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Molecular, phylogenetic and functional characterization of Burkholderia sp. DBT1, a bacterial strain involved in polycyclic aromatic hydrocarbons (PAHs) degradation
Full text linkCon il termine bonifica biologica si definiscono un insieme di metodiche in grado di usufruire delle capacità metaboliche di microrganismi e/o piante, al fine di recuperare siti contaminati da sostanze pericolose. In caso di forti contaminazioni, tuttavia, la sola stimolazione dei microrganismi autoctoni – mediante aggiunta d’ammendanti e/o tramite aerazione del suolo - risulterebbe troppo lenta. L’aggiunta di un inocula batterico direttamente in suolo o, alternativamente, in piante selezionate al fine di aumentare il potenziale biodegradativo in planta, può aumentare l’efficienza nel recupero del sito contaminato. D’altra parte, la selezione di microrganismi opportuni a tal fine, riveste una fase critica per buon esito di un protocollo. In particolar modo, l’efficienza di degradazione verso i composti interessati, e la non pericolosità per uomo e/o animali, sono due aspetti da tenere in forte considerazione a monte di un loro eventuale sversamento in situ. A questo scopo, un’attenta caratterizzazione di ceppi microbici potenzialmente utilizzabili in protocolli di bonifica biologica appare di fondamentale importanza.
Nel nostro laboratorio è stato isolato da una matrice inquinata da IPA un ceppo batterico appartenente al genere Burkholderia, denominato Burkholderia sp. DBT1. Questo ceppo batterico è in grado di trasformare in maniera molto efficiente il dibenzotiofene a HFBT tramite la “via di Kodama”.
Lo scopo, quindi, è la caratterizzazione molecolare, filogenetica e funzionale del ceppo B. sp. DBT1 al fine di valutare il suo utilizzo in protocolli di bonifica biologica per il recupero di suoli contaminati da IPA. Gli obiettivi generali della sperimentazione sono stati:
- Identificare e sequenziare la regione a valle del frammento genico p51, al fine di valutare la presenza delle sequenze geniche mancanti nella via di degradazione di Kodama.
- Condurre uno studio filogenetico del ceppo, al fine di collocare il ceppo DBT1 all’interno di una delle specie di Burkholderia ad oggi conosciute, o se, invece, esso andrà a costituire una nuova specie a se stante. Sarà inoltre fondamentale valutare se esso appartiene ad una specie potenzialmente patogena (e.g. Bcc).
- Valutare il potenziale metabolico del ceppo DBT1 verso i composti IPA non solo di natura tiofenica, maggiormente rappresentati nei suoli contaminati da idrocarburi.
- Condurre uno studio finalizzato ad una valutazione tossicologica del ceppo DBT1 verso cellule animali e umane.
- Caratterizzare, mediante tecniche molecolari e biochimiche, ceppi endofiti isolati da pioppo ibrido - in relazione con il ceppo DBT1 -, potenzialmente utilizzabili in protocolli di bonifica biologica di suoli contaminati da IPA.
L’analisi condotta al fine d’identificare la regione a valle del frammento genico p51 ha permesso l’identificazione di due sequenze geniche. Le indagini d’omologia in banche dati hanno permesso di rilevare la funzione dei relativi enzimi. La prima sequenza genica, denominata dbtAa, codifica per la componente ferrodossina reduttasi dell’enzima ISP; mentre la seconda, denominata dbtE, codifica per l’enzima idratasi-aldolasi. Dai risultati ottenuti si può quindi affermare di aver identificato il completo set genico, e quindi enzimatico, coinvolto nella degradazione del DBT mediante il pathway di Kodama all’interno degli operoni p51 e pH1A nel ceppo DBT1.
Il soggetto del presente studio, B. sp. DBT1, ha mostrato un’interessante capacità metabolica nei confronti di molecole IPA – dibenzotiofene, fenantrene, naftalene e fluorene - sia se forniti come unica fonte di carbonio ed energia, sia in condizione di cometabolismo. In quest’ultimo processo un composto è degradato da un enzima prodotto da organismi impegnati in altre reazioni e la degradazione del composto inquinante è considerato un evento fortuito, da cui i microrganismi non traggono energia. Di conseguenza, non dovendo supportare la crescita microbica, possono essere degradate anche concentrazioni molto basse d’inquinante. Stabilite le potenzialità metaboliche del ceppo DBT1, è stato importante assicurare la sua non tossicità e pericolosità di un suo eventuale utilizzo. Gli studi tassonomici hanno dimostrato che il ceppo DBT1 appartiene alla specie fungorum, una specie in cui sono presenti alcuni membri che sono stati isolati da uomini e animali affetti da alcuni tipi di patologie. In quanto il ruolo di questi ceppi nel decorso della malattia, a parte per un singolo caso, non è stato ancora determinato, è stato ritenuto importante effettuare uno studio più approfondito al fine di valutare le capacità di produrre tossine da parte del ceppo DBT1 verso sistemi animali e umani. I risultati hanno chiaramente evidenziato che il ceppo DBT1 non è in grado di danneggiare né il potenziale di membrana cellulare, né il gradiente protonico mitocondriale.
Da recenti studi, un protocollo di bonifica biologica che ha dimostrato una buon’efficienza nel recupero di siti contaminati è risultato essere l’utilizzo di un sistema in grado di sfruttare la capacità della pianta di assorbire i composti tossici, associata alle capacità degradative dei microrganismi presenti in essa. La caratterizzazione effettuata sui ceppi endofiti isolati da pioppo ha evidenziato la presenza di ceppi IPA degradatori.
Tra questi ceppi, dieci appartengono alla specie fungorum uno alla specie sordidicola e l’ultimo identificato con il nome di Burkholderia sp. R-701, un ceppo appartenente alla specie sartisoli. Mentre l’identificazione di specie quali fungorum o sordidicola all’interno d’organismi superiori quali piante e/o funghi sono stati già documentati, per la prima volta si è isolato un ceppo della specie sartisoli in tessuti vegetali. Le successive analisi di PCR hanno sorprendentemente evidenziato la presenza degli operoni pH1A e p51 nei dieci ceppi endofiti di fungorum e nel ceppo R-701. Analisi PCR-DGGE e analisi di restrizione non hanno mostrato variazioni nella sequenza di questi operoni tra i ceppi endofiti, rilevando, tuttavia, una notevole differenza con la sequenza di p51 e pH1A del ceppo DBT1. Le differenze riscontrate tra i ceppi di fungorum isolati dal pioppo ed il ceppo DBT1 non si sono rilevate essere solo a livello genico. Infatti, successive analisi biochimiche e microbiologiche hanno evidenziato che il ceppo DBT1 risulta essere più efficiente nella degradazione del fenantrene e del DBT rispetto ai ceppi endofiti fungorum sopra descritti. Ovviamente, con i dati ad oggi ricavati non si può correlare i diversi genotipi degli operoni p51 e pH1A con le diverse efficienze degradative degli IPA. Questi risultati incoraggiano un possibile utilizzo di DBT1 come ceppo endofita del pioppo, essendo anch’esso appartenente alla specie fungorum. Concludendo, i risultati ottenuti da questo lavoro di tesi incentivano l’utilizzo del ceppo Burkholderia fungorum DBT1 in protocolli di bonifica biologica per il recupero di siti contaminati da composti IPA; e suggerisce una reale fattività di DBT1 come ceppo endofita in pioppo al fine di migliorare la biodegradazione in planta.Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities. These compounds are largely suspected to act as potential mutagens, teratogens as well as carcinogens. Moreover, their low aqueous solubility and, consequently, their low bioavailability are a great obstacle to microbial degradation. The word “bioremediation” has been used to describe the process of using microorganisms to degrade or remove hazardous compounds and wastes such as PAHs from the environment. Nevertheless, before developing an efficient protocol for bioremediation is necessary to perform an upstream study, in order to isolate, identify and characterize organisms suitable to this purpose.
Burkholderia sp. DBT1 is a bacterial strain identified in an oil refinery wastewater which can degrade DBT nearly completely through the Kodama pathway within three days. Aimed to clarify the effective potential and actual utilization of such strain in bioremediation protocol, different aspects of B. sp. DBT1 have been investigated.
- Identification of DNA sequences flanking p51 operon: Molecular characterization of strain DBT1 has showed that six of eight genes required for DBT degradation by Kodama pathway are present in two operons – p51 and pH1A. p51 genetic fragment harbor dbtC,Ab,ORF6,ORF7 replicative unit. The sequence of p51 genetic fragment stopped at the end of ORF 7 and the transcription terminator was not yet detected. Therefore, identification of DNA sequence flanking p51 operon was carried out in order to detect possible gene sequence downstream ORF 7.
- Taxonomic analysis: Taxonomic status of Burkholderia sp. DBT1 has never been resolved. It is important to remark that several species of Burkholderia can cause food poisoning or can behave as plant and animal pathogens. Furthermore, different strains belonging to the Burkholderia cepacia complex (Bcc) are involved in life-threatening infections of humans such as cystic fibrosis.
- Study of PAHs degrading activity: Since normally several organic pollutants contribute together to the contamination at different sites, isolation and characterization of microbes able to use a wide range of PAHs compounds as sole source of carbon and energy are of great interest in order to select useful candidates for applications in bioremediation.
- Toxicology and pathogenic analysis: Several Burkholderia species are common soil inhabitants, nevertheless some species of this genus are known as toxin producer. Therefore, some tests will be carried out to even investigate the eco-toxicological safety of strain DBT1 for environmental use.
- Study of endophytes bacterial strains: Once it is been clarified the metabolic, taxonomic aspect of strain DBT1, it results very important to set up an efficient protocol for a future application in open field (in situ). A new promise strategy is to use endophitic bacterial equipped with appropriate degradation pathway in order to improve in planta PAHs degradation. Thus, selection and study of bacterial strains able both to degrade PAHs and to colonize host plants (e.g. Aspen) in order to verify the bioremediation potential of plant-endophytic bacteria systems, using both molecular and physiologic analysis.
The work here presented has demonstrated that the hydratase-aldolase and ferredoxin reductase sequences, the two genes missing, are collocated downstream the putative sequence ORF 7 within p51 operon. Thus, the missing enzymes have been recovered, demonstrating that the whole set of enzyme involved in Kodama pathway degradation is harbored in p51 and pH1A operons.
Moreover, the results so far achieved suggest that the strain DBT1 presents a versatile metabolism towards PAHs, and this is an important trait for the possible use of this strain in environmental clean up. This strain is able to use fluorene, naphtalene, DBT and phenanthrene for growing, although growth on the first two compounds needs a pre-induction. Therefore, it can be suggested that phenanthrene is metabolized through 2-carboxycinnamic acid, phthalic acid and further metabilized in protocatechol. The PAHs degradation can occur even by a co-metabolism process.
The application of bacterial strains in environmental clean up is severely subject to another crucial pre-requisites: the ecotoxicological safety of the selected strain and its probative exclusion from pathogenic species such as Burkholderia cepacia complex. The data presented in this study indicate that strain DBT1 can be considered a member of the species fungorum, for which the name Burkholderia fungorum strain DBT1 is here proposed. Since the original report, B. fungorum was identified in a wide range of environment such as soil, plant-associated samples, in infections of the central nervous system of a pig and a deer, and in the respiratory secretions of people with cystic fibrosis. Therefore, the investigation about possible toxic effects by strain DBT1 has been considered of prominent significance in the present study; and bioassay to detect mitochondrial toxicity in mammalian cells by JC-1 and PI staining of human cell lines would be useful to investigate toxic microbial metabolites. Results so far achieved show that B. DBT1 and B. fungorum type strain was unable to damage mitochondrial and human cells membranes. However, it is important to underline that this strategy does not rule out the possibility that the strain investigated might be pathogenic under specific circumstances or on different targets not yet ascertained, such as to substances affecting the synthesis of proteins or nucleic acids or their regulation.
Besides, as cited before, the second strategy for a better use the bioremediation potential of plant-endophytic bacteria systems is focused on isolating, identifying and characterizing the bacteria that already exist as bacterial endophytes in plants and which are applyable to phytoremediation protocols. Poplar trees (Populus spp.) are commonly used as phytoremediation tools because they are perennial, hardy, tolerant to high concentration of organic compounds, highly tolerant to flooding, fast growing, easily propagated and have a wide range adaptation. Thus, a careful screening and characterization of endophytes from poplar plants growth on PAHs contaminated soils were carried out. The results obtained confirm that natural bacteria degrading recalcitrant compounds are largely present among endophytic populations of plants growth in contaminated sites, this could mean that endophytes have a role in metabolizing these substances. Moreover, Burkholderia is resulted be the genera mainly involved in PAHs degradation, and fungorum the species more representative. Interestingly, the majorities of these bacteria are involved in phenanthrene and DBT degradation, and harbor p51 and pH1A, the operons formerly identify in DBT1 strain. However, the subsequent DGGE and restriction analysis on these DNA fragments, showed the presence of a single genotype among the endophytic bacteria, but different from DBT1. The difference between strains isolated in Finland and DBT1 is not only at genetic level. In fact, B. sp. DBT1 resulted to be more efficient in the degradation towards PAHs tested, especially in the metabolism of DBT. Moreover, the results suggest the application of B. sp. DBT1 as poplar endophyte.
Eventually, the results obtained from this thesis work incentives the use of the strain Burkholderia fungorum DBT1 for a possible exploitation in bioremediation protocols of PHA-contaminated sites; moreover it suggest an actual use of such strain as endophytes in poplar plant in order to improve in planta degradation
Trichoderma longibrachiatum Evx1 is a fungal biocatalyst suitable for the remediation of soils contaminated with diesel fuel and polycyclic aromatic hydrocarbons
No full textTrichoderma sp. strain Evx1 was isolated from a semi-deciduous forest soil in Southern Italy. It decolorizes polynuclear organic dyes and tolerates high concentrations of phenanthrene, anthracene, fluoranthene, and pyrene. The ability of this ascomycete fungus to degrade polycyclic aromatic hydrocarbons was verified in vitro and confirmed by its strong phenoloxidase activity in the presence of gallic acid. Phylogenetic characterization of Trichoderma sp. Evx1 positioned this strain within the species Trichoderma longibrachiatum. The potential use of this species for the bioremediation of contaminated environmental matrices was tested by inoculating diesel-spiked soil with a dense mycelial suspension. The biodegradation percentage of the C12-40 hydrocarbon fraction in the inoculated soil rose to 54.2 ± 1.6 %, much higher than that in non-inoculated soil or soil managed solely by a combination of watering and aeration. The survival and persistence of T. longibrachiatum Evx1 throughout the bioremediation trial was monitored by PCR-DGGE analysis. The fungal strain was still present in the soil 30 days after bioaugmentation. These findings indicate that T. longibrachiatum Evx1 may be a suitable inoculum in bioremediation protocols for the reclamation of soils contaminated by complex mixtures of hydrocarbons
Thauera sp. Sel9, a new bacterial strain for polyhydroxyalkanoates production from volatile fatty acids
Full text linkThauera is one of the main genera involved in polyhydroxyalkanoate (PHA) production in microbial mixed cultures (MMCs) from volatile fatty acids (VFAs). However, no Thauera strains involved in PHA accumulation have been obtained in pure culture so far. This study is the first report of the isolation and characterization of a Thauera sp. strain, namely Sel9, obtained from a sequencing batch reactor (S-SBR) set up for the selection of PHA storing biomass. The 16 S rRNA gene evidenced a high sequence similarity with T. butanivorans species. Genome sequencing identified all genes involved in PHA synthesis, regulation and degradation. The strain Sel9 was able to grow with an optimum of chemical oxygen demand-to-nitrogen (COD:N) ratio ranging from 4.7 to 18.9. Acetate, propionate, butyrate and valerate were used as sole carbon and energy sources: a lag phase of 72 h was observed in presence of propionate. Final production of PHAs, achieved with a COD:N ratio of 75.5, was 60.12 ± 2.60, 49.31 ± 0.7, 37.31 ± 0.43 an
Burkholderia sp. DBT1 a promising bacterial strain for bioremediation protocols non-related to the Burkholderia cepacia complex (BCC)
No full textBurkholderia sp. DBT1 is a bacterial strain formerly isolated from the wastewater dicharge pipeline of an oil refinery located in Tuscany, Italy. It is cable of biodegrading dibenzothiophene (DBT) in liquid culture through the “Kodama pathway” within three days of incubation. Molecular characterization of the strain DBT1 has shown the presence of an unusual genetic structure. Actually, the genes involved in dibenzothiophene transformation are harbored in two operons (namely, p51 and pH1A) and show low similarity to both nah-like and phn-like genes. Since DBT results to be a recalcitrant compound and tends to bioaccumulate throughout the food chain, isolation and characterization of bacterial strains able to use it as sole source of carbon and energy is of great interest for bioremediation purposes. Nevertheless for a safe exploitation of Burkholderia sp. DBT1 in bioremediation protocols, the exclusion of such strain from the Burkholderia cepacia complex (BCC) is of prominent importance. Actually, members of this complex are responsible for opportunistic human infections. Thus, the objective of the present study was to investigate the taxonomic position of DBT1 within the genus Burkholderia, in order to demonstrate no affiliation of this strain to BCC. Both classical (API 20E, API 20 NE, fatty acid composition, carbon source utilization) and molecular (PCR protocols, DNA sequencing, DNA-DNA hybridization) analyses were carried out. Burkholderia DBT1 has been compared with strains belonging to its phylogenetic surrounding, (namely, B. fungorum, B. graminis, B. cepacia and B. caledonica). All results obtained indicate a strong relationship of DBT1 with B. fungorum. In particular, the sequencing of both 16S hypervariable regions (V3 and V6-V8) and housekeeping protein-coding genes (i.e. RecA and GyrB) evidenced such a high similarity with B. fungorum as well as a great divergence from B. cepacia strains. Moreover, the PCR reaction aimed to detect in DBT1 the presence of esmR, a molecular markers encoding for “B. cepacia epidemic strain marker” (BCESM), gave a negative result. Finally, the DNA-DNA hybridization analysis definitively revealed the affiliation of DBT1 strain to Burkholderia fungorum species, with a percentage of hybridization of 78,2 ± 2,9%
Diversity of bacterial endophytes in 3 and 15 year-old grapevines of Vitis vinifera cv. Corvina and their potential for plant growth promotion and phytopathogen control
No full texttThis study represents the first investigation on ecology of endophytic bacteria isolated from 3 and 15 year-old vine stems of Vitis vinifera cv. Corvina. The analysis was performed by means of culture-dependenttechniques. The obtained results showed that new grapevine endophytic genera are being discovered.Moreover, Bacilli and Actinobacteria are frequently isolated from 3 year-old plants, whereas Alpha- andGamma- Proteobacteria classes are more prevalent in the 15 year-old plants. Shannon–Wiener (H) indexand analysis of rarefaction curves revealed greater genus richness in young grapevine plants. Further-more, results evidenced an increase of genotypic group number within specific genera (e.g., Rhizobiumand Pantoea).Among isolated strains from 3 and 15 year-old stems, respectively, 34 and 39% produce siderophores;22 and 15% secrete ammonia; 22 and 21% produce indole-3-acetic acid; 8.7 and 41% solubilize phosphate.Besides, two strains isolated from 15 year-old grapevines showed 1-aminocyclopropane-1-carboxylatedeaminase activity. Antifungal activity analysis evidenced that two Bacillus strains possess growth antag-onistic effect toward all the tested fungal strains. Therefore, the present study extends our knowledge ofthe diversity of the endophytic bacteria by providing new insights into the complexity of the grapevinemicrobiome
Characterization of selected species of Pichia and Candida for their growth capacity in apple and grape must and their biofilm parameters
No full text: Pichia and Candida species include biofilm-forming yeasts able to spoil foods and beverages. Strains belonging to 10 Pichia and Candida species isolated from apples, grape musts, and wines were analysed. They were subjected to molecular typing and characterized for their ability to grow and ferment must for cider and wine production, and for their biofilm properties. All strains grew similarly in apple and grape must. Glucose-fermenting strains displayed differentiated fermentation performances. Great variation in SO2 and ethanol sensitivity was observed among the strains. Pichia manshurica strains showed high tolerance to both molecules. Eleven and five surface-spreading biofilm (MAT) phenotypes were identified in solid and liquid media, respectively. Strains produced biofilms with variable thicknesses and widths in culture tubes. Cell adherence and aqueous-hydrocarbon biphasic hydrophobicity assays were carried out. Some Pichia manshurica and P. membranifaciens strains exhibited a high capacity to form a thick biofilm and had high cell adherence and hydrophobicity values. These strains could be more likely to colonize the internal surfaces of tanks. This study evidenced that some Pichia and Candida strains can proliferate during apple and grape must fermentation and may be detrimental the beverage quality, due to their specific biofilm properties
A basic bottom-up approach for small systems of safe-water supply: A decentralized case study in Uganda
No full textIn developing countries, diarrhea is known as the major cause of burden among children. Diarrhea is associated to poor quality of drinking water, inadequate sanitation and insufficient hygiene behavior. This work introduces a bottom-up approach for the implementation of a borehole installation in conjunction with proper water handling in rural areas. A pre-intervention survey was performed as a basic decision tool, and a post-intervention survey was performed to evaluate the quality of the intervention. In particular, information was collected regarding the water source, the health status, the water related behavior, hygiene and on other issues. Furthermore, coliforms and fecal contamination of the water sources used during the dry season were determined. Prior to the intervention the monthly diarrhea incidence was estimated to be around 22.0% among children. Microbiological analysis showed that sources of water (river, swamp and waterhole) presented a high fecal contamination (>250 for river and swamp, 110 most probable number index 100 mL–1 for waterhole). After the intervention, the monthly diarrhea incidence dropped to 10.2% among children, showing a significant reduction of 11.8% (p < 0.01). Even though this represents an exciting result, more intervention projects at household level are required in order to further reduce the diarrhea incidence
Biodegradative potential of Burkholderia sp. DBT1in the abatement of polycyclic aromatic hydrocarbons
No full textPolycyclic aromatic hydrocarbons (PAHs) tend to accumulate in both anthropized and natural habitats as a result of incomplete combustion of fossil fuels. From the environmental point of view, the main characteristics of PAHs – namely scarce solubility in water, low bio-availability, and high persistence in soil and groundwater – are seriously troublesome. Most PAHs also exert toxic and mutagenic effects and are potentially dangerous to the biological systems. Of the PAHs occurring in soil and groundwater, about 0.04 - 5% (wt/wt) corresponds to sulfur heterocycles. Among these latter, dibenzothiophene (DBT) represents the prevailing compound, which is therefore taken as model chemical structure in studies dealing either with the biodegradation of organo-sulfur contaminants through the “Kodama pathway” or with petroleum bio-desulfurisation through the “4-S pathway”. Since several organic pollutants usually contribute together to the contamination at different sites, isolation and characterization of microorganisms able to degrade a wide range of substrates surely play an important role in the bio-reclamation of polluted areas. Burkholderia sp. DBT1 is a bacterial strain isolated from an oil refinery wastewater which can degrade DBT nearly completely through the “Kodama pathway” within three days. Molecular characterization of the strain DBT1 has shown the presence of an unusual genetic structure. Actually, strain DBT1 genes involved in dibenzothiophene transformation are harbored in two operons and show low similarity to both nah-like and phn-like genes. These particular features encouraged studies aimed at clarifying the possible role of Burkholderia DBT1 in the degradation of PAHs other than condensed thiophenes, frequently occurring in oil-contaminated sites. The growth of strain DBT1 was thus tested in minimal medium supplied with different PAHs. In this way, the strain DBT1 has been demonstrated to efficiently grow on naphthalene, fluorene and phenanthrene. Burkholderia DBT1 has been even proved to degrade 2-carboxybenzaldehyde, phthalic acid and protocatechol, which are common intermediates in the phenanthrene degradation pathway. On the other hand, 2-hydroxy-1-naphthoic acid and 1-hydroxy-2-naphthoic acid – both key intermediates within the two possible upper pathways of phenanthrene degradation – can not function as sole carbon and energy sources for the strain DBT1. RT-PCR analysis and growth tests have been performed with two mutants of Burkholderia DBT1 in order to verify the possible involvement of the two operons already identified in phenanthrene metabolism. Evidence has been gained that the transcription of both operons is activated in presence of phenanthrene. Moreover, the results so far achieved suggest that the strain DBT1 presents a versatile metabolism towards PAHs. This behavior is quite interesting for the possible exploitation of Burkholderia DBT1 in bioremediation protocols of PHA-contaminated sites
Effects of wildfire on the level of high molecular weight (HMW) hydrocarbon compounds in forest soil: analysis of HMW hydrocarbons-degrading microbial communities and comparison of different in-situ bioremediation protocols
No full textThe present study firstly investigated the composition of both bacterial and fungal communities selected in two sampling points within a forest area (North of Italy) that has been affected by wildfire. Several bacterial and fungal strains were obtained in pure cultures and taxonomical characterized. Furthermore, each strain was tested
for its capability of degrading HMW hydrocarbons through plate assay with aromatic dyes in order to establish their potential bioremediation activity. Afterwards, an 'in field' experiment was carried out by comparing two different in-situ bioremediation protocols by means of two commercial products: (i) biostimulation with a fertilizer compound and (ii) bioaugmentation with Trichoderma sp. EV strain. The chemical analyses showed that at the beginning of the experimental trial, the average concentration of C12-40 hydrocarbons was about 180 mg kg-1. This value exceeds the limit establish by the Italian law fixed at 50 mg Kg-1 (D. Lgs. 152/06). Eventually, the biostimulation resulted the most efficient protocol. In fact, the lowest levels - ≤ 50 mg HMW hydrocarbons kg-1 - were reached in 60 days. Interestingly, the inoculation of Trichoderma sp. EV also enhanced the C12-40 degradation in comparison to the natural attenuation (control), which conversely reached the lowest level after 270 days
Post-fire rehabilitation of forest soils through integrated bioremediation strategies: a case study
No full textCombustion of fores biomass generates dangerous contaminants including polycyclic aromatic hydrocarbons (PAHs). Thus, removal of these compounds is a pre-requisite to accelerate environmental restoration of fire-affected areas. Here, two different bioremediation strategies, namely soil bioaugmentation by means of the addition of a mycelial suspension of a Trichoderma sp. strain and soil biostimulation through the dispersion of a commercial landfarming formulation to enhance the native hydrocarbonoclastic microbial community by simply adjusting soil nutrients, were compared to verify the biotreatability of wildfire-generated toxic hydrocarbons (BTEX, LMW PAHs and C12-40 hydrocarbon fraction)
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