Enrichment and isolation of a nitropropanol-metabolizing bacterium from the rumen

Anderson, Robin C.; Rasmussen, Mark A.; Allison, Milton J.

doi:10.1128/aem.62.10.3885-3886.1996

Cited by 34 publications

(13 citation statements)

References 18 publications

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“…Assuming that each micromole of NPA or NPOH reduced consumes six electrons or the equivalent of 3 μmol of hydrogen, based on stoichiometric estimates for the reduction of nitroethane by a Clostridium pasteurianum hydrogenase/ferredoxin system ( 50 ), the NPA and NPOH metabolized in this study would have consumed at most only 4.2 and 7.8 μmol hydrogen equivalents/mL, respectively. The lesser amounts of NPA and NPOH metabolized within the mixed cultures incubated with NPA- and NPOH-containing milkvetch incubations in experiment 1, which were not inoculated with D. detoxificans is not surprising, considering that D. detoxificans is usually present at low concentrations (<10 4 cells/mL) in rumen populations having no prior nitrocompound exposure ( 51 ). Based on these considerations, the more potent methane-inhibiting effect observed in the mixed cultures inoculated with D. detoxificans and incubated with the NPOH-containing milkvetch cannot be explained solely by competitive consumption of reducing substrates for the reduction of NPOH.…”

Section: Discussionmentioning

confidence: 99%

Ruminal Fermentation of Anti-Methanogenic Nitrate- and Nitro-Containing Forages In Vitro

et al. 2016

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Nitrate, 3-nitro-1-propionic acid (NPA) and 3-nitro-1-propanol (NPOH) can accumulate in forages and be poisonous to animals if consumed in high enough amounts. These chemicals are also recognized as potent anti-methanogenic compounds, but plants naturally containing these chemicals have been studied little in this regard. Presently, we found that nitrate-, NPA-, or NPOH-containing forages effectively decreased methane production, by 35–87%, during in vitro fermentation by mixed cultures of ruminal microbes compared to fermentation by cultures incubated similarly with alfalfa. Methane production was further decreased during the incubation of mixed cultures also inoculated with Denitrobacterium detoxificans, a ruminal bacterium known to metabolize nitrate, NPA, and NPOH. Inhibition of methanogens within the mixed cultures was greatest with the NPA- and NPOH-containing forages. Hydrogen accumulated in all the mixed cultures incubated with forages containing nitrate, NPA or NPOH and was dramatically higher, exceeding 40 μmol hydrogen/mL, in mixed cultures incubated with NPA-containing forage but not inoculated with D. detoxificans. This possibly reflects the inhibition of hydrogenase-catalyzed uptake of hydrogen produced via conversion of 50 μmol added formate per milliliter to hydrogen. Accumulations of volatile fatty acids revealed compensatory changes in fermentation in mixed cultures incubated with the nitrate-, NPA-, and NPOH-containing forages as evidenced by lower accumulations of acetate, and in some cases, higher accumulations of butyrate and lower accumulations of ammonia, iso-buytrate, and iso-valerate compared to cultures incubated with alfalfa. Results reveal that nitrate, NPA, and NPOH that accumulate naturally in forages can be made available within ruminal incubations to inhibit methanogenesis. Further research is warranted to determine if diets can be formulated with nitrate-, NPA-, and NPOH-containing forages to achieve efficacious mitigation in ruminant methane emissions without adversely affecting fermentative efficiency or risking toxicity to animals.

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Section: Discussionmentioning

confidence: 99%

Ruminal Fermentation of Anti-Methanogenic Nitrate- and Nitro-Containing Forages In Vitro

et al. 2016

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“…Presently, the ruminal bacterium Denitrobacterium detoxificans is the only known anaerobe to exhibit appreciable nitroalkane-reducing activity (Anderson et al, 1996 , 1997 , 2000 ). This bacterium conserves energy for growth exclusively via anaerobic respiration, oxidizing hydrogen, formate or lactate in the reduction of nitrate to ammonia and the reduction of 3-nitro-1-propionic acid, 3-nitro-1-propanol, and nitroethane to β-alanine, 3-amino-1-propanol and aminoethane, respectively (Anderson et al, 1993 , 1997 , 2000 ).…”

Section: Nitrocompound Metabolism Within the Rumenmentioning

confidence: 99%

Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds

Latham

Anderson

Pinchak³

et al. 2016

Front. Microbiol.

107

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Nitrate and certain short chain nitrocompounds and nitro-oxy compounds are being investigated as dietary supplements to reduce economic and environmental costs associated with ruminal methane emissions. Thermodynamically, nitrate is a preferred electron acceptor in the rumen that consumes electrons at the expense of methanogenesis during dissimilatory reduction to an intermediate, nitrite, which is primarily reduced to ammonia although small quantities of nitrous oxide may also be produced. Short chain nitrocompounds act as direct inhibitors of methanogenic bacteria although certain of these compounds may also consume electrons at the expense of methanogenesis and are effective inhibitors of important foodborne pathogens. Microbial and nutritional consequences of incorporating nitrate into ruminant diets typically results in increased acetate production. Unlike most other methane-inhibiting supplements, nitrate decreases or has no effect on propionate production. The type of nitrate salt added influences rates of nitrate reduction, rates of nitrite accumulation and efficacy of methane reduction, with sodium and potassium salts being more potent than calcium nitrate salts. Digestive consequences of adding nitrocompounds to ruminant diets are more variable and may in some cases increase propionate production. Concerns about the toxicity of nitrate's intermediate product, nitrite, to ruminants necessitate management, as animal poisoning may occur via methemoglobinemia. Certain of the naturally occurring nitrocompounds, such as 3-nitro-1-propionate or 3-nitro-1-propanol also cause poisoning but via inhibition of succinate dehydrogenase. Typical risk management procedures to avoid nitrite toxicity involve gradually adapting the animals to higher concentrations of nitrate and nitrite, which could possibly be used with the nitrocompounds as well. A number of organisms responsible for nitrate metabolism in the rumen have been characterized. To date a single rumen bacterium is identified as contributing appreciably to nitrocompound metabolism. Appropriate doses of the nitrocompounds and nitrate, singly or in combination with probiotic bacteria selected for nitrite and nitrocompound detoxification activity promise to alleviate risks of toxicity. Further studies are needed to more clearly define benefits and risk of these technologies to make them saleable for livestock producers.

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“…Majak and Cheng [18] in an earlier study with both pure and mixed cultures confirmed that some rumen bacteria were indeed capable of anerobic degradation of naturally occurring 3-nitropropanol or 3-nitropropionic acid, and the ability to degrade these nitrocompounds and the rate at which they were degraded depended essentially on the particular strains of rumen bacteria (e.g., Megasphaera elsdenii, Selenomonas ruminantium). In subsequent studies, a new bacterium capable of metabolizing the naturally occurring nitrotoxins, 3-nitro-1-propanol and 3-nitro-1-propionate, was isolated from a ruminal population enriched for enhanced rates of nitrotoxin metabolism [19] and was accommodated as Denitrobacterium detoxificans, a new genus and species capable of degrading nitrocompounds into nitrite and then ammonia [20,21]. Although the present study was done with mixed cultures instead of pure culture, rumen microbes should have more or less similar degradation or metabolic action to NE, NEOH, and NPOH, like the 3-nitro-1-propanol and 3-nitro-1-propionate noted in the aforementioned studies.…”

Section: Nitrocompounds' Degradation and Metabolic Fatementioning

confidence: 99%

The Antimethanogenic Nitrocompounds Can be Cleaved into Nitrite by Rumen Microorganisms: A Comparison of Nitroethane, 2-Nitroethanol, and 2-Nitro-1-propanol

Zhang

Wang

et al. 2019

Metabolites

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A class of aliphatic short chain nitrocompounds have been reported as being capable of CH4 reduction both in vitro and in vivo. However, the laboratory evidence associated with the metabolic fate of nitrocompounds in the rumen has not been well documented. The present study was conducted to compare in vitro degradation and metabolism of nitroethane (NE), 2-nitroethanol (NEOH), and 2-nitro-1-propanol (NPOH) incubated with mixed rumen microorganisms of dairy cows. After 10 mM supplementation of nitrocompounds, a serious of batch cultures were carried out for 120 h under the presence of two substrates differing in the ratio of maize meal to alfalfa hay (HF, 1:4; LF, 4:1). Compared to the control, methane production was reduced by 59% in NPOH and by >97% in both NE and NEOH, and such antimethanogenic effects were more pronounced in the LF than the HF group. Although NE, NEOH, and NPOH addition did not alter total VFA production, the rumen fermentation pattern shifted toward increasing propionate and butyrate and decreasing acetate production. The kinetic disappearance of each nitrocompound was well fitted to the one-compartment model, and the disappearance rate (k, %/h) of NE was 2.6 to 5.2 times greater than those of NEOH and NPOH. Higher intermediates of nitrite occurred in NEOH in comparison with NPOH and NE while ammonia N production was lowest in NEOH. Consequently, a stepwise accumulation of bacterial crude protein (BCP) in response to the nitrocompound addition was observed in both the HF and LF group. In brief, both NE and NEOH in comparison with NPOH presented greater antimethanogenic activity via the shift of rumen fermentation. In addition, the present study provided the first direct evidence that rumen microbes were able to cleave these nitrocompounds into nitrite, and the subsequent metabolism of nitrite into ammonia N may enhance the growth of rumen microbes or promote microbial activities.

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Enrichment and isolation of a nitropropanol-metabolizing bacterium from the rumen

Cited by 34 publications

References 18 publications

Ruminal Fermentation of Anti-Methanogenic Nitrate- and Nitro-Containing Forages In Vitro

Ruminal Fermentation of Anti-Methanogenic Nitrate- and Nitro-Containing Forages In Vitro

Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds

The Antimethanogenic Nitrocompounds Can be Cleaved into Nitrite by Rumen Microorganisms: A Comparison of Nitroethane, 2-Nitroethanol, and 2-Nitro-1-propanol

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