Carbohydrate metabolism in Spirochaeta recurrentis. 1. The metabolism of spirochaetes in vivo and in vitro

Integrated microbiome-metabolome-genome axis data of Laiwu and Lulai pigs

Excessive fat deposition can trigger metabolic diseases, and it is crucial to identify factors that can break the link between fat deposition and metabolic diseases. Healthy obese Laiwu pigs (LW) are high in fat content but resistant to metabolic diseases. In this study, we compared the fecal microbiome, fecal and blood metabolome, and genome of LW and Lulai pigs (LU) to identify factors that can block the link between fat deposition and metabolic diseases. Our results show significant differences in Spirochetes and Treponema, which are involved in carbohydrate metabolism, between LW and LU. The fecal and blood metabolome composition was similar, and some anti-metabolic disease components of blood metabolites were different between the two breeds of pigs. The predicted differential RNA is mainly enriched in lipid metabolism and glucose metabolism, which is consistent with the functions of differential microbiota and metabolites. The down-regulated gene RGP1 is strongly negatively correlated with Treponema. Our omics data would provide valuable resources for further scientific research on healthy obesity in both human and porcine.

Pyruvate protects pathogenic spirochetes from H2O2 killing

Pathogenic spirochetes cause clinically relevant diseases in humans and animals, such as Lyme disease and leptospirosis. The causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of leptospirosis, Leptospria interrogans, encounter reactive oxygen species (ROS) during their enzootic cycles. This report demonstrated that physiologically relevant concentrations of pyruvate, a potent H2O2 scavenger, and provided passive protection to B. burgdorferi and L. interrogans against H2O2. When extracellular pyruvate was absent, both spirochetes were sensitive to a low dose of H2O2 (≈0.6 µM per h) generated by glucose oxidase (GOX). Despite encoding a functional catalase, L. interrogans was more sensitive than B. burgdorferi to H2O2 generated by GOX, which may be due to the inherent resistance of B. burgdorferi because of the virtual absence of intracellular iron. In B. burgdorferi, the nucleotide excision repair (NER) and the DNA mismatch repair (MMR) pathways were important for survival during H2O2 challenge since deletion of the uvrB or the mutS genes enhanced its sensitivity to H2O2 killing; however, the presence of pyruvate fully protected ΔuvrB and ΔmutS from H2O2 killing further demonstrating the importance of pyruvate in protection. These findings demonstrated that pyruvate, in addition to its classical role in central carbon metabolism, serves as an important H2O2 scavenger for pathogenic spirochetes. Furthermore, pyruvate reduced ROS generated by human neutrophils in response to the Toll-like receptor 2 (TLR2) agonist zymosan. In addition, pyruvate reduced neutrophil-derived ROS in response to B. burgdorferi, which also activates host expression through TLR2 signaling. Thus, pathogenic spirochetes may exploit the metabolite pyruvate, present in blood and tissues, to survive H2O2 generated by the host antibacterial response generated during infection.

Metabolism of Common Substrates by the Reiter Strain of Treponema pallidum

The utilization of glucose, amino acids, fatty acids, bicarbonate, purines, and pyrimidines by the Reiter treponeme was studied by using carbon 14-labeled substrates. The distribution of carbon from the substrates into various cell components was determined. Radioactivity from labeled bicarbonate in the cellular protein was restricted to aspartic acid. The Reiter treponeme is capable of synthesizing glycine, serine, alanine, aspartic acid, glutamic acid, proline, and possibly ornithine. Phenylalanine, arginine, lysine, leucine, isoleucine, valine, threonine, and histidine do not appear to be synthesized by this treponeme. The Reiter treponeme cannot synthesize fatty acids, and thymine is not incorporated. Glucose is a major carbon and energy source. Arginine, histidine, serine, threonine, and glutamic acid are degraded by the Reiter treponeme and may serve as energy sources. It was calculated that exogenously supplied amino acids contribute 41 to 54% of the cellular material; fatty acids, 18%; and glucose, 28 to 43%.

Serine proteinases of the human body louse (Pediculus humanus): sequence characterization and expression patterns

After the previous characterization of one trypsin gene (Try1) of the human body louse Pediculus humanus, genes encoding a second trypsin (Try2) and a chymotrypsin (Chy1) have been cloned using degenerate serine proteinase primers and 5'- and 3'-RACE, and sequenced. The deduced 259 and 267 amino acid sequences of Try2 and Chy1 show an identity of 33%-40% to trypsinogens and chymotrypsinogens of other insects. Considering previously published partial sequences, P. humanus possesses at least one Try1 gene, five variants/isoforms of Try2 and six variants/isoforms of Chy1. The genomic DNA of Try2 contains three introns and Chy1 contains five introns. Using whole mount in situ hybridization, gene expression of Try1, Try2 and Chy1 has been localized not only in the distensible anterior region of the midgut of lice but sometimes also in the area following the distensible region. The Try2 gene was always expressed at much lower levels than Try1 or Chy1. This lower expression, the constitutive expression of Try1 and Chy1 at 1, 2, 6, 12 and 24 h after feeding of adults and the regional differences have been verified in quantitative real-time PCR.

Carbohydrate utilization by the Lyme borreliosis spirochete, Borrelia burgdorferi

Growth kinetic analyses of Borrelia burgdorferi indicated that this bacterium can utilize a limited number of carbon sources for energy: the monosaccharides glucose, mannose, and N-acetylglucosamine, the disaccharides maltose and chitobiose, and glycerol. All of these carbohydrates are likely to be available to B. burgdorferi during infection of either vertebrate and arthropod hosts, enabling development of a model describing energy sources potentially used by the Lyme borreliosis spirochete during its natural infectious cycle.

The relapsing fever agent Borrelia hermsii has multiple copies of its chromosome and linear plasmids

Borrelia hermsii, a spirochete which causes relapsing fever in humans and other mammals, eludes the immune response by antigenic variation of the "Vmp" proteins. This occurs by replacement of an expressed vmp gene with a copy of a silent vmp gene. Silent and expressed vmp genes are located on separate linear plasmids. To further characterize vmp recombination, copy numbers were determined for two linear plasmids and for the 1-megabase chromosome by comparing hybridization of probes to native DNA with hybridization to recombinant plasmids containing borrelial DNA. Plasmid copy numbers were also estimated by ethidium bromide fluorescence. Total cellular DNA content was determined by spectrophotometry. For borrelias grown in mice, copy numbers and 95% confidence intervals were 14 (12-17) for an expression plasmid, 8 (7-9) for a silent plasmid, and 16 (13-18) for the chromosome. Borrelias grown in broth medium had one-fourth to one-half this number of plasmids and chromosomes. Staining of cells with 4',6-diamidino-2-phenylindole revealed DNA to be distributed throughout most of the spirochete's length. These findings indicate that borrelias organize their total cellular DNA into several complete genomes and that cells undergoing serotype switches do one or more of the following: (1) coexpress Vmps from switched and unswitched expression plasmids for at least three to five generations, (2) suppress transcription from some expression plasmid copies, or (3) partition expression plasmids nonrandomly. The lower copy number of the silent plasmid indicates that nonreciprocal Vmp gene recombination may result from loss of recombinant silent plasmids by segregation.

Biology of Borrelia species

Images

Glucose and insulin homeostasis during the Jarisch-Herxheimer reaction

Plasma concentrations of glucose and insulin were measured in ten patients during the Jarisch-Herxheimer reaction of tetracycline-treated louse-borne relapsing fever. Plasma glucose fell significantly in eight of the ten patients associated with the peak of the reaction, but plasma insulin remained low. Glucoregulation by insulin was therefore normal. This evidence questions the role of macrophage mediator-induced pancreatic insulin release in causing hypoglycaemia in borreliosis or bacterial endotoxicosis.

Terminal changes in mice experimentally infected with Borrelia duttoni

The terminal changes following Borrelia duttoni infection in mice consisted of disseminated intravascular coagulation with associated depression in temperature, and in white cell and platelet counts with the development of a positive limulus lysate test. Apart from thrombosis and haemorrhage, similar changes were found in mice given cyclophosphamide prior to infection. The results suggest that neither intravascular coagulation nor immune complex formation are major factors in causing death in borreliosis.

Lipid catabolism of relapsing fever borreliae

Relapsing fever borreliae require lipid compounds for growth in vitro. In this study, the major pathways of lipid catabolism in three species of tick-borne relapsing fever borreliae were investigated. Thin-layer chromatography was used to compare chloroform-methanol extracts of fresh culture media with extracts of exhausted culture media after organisms were removed by centrifugation. The chromatographic data demonstrated that lysolecithin was removed from the culture media during growth of the spirochetes, whereas lecithin, sphingomyelin, triglycerides, and cholesterol esters were not affected by growth of the organisms. Sonic extracts of the organism were tested for the presence of specific enzymes of lipid catabolism. Lysolecithinase, glycerophosphorylcholine diesterase, and acid phosphatase activities were demonstrated. Thus, these organisms can sequentially dissimilate lysolecithin to fatty acids, choline, inorganic phosphate, and glycerol. Assays for phospholipases A, C, and D, alpha-glycerophosphate dehydrogenase, alkaline phosphatase, and lipase were negative.

Culture of Ethiopian strains of Borrelia recurrentis

A number of standard bacteriological media with supplements were tested for their ability to support in vitro growth of Ethiopian strains of Borrelia recurrentis. Propagation of 18 out of 21 strains occurred in Trypticase soy yeast broth to which bovine albumin (fraction V), N-acetyl glucosamine, and sodium pyruvate had been added. This medium supported a population of 10(7) organisms per ml and yielded a harvest of four to five times the original inoculum during the logarithmic phase of growth. Maximal yield varied from 1.4 x 10(7) to 3.4 x 10(7) organisms per ml. Generation time in optimal media was 11.3 h. Lesser multiplication of organisms occurred in other media tested. Strains from primary cultures were infective for the green monkey. Recovery of viable organisms from subculture has not been successful.

Cultivation of Borrelia hermsi

A medium has been developed which permits the isolation and growth of Borrelia hermsi, an organism that causes relapsing fever.

Carbohydrate metabolism in Spirochaeta stenostrepta

The pathways of carbohydrate metabolism in Spirochaeta stenostrepta, a free-living, strictly anaerobic spirochete, were studied. The organism fermented glucose to ethyl alcohol, acetate, lactate, CO(2), and H(2). Assays of enzymatic activities in cell extracts, and determinations of radioactivity distribution in products formed from (14)C-labeled glucose indicated that S. stenostrepta degraded glucose via the Embden-Meyerhof pathway. The spirochete utilized a clostridial-type clastic reaction to metabolize pyruvate to acetyl-coenzyme A, CO(2), and H(2), without production of formate. Acetyl-coenzyme A was converted to ethyl alcohol by nicotinamide adenine dinucleotide-dependent acetaldehyde and alcohol dehydrogenase activities. Phosphotransacetylase and acetate kinase catalyzed the formation of acetate from acetyl-coenzyme A. Hydrogenase and lactate dehydrogenase activities were detected in cell extracts. A rubredoxin was isolated from cell extracts of S. stenostrepta. Preparations of this rubredoxin stimulated acetyl phosphate formation from pyruvate by diethylaminoethyl cellulose-treated extracts of S. stenostrepta, an indication that rubredoxin may participate in pyruvate cleavage by this spirochete. Nutritional studies showed that S. stenostrepta fermented a variety of carbohydrates, but did not ferment amino acids or other organic acids. An unidentified growth factor present in yeast extract was required by the organism. Exogenous supplements of biotin, riboflavin, and vitamin B(12) were either stimulatory or required for growth.

Intermediate energy metabolism of Leptospira

Metabolic studies were performed on three representative serotypes of Leptospira: a water isolate designated B(16) and two pathogenic serotypes, pomona and schueffneri. Examination of whole cells of B(16) for their ability to oxidize various substrates revealed that oleate significantly stimulated oxygen uptake. The respiratory quotient of 0.7 implied that oleate was degraded to carbon dioxide and water. Other substrates, such as carbohydrates, alcohols, intermediates of the citric acid cycle, and short-chain acids, including selected amino acids, did not stimulate endogenous respiration of whole cells. No oxygen uptake could be measured when cell-free extracts were tested with the substrates used with whole cells. Enzymatic analyses of cell-free extracts of the three strains demonstrated enzymes of the citric acid cycle, enzymes of the glycolytic and pentose pathways, and the general acyl coenzyme A dehydrogenase required for beta-oxidation of fatty acids. Strain B(16) and the two pathogenic serotypes appeared to possess similar metabolic capabilities. Enzymatic data might also explain the apparent inability of B(16) to oxidize other substrates; kinases necessary for activation of common nonphosphorylated compounds were not detected in leptospiral extracts. These findings emphasized the dependence of leptospiral growth upon long-chain fatty acids.