THE ROLE OF ANAEROBIOSIS IN ASYMBIOTIC NITROGEN FIXATION
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Abstract:
Microbial fixation of atmospheric nitrogen was measured in soil amended with ground wheat straw and incubated at two moisture levels (field capacity and waterlogged). Fixation equivalent to 42–52 kg/ha in the soil at field capacity and 13–150 kg/ha in the waterlogged soil was observed using 15 N techniques when the soil was amended with 1% straw or less. Using both 15 N and Kjeldahl techniques, high rates of fixation (500–1000 kg/ha) were measured in soils amended with 5–20% straw and incubated under waterlogged conditions.The high levels of nitrogen fixation in this study can be attributed to a combination of (a) aerobic conditions required to break down the plant residues and (b) anaerobic sites which are essential for significant fixation rates. The Clostridia are strongly implicated in this process in nature. Upon incubation in the laboratory, the nitrogen-fixing clostridia increased 1000-fold in the water-saturated soil and 100-fold in the field capacity soil. These organisms were also active in field soils throughout the growing season. Identification studies indicated that these organisms were primarily Clostridium butyricum.Keywords:
Clostridia
Clostridium butyricum
Nitrogen Cycle
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A selective medium, Clostridium butyricum isolation medium (BIM), is described for the isolation of C. butyricum from human feces. The BIM is a synthetic minimal medium and contains trimethoprim (16 micrograms/ml), D-cycloserine (10 micrograms/ml), and polymyxin B sulfate (20 micrograms/ml) as selective inhibitory agents. Qualitative tests indicated that C. butyricum and other butyric acid-producing clostridia grew on BIM, Clostridium sphenoides and Bacillus cereus produced small colonies, and other clostridia and other obligate anaerobic or facultatively anerobic bacteria were inhibited. Quantitative recovery of C. butyricum from cultures or seeded fecal samples was comparable with BIM and with complex medium, but the quantitative recovery of the other butyric acid-producing clostridia tested (C. beijerinckii, C. acetobutylicum) was lower with BIM than with complex medium. The BIM should aid the rapid isolation of C. butyricum from fecal samples and should be useful for bacteriological investigation of neonatal necrotizing enterocolitis.
Clostridium butyricum
Clostridia
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Obligate anaerobe
Clostridium beijerinckii
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Clostridia
Clostridium butyricum
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Eight strains of clostridia of the butyricum group, resistant to penicillins were isolated from perinatal infections. MIC's of these strains vary from 1,000 to 3,000 micrograms/ml for benzyl-penicillin, and from 5 to 10 micrograms/ml for cefoxitin. The substrate profile of the enzymes is that of a penicillinase.
Clostridium butyricum
Clostridia
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Clostridium butyricum
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Summary Intravenous injections of suspensions of spores of Cl. butyricum (Strain M-55) produced a more or less extensive lysis of tumor tissue. A number of other strains of nonpathogenic clostridia did not show substantially improved results. In genreal, strains which were able to ferment carbohydrate performed equally well, whereas primarily proteolytic strains gave inferior results. Combination of Strain M-55 with Cl. felsineum , as well as a combination of Strain M-55 with culture filtrates of Cl. paraputrificum , did not yield improved results. All growth phases of Cl. butyricum could at least in principle produce the phenomenon of oncolysis, but the results were most unfavorable if vegetative forms were used. To some extent an enhancement of oncolysis could be obtained by a combination of spores with certain tumor extracts.
Clostridia
Clostridium butyricum
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Clostridium butyricum
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Microbial strains produce numerous volatile substances in the anaerobic conditions of the human intestines. The availability of CO(2) is known to be a prerequisite for bacterial growth in general. In experiments with anaerobic Lactobacillus brevis and Clostridium butyricum bacteria in the Portable Microbial Enrichment Unit (PMEU) it was shown that these strains interact; this interaction being mediated by CO(2) emission. CO(2) promoted clostridial growth in pure cultures and mixed cultures with lactobacilli. The growth of C. butyricum in pure cultures was much delayed or did not start at all without CO(2) from outside. Conversely, the onset of growth was provoked by a short (15 min) CO(2) burst. In mixed cultures the presence of lactobacilli in equal numbers speeded up the onset of clostridial growth by 10 h. If C. butyricum cultures designated as PMEU 1, 2, and 3 in cultivation syringes were chained by connecting the gas flow thereby allowing the volatiles of the preceding syringe culture to bubble to the next one, the growth started in 20, 10, or 6 h, respectively. This effect of gaseous emissions from other cultures speeding up the bacterial growth initiation was abolished if the gas was passed through sodium hydroxide to remove the CO(2). The positive contribution of lactobacilli to the growth of butyric-acid-producing clostridia documented in this simulation experiment with PMEU has in vivo implications and indicates molecular communication between the species. CO(2) is a necessary signal for the growth of clostridia, and lactobacilli can promote clostridial growth in mixed cultures where both bacteria grow well with mutual benefit.
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