Percorrer por autor "Schwan, Rosane Freitas"
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- Impact of lead (Pb2+) on the growth and biological activity of Serratia marcescens selected for wastewater treatment and identification of its zntR gene—a metal efflux regulatorPublication . dos Reis Ferreira, Gustavo Magno; Pires, Josiane Ferreira; Ribeiro, Luciana Silva; Dias Carlier, Jorge; Costa, Maria Clara; Schwan, Rosane Freitas; Silva, Cristina FerreiraMicroorganisms isolated from contaminated areas play an important role in bioremediation processes. They promote heavy metal removal from the environment by adsorbing ions onto the cell wall surface, accumulating them inside the cells, or reducing, complexing, or precipitating these substances in the environment. Microorganism-based bioremediation processes can be highly efcient, low-cost and have low environmental impact. Thus, the present study aimed to select Pb2+-resistant bacteria and evaluate the growth rate, biological activity, and the presence of genes associated with metal resistance. Serratia marcescens CCMA 1010, that was previously isolated from cofee processing wastewater, was selected since was able to growth in Pb2+ concentrations of up to 4.0 mM. The growth rate and generation time did not difer from those of the control (without Pb2+), although biological activity decreased in the frst hour of exposure to these ions and stabilized after this period. The presence of the zntR, zntA and pbrA genes was analysed, and only zntR was detected. The zntR gene encodes a protein responsible for regulating the production of ZntA, a transmembrane protein that facilitates Pb2+ extrusion out of the cell. S. marcescens CCMA 1010 demonstrated a potential for use as bioindicator that has potential to be used in bioremediation processes due to its resistance to high concentrations of Pb2+, ability to grow until 24 h of exposure, and possession of a gene that indicates the existence of mechanisms associated with resistance to lead (Pb2+).
- Pb2+ biosorption by Serratia marcescens CCMA 1010 and its relation with zntR gene expression and ZntA efflux pump regulationPublication . Carlier, Jorge; Ferreira, Gustavo Magno dos Reis; Schwan, Rosane Freitas; Silva, Cristina Ferreira da; Costa, Maria ClaraGlobal concerns about the preservation and restoration of aquatic environments are rising and pollution related to heavy metals is one of the main worries. Indeed, this issue has been a challenge for the metallurgical industry and other activities associated with metal contamination. Thus, over time, several physical and chemical methods have been developed and applied to remove metals from water. However, these methods can be associated with high costs, and bioremediation using plants, fungi, and bacteria is considered a viable alternative. This paper reports experiments on lead removal from an aqueous medium using active and inactive Serratia marcescens CCMA 1010 and a study on the effect of lead in this bacterial strain regarding the expression of the zntR gene, which produces the zntR protein known to have a role as a regulator of the ZntA efflux pump of metals (Pb2+, Cd2+, Zn2+). The amount of removed Pb2+ by active biomass remained below ~25 mg/L for the initial concentrations tested up to 120 mg/L but increased to removals of ~70 and ~167 mg/L for the tested concentrations of 220 and 300 mg/L, respectively. On the other hand, the removal of Pb2+ by inactive biomass increased in direct relation to the initial tested concentration, with removed percentages around 25 %. Interestingly, in cultures with 15 and 60 mg/L Pb2+ the expression of zntR was 27 to 74 and 87 to 177 times lower (respectively) than in cultures without Pb2+, while in cultures with 120 mg/L Pb2+, the zntR expression was just 1.3 to 9.3 times lower than in the absence of Pb2+. The results confirm the potential of S. marcescens CCMA 1010 for Pb2+ biosorption, the presence of Pb2+ resistance mechanisms in this strain, and contribute to a better understanding of the ZntA transmembrane protein regulation.