Denitrifying Bacteria in the Earthworm Gastrointestinal Tract and In Vivo Emission of Nitrous Oxide (N(inf2)O) by Earthworms

Earthworms (Lumbricus rubellus and Octolasium lacteum) and gut homogenates did not produce CH(inf4), and methanogens were not readily culturable from gut material. In contrast, the numbers of culturable denitrifiers averaged 7 x 10(sup7) and 9 x 10(sup6) per g (dry weight) of gut material for L. rubellus and O. lacteum, respectively; these values were 256- and 35-fold larger than the numbers of culturable denitrifiers in the soil from which the earthworms were obtained. Anaerobically incubated earthworm gut homogenates supplemented with nitrate produced N(inf2)O at rates exceeding that of soil homogenates. Furthermore, living earthworms emitted N(inf2)O under aerobic conditions, and N(inf2)O emission was stimulated by acetylene. For earthworms collected from a mildly acidic (pH 6) beech forest soil, the rates of N(inf2)O emission for earthworms and soil averaged 884 and 2 pmol per h per g (fresh weight), respectively. In contrast, for earthworms collected from a more acidic (pH 4.6) oak-beech forest soil, N(inf2)O emission by earthworms and soil averaged 145 and 45 pmol per h per g (fresh weight), respectively. Based on the extrapolation of this data, earthworms accounted for an estimated 16 and 0.25% of the total N(inf2)O produced at the stand level of these beech and oak-beech forest soils, respectively.     

Microbial degradation of hydrocarbons in soil during aerobic/anaerobic changes and under purely aerobic conditions

Microbial hydrocarbon degradation in soil was studied during periodical aerobic/anaerobic switching and under purely aerobic conditions by using a pilot-scale plant with diesel-fuel-contaminated sand. The system worked according to the percolation principle with controlled circulation of process water and aeration. Periodical switching between 4 h of aerobic and 2 h of anaerobic conditions was achieved by repeated saturation of the soil with water. Whatever the cultivation mode, less than 50% of the diesel was degraded after 650 h because the hydrocarbons were adsorbed. Contrary to expectations, aerobic/anaerobic changes neither accelerated the rate of degradation nor reduced the residual hydrocarbon content of the soil. Obviously the pollutant degradation rate was determined mainly by transport phenomena and less by the efficiency of microbial metabolism. The total mass of oxygen consumed and carbon dioxide produced was greater under aerobic/anaerobic changing than under aerobic conditions, although the mass of hydrocarbons degraded was nearly the same. As shown by an overall balance of microbial growth and by a carbon balance, the growth yield coefficient was smaller during aerobic/anaerobic changes than under aerobic conditions. Received: 25 November 1997 /  Received revision: 15 January 1998 / Accepted: 18 January 1998     

Viability of gut microbes as a complementary earthworm biomarker of metal exposure

Earthworms are standard species used in soil ecotoxicology to evaluate the adverse effects of soil contaminants. This study proposes the assessment of the viability of earthworm gut microbes as an indicator in a site-specific test of soil toxicity. Using slow centrifugation, the microbial community was extracted from the guts of earthworms that had been exposed to copper (Cu)- or nickel (Ni)-contaminated soil. Microbial cell viability was assessed using calcein acetoxymethyl ester staining and flow cytometric analysis. We confirmed a metal concentration-dependent decrease in the cell viability of the gut microbial community. The general endpoints, including survival, abnormalities, coelomocyte activity, and metal bioaccumulation, showed a metal concentration-dependent response, and were strongly associated with gut microbial viability in the Ni-exposure group. In contrast, the general endpoints in the Cu-exposure group were significantly different from those in the former group, because the soil penetration rate of the earthworms was very low on the Cu-contaminated soil. Our results indicated that the gut microbial community viability assay holds potential for assessing the toxicity of soil to field worms by simply and rapidly monitoring the viability of the earthworm gut microbial community.     

Functionally redundant cellobiose-degrading soil bacteria respond differentially to oxygen

The availability of oxygen (O(2)) in aerated (i.e., water-unsaturated) soils affects the metabolic activities of aerobic and anaerobic soil prokaryotes that degrade plant-derived saccharides. Fluctuating availabilities of O(2) were imposed on agricultural soil slurries supplemented with cellobiose. Slurries were subjected to oxic conditions (48 h), followed by an anoxic period (120 h) and a final oxic period (24 h). Redox potential was stable at 500 mV during oxic periods but decreased rapidly (within 10 h) under anoxic conditions to -330 mV. The consumption of cellobiose occurred without apparent delay at all redox potentials. The metabolic activities of seven previously identified saccharolytic family-level taxa of the investigated soil were measured with newly designed quantitative PCR assays targeting the 16S rRNA. Four taxa responded to the experimental conditions. The amounts of rRNAs of Micrococcaceae and Cellulomonadaceae (Actinobacteria) increased under oxic conditions. In contrast, the RNA contents of Clostridiaceae (cluster I, Firmicutes) and two uncultured family-level-taxa, i.e., "Cellu" and "Sphingo" (both Bacteroidetes) increased under anoxic conditions. That the degradation of cellobiose was independent of the availability of O(2) and that redox potentials decreased in response to anaerobic activities indicated that the degradation of cellobiose was linked to functionally redundant cellobiose-degrading taxa capable of altering redox conditions.     

Aerobic and anaerobic de-epoxydation of mycotoxin deoxynivalenol by bacteria originating from agricultural soil

One hundred and fifty soil samples collected from different crop fields in southern Ontario, Canada were screened to obtain microorganisms capable of transforming deoxynivalenol (DON) to de-epoxy DON (dE-DON). Microbial DON to dE-DON transformation (i.e. de-epoxydation) was monitored by using liquid chromatography-ultraviolet-mass spectrometry (LC-UV–MS). The effects of growth substrates, temperature, pH, incubation time and aerobic versus anaerobic conditions on the ability of the microbes to de-epoxydize DON were evaluated. A mixed microbial culture from one composite soil sample showed 100% DON to dE-DON biotransformation in mineral salts broth (MSB) after 144 h of incubation. Treatments of the culture with selective antibiotics followed an elevated temperature (50°C) for 1.5 h considerably reduced the microbial diversity. Partial 16S-rRNA gene sequence analysis of the bacteria in the enriched culture indicated the presence of at least six bacterial genera, namely Serratia, Clostridium, Citrobacter, Enterococcus, Stenotrophomonas and Streptomyces. The enriched culture completely de-epoxydized DON after 60 h of incubation. Bacterial de-epoxydation of DON occurred at pH 6.0–7.5, and a wide array of temperatures (12–40°C). The culture showed rapid de-epoxydation activity under aerobic conditions compared to anaerobic conditions. This is the first report on microbial DON to dE-DON transformation under aerobic conditions and moderate temperatures. The culture could be used to detoxify DON contaminated feed and might be a potential source for gene(s) for DON de-epoxydation.     

Earthworms and eco-consequences: Considerations to soil biological indicators and plant function: A review

Earthworms have been well reported to have a beneficial effect on soil microbes, soil microbial biomass (SMB), fungal community, soil structure, water retention and plant growth in different terrestrial ecosystems. However, the interactions between environmental stressors and various species of earthworms and the subsequent effect on soil microbes, organic matter, soil structure and plant growth are still uncertain. The purpose of this analysis was to test 1- the impact of environmental stressors on earthworm behaviour. 2- the effect of various earthworms on soil microbes, plant growth, soil structure and the carbon cycle. We noted that less fatal temperatures are generally unknown, but higher fatal temperatures range from 25 to 48 °C. Earthworms have a role to play, depending on the nature of organic residues, in both the formation and degradation of soil aggregates. Improvements in microbial biomass and plant growth have been established according to temperature, soil toxicity, soil type, earthworms abundance, organic residues types and field conditions. We observed that although the summer temperature in the arid area was approximately (°C 48), it was found that a particular type of earthworm (Namalycastis indica) was responsible for improving soil characteristics.While a great deal of analysis has been carried out on the role of earthworms within the soil ecology, such a review identifies important knowledge gaps, particularly in the determination of the impacts of earthworm species on the soil structure, microbial biomass and plant productivity, in particular since most papers focused on European species and overlooked the role of earthworms in the arid landscape. Further research is recommended to compare the impacts of different earthworms species on soil microbes and plant growth in various soil types, earthworm abundance, field conditions, organic residues locations, inorganic fertilizers, pesticides, fertile or non-fertile soils and diverse conditions of drought and moisture.     

N2O-producing microorganisms in the gut of the earthworm Aporrectodea caliginosa are indicative of ingested soil bacteria

The main objectives of this study were (i) to determine if gut wall-associated microorganisms are responsible for the capacity of earthworms to emit nitrous oxide (N(2)O) and (ii) to characterize the N(2)O-producing bacteria of the earthworm gut. The production of N(2)O in the gut of garden soil earthworms (Aporrectodea caliginosa) was mostly associated with the gut contents rather than the gut wall. Under anoxic conditions, nitrite and N(2)O were transient products when supplemental nitrate was reduced to N(2) by gut content homogenates. In contrast, nitrite and N(2)O were essentially not produced by nitrate-supplemented soil homogenates. The most probable numbers of fermentative anaerobes and microbes that used nitrate as a terminal electron acceptor were approximately 2 orders of magnitude higher in the earthworm gut than in the soil from which the earthworms originated. The fermentative anaerobes in the gut and soil displayed similar physiological functionalities. A total of 136 N(2)O-producing isolates that reduced either nitrate or nitrite were obtained from high serial dilutions of gut homogenates. Of the 25 representative N(2)O-producing isolates that were chosen for characterization, 22 isolates exhibited >99% 16S rRNA gene sequence similarity with their closest cultured relatives, which in most cases was a soil bacterium, most isolates were affiliated with the gamma subclass of the class Proteobacteria or with the gram-positive bacteria with low DNA G+C contents, and 5 isolates were denitrifiers and reduced nitrate to N(2)O or N(2). The initial N(2)O production rates of denitrifiers were 1 to 2 orders of magnitude greater than those of the nondenitrifying isolates. However, most nondenitrifying nitrate dissimilators produced nitrite and might therefore indirectly stimulate the production of N(2)O via nitrite-utilizing denitrifiers in the gut. The results of this study suggest that most of the N(2)O emitted by earthworms is due to the activation of ingested denitrifiers and other nitrate-dissimilating bacteria in the gut lumen.     

Isolation of facultatively aerobic actinomycetes from the gut, parent soil and mound materials of the termites Procubitermesaburiensis and Cubitermes severus

Abstract Isolates of the genus Streptomyces were readily obtained from the intestines of two African species of soil-feeding termites by an aerobic explant technique using starch casein medium, and from their parent soil and mound materials by dilution plating. Discriminant analysis of the isolates, based on 44 representative characters, showed that the population derived directly from the termites was significantly different from that of the feed soil or the mound. The termite gut was considered to be a good source of unusual actinomycetes, but strains isolated under aerobic conditions are likely to be allochthons selected by the intestinal environment, which is highly alkaline and anaerobic. An anaerobic, filamentous isolate was obtained which may be a component of the prokaryotic symbiont population mediating termite digestion.     

4种蚯蚓肠道微生物对砷毒性的响应差异研究

蚯蚓肠道是微生物多样性的一个潜在存储库。砷对蚯蚓肠道微生物群落的影响已被证实,但砷在不同蚯蚓肠道菌群中生物转化的差异仍不清楚。为了进一步阐述土壤中广泛存在的低浓度砷(浓度为5,15,25 mg/kg)对不同种类蚯蚓肠道微生物影响的差异,将4种典型蚯蚓暴露于砷污染土壤后,测定其肠道微生物组成变化,并分析砷对不同蚯蚓肠道内砷富集、形态和砷生物转化基因的影响。结果显示,所有蚯蚓组织内均存在明显的砷富集,其富集系数由高到低依次为:安德爱胜蚓(1.93)>加州腔蚓(0.80)>通俗腔蚓(0.78)>湖北远盲蚓(0.52),蚯蚓组织和肠道内砷形态主要以无机砷为主,其中As(III)含量比例> 80%,部分蚯蚓组织内还发现少量有机砷。4种蚯蚓肠道微生物群落在门水平上主要以变形菌、厚壁菌和放线菌为主,并与周围土壤细菌群落组成存在显著差异。同时,在土壤和肠道内共检测到17个砷转化基因,其中蚯蚓肠道内As(V)还原和砷转运相关基因相对丰度较高,而砷(去)甲基化基因丰度较低。此外,低浓度砷污染对蚯蚓生长无显著影响,却能引起蚯蚓肠道微生物群落的紊乱。蚯蚓种类和砷污染是引起蚯蚓肠道微生物...     

Effects of Environmental Parameters on the Formation and Turnover of Acetate by Forest Soils

The capacity to form acetate from endogenous matter was a common property of diverse forest soils when incubated under anaerobic conditions. At 15 to 20(deg)C, acetate synthesis occurred without appreciable delay when forest soils were incubated as buffered suspensions or in microcosms at various percentages of their maximum water holding capacity. Rates for acetate formation with soil suspensions ranged from 35 to 220 (mu)g of acetate per g (dry weight) of soil per 24 h, and maximal acetate concentrations obtained in soil suspensions were two- to threefold greater than those obtained with soil microcosms at the average water holding capacity of the soil. Cellobiose degradation in soil suspensions yielded H(inf2) as a transient product. Under anaerobic conditions, supplemental H(inf2) and CO(inf2) were directed towards the acetogenic synthesis of acetate, and enrichments yielded a syringate-H(inf2)-consuming acetogenic consortium. At in situ temperatures, acetate was a relatively stable anaerobic end product; however, extended incubation periods induced acetoclastic methanogenesis and sulfate reduction. Higher mesophilic and thermophilic temperatures greatly enhanced the capacity of soils to form methane. Although methanogenic and sulfate-reducing activities under in situ-relevant conditions were negligible, these findings nonetheless demonstrated the occurrence of methanogens and sulfate-reducing bacteria in these aerated terrestrial soils. In contrast to the protracted stability of acetate under anaerobic conditions at 15 to 20(deg)C with unsupplemented soils, acetate formed by forest soils was rapidly consumed in the presence of oxygen and nitrate, and substrate-product stoichiometries indicated that acetate turnover was coupled to oxygen-dependent respiration and denitrification. The collective results suggest that acetate formed under anaerobic conditions might constitute a trophic link between anaerobic and aerobic processes in forest soils.     

Bioremediation of soils contaminated with the herbicide 2-sec-butyl-4,6-dinitrophenol (dinoseb).

A novel soil treatment method for achieving the removal of dinoseb (2-sec-butyl-4,6-dinitrophenol) from contaminated soils was investigated. One soil contained dinoseb as the major contaminant, although several other hazardous compounds were also present. A second soil was highly contaminated with dinoseb. Dinoseb was not degraded in these soils under the aerobic conditions at each site. Pretreatment of the soils by the addition of a starchy potato-processing by-product and flooding with phosphate buffer stimulated the consumption of oxygen and nitrate from the soils, thereby lowering the redox potential and creating anaerobic conditions. Anaerobiosis (Eh less than -200 mV) promoted the establishment of an anaerobic microbial consortium that degraded dinoseb completely, without the formation of the polymerization products seen under aerobic or microaerophilic conditions. When dinoseb was present at low concentrations in a chronically contaminated soil, the natural microflora was capable of establishing anaerobic conditions and degrading dinoseb as a result of starch degradation. Inoculation of this soil with an aerobic starch-degrading microorganism and then an acclimated, anaerobic, dinoseb-degrading consortium did not improve dinoseb degradation. In a second acutely contaminated soil, these inoculations improved dinoseb degradation rates over those of uninoculated controls.     

Bioremediation of soils contaminated with the herbicide 2-sec-butyl-4,6-dinitrophenol (dinoseb).

A novel soil treatment method for achieving the removal of dinoseb (2-sec-butyl-4,6-dinitrophenol) from contaminated soils was investigated. One soil contained dinoseb as the major contaminant, although several other hazardous compounds were also present. A second soil was highly contaminated with dinoseb. Dinoseb was not degraded in these soils under the aerobic conditions at each site. Pretreatment of the soils by the addition of a starchy potato-processing by-product and flooding with phosphate buffer stimulated the consumption of oxygen and nitrate from the soils, thereby lowering the redox potential and creating anaerobic conditions. Anaerobiosis (Eh less than -200 mV) promoted the establishment of an anaerobic microbial consortium that degraded dinoseb completely, without the formation of the polymerization products seen under aerobic or microaerophilic conditions. When dinoseb was present at low concentrations in a chronically contaminated soil, the natural microflora was capable of establishing anaerobic conditions and degrading dinoseb as a result of starch degradation. Inoculation of this soil with an aerobic starch-degrading microorganism and then an acclimated, anaerobic, dinoseb-degrading consortium did not improve dinoseb degradation. In a second acutely contaminated soil, these inoculations improved dinoseb degradation rates over those of uninoculated controls.     

Bioremediation and phytoremediation of total petroleum hydrocarbons (TPH) under various conditions

Remediation of contaminated soils is often studied using fine-textured soils rather than low-fertility sandy soils, and few studies focus on recontamination events. This study compared aerobic and anaerobic treatments for remediation of freshly introduced used motor oil on a sandy soil previously phytoremediated and bioacclimated (microorganisms already adapted in the soil environment) with some residual total petroleum hydrocarbon (TPH) contamination. Vegetated and unvegetated conditions to remediate anthropogenic fill containing residual TPH that was spiked with nonaqueous phase liquids (NAPLs) were evaluated in a 90-day greenhouse pot study. Vegetated treatments used switchgrass (Panicum virgatum). The concentration of aerobic bacteria were orders of magnitude higher in vegetated treatments compared to unvegetated. Nevertheless, final TPH concentrations were low in all saturated soil treatments, and high in the presence of switchgrass. Concentrations were also low in unvegetated pots with fertilizer. Acclimated indigenous microbial communities were shown to be more effective in breaking down hydrocarbons than introducing microbes from the addition of plant treatments in sandy soils. Remediation of fresh introduced NAPLs on pre-phytoremediated and bioacclimated soil was most efficient in saturated, anaerobic environments, probably due to the already pre-established microbial associations, easily bioavailable contaminants, and optimized soil conditions for microbial establishment and survival.     

Biotransformation of PCBs in Contaminated Sludge: Potential for Novel Biological Technologies

In this study, the biological transformation of polychlorinated biphenyls (PCBs) was investigated in sludge from the Ralston Street Lagoon (RSL), a United States Environmental Protection Agency (USEPA) designated Toxic Substances Control Act (TSCA) site, in Gary, IN. A biological tilled soil reactor (BTSR) operating under cycling anaerobic‐aerobic conditions and vermicomposting bioreactors (VBs) inoculated with Eisenia foetida earthworms were both systematically investigated. Sludge heavily contaminated with PCBs (> 500 ppm PCB as Aroclor 1248) was loaded into the BTSRs and amended sequentially with PCB‐dechlorinating anaerobic sediments and then aerobic PCB biodegrading microbes. The VBs were loaded with sludge mixed in varying ratios with sterile soil and then inoculated with earthworms. Bioreactors were monitored for the duration of the studies (ranging from four to nine months) and samples were regularly removed, extracted and analyzed for PCB congener content. Appropriate biotic and negative abiotic controls were maintained under the various conditions to quantify and measure the biological transformation of the PCB's. All samples were analyzed for PCB congener concentrations by Soxhlet extraction followed by gas chromatography with electron capture detection (ECD). In the BTSRs loaded initially with 500 ppm of PCBs, a 75 % reduction of total PCB was obtained while the BTSR loaded with 140 ppm PCBs revealed only a 25 % reduction in total PCB level. Sample analyses from the VBs demonstrated total PCB reductions ranging from 55 to 66 %, although worm‐free control reactors showed PCB attenuations from 48 to 68 %. Analysis of earthworms showed an increase in PCB levels in the earthworm biomass, with concentrations reaching as high as 313 ppm. Mass balance analysis of the VB results demonstrated that most of the PCBs were bioaccumulated, although some PCB elimination was demonstrated. The results from both the anaerobic‐aerobic cycling BTSR and VB investigations demonstrate potential for application for site clean‐up and possible bioremediation of the Ralston Street Lagoon sludge.     

Role of Microorganisms in the Consumption and Production of Atmospheric Carbon Monoxide by Soil

Consumption and production of atmospheric CO was measured under field conditions in three different types of soil. CO was consumed by an apparent first-order reaction and produced by an apparent zero-order reaction, resulting in a dynamic equilibrium with the consumption of atmospheric CO as the net reaction. CO consumption was higher in summer than in winter. Laboratory experiments on five different soil types showed that CO consumption was strongly inhibited by the presence of streptomycin or cycloheximide (Actidione), or both. Thus, eucaryotic as well as procaryotic microorganisms were apparently responsible for the observed CO consumption. The aerobic carboxydobacterium Pseudomonas carboxydovorans added to sterile soil was able to utilize the low amounts (ca. 0.7 ppmv) of CO present in laboratory air. CO was consumed by soil under aerobic as well as anaerobic conditions. Anaerobic preincubation of the soil stimulated the anaerobic CO consumption and reduced the aerobic CO consumption. In contrast to CO consumption, CO production was stimulated by autoclaving, by ultraviolet-irradiation, by fumigation with NH₃ or CHCl₃, by treatment with streptomycin or cycloheximide or both, by addition of NaCN, NaN₃, or Na₂HAsO₄ (or all three) in the presence of glucose under an atmosphere of pure oxygen, or by a drying and rewetting procedure. The consumption of atmospheric CO by soil is a microbial process, but the production of CO is apparently not a metabolic process.     

Release and bioavailability of dissolved organic matter from floodplain litter: influence of origin and oxygen levels

1. We determined the rate of release and microbial uptake of dissolved organic carbon (DOC) leached from three components (leaves, bark and twigs) of river red gum ( Eucalyptus camaldulensis ) forest litter originating from different parts of a floodplain and under different oxygen levels.
2. Preliminary experiments showed that substantially more DOC was released from leaves than from bark or twigs; there was relatively little DOC release from coarse particulate matter or soil.
3. Both the amount of DOC released from each litter component and the amount metabolized by the microbial community were independent of position on the flood-plain or amount of oxygen available to microbes.
4. Although the bioavailability of DOC was independent of oxygen concentration, the microbial utilization of DOC under aerobic and anaerobic conditions differed. Under aerobic conditions, leaves were colonized by fungi, while bacteria were dominant under anoxic conditions.
5. Phospholipid fatty acid profiles of the microbial communities growing on leaf extracts showed that different microbial communities developed in each oxygen concentration treatment suggesting that, irrespective of flood conditions, a microbial community will develop to utilize a significant proportion of the DOC leached from litter.     

Epigeic earthworms exert a bottleneck effect on microbial communities through gut associated processes

Background

Earthworms play a critical role in organic matter decomposition because of the interactions they establish with microorganisms. The ingestion, digestion, assimilation of organic material in the gut and then casting is the first step in earthworm-microorganism interactions. The current knowledge of these direct effects is still limited for epigeic earthworm species, mainly those living in man-made environments. Here we tested whether and to what extent the earthworm Eisenia andrei is capable of altering the microbiological properties of fresh organic matter through gut associated processes; and if these direct effects are related to the earthworm diet.

Methodology

To address these questions we determined the microbial community structure (phospholipid fatty acid profiles) and microbial activity (fluorescein diacetate hydrolysis) in the earthworm casts derived from three types of animal manure (cow, horse and pig manure), which differed in microbial composition.

Principal Findings

The passage of the organic material through the gut of E. andrei reduced the total microbial biomass irrespective of the type of manure, and resulted in a decrease in bacterial biomass in all the manures; whilst leaving the fungi unaffected in the egested materials. However, unlike the microbial biomass, no such reduction was detected in the total microbial activity of cast samples derived from the pig manure. Moreover, no differences were found between cast samples derived from the different types of manure with regards to microbial community structure, which provides strong evidence for a bottleneck effect of worm digestion on microbial populations of the original material consumed.

Conclusions/Significance

Our data reveal that earthworm gut is a major shaper of microbial communities, thereby favouring the existence of a reduced but more active microbial population in the egested materials, which is of great importance to understand how biotic interactions within the decomposer food web influence on nutrient cycling.     

Bacteria isolated from the duodenum, ileum, and cecum of young chicks.

Facultatively anaerobic and strictly anaerobic bacteria colonizing the intestinal tracts of 14-day-old chicks fed a corn-based diet were enumerated, isolated, and identified. Colony counts from anaerobic roll tubes (rumen fluid medium) or aerobic plates (brain heart infusion agar) recovered from homogenates of the duodenum, upper and lower ileum, and cecum varied appreciably among samples from individual birds. Anaerobic and aerobic counts from the duodenum and ileum were similar. Anaerobic counts were highest from the cecum (0.7 X 10(11) to 1.6 X 10(11)/g of dry tissue) and exceeded aerobic plate counts by a factor of at least 10(2). Facultatively anaerobic groups (Streptococcus, Staphylococcus, Lactobacillus, and Escherichia coli) comprised the predominant flora of the duodenum and ileum, although large numbers of anaerobes (9 to 39% of the small intestine isolates), represented by species of Eubacterium, Propionibacterium, Clostridium, Gemmiger, and Fusobacterium, were also recovered. Strict anaerobes (anaerobic gram-positive cocci, Eubacterium, Clostridium Gemmiger, Fusobacterium, and Bacteriodes) made up nearly the entire microbial population of the cecum. Scanning electron microscopy of the intestinal epithelia of chicks revealed populations of microbes on the duodenal, ileal, and cecal mucosal surfaces.     

The role of carbon dioxide in the metabolism of adult Haemonchus contortus, in vitro

Adult Haemonchus contortus worms simultaneously excrete and fix CO2. Their initial content of CO2 was measured as 4.55 mumoles/100 mg wet weight and their excretion rate in air as 1 mumol/100 mg wet weight/h for at least 4 h. When the worms were incubated either aerobically or anaerobically with 14CO2 most of the metabolized radioactivity was associated with propan-1-ol and propionate but small amounts were found in succinate and lactate. No radioactivity was associated with ethanol or acetate, two major catabolites of glucose. Stepwise degradation of the metabolized radioactive propanol and propionate showed that all the radioactivity in both compounds was associated with carbon atom no. 1. These results show that H. contortus has much in common with the anaerobic energy metabolism of Ascaris lumbricoides but they are not inconsistent with the utilization of the tricarboxylic acid cycle by the worm. H. contortus worms were found to metabolize their excretory products. When they were incubated with either [2,3-14C]succinate or [2-14C]acetate, 14CO2 was excreted under aerobic but not under anaerobic conditions. These results are consistent with a pathway similar to that used by Ascaris operating aloneunder anaerobic conditions and together with the tricarboxylic acid cycle under aerobic conditions.