The oxidation of d-quinate and related acids by Acetomonas oxydans

1. Growing cells of a small number of strains of Acetomonas oxydans oxidized d-quinate to 5-dehydroquinate. 2. d-Shikimate was oxidized to 4,5-dihydroxy-3-oxocyclohex-1-ene-1-carboxylate (3-dehydroshikimate, formerly 5-dehydroshikimate). 3. d-Dihydroshikimate was oxidized to the corresponding 5-dehydro compound, but epidihydroshikimate oxidation by growing cells was not observed. 4. Cell-free extracts oxidized d-quinate to 5-dehydroquinate with the consumption of the stoicheiometric amount of oxygen, but oxidation of shikimate and dihydroshikimate did not go to completion. 5. Oxidation of quinate was brought about by a constitutive particulate enzyme probably localized in the cytoplasmic membrane. No evidence was found for the participation of NAD, NADP or free flavine compounds in electron transport, but the system was cytochrome-linked.     

Effects of phenolic acids on ammonia oxidation by terrestrial autotrophic nitrifying microorganisms

Abstract It has been hypothesized that vegetation in certain ecosystems inhibits nitrification in soil by producing phenolic compounds that inhibit oxidation of ammonia by nitrifying microorganisms. This hypothesis is based largely on a report that very low concentrations (10⁻⁶ M–10⁻⁸ M) of several phenolic acids (notably ferulic acid) completely inhibited NO₂⁻ production in an aqueous suspension of soil treated with (NH₄)₂SO₄ and a nutrient solution suitable for growth of Nitrosomonas and other autotrophic nitrifying microorganisms. To evaluate this hypothesis, we determined the effects of three ohenolic acids (ferulic acid, caffeic acid, and p -coumaric on nitrite production by representatives of three genera of terrestrial autotrophic nitrifying microorganisms ( Nitrosospira, Nitrosomonas , or Nitrosolubos ) grown on a defined medium containing NH₄⁺. We found that nitrite production by the Nitrososspira was not inhibited by ferulic acid, caffeic acid, or p -coumaric acid at concentrations of 10⁻⁶ or 10⁻⁵ M and was only slightly inhibited when these acids were at a concentration of 10⁻⁴ M. We also found that ferulic acid did not markedly inhibit nitrite production by the three genera of nitrifying microorganisms studied, even when its concentration was as high as 10⁻³ M. These observations invalidate the hypothesis tested because the phenolic acids studied did not significantly retard ammonia oxidation by autotrophic microorganisms even when their concentration in cultures of these microorganisms greatly exceeded their concentrations in soils.     

Bioavailability of phenolic acids

Two large classes of phenolic acids were comprised in this review: benzoic acid derivatives and cinnamic acid derivatives. They have been found to be very extended in fruits and vegetables at different concentrations. For example, hydroxycinnamic acids concentration was higher than that found for hydroxybenzoic acids. Concerning their consumption, hydroxycinnamic acids provide larger contributions to the total polyphenol intake than benzoic acid derivatives or flavonoids. This phenolic acid intake is led by the coffee intake since it has very rich concentrations in hydroxycinnamic acids. Moreover, several experimental and epidemiological studies report the protection of phenolic acids against various degenerative diseases. However, despite all these interesting attributions and even if phenolic acids are the main polyphenols consumed, their bioavailability has not received as attention as that flavonoids. This concept is an essential step to understand the health-promoting properties of phenolic acids and to serve as tool to design in vivo and in vitro experiments to know their biological properties. Therefore, a compilation of bioavailability data of phenolic acids have been presented here paying attention to the two types of phenolic acid bioavailability, direct and indirect derived from the direct phenolic acid and flavonoid consumption, respectively. Then, a new relevant concept which may be named as total bioavailability of phenolic acids includes the direct absorption and metabolism of phenolic acids from food consumption and phenolic acids bioavailability as a result of the cleavage on the main skeleton ring of flavonoids by the gut microflora.     

Antimutagenic effect of phenolic acids

In the present study, the Salmonella typhimurium tester strain TA 100 was used in the plate-incorporation test to examine the antimutagenic potential of caffeic, ferulic and cichoric acids extracted from plant species of genera Echinacea (L) Moench, as well as of another phenolic acids, on 3-(5-nitro-2-furyl)acrylic acid (5NFAA) and sodium azide mutagenicity. All tested compounds possess antimutagenic activity. In the case of 5NFAA, the antimutagenic potency of tested compounds was in the order of gallic acid > ferulic acid > caffeic acid > syringic acid > vanillic acid. The mutagenic effect of sodium azide was inhibited by tested phenolic acids by about 20-35 %. The most effective compound, gallic acid inhibits this effect by 82 % in the concentration of 500 mug/plate. The only exception from favourable properties of tested phenolic acids is cichoric acid, which in the contrary significantly increased the mutagenic effect of 5NFAA.     

酚酸类物质的抑草效应分析

运用正交旋转回归试验设计分析5种常见的化感物质替代物水饧酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸对田间伴生杂草稗草的抑制效应．结果表明,肉桂酸对稗草根长抑制率的影响最显著。其关系函数的二次项系数为-6．18,达极显著水平,水杨酸、对羟基苯甲酸和阿魏酸对稗草根长的抑制效应趋势与肉桂酸相同,效应曲线均为“n”形抛物线;而香草酸的效应曲线则为“U”形抛物线．当水饧酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸浓度水平分别为0．06、0．60、0．24、0．02和0．02mmol·L^-1时,混合物对稗草根长的抑制率最大,达到78．65％。     

Bacterial oxidation of propane

Abstract Much recent work in the field of biohydrometallurgy has been directed to the study of bio-oxidation of gold ores by acidophilic iron and sulfur oxidizing microorganisms. This work has been done worldwide and has resulted in several pilot plant and commercial scale operations for gold ore bio-oxidation. Bioleaching of gold by metabolic products of microorganisms has received less attention, but also offers opportunities for industrial application, especially if future regulations restrict the use of cyanide. This paper reviews recent progress in the use of microorganisms tooxidize the sulfidic matrix in refractory gold ores (bio-oxidation) and to solubilize elemental gold (bioleaching).     

Bacteria degrading phenolic acids isolated on a polymeric phenolic pigment

Thirty-eight bacterial strains were isolated from waste water of olive oil mills, olives and soil in chemically defined media containing the pigment of these wastes as sole carbon source. Most of the organisms were Pseudomonas spp. Four of the six phenolic acids associated with polymeric pigments in olive oil waste degradation were used by three strains. Only one Pseudomonas strain was able to use five acids.     

Bacterial oxidation of cycloparaffinic hydrocarbons

A series of 10 branched-chain alkanes and 4 cycloalkanes were employed individually as elective culture substrates for bacteria in soil. Only 2-methylbutane and 2-methylpentane yielded bacteria, one each. Both bacteria grew at the expense of eachn-alkane from C₁ to C₂₂ but they were very selective for branched-chain substrates. Compounds with less branching were most readily utilized. Neither organism grew at the expense of various cycloalkanes as sole sources of carbon and energy. The 2-methylbutane isolate was studied in detail. Resting cell suspensions were able to produce α-ketoglutaric acid from each of the compounds the bacterium was able to utilize for growth. “Non-growth hydrocarbons” were also oxidized; in each case only neutral ketonic substances were detected. A series of cycloparaffins, from C₃- to C₈-membered rings, was oxidized to the corresponding cyclomonoketones. No oxidation products of cyclododecane (C₁₂), 1,4-cyclohexadiene (C₆) or benzene could be detected. The metabolic products identified are consistent with the formation of a cyclomonoalcohol as the immediate precursor of the ketone. The alcohol is formed from cycloalkanes, the cycloalkenes, and cycloalkene oxide as substrates. Alcohol formation from the first two probably takes place by independent parallel, rather than sequential, reaction pathways. The epoxide may be a non-obligate intermediate in the cyclomonoolefin conversion to the alcohol. Significant aspects of these conversions are discussed.     

Structure-antioxidant activity relationships of flavonoids and phenolic acids

The recent explosion of interest in the bioactivity of the the flavonoids of higher plants is due, at least in part, to the potential health benefits of these polyphenolic components of major dietary constituents. This review article discusses the biological properties of the flavonoids and focuses on the relationship between their antioxidant activity, as hydrogen donating free radical scavengers, and their chemical structures. This culminates in a proposed hierarchy of antioxidant activity in the aqueous phase. The cumulative findings concerning structure-antioxidant activity relationships in the lipophilic phase derive from studies on fatty acids, liposomes, and low-density lipoproteins; the factors underlying the influence of the different classes of polyphenols in enhancing their resistance to oxidation are discussed and support the contention that the partition coefficients of the flavonoids as well as their rates of reaction with the relevant radicals define the antioxidant activities in the lipophilic phase.     

Bacterial replicases and related polymerases

Bacterial replicases are complex, tripartite replicative machines. They contain a polymerase, Pol III, a β(2) processivity factor and a DnaX complex ATPase that loads β(2) onto DNA and chaperones Pol III onto the newly loaded β(2). Many bacteria encode both a full length τ and a shorter γ form of DnaX by a variety of mechanisms. The polymerase catalytic subunit of Pol III, α, contains a PHP domain that not only binds to prototypical ? Mg(2+)-dependent exonuclease, but also contains a second Zn(2+)-dependent proofreading exonuclease, at least in some bacteria. Replication of the chromosomes of low GC Gram-positive bacteria require two Pol IIIs, one of which, DnaE, appears to extend RNA primers a only short distance before handing the product off to the major replicase, PolC. Other bacteria encode a second Pol III (ImuC) that apparently replaces Pol V, required for induced mutagenesis in E. coli. Approaches that permit simultaneous biochemical screening of all components of complex bacterial replicases promise inhibitors of specific protein targets and reaction stages.     

Bacterial and fungal oxidation of dibenzofuran.

Cunninghamella elegans and a mutant strain (B8/36) of Beijerinckia both oxidized dibenzofuran to 2,3-dihydroxy-2,3-dihydrodibenzofuran. The bacterial metabolite was extremely unstable and, in the presence of acid, was rapidly converted into a mixture of 2- and 3-hydroxydibenzofuran. In contrast, the 2,3-dihydroxy-2,3-dihydrodibenzofuran formed by C. elegans was stable and only yielded 2- and 3-hydroxydibenzofuran when heated under acidic conditions. The results suggest that Beijerinckia B8/36 and C. elegans form the respective cis- and trans-isomers of 2,3-dihydroxy-2,3-dihydrodibenzofuran. C. elegans also oxidized dibenzofuran to 2- and 3-hydroxydibenzofuran under conditions that would not lead to the dehydration of the trans-dihydrodiol. These observations implicate the initial formation of dibenzofuran- 2,3-epoxide in the fungal oxidation of dibenzofuran. Beijerinckia B8/36 also produced a second unstable dihydrodiol that was tentatively identified as cis-1,2-dihydroxy-1,2-dihydrodibenzofuran. This compound gave 2-hydroxydibenzofuran as the major dehydration product and the cis relative stereochemistry was suggested by the isolation and characterization of an isopropylidine derivative. A preparation of cis-naphthalene dihydrodiol dehydrogenase and cell extracts of the parent strain of Beijerinckia oxidized both bacterial dihydrodiols to catechols. Cell extracts prepared from C. elegans catalysed an analogous oxidation of trans-2,3-dihydroxy-2,3-dihydrodibenzofuran to 2,3-dihydroxydibenzofuran. The latter product was also isolated and identified from culture filtrates. The results suggest that bacteria and fungi utilize different mechanisms to initiate the oxidation of dibenzofuran.     

Lignin and Mn peroxidase-catalyzed oxidation of phenolic lignin oligomers

The oxidation of phenolic oligomers by lignin and manganese peroxidases was studied by transient-state kinetic methods. The reactivity of peroxidase intermediates compound I and compound II was studied with the phenol guaiacol along with a beta-O-4 phenolic dimer, trimer, and tetramer. Compound I of both peroxidases is much more reactive than compound II. The rate constants for these substrates with Mn peroxidase compound I range from 1.0 x 10(5) M-1 s-1 for guaiacol to 1.1 x 10(3) M-1 s-1 for the tetramer. Reactivity is much higher with lignin peroxidase compound I with rate constants ranging from 1.2 x 10(6) M-1s-1 for guaiacol to 3.6 x 10(5) M-1 s-1 for the tetramer. Rate constants with compound II are much lower with Mn peroxidase exhibiting very little reactivity. The rate constants dramatically decreased with both peroxidases as the size of the substrate increased. The extent of the decrease was much more dramatic with Mn peroxidase, leading us to conclude that, despite its ability to oxidize phenols, Mn2+ is the only physiologically significant substrate. The rate decrease associated with increasing substrate size was more gradual with lignin peroxidase. These data indicate that whereas Mn peroxidase cannot efficiently directly oxidize the lignin polymer, lignin peroxidase is well suited for direct oxidation of polymeric lignin.     

Enhancement and inhibition of luminol chemiluminescence by phenolic acids

We explored the behaviour of a series of phenolic acids used as enhancers or inhibitors of luminol chemiluminescence by three different methods to determine if behaviour was associated with phenolic acid structure and redox character. All the phenolic acids inhibited chemiluminescence when hexacyanoferrate(III) was reacted with the phenolic acids before adding luminol. The redox character of these compounds was clearly related to structure. When hexacyanoferrate(III)-luminol-O₂ chemiluminescence was initiated by phenolic acid-luminol mixtures some phenolic acids behaved as enhancers of chemiluminescence, and others as inhibitors. We propose a mechanism to explain these findings. We found direct relationships between the redox character of the phenolic acids and the enhancement or inhibition of the chemiluminescence of the luminol–H₂O₂–peroxidase system and we propose mechanism to explain these phenomena.