94 research outputs found
Amplified ribosomal DNA restriction analysis for the characterization of <i>Azotobacteraceae</i>: a contribution to the study of these free-living nitrogen-fixing bacteria
No full textA 16S rRNA gene-based fingerprinting method was developed for the identification of Azotobacteraceae and tested onto 48 soil isolates and 28 reference strains belonging to the free-living nitrogen-fixing bacterial group and to the most common species found in soil samples. According to this method, the 16S rRNA gene was amplified using universal primers for Eubacteria and PCR products were subsequently digested with RsaI, HhaI, HpaII, FnuDII, and AluI. The analysis of the restriction profiles obtained showed that the method is able to define a unique species-specific phylotype (SSP) for each of the eight Azotobacteraceae species tested. Cluster analysis was successfully employed for the identification of members of the family Azotobacteraceae, being assignation into species of the isolates confirmed by means of partial 16S rRNA gene sequencing
Restoration of copper-contaminated wastewater through bacterial biosorbents
No full textNowadays accumulation of heavy metals (HM) in water bodies represents a serious environmental and human health threat. Mechanisms of water decontamination exploit bacterial exopolymeric substances (EPS) as active surfaces for binding HM cations. Biofilm formation on microporous carriers inoculated with specific metal-resistant bacterial strains, can represent an operative implementation with respect to planktonic systems to be applied in the upscale of wastewater treatment systems.
The aim of the present study is to investigate the feasibility of using a copper-resistant (MIC of 476 mg L-1) Serratia plymuthica strain As3-5a(5) in a biofilm-based system to remove Cu(II) from electroplating wastewaters.
The strain was previously characterized for EPS production (90 mg g-1 d.w.) and biofilm formation. In non-proliferating cell planktonic system, it removed up to 92% of Cu(II) from a 200 mg L−1 solution and 90% from Cu contaminated (30 mg L-1) wastewater. Metal desorption achieved by 0.1 M nitric acid was in the order of 50%.
In different biofilm-based systems strain As3-5a(5) exhibited various Cu(II) removal within 4-minute contact time: 42% when on calcium alginate beads, 55% on perlite gardening substrate and 92% on sintered glass beads. In sintered glass beads column systems, As3-5a(5) biofilm removed up to 92% of Cu(II) in solution.
EPS production, quantified either by extraction and spectrophotometric method and by specific Concanavalin-A fluorescent lectin analysis in flow cytometry, was higher from cells grown for 24 than 72 hours whereas maximum metal adsorption was achieved after 72 hours of incubation. As determined by NMR analysis, the prevalent monosaccharides were mannose and rhamnose at all incubation times.
Data obtained so far indicate that S. plymuthica strain As3-5a(5) is promising for the development of a biofilm-based system to eliminate heavy metals from industrial wastewaters. Beside this, further work is necessary to understand the role of EPS or other cellular outer layers in metal binding. This could be of help for optimizing the strain ability in larger scale bioreactors
Studio sulla biodiversità di Azotobacteraceae isolati in suoli del centro Italia mediante ARDRA
No full textA recent class of chemosensory neurons developed in mouse and rat.
No full textIn most animal species, the vomeronasal organ ensures the individual recognition of conspecifics, a prerequisite for a successful reproduction. The vomeronasal organ expresses several receptors for pheromone detection. Mouse vomeronasal type-2 receptors (V2Rs) are restricted to the basal neurons of this organ and organized in four families. Family-A, B and D (family ABD) V2Rs are expressed monogenically (one receptor per neuron) and coexpress with either Vmn2r1 or Vmn2r2, two members of family-C V2Rs. Thus, basal neurons are characterized by specific combinations of two V2Rs. To investigate this issue, we raised antibodies against all family-C V2Rs and analyzed their expression pattern. We found that six out of seven family-C V2Rs (Vmn2r2-7) largely coexpressed and that none of the anti-Vmn2r2-7 antibodies significantly stained Vmn2r1 positive neurons. Thus, basal neurons are divided into two complementary subsets. The first subset (Vmn2r1-positive) preferentially coexpresses a distinct group of family-ABD V2Rs, whereas the second subset (Vmn2r2-7-positive) coexpresses the remaining group of V2Rs. Phylogenetic reconstruction and the analysis of genetic loci in various species reveal that receptors expressed by this second neuronal subset are recent branches of the V2R tree exclusively present in mouse and rat. Conversely, V2Rs expressed in Vmn2r1 positive neurons, are phylogenetically ancient and found in most vertebrates including rodents. Noticeably, the more recent neuronal subset expresses a type of Major Histocompatibility Complex genes only found in murine species. These results indicate that the expansion of the V2R repertoire in a murine ancestor occurred with the establishment of a new population of vomeronasal neurons in which coexists the polygenic expression of a recent group of family-C V2Rs (Vmn2r2-7) and the monogenic expression of a recent group of family-ABD V2Rs. This evolutionary innovation could provide a molecular rationale for the exquisite ability in individual recognition and mate choice of murine species
Appunti sulla fisionomia del Cavalca – autore
No full textAn analysis of the technical terminology used by Domenico Cavalca with respect to his activity of translating Latin texts in vernacular language demonstrates that the Preacher friar’s linguistic choices are extremely well pondered. Indeed, the author’s voice emerges in characteristic wordings such as ›tutto dì veggiamo‹ and ›per esperienza veggiamo‹, which refer to a concrete factual experience and hence to the everyday reality of his audience. The use of this kind of expression, which presents ties to the period’s scientific and rhetoric literature, and which appears also in Dante’s and Boccaccio’s prose, is particularly frequent in Cavalca’s last work, the ›Esposizione del Credo‹. In fact, this treatise proves to be of crucial importance for his self-constitution as a Dominican author.An analysis of the technical terminology used by Domenico Cavalca with respect to his activity of translating Latin texts in vernacular language demonstrates that the Preacher friar’s linguistic choices are extremely well pondered. Indeed, the author’s voice emerges in characteristic wordings such as ›tutto dì veggiamo‹ and ›per esperienza veggiamo‹, which refer to a concrete factual experience and hence to the everyday reality of his audience. The use of this kind of expression, which presents ties to the period’s scientific and rhetoric literature, and which appears also in Dante’s and Boccaccio’s prose, is particularly frequent in Cavalca’s last work, the ›Esposizione del Credo‹. In fact, this treatise proves to be of crucial importance for his self-constitution as a Dominican author
In field activities of chlorinated ethene biodegradation: spatial evolution of the contaminated plume microbial community after biostimulation
No full textBackground information
Chloroethenes are ones of the main contaminants worldwide due to their intensive used in industrial sector as solvents, in particular tetrachloroethene (PCE) and trichloroethene (TCE). These compounds are hardly degraded by chemical and physical treatments, whereas they are efficiently dechlorinated in anaerobic and reductive conditions through organohalide respiration (OHR) pathway by organohalide respiring bacteria (OHRB). These bacteria use chloroethenes as electron acceptors and hydrogen as electron donor to replace each chlorine atom with hydrogen atoms forming ethene as final product. OHR keystone bacteria are Dehalococcoides (Dhc) and Dehalogenimonas belonging to Chloroflexi, and Geobacter belonging to Desulfuromonadia. Only Dehalococcoides mccartyi strains BTF08 and 195 and Candidatus Dehalogenimonas etheniformans are able to completely dechlorinate chloroethenes, indeed, cis-dichloroethene (cis-DCE) and vinyl chloride (VC) are hardly dechlorinated and hence are accumulated in contaminated plumes. However, these compounds are efficiently mineralized in aerobic condition by different bacteria: Mycobacterium, Nocardioides, Pseudomonas, Rhodococcus and Ralstonia (Mattes et al., 2010).
Bioremediation treatments exploit these two transformation pathways to remediate chloroethenes contaminated sites through their biostimulation. Addition of reducing substrates and air and nutrients enhances OHR and aerobic biodegradation, respectively, thus improving the remediation efficacy (Dolinova et al., 2017).
Main results
In this study, a contaminated aquifer interested by anaerobic and aerobic bio-stimulation treatments was characterized for bioremediation activity and evolution of microbial community along the path of the plume. Reducing substrates derived from food wastes and biorefinery by-products were tested for their ability to enhance OHR.
The OHR enhancement efficacy of three reducing substrates (engineering molasse, by-product of lycopene extraction and whey) was tested in groundwater microcosm set up using landfill water of two piezometers (Pz25 and Pz22). In microcosms with Pz25 water, the presence of substrates increased the dechlorination activity of all chloroethenes after 2 months. After 6 months, the dechlorination of PCE improved whereas the other chloroethenes accumulated in all microcosms. Accumulation of all chloroethenes, except for PCE, persists after 10 months of incubation. Comparison of concentrations after 6 months and after 10 months of incubation showed a slight recovery of OHR activity for the dechlorination of cis-1,2-DCE and VC in microcosms amended with molasse.
In Pz22 microcosms, after 2 months of incubation, all chloroethenes were efficiently dechlorinated except for cis-1,2-DCE in microcosms amended with molasse and control ones. TCE dechlorination showed an improvement in microcosms amended with molasses, instead, VC was faster dechlorinated in microcosms with the addition of by-product of lycopene extraction.
Consequently, for the remediation of the aquifer (17 ha) affected by multiple contamination (hydrocarbons and chlorinated solvents, 5’850 and 219’487 ug L-1, respectively) far exceeding law limits (Directive 2000/60/EC), one anaerobic permeable reactive bio-barrier (500 meter long) was established and supplemented by molasse. After about 4 months of operation, TCE and PCE showed a decrease of one order of magnitude about from 800 ug L-1 to 70 ug L-1, but accumulation of DCE and VC occurred (3’700 and 45’000 ug L-1, respectively) at the distal part of the contaminated plume (350 meter apart). The construction of an aerobic bio-barrier (enriched with N, P and air, through injection of 1.97 to 2.05 kg/day of urea, 1.09 to 1.12 kg/day of ammonium phosphate and 1.0-1.8 m3/h of air) led to the decrease of DCE and VC of one order of magnitude reaching 470 and 4’100 ug L-1, respectively.
Phylogenetic and functional biomarkers, characteristic of dechlorination and aerobic biodegradation pathways, were quantified through qPCR in situ to monitor the effects of biostimulations. OHR biomarkers (Dehalococcoides, Geobacter, tceA and vcrA) were present in the order of 105-107 gene copies L-1 also in aerobic biobarrier, underlining the heterogeneity of conditions in the aquifer. Gene copies L-1 of aerobic degradation functional gene (alkene monooxygenase, etnC), present in the order of 106-107, increased during the time in aerobic biobarrier, in concomitance with the formation of VC.
Illumina sequencing of 16S rRNA of the aquifer showed that each OHRB were present with a relative abundance of about 1%, except for Dehalogenimonas that is present with a relative abundance of about 4%. OHRB and bacteria involved in VC oxidation were correlated with ORP and electric conductivity. OHRB relative abundance increased with more negative value of ORP, instead VC oxidizing bacteria increased in combination with ORP value. On the other hands, OHRB and VC oxidizing bacteria were positively and negatively correlated with electric conductivity, respectively. Beta diversity of bacterial and archaeal community were positively correlated with Mn concentrations. Biostimulation treatments affected the composition of bacterial community. Indeed, the similarity of piezometers bacterial community was influenced more by the biostimulation treatment to which they are subjected than their position in the site. In anaerobic biobarrier, the addition of molasses decreased the presence of methanogens. The treatment determined a modification of the microbial community, which returned to the original composition at the distal part of the contaminated plume, being then primed afterward by the aerobic treatment.
Conclusions
The present study demonstrated that the use of food industry wastes as bio-stimulants is a feasible approach for the enhancement of dechlorination, in the prospective of sustainable bioremediation techniques and in frame with circular economy concepts
Mechanisms of Hexavalent Chromium Reduction by Rhodococcus qingshengii strain SC26
No full textChromium represents a serious threat for both human health and ecosystems equilibrium. It is mainly present in two stable inorganic forms: trivalent and hexavalent, the latter one being more toxic due to its high solubility and mobility in biological systems. The major pollution sources are electroplating and tannery industries. Among possible remediation strategies, the use of biological systems can be proposed since microorganisms interact with metals by passive adsorption processes and active enzymatic reactions.
In the present study, Rhodococcus quingshengii strain SC26 was characterized for its ability to resist to hexavalent chromium (MIC of 300 mg L-1) and to reduce up to 51.14 mg L-1 hexavalent to trivalent chromium in growing-cell conditions. The reduction was always paralleled by cell growth. Part of the metal was present on cell pellet (1.9 mg g-1). Not proliferating cells were not able to reduce/adsorb hexavalent chromium, thus excluding passive adsorption processes. Trials conducted with contaminated electroplating wastewaters are ongoing to assess the bioremediation potential of R. qingshengii strain SC26 in close-to-real scenarios
Enhancing Reductive Dechlorination of Chloroethenes using Agri-Food Wastes
No full textChloroethenes (CE) are widely used as solvents in industrial activities. Their intensive use and inadequate disposal methods have resulted in their penetration in permeable groundwater aquifers and affecting high-quality water availability worldwide (Bertolini et al., 2023). Although parental compounds such as tetrachloroethene (PCE) and trichloroethene (TCE) are toxic to humans, dehalogenation products 1,1- and 1,2(cis-trans)-dichloroethene (DCE) and vinyl chloride (VC) are carcinogenic. Biodegradation rate of bacterial organohalide respiration is limited by the availability of electron donors that limit the possibility to conduct complete dehalogenation to ethene. Adding fermentable reducing substrates that increase hydrogen and small organic acids, supports organo-halide respiring bacteria. Agrifood wastes represent a valuable source of bio-based substrates and enhance sustainability of bioremediation processes.
In this study, fermentable substrates (i.e. molasses, tomato extract, pomace, whey and pumpkin seed extract) were analyzed at a microcosm scale to evaluate their effects on reductive dehalogenation process. Real groundwater contaminated by 150-300 mg/L CE from landfill leachate was used. Physico-chemical parameters (pH, ORP, and chemical oxygen demand) and CE concentrations were monitored after 1, 4 and 6 month-incubation.
GC-MS analyses demonstrated CE biological dehalogenation over a 4-month incubation. The degradation efficiency of PCE was 70% higher in the presence of reducing substrates if compared to natural attenuation. Concurrently, the accumulation rate of VC was lower in all treatments added of waste-derived substrates, due to complete dehalogenation to ethene. Biomarkers for TCE and VC reductases (tceA, vcrA) and for Dehalococcoides 16S rRNA genes, quantified by real-time quantitative PCR, ranged from 107 to 109 gene copies/mL and were higher in substrate-amended trials. Molasses and tomato extract were more effective than other substrates in stimulating Dehalococcoides population growth and reductive dehalogenation genes tceA and vcrA compared to other substrates and natural attenuation. The impact of substrate addition on the microbial community is being investigated using 16S rRNA Illumina libraries. Data analyses are currently running.
Agri-food waste substrates, particularly molasses and tomato extract, significantly enhanced CE degradation and stimulated key dechlorinating bacteria. This approach not only promotes effective remediation of CE-contaminated sites but also provides a sustainable solution for waste valorization
EFFECTS OF REDUCING SUBSTRATES ADDITION ON CONTAMINATED AQUIFER MICROBIAL POPULATION AND THE DECHLORINATION ACTIVITY
No full textTetrachloroethene (PCE) and trichloroethene (TCE) (chloroethenes) are intensively used in industrial sector due to their physical and chemical characteristics (low inflammability) that makes them excellent solvents. These compounds are hardly degraded through physical and chemical remediation techniques; but some bacteria can transform them. In anaerobic and reductive conditions, chloroethenes can be dechlorinated through organohalide respiration (OHR) where one atom of chlorine was substituted with a hydrogen atom. This pathway is efficient in dechlorination of highly chlorinated compounds (PCE and TCE), but their daughter compounds (dichloroethene, DCE, and vinyl chloride, VC) are hardly transformed creating an accumulation of these compounds. They are oxidated in aerobic conditions. Chloroethenes are toxic for human being and TCE and VC are carcinogenic.
In anaerobic conditions, fermentable substrates can be added to increase reducing power available for OHR bacteria (biostimulation). In the prospective of a more sustainable bioremediation techniques, chose of reducing substrates are focused on food industrial waste that are no longer used with food purposes.
In this study two reducing substrates (engineering molasses and tomato peels) were tested to determine their effects on enhancement of OHR activity at laboratory scale.
The microcosms were analyzed through monitoring of chloroethenes transformation by GC-MS, and chemical and physical parameters. In addition, through monitoring of dechlorination rate of chloroethenes (GC-MS analysis), and phylogenetic and functional biomarkers (qPCR analysis), the addition of engineering molasses was analyzed at filed scale.
The addition of the two substrates effected OHR activity with an increase of dechlorination highly chloroethenes. In the aquifer, biomarkers characteristic of dechlorination pathways were present in high amount (105-106 gene copies L-1).
The research was supported by Inail (National Institute for Insurance against Accidents at Work) in BRIC research fundin
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