Nutrient transport by ruminal bacteria: a review

Martin, Scott A.

doi:10.2527/1994.72113019x

Cited by 32 publications

(27 citation statements)

References 84 publications

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“…The gene encoding the XylB xylose kinase involved in the degradation of xylose was also up-regulated. Considering that many PTSs were down-regulated, the use of this alternative sugar, for which PTS systems have seldom been implicated [45] may be reconciled. Several genes of the "Protein Fate" functional class also showed up-regulation.…”

Section: Resultsmentioning

confidence: 99%

Transcriptional profiling of Actinobacillus pleuropneumoniae under iron-restricted conditions

et al. 2007

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Background: To better understand effects of iron restriction on Actinobacillus pleuropneumoniae and to identify new potential vaccine targets, we conducted transcript profiling studies using a DNA microarray containing all 2025 ORFs of the genome of A. pleuropneumoniae serotype 5b strain L20. This is the first study involving the use of microarray technology to monitor the transcriptome of A. pleuropneumoniae grown under iron restriction.

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Section: Resultsmentioning

confidence: 99%

Transcriptional profiling of Actinobacillus pleuropneumoniae under iron-restricted conditions

et al. 2007

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“…1B) that are the functional equivalents of succinateproducing rumen bacteria such as Actinobacillus succinogenes and Mannheimia succiniciproducens (5,(39)(40)(41). OAA is produced using an energy-conserving PEP-carboxykinase.…”

Section: Discussionmentioning

confidence: 99%

“…PEP is conserved to eliminate the need for energy-expensive regeneration (2-ATP equivalents) by using glucose permeases (and glucokinase) rather than the PEP-dependent phosphotransferase system for glucose uptake. Note that among rumen bacteria producing other fermentation products, the phosphotransferase system is widely used for glucose uptake (40). The most promising E. coli strains for succinate production, KJ060 and KJ073, produced Ϸ700 mM succinate with a yield of 1.2 mol succinate per mol glucose (3), comparable to the best natural succinate-producing rumen bacteria, Actinobacillus succinogenes (20).…”

Section: Discussionmentioning

confidence: 99%

Metabolic evolution of energy-conserving pathways for succinate production in Escherichia coli

Zhang

Jantama

Moore

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

218

192

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During metabolic evolution to improve succinate production in Escherichia coli strains, significant changes in cellular metabolism were acquired that increased energy efficiency in two respects. The energyconserving phosphoenolpyruvate (PEP) carboxykinase (pck), which normally functions in the reverse direction (gluconeogenesis; glucose repressed) during the oxidative metabolism of organic acids, evolved to become the major carboxylation pathway for succinate production. Both PCK enzyme activity and gene expression levels increased significantly in two stages because of several mutations during the metabolic evolution process. High-level expression of this enzymedominated CO 2 fixation and increased ATP yield (1 ATP per oxaloacetate). In addition, the native PEP-dependent phosphotransferase system for glucose uptake was inactivated by a mutation in ptsI. This glucose transport function was replaced by increased expression of the GalP permease (galP) and glucokinase (glk). Results of deleting individual transport genes confirmed that GalP served as the dominant glucose transporter in evolved strains. Using this alternative transport system would increase the pool of PEP available for redox balance. This change would also increase energy efficiency by eliminating the need to produce additional PEP from pyruvate, a reaction that requires two ATP equivalents. Together, these changes converted the wild-type E. coli fermentation pathway for succinate into a functional equivalent of the native pathway that nature evolved in succinate-producing rumen bacteria.biocatalyst ͉ metabolic engineering ͉ succinic acid S uccinate, a four-carbon dicarboxylic acid, is currently used as a specialty chemical in the food, agricultural, and pharmaceutical industries (1). Succinic acid can also serve as a starting point for the synthesis of many commodity chemicals used in plastics and solvents with a potential global market of $15 billion (2). Although succinate is primarily produced from petroleum, recent increases in costs have generated considerable interest in the fermentative production of succinate from sugars using Escherichia coli and other biocatalysts (2, 3).The yield of succinate from glucose fermentation is primarily determined by carbon partitioning at the phosphoenolpyruvate (PEP) node (Fig. 1A). In rumen bacteria such as Anaerobiospirillum succiniciproducens (4), Actinobacillus succinogenes (5, 6) and Mannheimia succiniciproducens (7,8), more than half of the phosphoenolpyruvate formed from glucose is carboxylated to oxaloacetate and converted to succinate, the primary fermentation product. However, requirements for complex nutrients by these bacteria increase both the cost and process complexity. Native strains of E. coli ferment glucose effectively in simple mineral salts medium but produce succinate only as a minor product (9). In E. coli, half of the PEP from glucose is metabolized directly to pyruvate by the PEP-dependent phosphotransferase system for glucose uptake. Most of the remaining PEP is used for ATP produc...

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“…Although the rumen is colonised with prokaryotes, protozoa, fungi and methanogenic Archaea, we have focused our attention on the bacterial population as they are thought to be the most diverse micro-organism group and represent more than half of the biomass (10 10 to 10 11 cells/mL) [10]. This remains a challenge as more than 200 bacterial species have already been isolated, identified and their metabolism studied in pure culture whilst new advances in rRNA based microbial ecology have revealed that many more bacterial species inhabit the rumen [11].…”

Section: Introductionmentioning

confidence: 99%

The Effects of a Probiotic Yeast on the Bacterial Diversity and Population Structure in the Rumen of Cattle

et al. 2013

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It has been suggested that the ability of live yeast to improve milk yield and weight gain in cattle is because the yeast stimulates bacterial activity within the rumen. However it remains unclear if this is a general stimulation of all species or a specific stimulation of certain species. Here we characterised the change in the bacterial population within the rumen of cattle fed supplemental live yeast. Three cannulated lactating cows received a daily ration (24 kg/d) of corn silage (61% of DM), concentrates (30% of DM), dehydrated alfalfa (9% of DM) and a minerals and vitamins mix (1% of DM). The effect of yeast (BIOSAF SC 47, Lesaffre Feed Additives, France; 0.5 or 5 g/d) was compared to a control (no additive) in a 3×3 Latin square design. The variation in the rumen bacterial community between treatments was assessed using Serial Analysis of V1 Ribosomal Sequence Tag (SARST-V1) and 454 pyrosequencing based on analysis of the 16S rRNA gene. Compared to the control diet supplementation of probiotic yeast maintained a healthy fermentation in the rumen of lactating cattle (higher VFA concentration [high yeast dose only], higher rumen pH, and lower Eh and lactate). These improvements were accompanied with a shift in the main fibrolytic group (Fibrobacter and Ruminococcus) and lactate utilising bacteria (Megasphaera and Selenomonas). In addition we have shown that the analysis of short V1 region of 16s rRNA gene (50–60 bp) could give as much phylogenetic information as a longer read (454 pyrosequencing of 250 bp). This study also highlights the difficulty of drawing conclusions on composition and diversity of complex microbiota because of the variation caused by the use of different methods (sequencing technology and/or analysis).

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Nutrient transport by ruminal bacteria: a review

Cited by 32 publications

References 84 publications

Transcriptional profiling of Actinobacillus pleuropneumoniae under iron-restricted conditions

Transcriptional profiling of Actinobacillus pleuropneumoniae under iron-restricted conditions

Metabolic evolution of energy-conserving pathways for succinate production in Escherichia coli

The Effects of a Probiotic Yeast on the Bacterial Diversity and Population Structure in the Rumen of Cattle

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