Browsing by Author "Carvalho, Maria F."
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- Arbuscular mycorrhizal fungi are an alternative to the application of chemical fertilizer in the production of the medicinal and aromatic plantCoriandrum sativumLPublication . Oliveira, Rui S.; Ma, Ying; Rocha, Inês; Carvalho, Maria F.; Vosátka, Miroslav; Freitas, HelenaThe widespread use of agrochemicals is detrimental to the environment and may exert harmful effects on human health. The consumer demand for organic food plants has been increasing. There is thus a rising need for alternatives to agrochemicals that can foster sustainable plant production. The aim of this study was to evaluate the potential use of an arbuscular mycorrhizal (AM) fungus as an alternative to application of chemical fertilizer for improving growth performance of the medicinal and aromatic plant Coriandrum sativum. Plants were inoculated with the AM fungus Rhizophagus irregularis BEG163 and/or supplemented with a commercial chemical fertilizer (Plant Marvel, Nutriculture Bent Special) in agricultural soil. Plant growth, nutrition, and development of AM fungus were assessed. Plants inoculated with R. irregularis and those supplemented with chemical fertilizer displayed significantly improved growth performances when compared with controls. There were no significant differences in total fresh weight between plants inoculated with R. irregularis or those supplemented with chemical fertilizer. Leaf chlorophyll a + b (82%), shoot nitrogen (44%), phosphorus (254%), and potassium (27%) concentrations increased in plants inoculated with R. irregularis compared to controls. Application of chemical fertilizer inhibited root mycorrhizal colonization and the length of the extraradical mycelium of R. irregularis. Inoculation with R. irregularis was equally or more efficient than application of chemical fertilizer in promoting growth and nutrition of C. sativum. AM fungi may thus contribute to improve biologically based production of food plants and reduce the dependence on agrochemicals in agriculture.
- Biodegradation of mono-, di- and trifluoroacetate by microbial cultures with different originsPublication . Alexandrino, Diogo A.M.; Ribeiro, Inês; Pinto, Luís M.; Cambra, Rafael; Oliveira, Rui S.; Pereira, Filipe; Carvalho, Maria F.This work focused on the biodegradation of three structurally related fluoroacetates (FAs), mono- (MFA), di- (DFA) and trifluoroacetate (TFA), using as microbial inocula samples collected from a site with a long history of industrial contamination and activated sludge obtained from a municipal wastewater treatment plant. Biodegradation experiments were carried out under different modes of substrate supplementation, which included (i) FAs fed as sole carbon sources; (ii) FAs (only for DFA and TFA) fed in co-metabolism with sodium acetate; and (iii) mixtures of MFA with DFA or TFA. Biodegradation of the target compounds was assessed through fluoride ion release. Defluorination was obtained in the cultures fed with MFA, while DFA and TFA were recalcitrant in all tested conditions. When present in mixture, DFA was shown to inhibit biodegradation of MFA, while TFA had no effect. A total of 13 bacterial isolates obtained from MFA degrading cultures were found to degrade 20mgL-1 of this compound, as single strains, when supplemented as a sole carbon source. Sequencing of the 16S rRNA gene indicated that among these degrading bacteria only Delftia acidovorans had been previously reported to be able to degrade MFA. This work shows that, despite their similar chemical structures, biodegradation of the three tested FAs is very distinct and draws attention to the unknown impacts that the accumulation of DFA and TFA may have in the environment as a result of their high recalcitrance.
- Combined effects of temperature and dietary lipid level on body composition, growth, and freshness profile in european seabass, dicentrarchus labraxPublication . Cardoso, Patrícia G.; Gonçalves, Odete; Cavalheri, Thais; Amorim, Vânia E.; Cao, Weiwei; Alexandrino, Diogo A. M.; Jia, Zhongjun; Carvalho, Maria F.; Vaz-Pires, Paulo; Ozório, Rodrigo O. A.The effects of increasing temperature and dietary lipid level on the body composition, growth performance, and freshness profile of the European seabass (Dicentrarchus labrax) were evaluated through a fish trial lasting 56 days. Findings demonstrated that fish reared at 24 °C presented a lower lipid level and a higher daily growth index than those reared at 20 °C. On the other hand, the sea bass condition index did not change among treatments. Additionally, sensory analysis (the Quality Index Method) and microbiological analysis revealed that fish reared at 24 °C showed better freshness conditions than those at 20 °C. Nevertheless, the dietary lipid level did not have any influence on fish freshness conditions. Therefore, our data suggest that the increase in temperature to 24 °C is beneficial for the growth and freshness profile of this particular species in aquaculture.
- Exploring the possible link between fluoride sensitivity and bacterial defluorinationPublication . Maia, Tiago; Carvalho, Maria F.; Alexandrino, Diogo A. M.; Alexandrino, DiogoFluoorganic compounds are ubiquitous environmental pollutants due to their widespread use and high environmental persistence, mostly attributed to the stability of their carbon-fluoride bonds. The biotransformation of these compounds has been observed in some microorganisms, but defluorination (cleavage of carbon-fluorine bonds) remains the limiting step. Intracellular accumulation of fluoride occurs during microbial defluorination, which can cause several toxic effects. This work hypothesizes that intracellular fluoride stress may potentially affect the defluorination process in bacteria, limiting this critical catabolic step for the eventual mineralization of fluoroorganic pollutants. Fluoride sensitivity was first ascertained in defluorinating bacteria Labrys portucalensis F11 and Delftia acidovorans MFA5 (known degraders of fluorobenze1 and fluoroacetate2, respectively), with an Escherichia coli strain as the non-defluorinating control. Sensitivity was tested for increasing concentrations of f luoride (0-0.6 mM NaF) both in oligotrophic (minimal salts medium with acetate) and mesotrophic media (Nutrient Broth), based on bacterial growth inhibition for 48 hours at 28 ºC. After ascertaining their sensitivity thresholds, these strains are now being tested for their defluorination ability, against their preferred fluorinated substrates, when exposed to the NaF concentration with the highest observed growth inhibition. Results showed that fluoride stress was more severe in oligotrophic media, with 0.4 mM NaF presenting the highest growth inhibition among tested strains. Strain MFA5 was also shown to be the least sensitive to fluoride, while F11 was the most affected. Conclusions: Fluoride can exert cytostatic effects even in bacterial strains with proven ability to biodegrade fluorinated compounds. These results will allow to enlighten the ties between fluoride sensitivity and bacterial defluorination, thus broadening the knowledge on influencing factors of a critical catabolic reaction.
- Improved grain yield of cowpea (Vigna unguiculata) under water deficit after inoculation with Bradyrhizobium elkanii and Rhizophagus irregularisPublication . Oliveira, Rui S.; Carvalho, Patricia; Marques, Guilhermina; Ferreira, Luís; Pereira, Sandra; Nunes, Mafalda; Rocha, Inês; Ma, Ying; Carvalho, Maria F.; Vosátka, Miroslav; Freitas, HelenaCowpea (Vigna unguiculata (L.) Walp.), a plant broadly cultivated for human consumption and animal feed, is among the most nutritious grain legumes. Most of the areas where cowpea is grown are drought-prone, and there is a need to address this issue, with water scarcity becoming a major concern in agriculture. Cowpea is known to form mutualistic associations with nitrogen-fixing (NF) bacteria and arbuscular mycorrhizal (AM) fungi. These beneficial soil microorganisms have the capacity to benefit plants by reducing the effects of environmental stresses, including drought. Our aim was to study the effect of inoculation with Bradyrhizobium elkanii and Rhizophagus irregularis on the growth and grain yield of cowpea under water-deficit conditions. Under moderate water deficit, grain yield was increased by 63%, 55% and 84% in plants inoculated with B. elkanii, R. irregularis and B. elkanii R. irregularis, respectively. Under severe water deficit, inoculation with B. elkanii and B. elkanii R. irregularis resulted in grain-yield enhancement of 45% and 42%, respectively. The use of cowpea inoculated with NF bacteria and AM fungi has great potential for sustainable agricultural production under drought conditions.
- Isolation of Actinomycetes from marine sediments with potential to produce bioactive compoundsPublication . Ribeiro, Inês; Alexandrino, Diogo A. M.; Oliveira, Rui S.; Santos, Chiara; Pereira, Filipe; Mucha, Ana P.; Carvalho, Maria F.The various health problems experienced by the humanity, together with an increasing number of antibiotic-resistant microorganisms have been driven scientists to look for additional reserves of new bioactive substances. Actinomycetes are an important source of bioactive compounds with industrial and pharmaceutical interest. The distribution of this vast microbial group in the oceans is largely unexplored, making oceans an untapped and promising source of novel bioactive compounds.
- Natural production of fluorinated compounds and biotechnological prospects of the fluorinase enzymePublication . Carvalho, Maria F.; Oliveira, Rui S.Fluorinated compounds are finding increasing uses in several applications. They are employed in almost all areas of modern society. These compounds are all produced by chemical synthesis and their abundance highly contrasts with fluorinated molecules of natural origin. To date, only some plants and a handful of actinomycetes species are known to produce a small number of fluorinated compounds that include fluoroacetate (FA), some ω-fluorinated fatty acids, nucleocidin, 4-fluorothreonine (4-FT), and the more recently identified (2R3S4S)-5-fluoro-2,3,4-trihydroxypentanoic acid. This largely differs from other naturally produced halogenated compounds, which totals more than 5000. The mechanisms underlying biological fluorination have been uncovered after discovering the first actinomycete species, Streptomyces cattleya, that is capable of producing FA and 4-FT, and a fluorinase has been identified as the enzyme responsible for the formation of the C-F bond. The discovery of this enzyme has opened new perspectives for the biotechnological production of fluorinated compounds and many advancements have been achieved in its application mainly as a biocatalyst for the synthesis of [18F]-labeled radiotracers for medical imaging. Natural fluorinated compounds may also be derived from abiogenic sources, such as volcanoes and rocks, though their concentrations and production mechanisms are not well known. This review provides an outlook of what is currently known about fluorinated compounds with natural origin. The paucity of these compounds and the biological mechanisms responsible for their production are addressed. Due to its relevance, special emphasis is given to the discovery, characterization and biotechnological potential of the unique fluorinase enzyme.
- Seed coating with inocula of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria for nutritional enhancement of maize under different fertilisation regimesPublication . Rocha, Inês; Ma, Ying; Carvalho, Maria F.; Magalhães, Catarina; Janoušková, Martina; Vosátka, Miroslav; Freitas, Helena; Oliveira, Rui S.Arbuscular mycorrhizal (AM) fungi and plant growth-promoting rhizobacteria, responsible for enhancing plant nutrition, vigour and growth, may be used to reduce dosages of chemical fertilisers. Technologies that allow an economically viable and efficient application of these beneficial microbes in large scale agriculture must be studied. Seed coating is a potential delivery system for efficiently introducing minor amounts of bioinoculants. Despite the dramatic reduction on inoculum dose per plant, inoculation of AM fungi via seed coating was as effective as conventional soil inoculation. Fertilisation and inoculation had a significant impact on maize shoots nutrient concentrations. Different fertilisation regimes did not influence mycorrhizal colonisation. Plants without fertilisation and singly inoculated with R. irregularis showed shoot nutrient concentration increments of 110, 93, 88 and 175% for nitrogen, phosphorus, potassium and zinc, respectively, comparing with non-inoculated controls. Plants singly inoculated with P. fluorescens via seed coating under full fertilisation, presented enhancements of 100, 75 and 141% for magnesium, zinc and manganese, respectively, comparing with non-inoculated controls. Seed coating is a promising tool for delivering microbial inoculants into the soil, while promoting sustainable production of maize. This technology is particularly pertinent in low input agriculture, with potential environmental profits and food quality improvements.