Silvana Bernasconi

Distribution of catabolic pathways in some hydrocarbon-degrading bacteria from a subsurface polluted soil

Enrichment cultures on naphtha solvent were used to select aromatic hydrocarbon-degrading bacteria from a BTEX (benzene, toluene, ethylbenzene, xylene)-contaminated subsoil obtained from beneath a paint factory located in Milan, Italy. Fifteen isolated strains were studied for their different biodegradative capacities. Among these, 13 were able to grow on naphtha solvent. Ten were identified as Pseudomonas putida and three as Pseudomonas aureofaciens. Two other degraders were identified as Pseudomonas aeruginosa and Alcaligenes xylosoxidans subsp. denitrificans. Further molecular characterization of the isolates was carried out by randomly amplified polymorphic DNA analysis to ascertain that all the studied strains belonged to different haplotypes. The isolates were characterized for the presence of genes encoding for toluene dioxygenase, xylene monooxygenase and catechol 2,3-dioxygenase by polymerase chain reaction analysis and by Southern analysis. P. putida strain CM23, which showed homology with xylA,M, xylE and todC1C2BA genes, possessed multiple pathways which enabled the strain to grow on benzene, toluene and m-xylene.

Nutritional Traits of Bean (Phaseolus vulgaris) Seeds from Plants Chronically Exposed to Ozone Pollution

The effect of chronic exposure to ozone pollution on nutritional traits of bean ( Phaseolus vulgaris L. cv. Borlotto Nano Lingua di Fuoco) seeds from plants grown in filtered and nonfiltered open-top chambers (OTCs) has been investigated. Results showed that, among seed macronutrients, ozone significantly raised total lipids, crude proteins, and dietary fiber and slightly decreased total free amino acid content, although with a significant reduction of asparagine, lysine, valine, methionine, and glycine, compensated by a conspicuous augmentation of ornithine and tryptophan. Phytosterol analysis showed a marked increase of beta-sitosterol, stigmasterol, and campesterol in seeds collected from nonfiltered OTCs. With regard to secondary metabolites, ozone exposure induced a slight increase of total polyphenol content, although causing a significant reduction of some flavonols (aglycone kaempferol and its 3-glucoside derivative) and hydroxycinnamates (caffeic, p-coumaric, and sinapic acids). Total anthocyanins decreased significantly, too. Nevertheless, ozone-exposed seeds showed higher antioxidant activity, with higher Trolox equivalent antioxidant capacity (TEAC) values than those measured in seeds collected from filtered air.

Biotransformation of ferulic acid and related compounds by mutant strains of Pseudomonas fluorescens

Pseudomonas fluorescens strain FE2 isolated in the presence of ferulic acid was able to grow on hydroxylated and methoxylated compounds bearing the hydroxyl group in the para position. By ethylmethansulphonate (EMS) and transposon mutagenesis, mutants unable to utilize ferulic acid have been selected. The metabolic characterization of the wild-type strain and its mutants indicates that ferulic acid was degraded through the formation of vanillic acid. Mutant FE2B in co-oxidation experiments with glutamate, is able to transform ferulic and dihydroferulic acid into vanillic acid, 4-hydroxycinnamic acid and 3 (4-hydroxyphenyl)-propanoic acid into 4-hydroxybenzoic acid, and 3-hydroxycinnamic acid into 3-hydroxybenzoic acid. The bioconversion of hydroxylated aromatic substrates by the FE2B mutants suggests that the presence of a hydroxyl group on the aromatic ring is required for deacetylase activity.

Degradation of 2,4,6‐trichlorophenol by a specialized organism and by indigenous soil microflora: bioaugmentation and self‐remediability for soil restoration

A selected mixed culture and a strain of Alcaligenes eutrophus TCP were able to totally degrade 2,4,6‐TCP with stoichiometric release of Cl−. In cultures of Alc. eutrophus TCP, a dioxygenated dichlorinated metabolite was detected after 48 h of incubation. Experiments conducted with soil microcosms gave evidence that : the degradative process had a biotic nature and was accompanied by microbial growth ; the soil used presented an intrinsic degradative capacity versus 2,4,6‐TCP ; the specialized organism used as inoculum was effective in degrading 2,4,6‐TCP in a short time. These results could be utilized for the adoption of appropriate remediation techniques for contaminated soil.

Bioconversion of substituted styrenes to the corresponding enantiomerically pure epoxides by a recombinant Escherichia coli strain

Abstract Enantiomerically pure epoxides are produced by bioconversion of the corresponding styrenes using a recombinant Escherichia coli strain containing the styrene monooxygenase gene cloned from Pseudomonas fluorescens ST. Different procedures were used to optimise yields and to permit product isolation. Conversion rates depend on the position and nature of the styrene substituent.

Phytosterols in grapes and wine, and effects of agrochemicals on their levels

To improve the knowledge on the chemical diversity and complexity of grapevine, we investigated the plant sterol content of berry and seed tissues at pre-véraison and véraison stages in 2009 and 2010. We also assessed the effects of benzothiadiazole and chitosan elicitors on content of sterols in grapes and their levels in the corresponding experimental wines. β-Sitosterol was the most abundant component in berry tissues, in both growth stages and years, with the highest amounts in the flesh and skin at pre-véraison and véraison, respectively. Stigmasterol and campesterol were present in lower concentrations in both phenological stages and vintages. During the transition from pre-véraison to véraison, phytosterols decreased in all tissues, in both years, apart from stigmasterol in seeds. In addition, the results showed that the plant activators were more effective than conventional fungicides in rising the levels of sterols, particularly β-sitosterol, both in grapes and in microvinificates.

Metabolism of lignin-related compounds by Rhodococcus rhodochrous: bioconversion of anisoin

SummaryThe ability of the nocardioform actinomycete Rhodococcus rhodochrous to metabolize selected lignin model compounds was studied. The compounds studied included cinnamic and ferulic acids and dimers possessing intermonomeric linkages that are characteristic of the lignin molecule. R. rhodochrous reduced the carbonyl group of anisoin, a 1,2-diarylethane (β-1) structure to (1R,2R)-1,2-bis(4-methoxyphenyl)ethane-1,2-diol with an enantiomeric excess of .98%. Cleavage of 1,2-diarylethane and β-O-4 structures by this strain could not be detected under our metabolic conditions.

3-chloro-, 2,3- and 3,5-dichlorobenzoate co-metabolism in a 2-chlorobenzoate-degrading consortium: role of 3,5-dichlorobenzoate as antagonist of 2-chlorobenzoate degradation. Metabolism and co-metabolism of chlorobenzoates.

A study was made of the metabolic and co-metabolic intermediates of 2- and 3-chlorobenzoate, 2,3- and 3,5-dichlorobenzoate to elucidate the mechanism(s) involved in the negative effects observed on the growth of a chlorobenzoate-degrading microbial consortium in the presence of mixed chlorobenzoates. 2-Chloro-muconate accumulated as the end-product in the cultural broths of the microbial consortium during growth on 2-chlorobenzoate; the same 2-chloromuconate was identified in the reaction mixtures of resting cells pre-grown on 2-chlorobenzoate and exposed to 3-chloro- and 2,3-dichlorobenzoate, while in similar experiments 1,2-dihydroxy-3,5-dichloro-cyclohexa-3,5-dienoate was detected as dead-end product of 3,5-dichlorobenzoate co-metabolism. These results suggest an initial degradative attack by 2-chlorobenzoate induced dioxygenase(s). The role of 3,5-dichlorobenzoate as an antagonist of 2-chlorobenzoate degradation was also studied: in the presence of mixed 2-chloro- and 3,5-dichlorobenzoate, the 3,5-dichlorobenzoate preferential uptake by the resting cells of the chlorobenzoate-degrading consortium was observed. 2-Chlorobenzoate entered the cells only after the complete removal of the co-substrate. In growing cells experiments, the addition of 1,2-dihydroxy-3,5-dichloro-cyclohexa-3,5-dienoate, the 3,5-dichlorobenzoate co-metabolite, to 2-chlorobenzoate exerted the same antagonistic effect of the parent compound, inhibiting both the microbial growth and the degradative process. These data are discussed, allowing us to attribute the inhibitory effects observed to a substrate/co-substrate competition, though other additional causes may not be totally excluded.

Effects of elicitors and Ca2+ deprivation on the levels of sterols and 1α,25-dihydroxy vitamin D3 in cell cultures of Solanum malacoxylon

1α,25-dihydroxy vitamin D3 [1α,25(OH)2D3], the hormonal form of vitamin D3 that is essential for the maintenance of calcium-phosphorus homeostasis in birds and mammals, has been found in several plants. In order to study the metabolic role of 1α,25(OH)2D3 in plant cells, we monitored the changes of cellular levels of 1α,25(OH)2D3 in cell suspension cultures of Solanum malacoxylon Sendt. under different experimental conditions. We also measured the levels of cholesterol, the assumed precursor of vitamin D3, and other end-product sterols such as β-sitosterol, stigmasterol and campesterol. It was found that when cells are incubated in a calcium-deprived medium, the level of 1α,25(OH)2D3 increases markedly within a few hours. Treatment with methyl jasmonate (MeJ), a linolenic acid-derived compound that accumulates during wounding stress, was found to reduce the cellular level of 1α,25(OH)2D3 and to promote its secretion into the culture medium. After treatment with cellulysin, a cellulase of fungal origin, the metabolite was no longer detectable, either in the medium or in the cells. Calcium deprivation in the medium and treatment with the elicitors MeJ and cellulase lowered the cellular level of all the sterols tested. The possible role of 1α,25(OH)2D3 is discussed in light of these results.

Biotransformation of alkyl and aryl carbonates. Microbial degradation

SummaryAn enriched mixed culture was successfully grown on model alkyl and aryl carbonates. These compounds were degraded by microorganisms at different rates.P-Chlorophenyl-2-octyl carbonate andp-nitrobenzyl-2-octyl carbonate were metabolized through the formation ofp-chlorophenol andp-nitrobenzyl alcohol respectively. A strain ofAcinetobacter calcoacefcus isolated from the mixed culture utilized phenyl-2-octyl carbonate by an intracellular hydrolase to phenol and 2-octanol which were further metabolized.