1,721,144 research outputs found
Arsenico nell’ambiente, il progetto “Bata” e le azioni di mitigazione per proteggere la salute
No full textFunctional biomarkers for monitoring propylene glicol degrading bacteria in contaminated sites
No full textSelezione di colture batteriche degradanti POP e loro monitoraggio in processi di bioarricchimento di suoli
No full textCaratterizzazione di popolazioni microbiche capaci di utilizzare inquinanti organici poco solubili in fase acquosa (NAPL)
No full textContributo di batteri PGP arsenico-resistenti nella mobilizzazione e traslocazione in Helianthus annuus (L.)
No full textPerformance of Cd-resistant rhizobacteria to improve Brassica napus growth under cadmium stress
No full textCadmium is one of the most toxic heavy metal for plants, inhibiting root and shoot growth and affecting nutrient uptake and homeostasis. Plant growth promoting rhizobacteria (PGPR) can improve plant nutrition and growth, competitiveness and responses to external stress factors.
The plant growth promoting activity of four cadmium-resistant rhizobacteria (Pseudomonas tolaasii ACC23, Pseudomonas fluorescens ACC9, Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14) with multiple PGP traits was assessed on canola (Brassica napus) in presence and in absence of Cd. The considered PGP traits were the production of indole acetic acid (IAA) and siderophores and the capability of consuming 1-aminocyclopropane-1-carboxylate (ACC), the immediate precursor of ethylene. All the studied strains had in vitro ACC deaminase (ACCD) activity. The strains produced IAA and siderophores more actively under Cd-stress and the ACCD activity of only two strains was reduced by the metal. Root elongation assay conducted on B. napus under gnotobiotic conditions demonstrated significant increases in root elongation of inoculated canola seedlings grown in the presence or in the absence of cadmium (from 21 to 104% and from 34 to 97%, respectively ) compared to the control plants. The pot culture experiment with treated (15 g Cd2+ g-1 dw) and un-treated soil clearly demonstrated the beneficial effects of the inoculations with P. tolaasii ACC23, P. fluorescens ACC9 and Mycobacterium sp. ACC14.
The PGPR protected plants from growth inhibition caused by the metal, as demonstrated by dry-weight biomass data, without influencing the specific accumulation of cadmium in root and shoot systems. However, total Cd uptake per plant significantly increased, thus resulting in a higher metal removal. In particular, the maximum growth and Cd uptake were obtained with P. tolaasii ACC23 and P. fluorescens ACC9.
The isolated bacteria c as inoculants to improve B. napus growth in the presence of toxic concentration of cadmium. Field experiment will confirm the PREP activity of the strains on plant growth in order to stabilize, revegetate and remediate metal-polluted soils
Isolation and characterization of arsenic resistant bacteria from arsenic contaminated soils
No full textGlenodinium sanguineum March. and the reddening phenomenon of Lake Tovel: biological and environmental aspects
No full textGlenodinium sanguineum March. is known to be responsible of reddening in alpine Lake Tovel (Trento, Italy) in Brenta's Dolomites. The dinoflagellate has no longer significantly bloomed since 1964 AD, failing to give red color to the lake's water. Nowadays this is an oligotrophic lake, but very few physical and chemical data are available for the period pre-1964 because many studies focussed on the taxonomic position of the algae and on the reddening mechanisms. Several hypothesis have been formulated over the years to explain the ending of the blooms, among which lower surface water temperatures due to modifications in the hydraulic regime and changes in nutrient status are the most accredited. Recently, short-term enclosure experiments demonstrated that phosphorus is a key factor in regulating the G. sanguineum blooming. In this review, we outline all the hypotheses formulated but not yet demonstrated over the years, in an effort to better understand the cause of the lack of the algal reddening phenomenon on Lake Tovel. Finally, new avenues for future studies are suggested with special reference to the elucidation of possible impact of environmental conditions on Glenodinium cycle and carotenogenesis
Improvement of Brassica napus growth under cadmium stress by cadmium-resistant rhizobacteria
No full textThis study focuses on the characterization of four bacterial isolates from heavy metal-polluted rhizosphere in order to examine their plant growth promoting (PGP) activity. The PGP activity on the canola (Brassica napus) of the strains which showed cadmium resistance and multiple PGP traits was assessed in the presence and in the absence of Cd2+. The strains, Pseudomonas tolaasii ACC23, Pseudomonas fluorescens ACC9, Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14 showed 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity. They also synthesized ACCD enzyme in vitro when 0.4 mM Cd2+ was added to the growth medium. The presence of the metal, however, reduced the ACCD activity in Alcaligenes sp. ZN4 and Mycobacterium sp. ACC14, while it did not affect the ACCD activity of P. tolaasii ACC23 and P. fluorescens ACC9. ACC9 and ACC23 produced indole acetic acid (IAA) and siderophores, while ACC14 produced only IAA. IAA and siderophores were produced more actively under Cd-stress.
Root elongation assays conducted on B. napus under gnotobiotic conditions demonstrated increases (from 34% up to 97%) in root elongation of inoculated canola seedlings compared to the control plants. Subsequently, the effect of inoculation with these strains on growth and uptake of Cd2+ in roots and shoots of canola was studied in pot experiments using Cd-free and Cd-treated (15 μg Cd2+ g−1 dw) soil. Inoculation with P. tolaasii ACC23, P. fluorescens ACC9 and Mycobacterium sp. ACC14 promoted the growth of plants at concentrations of 0 and 15 μg Cd2+ g−1 soil. The maximum growth was observed in the plants inoculated with P. tolaasii ACC23. The strains did not influence the specific accumulation of cadmium in the root and shoot systems, but all increased the plant biomass and consequently the total cadmium accumulation.
The present observations showed that the bacterial strains used in this study protect the plants against the inhibitory effects of cadmium, probably due to the production of IAA, siderophores and ACCD activity
Arsenic resistant bacteria isolated from agricultural soils of Bangladesh and characterization of arsenate reducing strains
Full text linkAims:
To analyse the arsenic-resistant bacterial communities of two agricultural soils of Bangladesh, to isolate arsenic-resistant bacteria, to study their potential role in arsenic transformation and to investigate the genetic determinants for arsenic resistance among the isolates.
Methods and Results:
Enrichment cultures were performed in a minimal medium in the presence of As(III) and As(V) to isolate resistant bacteria. Twenty-one arsenic-resistant bacteria belonging to different genera of Gram-positive and Gram-negative bacteria were isolated. The isolates, with the exception of Oceanimonas doudoroffii Dhal Rw, reduced 2 mmol l−1 As(V) completely to As(III) in aerobic conditions. Putative gene fragments for arsenite efflux pumps were amplified in isolates from Dhal soil and a putative arsenate reductase gene fragment was amplified from a Bacillus sp. from Rice soil.
Conclusions:
Phylogenetically diverse arsenic-resistant bacteria present in agricultural soils of Bangladesh are capable of reducing arsenate to arsenite under aerobic conditions apparently for detoxification purpose.
Significance and Impact of the Study:
This study provides results on identification, levels of arsenic resistance and reduction of arsenate by the bacterial isolates which could play an important role in arsenic cycling in the two arsenic-contaminated soils in Bangladesh
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