Anaerobic Degradation of Uric Acid by Gut Bacteria of Termites

A study was done of anaerobic degradation of uric acid (UA) by representative strains of uricolytic bacteria isolated from guts of Reticulitermes flavipes termites. Streptococcus strain UAD-1 degraded UA incompletely, secreting a fluorescent compound into the medium, unless formate (or a formicogenic compound) was present as a cosubstrate. Formate functioned as a reductant, and its oxidation to CO₂ by formate dehydrogenase provided 2H⁺ + 2e⁻ needed to drive uricolysis to completion. Uricolysis by Streptococcus UAD-1 thus corresponded to the following equation: 1UA + 1formate → 4CO₂ + 1acetate + 4NH₃. Urea did not appear to be an intermediate in CO₂ and NH₃ formation during uricolysis by strain UAD-1. Formate dehydrogenase and uricolytic activities of strain UAD-1 were inducible by growth of cells on UA. Bacteroides termitidis strain UAD-50 degraded UA as follows: 1UA → 3.5 CO₂ + 0.75acetate + 4NH₃. Exogenous formate was neither required for nor stimulatory to uricolysis by strain UAD-50. Studies of UA catabolism by Citrobacter strains were limited, because only small amounts of UA were metabolized by cells in liquid medium. Uricolytic activity of such bacteria in situ could be important to the carbon, nitrogen, and energy economy of R. flavipes.     

Aerobic Microbial Degradation of Glucoisosaccharinic Acid

α-Glucoisosaccharinic acid (GISA), a major by-product of kraft paper manufacture, was synthesized from lactose and used as the carbon source for microbial media. Ten strains of aerobic bacteria capable of growth on GISA were isolated from kraft pulp mill environments. The highest growth yields were obtained with Ancylobacter spp. at pH 7.2 to 9.5. GISA was completely degraded by cultures of an Ancylobacter isolate. Ancylobacter cell suspensions consumed oxygen and produced carbon dioxide in response to GISA addition. A total of 22 laboratory strains of bacteria were tested, and none was capable of growth on GISA. GISA-degrading isolates were not found in forest soils.     

Molar Growth Yields of Certain Lactic Acid Bacteria as Influenced by Autolysis

Molar growth yields determined from batch cultures of Streptococcus diacetilactis and S. faecalis were appreciably greater at the peaks of maximal growth than after continued incubation and considerable autolysis. The higher molar growth yields were about equal to those determined in a continuous culture. Autolysis during logarithmic growth was minimal. The average Y value for adenosine triphosphate (ATP), determined by using limiting concentrations of glucose, galactose, lactose, and maltose for growing S. diacetilactis and limiting concentrations of glucose for growing S. lactis, S. cremoris, and S. faecalis, was 17.0. This is close to the Y (arginine) value of 17.8 determined with S. faecalis, but 62% greater than the generally accepted value of 10.5. Data are presented indicating that the often-used Y (ATP) value of 10.5 is erroneously low.     

Freon 11 Extraction of Volatile Metabolites Formed by Certain Lactic Acid Bacteria

The volatile metabolites formed by 18 lactic acid bacteria, representing three genera, were extracted from a complex medium by using a Freon 11 extraction method. The Freon extracts were then analyzed by capillary gas chromatography, and certain extracts were analyzed by gas chromatography-mass spectrometry. A total of 35 major peaks, of which 20 were positively identified, were used to differentiate between the various strains. On the basis of the results obtained, it was possible to differentiate between the members of the genera Lactobacillus, Pediococcus, and Leuconostoc, as well as between various species within the genus Leuconostoc. Of the 10 Leuconostoc oenos strains included in this study, 9 yielded similar results, but it was still possible to differentiate between the various strains. L. oenos B66 differed from the other L. oenos strains. Use of the Freon 11 extraction technique to determine volatile metabolites formed by lactic acid bacteria was shown to be highly reproducible and of great value. Furthermore, certain compounds not previously known to be formed by lactic acid bacteria were found.     

Aerobic Heterotrophic Bacteria Indigenous to pH 2.8 Acid Mine Water: Predominant Slime-Producing Bacteria in Acid Streamers

Five gram-negative bacteria, two gram-positive bacteria, and one yeast were isolated from "acid streamers" taken from acid mine water. One gram-positive rod which has been tentatively identified as a Bacillus species appeared to be the predominant organism in the streamers. This isolate produced copious amounts of extracellular polymer at 10 C in the laboratory and was considered to be the primary source of polymer in the "acid streamer" slime matrix. The organism grew slowly at pH 2.8 in mine water media, but the optimal pH was approximately 7.0.     

Molybdenum Involvement in Aerobic Degradation of 2-Furoic Acid by Pseudomonas putida Fu1

An organism identified as Pseudomonas putida was isolated from an enrichment culture with 2-furoic acid as its sole source of carbon and energy. The organism contained a 2-furoyl-coenzyme A (CoA) synthetase to form 2-furoyl-CoA and a 2-furoyl-CoA dehydrogenase to form 5-hydroxy-2-furoyl-CoA as the first two enzymes involved in the degradation. Tungstate, the specific antagonist of molybdate, decreased growth rate and consumption of 2-furoic acid but had no influence on growth with succinate. Correspondingly, the 2-furoyl-CoA dehydrogenase activity decreased when the organism was grown on 2-furoic acid in the presence of increasing amounts of tungstate. The addition of molybdate reversed the negative effect on 2-furoyl-CoA dehydrogenase activity, which points to the involvement of a molybdoenzyme in this reaction. Both enzymes studied were inducible. No plasmid was detected in this organism.     

一株人肠源性高效尿酸降解菌的分离、鉴定及降尿酸条件优化

摘要 目的：肠道作为人体的重要消化器官，其内定植的微生物在尿酸合成和代谢过程中发挥着重要作用，本研究利用含尿酸靶向培养基筛选正常人群肠道内具有降尿酸功能的细菌并鉴定。方法：依据尿酸的摩尔质量制备含不同浓度尿酸的BHI培养基，液体培养基扩增并驯化肠道粪便微生物，固体培养基分离和纯化具有尿酸降解功能的细菌。挑取固体培养基上形态一致的单个菌落进行革兰氏染色和镜检，筛选出已纯化菌株，在需氧和厌氧培养条件下测定尿酸降解率，选取降解率≥50%以上的菌株为高效尿酸降解菌的候选菌株，再测定不同温度和pH值条件下的尿酸降解率，进行降尿酸条件优化。利用16S rDNA序列测定法对尿酸降解菌进行鉴定，药敏实验测定该菌对抗生素的敏感性。结果：正常人群粪便微生物中分离获得一株高效尿酸降解菌B5C，第5天需氧条件下的尿酸降解率均>50%，与初始尿酸浓度相比具有统计学意义（P＜0.05）。优化降尿酸条件后，在37℃、pH7.0时，降解率可达88.7%，经鉴定为粪肠球菌，对常见的抗生素如阿莫西林、氨苄西林和青霉素G等具有较高的敏感性。结论：本研究利用含不同尿酸浓度的靶向培养基驯化、分离和鉴定出一株人肠源性细菌，在需氧条件下也具有较高的尿酸降解率，可为今后临床降尿酸微生物制剂的开发和利用提供新的菌种资源。     

Phytol Degradation by Marine Bacteria

Microbial degradation of phytol is often proposed to be the primary source of the acyclic isoprenoid acids observed in sediments, yet only a limited number of these acids have been found in bacterial cultures grown on phytol. This study reports detailed capillary gas chromatography and gas chromatography-mass spectrometry analyses of the products resulting from growth of marine bacteria on phytol as the sole carbon source. We examined two strains of bacteria which were able to oxidize phytol to phytenic acid but were unable to further degrade phytol. The third isolate studied converted phytol to a mixture of five saturated isoprenoid acids. The C₁₇ isoprenoid acid produced was of particular interest, since its genesis from phytol would have involved several unusual intermediates. It is suggested that this acid is produced by bacterial metabolism of the C₁₈ isoprenoid ketone (produced from phytol abiologically under oxic conditions) and that its abundance is thus a sensitive indicator of sedimentary depositional conditions.     

Poplar Lignin Decomposition by Gram-Negative Aerobic Bacteria

Eleven gram-negative aerobic bacteria (Pseudomonadaceae and Neisseriaceae) out of 122 soil isolates were selected for their ability to assimilate poplar dioxane lignin without a cosubstrate. Dioxane lignin and milled wood lignin degradation rates ranged between 20 and 40% of initial content after 7 days in mineral medium, as determined by a loss of absorbance at 280 nm; 10 strains could degrade in situ lignin, as evidenced by the decrease of the acetyl bromide lignin content of microtome wood sections. No degradation of wood polysaccharides was detected. Lignin biodegradation by Pseudomonas 106 was confirmed by ¹⁴CO₂ release from labeled poplar wood, although in lower yields compared with results obtained through chemical analysis based on acetyl bromide residual lignin determination.     

Inactivation of Nitric Oxide by Uric Acid

The 1980 identification of nitric oxide (NO) as an endothelial cell-derived relaxing factor resulted in an unprecedented biomedical research of NO and established NO as one of the most important cardiovascular, nervous and immune system regulatory molecule. A reduction in endothelial cell NO levels leading to “endothelial dysfunction” has been identified as a key pathogenic event preceding the development of hypertension, metabolic syndrome, and cardiovascular disease. The reduction in endothelial NO in cardiovascular disease has been attributed to the action of oxidants that either directly react with NO or uncouple its substrate enzyme. In this report, we demonstrate that uric acid (UA), the most abundant antioxidant in plasma, reacts directly with NO in a rapid irreversible reaction resulting in the formation of 6-aminouracil and depletion of NO. We further show that this reaction occurs preferentially with NO even in the presence of oxidants peroxynitrite and hydrogen peroxide and that the reaction is at least partially blocked by glutathione. This study shows a potential mechanism by which UA may deplete NO and cause endothelial dysfunction, particularly under conditions of oxidative stress in which UA is elevated and intracellular glutathione is depleted.     

Biodegradation of Asphalt Cement-20 by Aerobic Bacteria

Seven gram-negative, aerobic bacteria were isolated from a mixed culture enriched for asphalt-degrading bacteria. The predominant genera of these isolates were Pseudomonas, Acinetobacter, Alcaligenes, Flavimonas, and Flavobacterium. The mixed culture preferentially degraded the saturate and naphthene aromatic fractions of asphalt cement-20. A residue remained on the surface which was resistant to biodegradation and protected the underlying asphalt from biodegradation. The most potent asphalt-degrading bacterium, Acinetobacter calcoaceticus NAV2, excretes an emulsifier which is capable of emulsifying the saturate and naphthene aromatic fractions of asphalt cement-20. This emulsifier is not denatured by phenol.     

Biotransformation Patterns of 2,4,6-Trinitrotoluene by Aerobic Bacteria

2,4,6-Trinitrotoluene (TNT), a toxic nitroaromatic explosive, accumulates in the environment, making necessary the remediation of contaminated areas and unused materials. Although bioremediation has been utilized to detoxify TNT, the metabolic processes involved in the metabolism of TNT have proven to be complex. The three aerobic bacterial strains reported here (Pseudomonas aeruginosa, Bacillus sp., and Staphylococcus sp.) differ in their ability to biotransform TNT and in their growth characteristics in the presence of TNT. In addition, enzymatic activities have been identified that differ in the reduction of nitro groups, cofactor preferences, and the ability to eliminate-NO₂ from the ring. The Bacillus sp. has the most diverse bioremediation potential owing to its growth in the presence of TNT, high level of reductive ability, and capability of removing-NO₂ from the nitroaromatic ring. Received: 16 May 1997 / Accepted: 19 July 1997     

Degradation of N-Nitrosamines by Intestinal Bacteria

A major proportion of bacterial types, common in the gastrointestinal tract of many animals and man, were active in degrading diphenylnitrosamine and dimethylnitrosamine, the former being degraded more rapidly than the latter. At low nitrosamine concentrations (<0.05 μmol/ml), approximately 55% of added diphenylnitrosamine, 30% of N-nitrosopyrrolidine, and 4% of dimethylnitrosamine were degraded. The route of nitrosamine metabolism by bacteria appears to be different from that proposed for breakdown by mammalian enzyme systems in that carbon dioxide and formate were not produced. In bacteria, the nitrosamines were converted to the parent amine and nitrite ion and, in addition, certain unidentified volatile metabolites were produced from dimethylnitrosamine by bacteria. The importance of bacteria in reducing the potential hazard to man of nitrosamines is discussed.