Annamaria Ferrari

Isolation and characterization ofMethanobrevibacter oralis sp. nov.

A new coccobacillary, nonmotile, Gram-positive, methane-producing organism was isolated from human subgingival plaque. Both hydrogen and carbon dioxide were required for growth. No methane was produced from acetate, formate, or methanol. The optimum pH was 6.9–7.4, and the optimum temperature was 36–38°C. Fecal extract was required for growth, and a volatile fatty acid mixture was highly stimulatory. The DNA G+C content was 28 mol%. On the basis of these characteristics, DNA-DNA hybridization studies, and electrophoretic analysis of cellular proteins, the isolate was considered a new species and namedMethanobrevibacter oralis.

Inactivation of fecal bacteria in sewage sludge by alkaline treatment

The efficacy of aqueous alkaline solutions to purify wastewater sludges destined for agricultural land application was evaluated. Some fecal bacteria were tested as sanitary-quality indices, these included fecal streptococci, which were found to be more resistant than coliforms. Hygienization within 10 days was obtained with ammonium hydrate at a dose that brought the pH of the sludge to about 10. Such a treatment was effective above 10°C. The total-bacteria number dropped only slightly, so that the sludge retained its potential biological activity. The efficacy of the treatment with NH4OH was better than that observed with KOH.

Plant quality and soil residual fertility six years after a compost treatment

Abstract The final results of a 6-year pot experiment on the organic fertilization of sunflower crops using compost prepared from vegetable and animal wastes are reported. Comparisons were made of the plant quality and residual fertility of different soil-fertilizer-compost mixtures ranging from untreated soil (no fertilizer or compost additions) to a 5% soil-95% compost mixture. Crop yields, together with the percentage dry matter, protein, and lipids in the seeds were taken as a measure of plant quality, whereas residual fertility was indicated by the microbial and plant nutrient content of the soil-fertilizer-compost mixtures. After 6 years of cropping with no additional mineral or organic fertilization, improvements in crop yields were still apparent in the mixtures with the highest compost contents. The improved crop production was related to the persistence of improved conditions of residual fertility. It is concluded that the use of compost can lead to improved soil fertility, even after several years, which in turn results in a quantitative improvement in crop yield and product quality.

Methanogens in the human intestinal tract and oral cavity

The incidence and concentration of methanobacteria in the human intestinal tract have not been well evaluated. Only recently were such microorganisms found in the oral cavity. We determined the counts of methanogens in the feces of healthy subjects on a Mediterranean diet and evaluated whether individuals with methanobacteria in the intestine also harbor such bacteria in the oral cavity. Methanobacteria were observed in the feces of 18 of the 20 subjects, at a level ranging from 103 to 1010/g dry wt. Only 45% of the subjects harbored methanobacteria in the plaque and saliva, showing that the presence of methanogens in the oral cavity was not correlated with their presence in the feces. The presence and number of methanobacteria appeared to remain constant after 3 months. A short rod arranged in chains, similar to theMethanobrevibacter smithii which predominates in feces, was the methanogenic form present in the mouth.

Enzymatic synthesis of 12-ketoursodeoxycholic acid from dehydrocholic acid in a membrane reactor

SummaryDehydrocholic acid (3,7,12-trioxo-5β-cholanic acid) (0.5% concentration) was completely and selectively reduced to 12-ketoursodeoxycholic acid (3α, 7β-dihydroxy-12-oxo- 5β-cholanic acid) in a membrane reactor by means of 3α-hydroxysteroid dehydrogenase and 7β-hydroxysteroid dehydrogenase. Coenzyme regeneration was carried out with the glucose-glucose dehydrogenase system.

Influence of long-term feeding of different purified dietary fibers on the volatile fatty acid (VFA) profile, pH and fiber-degrading activity of the cecal contents in rats

Abstract The aim of this study was to investigate the effect of four weeks ingestion of 10% fiber diets (cellulose, lignocellulose, pectin or guar gum) and fiber free diets on volatile fatty acid (VFA) concentration, pH, and in vitro fiber-degrading activity of the cecal contents of female Sprague Dawley rats. The pH was significantly lower (p

Prevalence of oxygen-intolerant microorganisms in primary bile acid 7α-dehydroxylating mouse intestinal microflora

The in vitro 7α-dehydroxylation of cholic and chenodeoxycholic acids by mixed cultures of mouse cecal microorganisms was studied. Conventional anaerobic techniques and rigorous oxygen-free anaerobic experimental conditions were compared. It was found that the total number of anaerobic oxygen-intolerant microorganisms was about 10 times higher than that of anaerobic microorganisms that tolerate oxygen. Among the anaerobic 7α-dehydroxylating microorganisms, the oxygen-intolerant ones are about 1,000 to 10,000 times more numerous than the oxygen-tolerant ones. It can be concluded that the 7α-dehydroxylating activity is more common among oxygenintolerant than oxygen-tolerant anaerobic microorganisms.

Influence of the herbicide bentazon on soil microbial community.

Changes in microbial numbers and activities in a soil in response to bentazon applied at 10 and 100 ppm were studied after 4 and 30 weeks of incubation in laboratory conditions. As regards the eight general and functional microbial groups studied (aerobic and anaerobic bacteria, fungi, aerobic and anaerobic N2-fixing bacteria, nitrifiers, aerobic and anaerobic cellulolytic microorganisms), only the number of anaerobic N2-fixing bacteria significantly decreased, in the presence of the highest herbicide concentration for 30 weeks. At both the incubation times, only the higher dose of bentazon markedly inhibited soil nitrification and CO2 emission. Methanogenesis was inhibited by 1000 ppm bentazon added to anaerobic liquid cultures containing 5% soil for at least 2 weeks. There was an incomplete recovery of the herbicide at the two incubation times: < 5% of 10 ppm after 4 weeks and about 30% of 100 ppm after 30 weeks. No biodegradation of the compound was observed in liquid cultures under aerobic or anaerobic conditions. It is concluded that a bentazon concentration no higher than the field rate distributed within a 2-cm layer of soil does not considerably affect the microflora even in the absence of microbial degradation.

Quantitative determination of methanogenic bacteria in the feces of different mammals

In this research on fresh human, cattle, swine, and rabbit feces, methanogenic bacteria were found in all samples examined, at the following concentrations per gram dry weight: swine, 108; human, 107; cattle, 106; and rabbit, 104. Anaerobic heterotrophic bacteria were found in the following concentrations per gram dry weight: human, 1011; swine, 1011; cattle, 1011; and rabbit, 1010. The total number of O2-intolerant was higher than that of O2-tolerant bacteria: about 10–100 times for methanogenic and 100–1000 times for anaerobic heterotrophic bacteria.

Oxygen tolerance of anaerobic bacteria isolated from human feces

The large bowel intestinal flora of mammals is made up mostly of O2-intolerant anaerobic microorganisms which are irreversibly damaged by brief exposure to air. The aim of our work was to investigate the effect of atmospheric O2 on human intestinal anaerobic microorganisms. Thirty O2-intolerant bacterial strains that reached 100% mortality after 120 min of air exposure were isolated. Ten of these strains were tested for their atmospheric O2 sensitivity as a function of air exposure time; all tested microorganisms showed a similar mortality trend on exposure to air. In fact, 50% of cells survive, on the average, after 4–5 min of atmospheric O2; this percentage decreases to 3–5% after only 20 min, and after 40 min only one cell in a thousand survives; all strains reached 100% mortality in a time range of 100–120 min. The strains examined were identified as belonging to the generaEubacterium, Peptostreptococcus, andCoprococcus.