Browsing by Author "Becerra-Castro, Cristina"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
- Assessment of copper and zinc salts as selectors of antibiotic resistance in Gram-negative bacteriaPublication . Becerra-Castro, Cristina; Machado, Rita A.; Vaz-Moreira, Ivone; Manaia, Célia M.Some metals are nowadays considered environmental pollutants. Although some, like Cu and Zn, are essential for microorganisms, at high concentrations they can be toxic or exert selective pressures on bacteria. This study aimed to assess the potential of Cu or Zn as selectors of specific bacterial populations thriving in wastewater. Populations of Escherichia coli recovered on metal-free and metal-supplemented culture medium were compared based on antibiotic resistance phenotype and other traits. In addition, the bacterial groups enriched after successive transfers in metal-supplemented culture medium were identified. At a concentration of 1 mM, Zn produced a stronger inhibitory effect than Cu on the culturability of Enterobacteriaceae. It was suggested that Zn selected populations with increased resistance prevalence to sulfamethoxazole or ciprofloxacin. In non-selective culture media, Zn or Cu selected for mono-species populations of ubiquitous Betaproteobacteria and Flavobacteriia, such as Ralstonia pickettii or Elizabethkingia anophelis, yielding multidrug resistance profiles including resistance against carbapenems and third generation cephalosporins, confirming the potential of Cu or Zn as selectors of antibiotic resistant bacteria.
- Characterization of bacterial communities from Masseiras, a unique Portuguese greenhouse agricultural systemPublication . Becerra-Castro, Cristina; Lopes, Ana Rita; Teixeira, Sara; Silva, M. Elisabete F.; Pimenta, Elisabete; Manaia, Célia M.; Nunes, Olga C."Masseiras" is an ancient Portuguese agriculture system, where soil was developed from sand dunes enriched with seaweeds over more than a century. Due to the importance for the local economy, this system evolved for greenhouse structures. In this study we compared the bacterial community composition and structure of "Masseiras" soil, aiming at assessing the potential impact of different agricultural practices. The bulk soil of two greenhouses (following or not the recommended agriculture good practices, FGP and NFGP, respectively) was compared based on their physicochemical properties and bacterial community. In both FGP and NFGP, Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Gemmatimonadetes were in a proportion of 5:1:1:1:1:1. However, the bacterial community of soil FGP was richer and more diverse than that of soil NFGP. Members of the classes Bacilli and Gemm-1, with higher relative abundance in NFGP and FGP, respectively, were those contributing most for distinguishing the bacterial communities of both soils. The differences in the structure of the bacterial communities correlated (Mantel test) with some soil physicochemical properties, such as electrical conductivity and nitrate and Zn contents, which were significantly higher in soil NFGP than in soil FGP.
- Diversity and antibiotic resistance patterns of gram-negative bacteria isolated from wastewater in the presence of copper or zinc saltsPublication . Becerra-Castro, Cristina; Vaz-Moreira, Ivone; Machado, Rita J.; Manaia, C. M.
- Irrigation with treated wastewater: potential impacts on microbial function and diversity in agricultural soilsPublication . Lopes, Ana Rita; Becerra-Castro, Cristina; Vaz-Moreira, Ivone; Silva, M. Elisabete F.; Nunes, Olga C.; Manaia, C. M.The reuse of treated wastewater could be a promising measure to attenuate the water scarcity burden. In agriculture, irrigation with wastewater may contribute to improve production yields, reduce the ecological footprint and promote socioeconomic benefits. However, it cannot be considered exempt of adverse consequences in environmental and human health. Apart from the introduction of some biological and chemical hazardous agents, the disturbance of the indigenous soil microbial communities and, thus, of vital soil functions impacting soil fertility may occur. The consequences of these disturbances are still poorly understood. This chapter summarises the physicochemical and microbiological alterations in soil resultant from irrigation with treated wastewater that are described in scientific literature. These alterations, which involve a high complexity of variables (soil, wastewater, climate, vegetal cover), may have impacts on soil quality and productivity. In addition, possible health risks may arise, in particular through the direct or indirect contamination of the food chain with micropollutants, pathogens or antibiotic resistance determinants. The current state of the art suggests that irrigation with treated wastewater may have a multitude of long-term implications on soil productivity and public health. Although further research is needed, it seems evident that the analysis of risks associated with irrigation with treated wastewater must take into account not only the quality of water, but other aspects as diverse as soil microbiota, soil type or the cultivated plant species.
- Ozonation and UV254nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewaterPublication . Sousa, José M.; Macedo, Gonçalo; Pedrosa, Marta; Becerra-Castro, Cristina; Castro-Silva, Sérgio; Pereira, M. Fernando R.; Silva, Adrián M. T.; Nunes, Olga C.; Manaia, Célia M.Conventional wastewater treatment has a limited capacity to reduce antibiotic resistant bacteria and genes (ARB&ARG). Tertiary treatment processes are promising solutions, although the transitory inactivation of bacteria may select ARB&ARG. This study aimed at assessing the potential of ozonation and UV254nm radiation to inactivate cultivable fungal and bacterial populations, and the selected genes 16S rRNA (common to all bacteria), intI1 (common in Gram-negative bacteria) and the ARG vanA, blaTEM, sul1 and qnrS. The abundance of the different microbiological parameters per volume of wastewater was reduced by ∼2 log units for cultivable fungi and 16S rRNA and intI1 genes, by∼3-4 log units, for total heterotrophs, enterobacteria and enterococci, and to values close or below the limits of quantification for ARG, for both processes, after a contact time of 30min. Yet, most of the cultivable populations, the 16S rRNA and intI1 genes as well as the ARG, except qnrS after ozonation, reached pre-treatment levels after 3days storage, suggesting a transitory rather than permanent microbial inactivation. Noticeably, normalization per 16S rRNA gene evidenced an increase of the ARG and intI1 prevalence, mainly after UV254nm treatment. The results suggest that these tertiary treatments may be selecting for ARB&ARG populations.
- Proteobacteria become predominant during regrowth after water disinfectionPublication . Becerra-Castro, Cristina; Macedo, Gonçalo; Silva, Adrian M.T.; Manaia, C. M.; Nunes, Olga C.Disinfection processes aimat reducing the number of viable cells through the generation of damages in different cellular structures and molecules. Since disinfection involves unspecific mechanisms, some microbial populationsmay be selected due to resilience to treatment and/or to high post-treatment fitness. In this study, the bacterial community composition of secondarily treated urban wastewater and of surface water collected in the intake area of a drinking water treatment plant was compared before and 3-days after disinfection with ultraviolet radiation, ozonation or photocatalytic ozonation. The aim was to assess the dynamics of the bacterial communities during regrowth after disinfection. In all the freshly collected samples, Proteobacteria and Bacteroidetes were the predominant phyla (40–50% and 20–30% of the reads, respectively). Surface water differed from wastewater mainly in the relative abundance of Actinobacteria (17% and b5% of the reads, respectively). After 3-days storage at light and room temperature, disinfected samples presented a shift of Gammaproteobacteria (from 8 to 10% to 33–65% of the reads) and Betaproteobacteria (from 14 to 20% to 31–37% of the reads), irrespective of the type of water and disinfection process used. Genera such as Pseudomonas, Acinetobacter or Rheinheimera presented a selective advantage after water disinfection. These variations were not observed in the non-disinfected controls. Given the ubiquity and genome plasticity of these bacteria, the results obtained suggest that disinfection processes may have implications on the microbiological quality of the disinfected water.
- A rationale for the high limits of quantification of antibiotic resistance genes in soilPublication . Fortunato, Gianuario; Vaz-Moreira, Ivone; Becerra-Castro, Cristina; Nunes, Olga C.; Manaia, Célia M.The determination of values of abundance of antibiotic resistance genes (ARGs) per mass of soil is extremely useful to assess the potential impacts of relevant sources of antibiotic resistance, such as irrigation with treated wastewater or manure application. Culture-independent methods and, in particular, quantitative PCR (qPCR), have been regarded as suitable approaches for such a purpose. However, it is arguable if these methods are sensitive enough to measure ARGs abundance at levels that may represent a risk for environmental and human health. This study aimed at demonstrating the range of values of ARGs quantification that can be expected based on currently used procedures of DNA extraction and qPCR analyses. The demonstration was based on the use of soil samples spiked with known amounts of wastewater antibiotic resistant bacteria (ARB) (Enterococcus faecalis, Escherichia coli, Acinetobacter johnsonii, or Pseudomonas aeruginosa), harbouring known ARGs, and also on the calculation of expected values determined based on qPCR. The limits of quantification (LOQ) of the ARGs (vanA, qnrS, blaTEM, blaOXA, blaIMP, blaVIM) were observed to be approximately 4 log-units per gram of soil dry weight, irrespective of the type of soil tested. These values were close to the theoretical LOQ values calculated based on currently used DNA extraction methods and qPCR procedures. The observed LOQ values can be considered extremely high to perform an accurate assessment of the impacts of ARGs discharges in soils. A key message is that ARGs accumulation will be noticeable only at very high doses. The assessment of the impacts of ARGs discharges in soils, of associated risks of propagation and potential transmission to humans, must take into consideration this type of evidence, and avoid the simplistic assumption that no detection corresponds to risk absence.
- Rhizobacterial communities associated with the flora of three serpentine outcrops of the Iberian PeninsulaPublication . Álvarez-López, Vanessa; Prieto-Fernández, Ángeles; Becerra-Castro, Cristina; Monterroso, Carmela; Kidd, Petra S.Aim Plant -associated bacteria can improve phytoextraction by increasing plant growth and/or metal uptake. This study aimed to characterise the culturable rhizobacterial community associated with two Nihyperaccumulators and to obtain a collection of isolates for application in Ni phytomining. Methods Non-vegetated and rhizosphere soil samples were collected from the Ni-hyperaccumulator Alyssum serpyllifolium ssp. lusitanicum (three populations) and Alyssum serpyllifolium ssp. malacitanum (one population), as well as from non-hyperaccumulating plants (Dactylis glomerata, Santolina semidentata and Alyssum serpyllifolium ssp. serpyllifolium). Rhizobacteria were isolated and characterised genotypically (BOX-PCR, 16S rDNA sequencing) and phenotypically (Ni tolerance, plant growth promoting (PGP) traits, biosurfactant production). Results Hyperaccumulating Alyssum subspecies hosted higher densities of bacteria compared to either nonhyperaccumulators or non-vegetated soil. In some cases hyperaccumulators showed selective enrichment of Nitolerant bacteria. Most bacterial strains belonged to the Actinobacteria phylum and presented Ni resistance. Phosphorus-solubilisers were mostly associated with the hyperaccumulators, siderophore-producers with D. glomerata, and IAA-producers with both these species. Conclusion Taxonomic diversity and phenotypic characteristics were soil-, plant species- and plant population- specific. Moreover, differences were observed between the two Ni-hyperaccumulating subspecies and amongst plant populations. Several strains presented PGP characteristics which could be useful when selecting microorganisms for bioaugmentation trials.
- Wastewater reuse in irrigation: a microbiological perspective on implications in soil fertility and human and environmental healthPublication . Becerra-Castro, Cristina; Lopes, Ana Rita; Vaz-Moreira, Ivone; Silva, Elisabete F.; Manaia, Célia M.; Nunes, Olga C.The reuse of treated wastewater, in particular for irrigation, is an increasingly common practice, encouraged by governments and official entities worldwide. Irrigation with wastewater may have implications at two different levels: alter the physicochemical and microbiological properties of the soil and/or introduce and contribute to the accumulation of chemical and biological contaminants in soil. The first may affect soil productivity and fertility; the second may pose serious risks to the human and environmental health. The sustainable wastewater reuse in agriculture should prevent both types of effects, requiring a holistic and integrated risk assessment. In this article we critically review possible effects of irrigation with treated wastewater, with special emphasis on soil microbiota. The maintenance of a rich and diversified autochthonous soil microbiota and the use of treated wastewater with minimal levels of potential soil contaminants are proposed as sine qua non conditions to achieve a sustainable wastewater reuse for irrigation.