogenic rice soil at 15 °C but was more important at elevated H2/CO2 concentrations.

Microorganisms colonize plant roots for mutual benefits. Colonization is initiated by the soil microbial community but is also affected by soil conditions and plant type. Rice typically grows under wetland conditions that are anoxic, thus being supportive for an anaerobic methanogenic microbial community. Maize, however, grows under upland conditions that are oxic, thus being supportive for an aerobic microbial community. Crop rotation between wetland rice and upland maize is not uncommon, but the effect of this management on microbial colonization of plant roots is largely unknown and was the aim of our study. We used the roots of rice and maize from a two-year study in the Philippines, where on the same soil wetland rice was cultivated either in both wet and dry season or was rotated with upland maize in the dry season. The microbial colonization of the root ecto- and endorhizosphere was assessed by using quantitative PCR and illumina sequencing of the bacterial and archaeal 16S rRNA genes. The data showed that maize roots had completely different microbial community structures than the rice roots from continuous wetland cultivation, while rice roots from crop rotation were in-between. These effects of management were seen for each of the different bacterial phyla. For example, among the most abundant operational taxonomic units (OTUs) Firmicutes, Deltaproteobacteria and the methanogenic Methanocella spp. were less abundant while Alphaproteobacteria and the methanogenic Methanobacterium spp. were more abundant on maize than on rice roots. Our study showed that root colonization by Archaea and Bacteria was strongly affected by crop rotation between wetland rice and upland maize.

We measured CH 4 concentration, CH 4 oxidation in the water column and total CH 4 emissions to the atmosphere (diffusion and ebullition) in three weir impoundments and river reaches between them, in order to understand their role in river methane (CH 4 ) dynamics. Sediment samples were also collected to determine CH 4 consumption and production potentials together with the contribution of individual methanogenic pathways. The CH 4 surface water concentration increased 7.5 times in the 16 km long river stretch. Microbial CH 4 oxidation in the water column reached values ranging from 51 to 403 nmol l − 1 d − 1 and substantially contributed to the CH 4 removal from surface water, together with CH 4 emissions. The total CH 4 emissions to the atmosphere varied between 0.8 and 207.1 mmol CH 4 m − 2 d − 1 with the highest values observed upstream of the weirs (mean 68.5 ± 29.9 mmol CH 4 m − 2 d − 1 ). Most of the CH 4 was transported through the air-water interface by ebullition upstream of the weirs, while the ebullition accounted for 95.8 ± 2.0% of the total CH 4 emissions. Both CH 4 production and oxidation potential of sediments were higher upstream of the weirs compared to downstream of the weirs. The contribution of hydrogenotrophic methanogenesis to total CH 4 sediment production was 36.7–89.4% and prevailed upstream of the weirs. Our findings indicate that weirs might influence river CH 4 dynamics, especially by increased CH 4 production and consumption by sediments, followed by increasing CH 4 emissions to the atmosphere.

Digital control of a power supply is the use of digitally implemented functions to provide configuration, monitoring and supervising which extend to full loop control using digital hardware and software algorithms. Digital Power Control is widely used in industrial applications and is getting more and more into the focus for space applications as well. This technology is not only limited to transferring from analog to Digital Control. It additionally allows superior controller structures and even complete new control strategies. This paper describes possibilities of digital power control for space applications.

While the structure of microbial communities can nowadays be determined by applying molecular analytical tools to soil samples, microbial function can usually only be determined by physiological experiments requiring incubation of samples. However, analysis of stable isotope fractionation might be able to analyse microbial function without incubation in soil samples. We describe the limitations of diagnosing and quantifying carbon flux pathways in soil by using the determination of stable carbon isotope composition in soil compounds and emphasize the importance of determining stable isotope fractionation factors for defined biochemical pathways. Fractionation factors are sufficiently different for some central biochemical pathways in anaerobic degradation of organic carbon. Thus, it is possible to quantify the relative contribution of CH4 production by hydrogenotrophic or aceticlastic methanogenic pathways, and of acetate formation by chemolithotrophic (acetyl-CoA synthase) or heterotrophic (fermentation) pathways. In addition, stable isotope analysis may allow the differentiation between different organic substrates used for degradation, for example, the relative contribution of root exudation versus soil organic matter degradation, provided the different substrates are sufficiently distinct in their isotopic compositions (e.g., mixture of C3 and C4 plants) and the carbon conversion pathways display only small fractionation factors or are identical for the different substrates.

Homoacetogenic bacteria are versatile microbes that use the acetyl coenzyme A (acetyl-CoA) pathway to synthesize acetate from CO 2 and hydrogen. Likewise, the acetyl-CoA pathway may be used to incorporate other 1-carbon substrates (e.g., methanol or formate) into acetate or to homoferment monosaccharides completely to acetate. In this study, we analyzed the fractionation of pure acetogenic cultures grown on different carbon substrates. While the fractionation of Sporomusa sphaeroides grown on C 1 compounds was strong (ε C1 , −49‰ to −64‰), the fractionation of Moorella thermoacetica and Thermoanaerobacter kivui using glucose (ε Glu = −14.1‰) was roughly one-third as strong, suggesting a contribution of less-depleted acetate from fermentative processes. For M. thermoacetica , this could indeed be validated by the addition of nitrate, which inhibited the acetyl-CoA pathway, resulting in fractionation during fermentation (ε ferm = −0.4‰). In addition, we determined the fractionation into microbial biomass of T. kivui grown on H 2 /CO 2 (ε anabol. = −28.6‰) as well as on glucose (ε anabol. = +2.9‰).

Crop rotation of flooded rice with upland crops is a common management scheme allowing the reduction of water consumption along with the reduction of methane emission. The introduction of an upland crop into the paddy rice ecosystem leads to dramatic changes in field conditions (oxygen availability, redox conditions). However, the impact of this practice on the archaeal and bacterial communities has scarcely been studied. Here, we provide a comprehensive study focusing on the crop rotation between flooded rice in the wet season and upland maize (RM) in the dry season in comparison with flooded rice (RR) in both seasons. The composition of the resident and active microbial communities was assessed by 454 pyrosequencing targeting the archaeal and bacterial 16S rRNA gene and 16S rRNA. The archaeal community composition changed dramatically in the rotational fields indicated by a decrease of anaerobic methanogenic lineages and an increase of aerobic Thaumarchaeota. Members of Methanomicrobiales, Methanosarcinaceae, Methanosaetaceae and Methanocellaceae were equally suppressed in the rotational fields indicating influence on both acetoclastic and hydrogenotrophic methanogens. On the contrary, members of soil crenarchaeotic group, mainly Candidatus Nitrososphaera, were higher in the rotational fields, possibly indicating increasing importance of ammonia oxidation during drainage. In contrast, minor effects on the bacterial community were observed. Acidobacteria and Anaeromyxobacter spp. were enriched in the rotational fields, whereas members of anaerobic Chloroflexi and sulfate-reducing members of Deltaproteobacteria were found in higher abundance in the rice fields. Combining quantitative polymerase chain reaction and pyrosequencing data revealed increased ribosomal numbers per cell for methanogenic species during crop rotation. This stress response, however, did not allow the methanogenic community to recover in the rotational fields during re-flooding and rice cultivation. In summary, the analyses showed that crop rotation with upland maize led to dramatic changes in the archaeal community composition whereas the bacterial community was only little affected.

Chemolithotrophic homoacetogenic bacteria apparently express a characteristic stable carbon isotope fractionation and may contribute significantly to acetate production in anoxic environments. However, fractionation factors (e) in bacterial cultures have rarely been determined and the effect of substrate availability has not been assessed. We therefore studied the kinetic carbon isotope effect in cultures of Thermoanaerobacter kivui grown at 55 °C. The fractionation factor in HCO3− buffered medium was ca. 15‰ more negative than that in PO43− buffered medium. To test whether the difference was caused by the initial substrate ratio of H2 and total inorganic carbon (TIC; 0.5 in HCO3− vs. 4.0 in PO43− buffered medium), T. kivui was grown in either [3-(N-morpholino) propanesulfonic acid, MOPS] buffered or PO43− buffered media with different HCO3− concentration. Indeed, the fractionation factor became more negative with increasing HCO3− concentration and decreasing H2/TIC ratio. While pH had only a small effect, the fractionation was generally more negative in MOPS buffered than in phosphate buffered media, indicating that the buffer system also affected fractionation. Collectively, the results show that substrate availability and other environmental factors affect the magnitude of isotope fractionation during acetate production by chemolithotrophic homoacetogenesis.

Studies on methanogenesis from freshwater sediments have so far primarily focused on lake sediments. To expand our knowledge on the community composition of methanogenic archaea in river sediments, we studied the abundance and diversity of methanogenic archaea at two localities along a vertical profile (top 50 cm) obtained from sediment samples from Sitka stream (the Czech Republic). In this study, we compare two sites which previously have been shown to have a 10‐fold different methane emission. Archaeal and methanogen abundance were analyzed by real‐time PCR and T‐RFLP. Our results show that the absolute numbers for the methanogenic community (qPCR) are relatively stable along a vertical profile as well as for both study sites. This was also true for the archaeal community and for the three major methanogenic orders in our samples (Methanosarcinales, Methanomicrobiales, and Methanobacteriales). However, the underlying community structure (T‐RFLP) reveals different community compositions of the methanogens for both locations as well as for different depth layers and over different sampling times. In general, our data confirm that Methanosarcinales together with Methanomicrobiales are the two dominant methanogenic orders in river sediments, while members of Methanobacteriales contribute a smaller community and Methanocellales are only rarely present in this sediment. Our results show that the previously observed 10‐fold difference in methane emission of the two sites could not be explained by molecular methods alone.

Temperature is the major driving force for many biological as well as chemical reactions and may impact the fractionation of stable carbon isotopes. Thus, a good correlation between temperature and fractionation is observed in many chemical systems that are controlled by an equilibrium isotope effect. In contrast, biological systems that are usually controlled by a kinetic isotope effect are less well studied with respect to temperature effects and have shown contrasting results. We studied three different biological pathways (methylotrophic methanogenesis, hydrogenotrophic methanogenesis, acetogenesis by the acetyl-CoA pathway) which are characterized by very strong carbon isotope enrichment factors (−50‰ to −83‰). The microorganisms ( Methanosarcina barkeri , Methanosarcina acetivorans , Methanolobus zinderi , Methanothermobacter marburgensis , Methanothermobacter thermoautotrophicus , Thermoanaerobacter kivui ) exhibiting these pathways were grown at different temperatures ranging between 25 and 68 °C, and the fractionation factors were determined from 13 C/ 12 C isotope discrimination during substrate depletion and product formation. Our experiments showed that the fractionation factors were different for the different metabolic pathways but were not much affected by the different growth temperatures. Slight variations were well within the standard errors of replication and regression analysis. Our results showed that temperature had no significant effect on the fractionation of stable carbon isotopes during anaerobic microbial metabolism with relatively strong isotope fractionation.

Methane (CH4) is an important atmospheric trace gas mostly released from wet anoxic soils and sediments. While many studies have focused on relatively homogenous environments like rice fields and lake sediments, the changing contribution of heterogeneous sediments e.g. along the longitudinal profile of a rivers has not been covered very frequently. Here we investigated sediment samples from 11 locations of the Elbe River. Sediments were incubated to measure methanogenic/methanotrophic potentials and contribution of individual methanogenic pathways using isotope analysis of δ13C. Additionally, we determined the diversity of the methanogenic communities (analysis of T-RFLP targeting the mcr-A gene in the sediment samples), while abundances of archaea, methanogens and methanotrophs were determined by qPCR. The CH4 production was detected in six samples (out of 11 examined) and ranged from 0.12 to 644.72 nmol gDW−1 d−1. Methanotrophy was found in all examined sediment samples and ranged from 654 to 10,875 nmol gDW−1 d−1. Abundance of methanogens and methanotrophs (Mcr-A and pmo-A gene copy numbers) was not significantly different and quite stable around 106 to 107 copies gDW−1. The group specific qPCR showed high fluctuations, while the highest counts were reported for Methanomicrobiales and Methanosarcinales (105 to 108 copies per gram dry sediment), followed by Methanobacteriales (103 to 105 copies per gram dry sediment). A significant proportion of unidentified methanogens was found in almost every locality. Isotope analysis of δ13C showed that (CH4) is produced mainly by hydrogenotrophic methanogens. We see no trend in the studied parameters along the Elbe River. The molecular data showed no spatial characteristics, while we found hotspots of the measured CH4 processes (CH4 production and oxidation) due to other local driving factors (e.g. carbon content). Thus, out results indicate that the observed variability of the CH4 production and oxidation rates is only indirectly linked to the presence or quantities of different microbial guilds.

4-Hydroxyphenylacetate decarboxylase is a [4Fe-4S] cluster containing glycyl radical enzyme proposed to use a glycyl/thiyl radical dyad to catalyze the last step of tyrosine fermentation in clostridia. The decarboxylation product p-cresol (4-methylphenol) is a virulence factor of the human pathogen Clostridium difficile . Here we describe the crystal structures at 1.75 and 1.81 Å resolution of substrate-free and substrate-bound 4-hydroxyphenylacetate decarboxylase from the related Clostridium scatologenes . The structures show a (βγ)(4) tetramer of heterodimers composed of a catalytic β-subunit harboring the putative glycyl/thiyl dyad and a distinct small γ-subunit with two [4Fe-4S] clusters at 40 Å distance from the active site. The γ-subunit comprises two domains displaying pseudo-2-fold symmetry that are structurally related to the [4Fe-4S] cluster-binding scaffold of high-potential iron-sulfur proteins. The N-terminal domain coordinates one cluster with one histidine and three cysteines, and the C-terminal domain coordinates the second cluster with four cysteines. Whereas the C-terminal cluster is buried in the βγ heterodimer interface, the N-terminal cluster is not part of the interface. The previously postulated decarboxylation mechanism required the substrate's hydroxyl group in the vicinity of the active cysteine residue. In contrast to expectation, the substrate-bound state shows a direct interaction between the substrate's carboxyl group and the active site Cys503, while His536 and Glu637 at the opposite side of the active site pocket anchor the hydroxyl group. This state captures a possible catalytically competent complex and suggests a Kolbe-type decarboxylation for p-cresol formation.

One of the most exciting scientific advances in recent years has been the realization that commensal microorganisms are not simple 'passengers' in our bodies, but instead have key roles in our physiology, including our immune responses and metabolism, as well as in disease. These insights have been obtained, in part, through the work of large-scale, consortium-driven metagenomic projects. Here, five experts in the field of microbiome research discuss the most surprising and exciting new findings, and outline the future steps that will be necessary to elucidate the numerous roles of the microbiota in human health and disease and to develop viable therapeutic strategies.

In natural environments methane is usually produced by aceticlastic and hydrogenotrophic methanogenic archaea. However, some methanogens can use C 1 compounds such as methanol as the substrate. To determine the contributions of individual substrates to methane production, the stable-isotope values of the substrates and the released methane are often used. Additional information can be obtained by using selective inhibitors (e.g., methyl fluoride, a selective inhibitor of acetoclastic methanogenesis). We studied stable carbon isotope fractionation during the conversion of methanol to methane in Methanosarcina acetivorans , Methanosarcina barkeri , and Methanolobus zinderi and generally found large fractionation factors (−83‰ to −72‰). We further tested whether methyl fluoride impairs methylotrophic methanogenesis. Our experiments showed that even though a slight inhibition occurred, the carbon isotope fractionation was not affected. Therefore, the production of isotopically light methane observed in the presence of methyl fluoride may be due to the strong fractionation by methylotrophic methanogens and not only by hydrogenotrophic methanogens as previously assumed.

The objective of the present study was to describe the arthroscopic anatomy of the bovine fetlock joint using one palmar/plantar and three dorsal joint approaches. A comparative anatomic, ultrasonographic and arthroscopic study using 20 cadaveric feet from 13 non-lame adult dairy cows was performed. Arthroscopy was accomplished using a rigid arthroscope to view the synovial cavities with their synovial villi and parts of the following structures: the distal ends of the metacarpal/metatarsal III/IV bones with their trochleae and sagittal ridges, synovial grooves, the articular surfaces of the proximal sesamoid bones, the proximal aspects of the first phalanges, the lateral and medial collateral ligaments, the suspensory ligament and the interdigital ligaments as parts of the interosseus muscle, the cruciate sesamoidean ligaments, the communication site between the lateral and medial pouch in the palmar/plantar area, and dorsally the septum between the lateral and the medial pouch. The technique allowed a good overall view of most relevant structures in the sound cadaver joint. Further investigations are warranted to evaluate the diagnostic, therapeutic and prognostic applications of these techniques in the treatment of septic arthritis.

The high molecular mass (97-149 kDa) surface array proteins (SAP) of Campylobacter fetus are critical to virulence. We created a bank of 160,000 random 1.0-6.5-kilobase (kb) chromosomal DNA fragments of C. fetus strain 84-32 (23D) using lambda gt11. Screening this bank in Escherichia coli Y1090 with antibody raised against purified SAP permitted isolation and purification of a clone with a 4.0-kb insert. Subcloning this insert in the E. coli vector, pUC9, permitted expression of a protein of approximately 100 kDa, not fused with beta-galactoside or inducible by isopropyl-beta-D-thiogalactopyranoside. Digestion with restriction endonucleases, and construction of deletion mutations indicated that the gene extended over 2.8 kb, proceeding toward the start of the beta-galactosidase gene. Taking advantage of a unique PstI site at 1.7 kb, we subcloned PstI-EcoRI fragments in both orientations into M13 vectors, then generated and sequenced 48 deletion mutants. In the 3974-base insert, an open reading frame, beginning at nucleotide 24 and terminating at 2825, was found to encode a 933-amino acid polypeptide having a calculated molecular mass of 96,758 daltons. The first 20 amino acids exactly match those determined from amino-terminal sequencing, indicating that this protein is secreted without a leader sequence. The deduced amino acid composition matches that of the purified SAP. We identified a ribosomal binding site 9 bases upstream, and a putative transcription terminator (delta G = -12.4) 21 bases downstream. There is partial homology of primary and secondary structure with five other bacterial S-layer proteins.

Class IgA secretory antibodies (SigA) are an early line of antigen-specific immune defenses that are influenced by commensal microbial populations. Perinatal antibiotic exposures may affect the host microbiota and have long-term consequences on host immunity. We hypothesize that early-life pulsed antibiotic treatment (PAT) perturbs the intestinal microbiota leading to alterations in sIgA expression. To test this hypothesis, C57BL/6 mice were exposed to 5 therapeutic doses of the β-lactam, amoxicillin, or the macrolide, tylosin. Exposure to either the tylosin or amoxicillin delayed sIgA expression. sIgA expression recovered in β-lactam-exposed mice but was abrogated with macrolide exposure. Compared to age-matched controls, 1 or 3 tylosin pulses decreased sIgA levels by 40% and 75%, respectively. Alterations in sIgA production were associated with decreased bacterial richness (α-diversity), altered community structure (β-diversity), and changes in microbial compositional, including increased abundance of Enterobacteriaceae and Bacteroides uniformis. Whereas tylosin had multiple immunological effects on conventional mice, essentially none were detected in germ-free animals; indicating that an antibiotic-perturbed microbiota influences developing immunity. These results provide evidence that early-life alterations of the intestinal microbiota by PAT modulates sIgA production, phenotypes that may persist after microbial recovery, with long-term consequences to host immunity.

Broad-spectrum antibiotics are frequently prescribed for children. The gut microbiota have functional roles in the development and differentiation of the host immune system. Early-life antibiotic use may have dynamic effects on the host microbiota, promoting long-term immunologic dysregulation and subsequent allergic and autoimmune pathology. Using a model of early-life antibiotic use, we hypothesize that early-life pulsed antibiotic treatment (PAT) -induced perturbation of the intestinal microbiota leads to alterations in tissue-specific and systemic T-cell populations. To test this hypothesis, we characterized splenic and ileal T-cell populations in control and PAT-treated C57BL/6 mice. Flow cytometric analysis demonstrated that early-life PAT significantly (p

Perivaginal fat protrusion is a complication of soft tissue laceration in cases of dystocia in cattle. The vaginal wall is able to heal around the perivaginal fat prolapse, leaving a pedunculated mass of fat covered with granulation tissue (Hull 1995). When the cow lies down or strains, this mass protrudes through the vulva, and the surface often becomes necrotic due to recurrent exposure. The prolapsed tissue usually originates from the lateral vaginal wall. Pedunculated masses of perivaginal fat are often misdiagnosed as tumours (Hull 1995). Arbeiter and Mayer (1967) have described fat tissue protrusion through the vaginal wall in primiparous as well as in multiparous cows. The protrusion was always located in the region of the hymen (Arbeiter and Mayer 1967). Each case described in their study had a history of assisted calving one to two weeks before being referred for treatment. Particularly at first calving, livestock owners underestimate the time needed for dilatation of soft tissue, leading to premature forced extraction. Different techniques are described for the excision of the protruded fat tissue: Arbeiter and Mayer (1967) propose an episiotomy and the excision of the fat prolapse with a scalpel and the tamponade of the wound cavity with a resorbable sponge (Spongostan Johnson & Johnson Medical GmbH). Hull (1995) proposed making small cuts in the surface of the protruded fat to produce a gradual protrusion of fat from the inside and then the stepwise excision of the fat tissue avoiding the risk of deep dissection and massive bleeding. Wolfe and Carson (1998) finally described the removal of the fat tissue with an emasculator. The aim of the present case series is to describe a novel surgical technique to easily and safely remove prolapsed perivaginal fat tissue. Six adult Eringer cows (numbers 1–6; number 6 was referred …

Urease activity has recently been shown to be an important virulence determinant for Helicobacter pylori, allowing it to survive the low pH of the stomach during colonization. Experimental murine infection with Helicobacter felis is now being used as a model for H. pylori infection to study the effects of vaccines, antibiotics, and urease inhibitors on colonization. However, little information comparing the ureases of H. felis and H. pylori is available. Urease was partially purified from the cell surface of H. felis ATCC 49179 by A-5M agarose chromatography, resulting in an eightfold increase in specific activity over that of crude urease. The apparent Km for urea for the partially purified urease was 0.4 mM, and the enzyme was inhibited in a competitive manner by flurofamide (50% inhibitory concentration = 0.12 microM). Antiserum to whole cells of H. pylori recognized both H. pylori and H. felis urease B subunits. Antiserum raised against H. felis whole cells recognized the large and small autologous urease subunits and the cpn60 heat shock molecule in both H. felis and H. pylori. However, this antiserum showed only a weak reaction with the B subunit of H. pylori urease. Two oligomeric DNA sequences were used as probes to evaluate the relatedness of H. felis and H. pylori urease gene sequences. One 30-mer from the ureA sequence, which had been shown previously to be specific for H. pylori, failed to hybridize to H. felis genomic DNA. A probe to the putative coding sequence for the active site of the H. pylori ureB subunit hybridized at low intensity to a 2.8-kb fragment of BamHI-HindIII-digested H. felis DNA, suggesting that the sequences were homologous but not identical, a result confirmed from the recently published sequences of ureA and ureB from H. felis.

Helicobacter pylori and Campylobacter fetus are two spiral Gram-negative bacteria that have evolved lifestyles centred on long-term persistence in the mucus gel overlapping epithelial tissues. Since the discovery of H. pylori in 1983 there has been intense interest in this organism because of its relationship to ulcer disease, among other maladies. However, the pathophysiology of H. pylori infection is largely unknown. In this chapter I review the major points that have been learned about H. pylori pathogenesis, and then review what is known about the pathogenesis of C. fetus infection. It is hoped that bringing together information about these two different organisms that contend with parallel constraints can provide new insights.

Campylobacter fetus ss. jejuni has recently been recognised as a human enteric pathogen. Five cases of campylobacter enteritis are described. All five patients had abdominal pain and diarrhœa. Two of the five patients had bloody diarrhœa and relapses. All the patients had been in contact with young dogs which had had diarrhœa. Campylobacter fetus ss. jejuni was isolated from these dogs or from their litter-mates. Canine infection with Campylobacter fetus ss. jejuni may be an important source of infection causing diarrhœa in man.