1,721,033 research outputs found
Influence of humic acids on laurel growth, associated rhizosphere microorganisms, and mycorrhizal fungi
No full textIncreasing concentrations of humic acids were tested in order to determine their effects on the microbial rhizosphere and the growth of laurel (Laurus nobilis L.). Plants that were treated with 300 mg kg-1 of humic acids had the heaviest weights of both fresh and dry shoots; however, doses of 3000 mg kg-1 were highly phytotoxic and inhibited the growth of laurel. Total aerobic bacteria and actinomycetes were stimulated by doses of 1500 and 3000 mg kg-1 of humic acids at the first harvest. Nevertheless, at the end of the experiment no significant differences were found among the different doses. The number of fungi living in the laurel rhizosphere was not affected by any concentration of humic acids. Vesicular-arbuscular mycorrhizal (VAM) colonization was only slightly affected by the addition of increasing concentrations of humic substances to the soil, while the hyphal growth of Glomus mosseae was reduced
Humic acids stimulate growth and activity of in vitro tested axenic cultures of soil autotrophic nitrifying bacteria
No full textIn the present study, the effect of humic acids on activity and growth of Nitrosomonas europaea and Nitrobacter agilis was investigated in vitro under axenic conditions. Humates from compost-stabilized vegetable waste or leonardite were added to the chemolithotrophic culturing medium at concentrations of 0, 5, 50 and 100 mg l -1. It was found that both types of humic acids increased either NH 4/ + or NO 2 oxidation and cell growth of nitrifying bacteria in a dose-independent manner. By combining these results with data from a comparative growth evaluation of N. agilis based on possible utilization of humates or pyruvate in heterotrophic conditions, evidence was obtained that nitrifiers cannot use humic acids as an alternative carbon and energy source. Thus, the stimulating effect of this fraction of soil organic matter on chemolithotrophic ammonia and nitrite oxidizers might be attributed to an increase in microbial membrane permeability favouring a better utilization of nutrient
Bonifica biologica di suoli contaminati mediante sfruttamento della biodegradazione indotta dalla rizosfera
No full textBiodegradation of 4-(1-nonyl)phenol by axenic cultures of the yeast Candida aquaetextoris. Identification of microbial breakdown products and proposal of a possible metabolic pathway
No full textCandida aquaetextoris, a yeast recently described for its ability to use 4-(1-nonyl)phenol (pNP) as the sole carbon and energy source
in aerobic conditions, has been studied in order to determine the degradation products deriving from the growth on such a compound which
is of environmental concern because of its proved toxicity to several organisms. Two main metabolites, namely trans-4-hydroxy-cinnamic
acid and 4-hydroxy-acetophenone (4-acetylphenol), have been identi'ed through either TLC and NMR spectrometry analyses of liquid
substrate from cultures of C. aquaetextoris grown on pNP, with 4-acetylphenol that accumulates without any further degradation. These
'ndings suggest that C. aquaetextoris might metabolise pNP via terminal oxidation of the alkyl chain, followed by a beta-oxidation pathway.
On the basis of this evidence, a novel metabolic route for the microbial degradation of 4-(1-nonyl)phenol, at least in certain yeasts, is
proposed
Mesocosm‐based simulations to optimize a bioremediation strategy for the effective restoration of wildfire‐impacted soils contaminated with high‐molecular‐weight hydrocarbons
Full text linkAims: We obtained four microbial isolates from soil exposed to forest fire and evaluated their potential bioremediation activity when combined with a biosurfactant-producing bacterial strain for the decontamination of wildfire-impacted soil polluted with high-molecular-weight (HMW) hydrocarbons. Methods and Results: We established mesocosm trials to compare three bioremediation strategies: natural attenuation, bioaugmentation and biostimulation. Chemical analysis, culture-dependent and culture-independent methods were used to evaluate the bioremediation efficiency and speciation of the microbial cenoses based on these approaches. After treatment for 90 days, bioaugmentation removed 75·2–75·9% of the HMW hydrocarbons, biostimulation removed 63·2–69·5% and natural attenuation removed ~22·5%. Hydrocarbon degradation was significantly enhanced in the mesocosm supplemented with the biosurfactant-producing bacterial strain after 20 and 50 days of treatment compared to the other bioremediation strategies. Conclusions: We found that the bioaugmentation approach was more effective than biostimulation and natural attenuation for the removal of HMW hydrocarbons from fire-impacted soil. Significance and Impact of the Study: Our study showed that micro-organisms from wildfire-impacted soil show significant potential for bioremediation, and that biosurfactant-producing bacterial strains can be combined with them as part of an effective bioremediation strategy
Influenza degli acidi humici estratti da compost sull'attivitá dei batteri nitrificanti chemiolitotrofi del terreno: possibili implicazioni negli interventi di bonifica biologica dei siti contaminati
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Bacteria from black crusts on stone monuments can precipitate CaCO3 allowing the development of a new bio-consolidation protocol for ornamental stone
No full textThe microbial precipitation of CaCO3 is an emerging strategy for the consolidation of decayed limestone. Strains of Bacillus sp. and Micrococcus sp. isolated from black crusts were selected by polycyclic aromatic hydrocarbon enrichment culture and tested for their ability to precipitate CaCO3 by induced mineralization. Among the isolates, Bacillus sp. A2, B1, B5 and Micrococcus sp. A10 produced the largest quantities of biogenic calcite. Stone bio-consolidation was then tested using Carbogel as a carrier. The most efficient bio-cementation on limestone slabs was achieved by Bacillus sp. A2 and B1 and Micrococcus sp. A10. Bio-consolidation treatments were also applied to fragmented stones from the Church of Santa Maria dei Miracoli by inoculating the three bacterial strains individually or as a mixture. Bacillus sp. A2, Micrococcus sp. A10 and the mixture achieved the most efficient consolidation. Our data showed that Carbogel provides an appropriate substitute for natural biofilm formation in bio-consolidation protocols. Scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed calcified bacterial cells filling the pores of stone specimens, increasing the calcium content by 100% more than a non-inoculated control treatment under the same conditions. Our new bio-consolidation protocol therefore provides an effective strategy to prevent the further deterioration of stone monuments
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