Enzymes associated with metabolism of xylose and other pentoses by Prevotella (Bacteroides) ruminicola strains, Selenomonas ruminantium D, and Fibrobacter succinogenes S85

1992 ◽  
Vol 38 (5) ◽  
pp. 370-376 ◽  
Author(s):  
Allan Matte ◽  
Cecil W. Forsberg ◽  
Ann M. Verrinder Gibbins
Keyword(s):  
Xylose Isomerase ◽  
Sole Source ◽  
Pentose Phosphate ◽  
Binding Potential ◽  
Fibrobacter Succinogenes ◽  
Xylose Metabolism ◽  
Ruminal Bacteria ◽  
Selenomonas Ruminantium ◽  
Pentose Phosphate Cycle ◽  
Prevotella Ruminicola

Prevotella (Bacteroides) ruminicola strains B14 and S23 and Selenomonas ruminantium strain D used xylose as the sole source of carbohyrate for growth, whereas Fibrobacter succinogenes was unable to metabolize xylose. Prevotella ruminicola strain B14 exhibited transport activity for xylose. In contrast, F. succinogenes lacked typical xylose uptake activity but did exhibit low binding potential for the sugar. Prevotella ruminicola strains B14 and S23 as well as S. ruminantium D showed low xylose isomerase activities but higher xylulokinase activities, using assays that gave high activities for these enzymes in Escherichia coli. Xylose isomerase appeared to be produced constitutively in these ruminal bacteria, but xylulokinase was induced to varying degrees with xylose as the source of carbohydrate. Fibrobacter succinogenes lacked xylose isomerase and xylulokinase. All three species of ruminal bacteria possessed transketolase,xylulose-5-phosphate epimerase, and ribose-5-phosphate isomerase activities. Neither P. ruminicola B14 nor F. succinogenes S85 showed significant phosphoketolase activity. The data indicate that F. succinogenes is unable to either actively uptake or metabolize xylose as a result of the absence of functional xylose permease, xylose isomerase, and xylulokinase activities, although it and both P. ruminicola and S. ruminantium possess the essential enzymes of the nonoxidative branch of the pentose phosphate cycle. Key words: Fibrobacter succinogenes, Prevotella, Selenomonas, xylose metabolism, rumen bacteria, pentose phosphate cycle.

scholarly journals Confirmation and Elimination of Xylose Metabolism Bottlenecks in Glucose Phosphoenolpyruvate-Dependent Phosphotransferase System-Deficient Clostridium acetobutylicum for Simultaneous Utilization of Glucose, Xylose, and Arabinose

2011 ◽  
Vol 77 (22) ◽  
pp. 7886-7895 ◽  
Author(s):  
Han Xiao ◽  
Yang Gu ◽  
Yuanyuan Ning ◽  
Yunliu Yang ◽  
Wilfrid J. Mitchell ◽  
...  
Keyword(s):  
Clostridium Acetobutylicum ◽  
Xylose Isomerase ◽  
Cost Effective ◽  
Pentose Phosphate ◽  
Xylose Metabolism ◽  
Phosphotransferase System ◽  
Gene Encoding ◽  
Content Type ◽  
Sugar Mixtures ◽  
Residual Glucose

ABSTRACTEfficient cofermentation ofd-glucose,d-xylose, andl-arabinose, three major sugars present in lignocellulose, is a fundamental requirement for cost-effective utilization of lignocellulosic biomass. The Gram-positive anaerobic bacteriumClostridium acetobutylicum, known for its excellent capability of producing ABE (acetone, butanol, and ethanol) solvent, is limited in using lignocellulose because of inefficient pentose consumption when fermenting sugar mixtures. To overcome this substrate utilization defect, a predictedglcGgene, encoding enzyme II of thed-glucose phosphoenolpyruvate-dependent phosphotransferase system (PTS), was first disrupted in the ABE-producing model strainClostridium acetobutylicumATCC 824, resulting in greatly improvedd-xylose andl-arabinose consumption in the presence ofd-glucose. Interestingly, despite the loss of GlcG, the resulting mutant strain 824glcG fermentedd-glucose as efficiently as did the parent strain. This could be attributed to residual glucose PTS activity, although an increased activity of glucose kinase suggested that non-PTS glucose uptake might also be elevated as a result ofglcGdisruption. Furthermore, the inherent rate-limiting steps of thed-xylose metabolic pathway were observed prior to the pentose phosphate pathway (PPP) in strain ATCC 824 and then overcome by co-overexpression of thed-xylose proton-symporter (cac1345),d-xylose isomerase (cac2610), and xylulokinase (cac2612). As a result, an engineered strain (824glcG-TBA), obtained by integratingglcGdisruption and genetic overexpression of the xylose pathway, was able to efficiently coferment mixtures ofd-glucose,d-xylose, andl-arabinose, reaching a 24% higher ABE solvent titer (16.06 g/liter) and a 5% higher yield (0.28 g/g) compared to those of the wild-type strain. This strain will be a promising platform host toward commercial exploitation of lignocellulose to produce solvents and biofuels.

scholarly journals Refactoring the upper sugar metabolism ofPseudomonas putidafor co-utilization of disaccharides, pentoses, and hexoses

2018 ◽  
Author(s):  
Pavel Dvořák ◽  
Víctor de Lorenzo
Keyword(s):  
Glucose Dehydrogenase ◽  
Sugar Metabolism ◽  
Xylose Isomerase ◽  
Pentose Phosphate ◽  
Soil Bacterium ◽  
Biochemical Network ◽  
Xylose Metabolism ◽  
Native Proteins ◽  
Dead End ◽  
A Genome

AbstractGiven its capacity to tolerate stress, NAD(P)H/ NAD(P) balance, and increased ATP levels, the platform strainPseudomonas putidaEM42, a genome-edited derivative of the soil bacteriumP. putidaKT2440, can efficiently host a suite of harsh reactions of biotechnological interest. Because of the lifestyle of the original isolate, however, the nutritional repertoire ofP. putidaEM42 is centered largely on organic acids, aromatic compounds and some hexoses (glucose and fructose). To enlarge the biochemical network ofP. putidaEM42 to include disaccharides and pentoses, we implanted heterologous genetic modules for D-cellobiose and D-xylose metabolism into the enzymatic complement of this strain. Cellobiose was actively transported into the cells through the ABC complex formed by native proteins PP1015-PP1018. The knocked-in β-glucosidase BglC fromThermobifida fuscacatalyzed intracellular cleavage of the disaccharide to D-glucose, which was then channelled to the default central metabolism. Xylose oxidation to the dead end product D-xylonate was prevented by by deleting thegcdgene that encodes the broad substrate range quinone-dependent glucose dehydrogenase. Intracellular intake was then engineered by expressing theEscherichia coliproton-coupled symporter XylE. The sugar was further metabolized by the products ofE. coli xylA(xylose isomerase) andxylB(xylulokinase) towards the pentose phosphate pathway. The resultingP. putidastrain co-utilized xylose with glucose or cellobiose to complete depletion of the sugars. These results not only show the broadening of the metabolic capacity of a soil bacterium towards new substrates, but also promoteP. putidaEM42 as a platform for plug-in of new biochemical pathways for utilization and valorization of carbohydrate mixtures from lignocellulose processing.

scholarly journals De Novo Synthesis of Amino Acids by the Ruminal Bacteria Prevotella bryantii B14,Selenomonas ruminantium HD4, and Streptococcus bovis ES1

1998 ◽  
Vol 64 (8) ◽  
pp. 2836-2843 ◽  
Author(s):  
Cengiz Atasoglu ◽  
Carmen Valdés ◽  
Nicola D. Walker ◽  
C. James Newbold ◽  
R. John Wallace
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
De Novo ◽  
Dependent Manner ◽  
Streptococcus Bovis ◽  
De Novo Synthesis ◽  
Ruminal Bacteria ◽  
Total N ◽  
Selenomonas Ruminantium ◽  
Prevotella Bryantii

ABSTRACT The influence of peptides and amino acids on ammonia assimilation and de novo synthesis of amino acids by three predominant noncellulolytic species of ruminal bacteria, Prevotella bryantii B14, Selenomonas ruminantiumHD4, and Streptococcus bovis ES1, was determined by growing these bacteria in media containing 15NH4Cl and various additions of pancreatic hydrolysates of casein (peptides) or amino acids. The proportion of cell N and amino acids formed de novo decreased as the concentration of peptides increased. At high concentrations of peptides (10 and 30 g/liter), the incorporation of ammonia accounted for less than 0.16 of bacterial amino acid N and less than 0.30 of total N. At 1 g/liter, which is more similar to peptide concentrations found in the rumen, 0.68, 0.87, and 0.46 of bacterial amino acid N and 0.83, 0.89, and 0.64 of total N were derived from ammonia by P. bryantii, S. ruminantium, andS. bovis, respectively. Concentration-dependent responses were also obtained with amino acids. No individual amino acid was exhausted in any incubation medium. For cultures of P. bryantii, peptides were incorporated and stimulated growth more effectively than amino acids, while cultures of the other species showed no preference for peptides or amino acids. Apparent growth yields increased by between 8 and 57%, depending on the species, when 1 g of peptides or amino acids per liter was added to the medium. Proline synthesis was greatly decreased when peptides or amino acids were added to the medium, while glutamate and aspartate were enriched to a greater extent than other amino acids under all conditions. Thus, the proportion of bacterial protein formed de novo in noncellulolytic ruminal bacteria varies according to species and the form and identity of the amino acid and in a concentration-dependent manner.

scholarly journals Concomitant Regulation by a LacI-Type Transcriptional Repressor XylR on Genes Involved in Xylan and Xylose Metabolism and the Type III Secretion System in Rice Pathogen Xanthomonas oryzae pv. oryzae

2018 ◽  
Vol 31 (6) ◽  
pp. 605-613 ◽  
Author(s):  
Yumi Ikawa ◽  
Sayaka Ohnishi ◽  
Akiko Shoji ◽  
Ayako Furutani ◽  
Seiji Tsuge
Keyword(s):  
Gene Expression ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Xylose Isomerase ◽  
Secretion System ◽  
Xanthomonas Oryzae ◽  
Upstream Region ◽  
Xylose Metabolism ◽  
Type Iii ◽  
Hrp Genes

The hypersensitive response and pathogenicity (hrp) genes of Xanthomonas oryzae pv. oryzae, the causal agent of bacterial leaf blight of rice, encode components of the type III secretion system and are essential for virulence. Expression of hrp genes is regulated by two key hrp regulators, HrpG and HrpX; HrpG regulates hrpX and hrpA, and HrpX regulates the other hrp genes on hrpB-hrpF operons. We previously reported the sugar-dependent quantitative regulation of HrpX; the regulator highly accumulates in the presence of xylose, followed by high hrp gene expression. Here, we found that, in a mutant lacking the LacI-type transcriptional regulator XylR, HrpX accumulation and hrp gene expression were high even in the medium without xylose, reaching the similar levels present in the wild type incubated in the xylose-containing medium. XylR also negatively regulated one of two xylose isomerase genes (xylA2 but not xylA1) by binding to the motif sequence in the upstream region of the gene. Xylose isomerase is an essential enzyme in xylose metabolism and interconverts between xylose and xylulose. Our results suggest that, in the presence of xylose, inactivation of XylR leads to greater xylan and xylose utilization and, simultaneously, to higher accumulation of HrpX, followed by higher hrp gene expression in the bacterium.

Thiamine deficiency and the hepatic pentose phosphate cycle

1975 ◽  
Vol 14 (4) ◽  
pp. 384-390 ◽  
Author(s):  
David W. McCandless ◽  
Carol E. Cassidy ◽  
Alison D. Curley
Keyword(s):  
Thiamine Deficiency ◽  
Pentose Phosphate ◽  
Pentose Phosphate Cycle
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