Molybdenum nutrition of isolates of four Aspergillus species

The molybdenum requirement for growth and conidial formation by Aspergillus flavus, A. terreus, and A. sulphureus was found to be 0.2 ppb, which was one-fifth that of an A. niger isolate. Molybdenum deficiency depressed growth, conidial formation, dry weight, soluble protein, and the specific activities of nitrate reductase, succinic dehydrogenase, and aconitase in all the isolates of Aspergillus studied, but the specific activities of catalase and peroxidase were depressed only in isolates of A. niger, A. terreus, and A. flavus. Also, molybdenum deficiency stimulated the specific activities of acid phosphatase and ribonuclease in the A. flavus isolate, although the specific activities of these enzymes decreased in other isolates. Eighteen hours after the addition of molybdenum (5 ppb) to molybdenum-deficient (0.02 ppb) cultures of A. niger, the specific activities of catalase, peroxidase and succinic dehydrogenase were restored in the absence of cycloheximide, while the specific activity of nitrate reductase was recovered even in the presence of the inhibitor. There was no effect on the specific activities of aconitase and acid phosphatase following the addition of molybdenum to molybdenum-deficient cultures of A. niger.     

Degradation of procyanidins by Aspergillus fumigatus: identification of a novel aromatic ring cleavage product

Aspergillus fumigatus was able to grow on apple-purified procyanidins (PCs). PCs concentration decreased 30% over the first 60 h of liquid fermentation. The mean degree of polymerization (DPn) of apple-purified PCs increased from 8 to 15 during the fermentation. A fungal enzyme extract from the liquid fermentation was used to study procyanidin B2 [(-)-epicatechin-(4beta-8)-(-)-epicatechin] degradation. The major degradation product (PB2-X) had a retention time of 10.5 min and a molecular mass at m/z 609. High-performance liquid chromatography/multiple fragment mass spectrometry (HPLC/MS(n)) was used for the structural characterization of PB2-X as well as that of thiolysis-treated PB2-X. Twelve fragment ions at m/z 565, 547, 457, 439 (two fragment ions), 421, 413, 377, 395, 351, 287 and 277 were completely identified. It was therefore deduced that the terminal unit of procyanidin B2 dimer was modified by an oxygenase from A. fumigatus leaving the extension unit intact. In addition, FT-IR analysis confirmed a lactone formation in (-)-epicatechin moiety involved in oxidative degradation. Two reaction schemes were postulated for the interpretation of the results.     

Catabolism of arylboronic acids by Arthrobacter nicotinovorans strain PBA

Arthrobacter sp. strain PBA metabolized phenylboronic acid to phenol. The oxygen atom in phenol was shown to be derived from the atmosphere using (18)O(2). 1-Naphthalene-, 2-naphthalene-, 3-cyanophenyl-, 2,5-fluorophenyl-, and 3-thiophene-boronic acids were also transformed to monooxygenated products. The oxygen atom in the product was bonded to the ring carbon atom originally bearing the boronic acid substituent with all the substrates tested.     

Regulation of chorismate mutase activity of various yeast species by aromatic amino acids

The regulatory properties of chorismate mutase, its cellular localization and isoenzyme pattern were investigated in 23 yeast species. All yeasts contained only a single form of the enzyme, which is localized exclusively in the cytosol. The enzyme activity from all sources was activated 3-(Rhodotorula aurantiaca) to 185-fold (Candida maltosa) by tryptophan. The tryphtophan concentration, which was necessary to obtain half maximum velocity was determined to be between 2 (Pichia guilliermondii) and 95 M (Yarrowia lipolytica). Ten yeast species possessed an enzyme that was inhibited by both phenylalanine and tyrosine. The chorismate mutase from four strains was inhibited only by tyrosine and the enzyme from two species was inhibited by phenylalanine alone. The enzyme inhibition by phenylalanine and tyrosine was completely reversed by tryptophan. Six enzyme sources were not inhibited and theY. lipolytica chorismate mutase was slightly activated by both amino acids.     

Catabolism of 3,5-dichlorosalicylate by Pseudomonas species strain JWS

Abstract A Pseudomonas sp. strain JWS was isolated from an enrichment culture with 3,5-dichlorosalicylate as the sole source of carbon and energy. Additionally, 3-chloro-, 5-chloro-, and 3,5-dibromosalicylate, but not 4-chlorosalicylate were mineralized by the organism. During growth on the chlorosalicylates, stoichiometric amounts of chloride were released into the culture medium. In the presence of both salicylate and 3,5-dichlorosalicylate, high activities were induced for the turnover of non-halogenated as well as halogenated salicylates. Enzyme activities assayed in crude cell extracts which are responsible for the oxidation of catechol and its halogenated derivatives as well as those for cycloisomerization of cis,cis -muconate and its 2,4-dichloro derivative provided indications for the involvement of inducible type II catechol 1,2-dioxygenase and muconate cycloisomerase in biodegradation of halogenated salicylates.     

Phylogenetic analysis of Aspergillus species using DNA sequences from four loci

DNA sequences were determined for beta tubulin (BT2), calmodulin (CF), ITS and lsu rDNA (ID) and RNA polymerase II (RPB2) from ca. 460 Aspergillus isolates. RPB2 and rDNA sequences were combined and analyzed to determine relationships in the genus and in the family Trichocomaceae. Eupenicillium species form a statistically supported clade with origins among the Aspergillus clades. A. crystallinus, A. malodoratus and H. paradoxus are members of the Eupenicillium clade. A. zonatus, A. clavatoflvus and W. spinulosa occur in a clade along with Hamigera sp. Other than these exceptional species, Aspergillus species and sections occur on three strongly supported clades that descend from a polytomy. Section Versicolores as a monophyletic group includes only A. versicolor and A. sydowii and is superfluous. The other sections were retained but modified. All four loci were used in genealogical concordance analysis of species boundaries. Fennellia flavipes and F. nivea are not conspecific with their supposed anamorphs A. flavipes and A. nivea. Synonymies were found for some species and more than 20 undescribed taxa were identified in genealogical concordance analysis. Newly discovered taxa will be described elsewhere. Possibly paralogous gene fragments were amplified with the BT2 primers in sections Nidulantes, Usti and Nigri. Use of nonhomologous sequences in genealogical concordance analysis could lead to false conclusions and so BT2 sequences were not used in analysis of those sections.     

Ochratoxin production by Aspergillus species.

Ochratoxin production was tested in 172 strains representing species in sections Fumigati, Circumdati, Candidi, and Wentii of the genus Aspergillus by an immunochemical method using a monoclonal antibody preparation against ochratoxin A. Ochratoxin A was detected in Aspergillus ochraceus, A. alliaceus, A. sclerotiorum, A. sulphureus, A. albertensis, A. auricomus, and A. wentii strains. This is the first report of production of ochratoxins in the latter three species. Ochratoxin production by these species was confirmed by high-performance thin-layer chromatography and by high-performance liquid chromatography. The chemical methods also indicated the production of ochratoxin B by all of the Aspergillus strains mentioned above.     

Catabolism of carbohydrates and organic acids and expression of nitrogenase by azospirilla

Fructose, galactose, L-arabinose, gluconate, and several organic acids support rapid growth and N2 fixation of Azospirillum brasiliense ATCC 29145 (strain Sp7) as a sole source of carbon and energy. Growth of Azospirillum lipoferum ATCC 29707 (strain Sp59b) is also supported by glucose, mannose, mannitol, and alpha-ketoglutarate. Oxidation of fructose and gluconate by A. brasiliense Sp7 and of glucose, gluconate, and fructose by A. lipoferum Sp59b was achieved through inducible enzymatic mechanisms. Both strains exhibited all of the enzymes of the Embden-Meyerhof-Parnas pathway, and strain Sp59b also possesses all the enzymes of the Entner-Doudoroff pathway. Fluoride inhibited growth on fructose (strains Sp7 and Sp59b) or on glucose (strain Sp59b) but not on malate. There was no activity via the oxidative hexose monophosphate pathway in either strain. There was greater activity with 1-phosphofructokinase than with 6-phosphofructokinase in both strains. Strain Sp59b formed fructose-6-phosphate via hexokinase, an enzyme that is lacking in strain Sp7. A. brasiliense and A. lipoferum exhibited the enzymes both of the tricarboxylic acid cycle and of the glyoxylate shunt; iodoacetate, fluoropyruvate, and malonate were inhibitory. A. brasiliense Sp7 could not transport [14C]glucose and alpha-[14C]ketoglutarate into its cells.     

Synthesis of lead nanoparticles by Aspergillus species

In the context of the current demand to develop green technologies in material synthesis, a natural process in the synthesis of lead particles by Aspergillus species to suit such technology is reported. The fungal strain was grown in medium containing different concentrations of lead (0.2-1.5 mM) to determine its resistance to heavy metals. The organism was found to utilize some mechanism and accumulate lead particles outside and inside the cell. The extracellular presence of lead particles in the range of 1.77-5.8 microm was characterized by scanning electron microscopy. The presence of particles of lead in the 5-20 nm size range was found on the cell surface, in the periplasmic space and in the cytoplasm and was analyzed by transmission electron microscopy.     

Aspergillic acids produced by mixed cultures of Aspergillus flavus and Aspergillus nidulans

A mixed culture of Aspergillus nidulans (GH79) and Aspergillus flavus (CMI 91019B) produced two antibiotics, designated VI and VII, which were not elaborated when either fungus was grown alone. Chemical and spectroscopic analysis of VI, the major component, indicated that this compound was identical to hydroxyaspergillic acid. The minor component, VII, was produced in too low a yield for its identity to be established. However, partial characterization suggests that this antibiotic also belongs to the aspergillic acid group of mycotoxins.     

Isolation and identification of a yeast strain capable of degrading four and five ring aromatic hydrocarbons

A yeast strain AEH was isolated from oil contaminated soil and identified by analysis of 18S and 26S ribosomal DNA sequences asPichia anomala. Strain AEH was capable of degrading naphthalene, phenanthrene and chrysene, singly, and benzo(a)pyrene in combination. The yeast degraded 5.36 mg naphthalene l^?1 within 2 days, and 5.04 mg phenanthrene l^?1 and 1.54 mg chrysene 1^?1 within 10 days. When a mixture of the four polycyclic aromatic hydrocarbons (PAHs) was treated at a concentration between 2.98 mg l^?1 and 6.89 mg l^?1, degradation rates were delayed for naphthalene and phenanthrene (3.79 mg l^?1 and, 4.20 mg l^?1 within 10 days, respectively), but enhanced for chrysene and benzo(a)pyrene (3.37 mg l^?1 and, 1.91 mg l^?1 within 10 days, respectively). In a binary system, all of the other 3 PAHs could be utilized as the carbon source for the cometabolic degradation of benzo(a)pyrene with naphthale ne as the best one.     

Degradation of methoxylated aromatic acids by Pseudomonas putida

J.E. TURNER AND N. ALLISON. 1995. A newly-isolated strain of Pseudomonas putida (HVA-1) utilized homovanillic acid as sole carbon and energy source. Homovanillate-grown bacteria oxidized homovanillate and homoprotocatechuate but monohydroxylated and other methoxylated phenylacetic acids were oxidized poorly; methoxy-substituted benzoates were not oxidized. Extracts of homovanillate-grown cells contained homoprotocatechuate 2,3-dioxygenase but the primary homovanillate-degrading enzyme could not be detected. No other methoxylated phenylacetic acid supported growth of the organism but vanillate was utilized as a carbon and energy source. When homovanillate-grown cells were used to inoculate media containing vanillate a 26 h lag period occurred before growth commenced. Vanillate-grown bacteria oxidized vanillate and protocatechuate but no significant oxygen uptake was obtained with homovanillate and other phenylacetic acid derivatives. Analysis of pathway intermediates revealed that homovanillate-grown bacteria produced homoprotocatechuate, formaldehyde and the ring-cleavage product 5-carboxymethyl 2-hydroxymuconic semialdehyde (CHMS) when incubated with homovanillate but monohydroxylated or monomethoxylated phenylacetic acids were not detected. These results suggest that homovanillate is degraded directly to the ring-cleavage substrate homoprotocatechuate by an unstable but highly specific demethylase and then undergoes extradiol cleavage to CHMS. It would also appear that the uptake/degradatory pathways for homovanillate and vanillate in this organism are entirely separate and independently controlled. If stabilization of the homovanillate demethylase can be achieved, there is potential for exploiting the substrate specificity of this enzyme in both medical diagnosis and in the paper industry.     

Biodegradation of aromatic carboxylic acids by Pseudomonas mira

Abstract Biodegradation of aromatic acids (ferulic, vanillic and sipapinic acids) by the soil bacterium Pseudomonas mira was studied by high-pressure liquid chromatography. The presence of glucose in the culture medium slowed down the degradation process but did not affect its mechanism. In addition to vanillic acid and hydroquinone, the products of degradation were found to include acetophenone derivatives. Probably, a mechanism capable of shortening the side chain by spontaneous decarboxylation of unstable 3- keto -3-phenylpropionic acid was present, in addition to the elimination of acetic acid via degradation of the cinnamic acid-type compounds.