Microbial H2/CO2 acetogenesis in animal guts: nature and nutritional significance

Breznak, John A.

doi:10.1016/0378-1097(90)90471-2

Cited by 35 publications

(49 citation statements)

References 20 publications

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“…Interestingly, the acetogen Acetobacterium woodii was unable to consume current [18,19]. Methanogenic and acetogenic bacteria usually share the same ecosystem [1,15]. The possibility of simultaneously producing methane and acetate from carbon dioxide in BESs based on mixed cultures has been reported only very recently, both by Marshall et al [14] and in our previous study [8].…”

Section: Introductionmentioning

confidence: 65%

Production of Acetate from Carbon Dioxide in Bioelectrochemical Systems Based on Autotrophic Mixed Culture

Jiang²,

2013

J. Microbiol. Biotechnol.

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Section: Introductionmentioning

confidence: 65%

Production of Acetate from Carbon Dioxide in Bioelectrochemical Systems Based on Autotrophic Mixed Culture

Jiang²,

2013

J. Microbiol. Biotechnol.

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“…In the termite gut, where A. longum is naturally found, cellulose hydrolysis and subsequent fermentation of the released sugars are accomplished mainly by flagellate protozoa, which produce large amounts of CO 2 and H 2 in the process. Acetogenic bacteria such as A. longum then use these gasses to form acetate, thus contributing to the efficiency of the termite gut system by increasing the amount of acetate available for termite metabolism (29)(30)(31). In addition, it is known that A. longum can ferment fructose, mannose, mannitol, ribose, pyruvate, and oxaloacetate, resulting in the production of butyrate and acetate (15).…”

Section: Discussionmentioning

confidence: 99%

Structure and Expression of Propanediol Utilization Microcompartments in Acetonema longum

et al. 2014

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c Numerous bacteria assemble proteinaceous microcompartments to isolate certain biochemical reactions within the cytoplasm. The assembly, structure, contents, and functions of these microcompartments are active areas of research. Here we show that the Gram-negative sporulating bacterium Acetonema longum synthesizes propanediol utilization (PDU) microcompartments when starved or grown on 1,2-propanediol (1,2-PD) or rhamnose. Electron cryotomography of intact cells revealed that PDU microcompartments are highly irregular in shape and size, similar to purified PDU microcompartments from Salmonella enterica serovar Typhimurium LT2 that were imaged previously. Homology searches identified a 20-gene operon in A. longum that contains most of the structural, enzymatic, and regulatory genes thought to be involved in PDU microcompartment assembly and function. Transcriptional data on PduU and PduC, which are major structural and enzymatic proteins, respectively, as well as imaging, indicate that PDU microcompartment synthesis is induced within 24 h of growth on 1,2-PD and after 48 h of growth on rhamnose. Bacterial microcompartments are small, cytoplasmic, organelle-like bodies consisting of a thin, selectively permeable proteinaceous shell that surrounds a cluster of enzymes. Together, these isolate certain metabolic pathways away from the rest of the cytoplasm. Microcompartments may increase metabolic efficiency by concentrating enzymes and substrates, inhibiting nonproductive side reactions, or sequestering toxic by-products (1, 2). The best-studied microcompartments are the "carboxysomes" that sequester ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) and facilitate carbon fixation (3, 4). After early electron microscopy images of carboxysomes revealed their general size and shape (5), crystal structures of the shell proteins led to pseudoatomic models of carboxysomes as irregular polyhedra with hexagonally packed faces joined at the vertices by pentagonal disclinations (6, 7). In the case of carboxysomes, it was also recently shown that the RubisCO enzymes destined to be internalized cluster together and then nucleate the assembly of the shell (8). Electron cryotomography (ECT) (9) of purified carboxysomes (10) and then of intact cells producing carboxysomes (11) has shown that while purification enriches for more-nearly-icosahedral shapes, carboxysomes inside cells are more heterogeneous, exhibit ordered layers of enzymes packed against the shell, and harbor small internal storage granules as well as elaborate connections to larger, external storage granules (11).In addition to carboxysomes, there are several other types of bacterial microcompartments, including propanediol utilization (PDU) and ethanolamine microcompartments (12, 13). Whether or not all microcompartments share similar assembly and structural features remains unclear. Projection images of plastic-embedded sections of PDU and ethanolamine microcompartments from Salmonella enterica and Lactobacillus reuteri have shown that these are also irre...

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“…rumen and hindgut, providing both methanogens and reductive acetogens with 'substrates' for their autotrophic growth. However, circumstances in the rumen seem unfavourable for reductive acetogens to grow autotrophically (Greening and Leedle, 1989;Breznak and Kane, 1990). Since they are able to grow mixotrophically (heterotrophically in absence of H,-CO,) they persist in this anaerobic ecosystem (Braun and Gottschalk, 1981;Gibson et al, 1993) in amounts similar to those of the methanogens (Genther et al, 1981;Leedle and Greening, 1988;Greening and Leedle, 1989).…”

Section: A3 Competition and Similarity Between M And Ramentioning

confidence: 99%

Reductive Acetogenesis in the Hindgut and Attempts to its Induction in the Rumen—A Review

Fievez

Piattoni

Mbanzamihigo

et al. 1999

Journal of Applied Animal Research

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Fievez, V., Piattoni, F., Mbanzamihigo, L. and Demeyer, D. 1999. Reductive acetogenesis in the hindgut and attempts to its induction in the rumen-A review. J. Appl. Anim. Res., 16: 1-22. Hiridgut ferrneiitatiori differs froin ruinen fermentation b. y a. lower methane production and the presence of reductive acetogenesis (RA).Moreover, it has been showii tha.t with ageing RA is rephced coinpletely (ruinen) or partially (hindgut) A. IntroductionBesides methanogenesis (M), non assimilatory sulphate reduction and/ or reductive acetogenesis (RA) have been identified as major pathways of microbial competition for metabolic hydrogen, formed during bacterial fermentation in anaerobic microbial ecosystems. However, these alternative hydrogen sinks to M do not function in the rumen, although bacteria able to use them have been isolated . After a short introduction to the characteristics of RA, this paper intends to give a global review of the research carried out in our laboratory over the past five years, related both to the relative importance of RA and M and to the possibilities for induction of RA in the rumen. A.1. RA in the gastro-intestinal tractBacteria are defined as reductive acetogens when they are able to reduce 2 moles of CO, to 1 mole of acetate, either autotrophically or heterotrophically, e.g. homoacetogenesis (Fisher et al., 1932; Wieringa, 1936, Prins andLankhorst, 1977).The heterotrophic growth of hom,oacetogens is characterised by the (almost) complete conversion of monosaccharides to acetate (Ljungdahl, 1986 Moreover, most of the hoinoacetogens are able to reduce exogenous CO,> autotrophically with molecular H,: 2 CO, + 4H, 3 CH,COOH + 2HiO ( 3 ) . This ability of mixothrophic growth (i.e. autotrophically on CO,-H, --a n d heterotrophically on monosaccharides) enables these acetogens to survive in almost every anaerobic environment and could explain their rather high growth yields (Ljungdahl, 1986). A.2. Detection of the occurrence of RAThe amounts of end products formed in ruinen fermentation are related through the stoichiometery of the overall reaction concerned (Wolin, 1960). This allows calculation of the net amounts of "metabolic hydrogen" produced and recovered in reduced end products. The agreement of the amounts of end products formed within a fermentation, with the overall reactions proposed, can then be evaluated by calculation of a "hydrogen recovery (2Hr)" (Marty and Demeyer, 1973): 100 * (2P + 2B + 4CHJ / (2A + P + 4B), with A, P, B and CH, equal to the molar amounts of acetate, propionate, butyrate and methane, respectively.With rumen contents such recoveries range between 80 and 90% (Demeyer, 1991), whereas with hindgut contents from different species, values were much lower, suggesting the presence of other hydrogen consuming reactions, mainly RA (Henderson a n d Deineyer and De Graeve, 1991). However, this calculation does not allow to differentiate reaction (2) from (3) and, therefore, in this paper RA is used for both reactions. A.3. Competition and similarity betwee...

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Microbial H2/CO2 acetogenesis in animal guts: nature and nutritional significance

Cited by 35 publications

References 20 publications

Production of Acetate from Carbon Dioxide in Bioelectrochemical Systems Based on Autotrophic Mixed Culture

Production of Acetate from Carbon Dioxide in Bioelectrochemical Systems Based on Autotrophic Mixed Culture

Structure and Expression of Propanediol Utilization Microcompartments in Acetonema longum

Reductive Acetogenesis in the Hindgut and Attempts to its Induction in the Rumen—A Review

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