Metals and linear alkylbenzene sulphonate as inhibitors of the algae Pseudokirchneriella subcapitata acid phosphatase activity.

Sewage sludge applied to soils as a fertilizer often contains metals and linear alkylbenzene sulphonate (LAS) as contaminants. These pollutants can be transported to the aquatic environment where they can alter the phosphatase activity in living organisms. The acid phosphatase of algae plays important roles in metabolism such as decomposing organic phosphate into free phosphate and autophagic digestive processes. The order of in vitro inhi- bition of Pseudokirchneriella subcapitata acid phosphatase at the highest concentration tested was LAS[Hg2? = Al 3?[Se4? = Pb2?[Cd2?. A non-competitive inhibi- tion mechanism was obtained for Hg2? (Ki = 0.040 mM) and a competitive inhibition for LAS (Ki = 0.007 mM). In vivo studies with treated algae cultures showed that the inhibition of specific activity was observed in algae exposed during 7 days, in contrast to short term (24 h) treatments with both these chemicals. Our results suggest that the inhibition parameters in vitro did not markedly differ between the two chemicals. On the other hand, in vivo evaluations showed strong differences between both pollu- tants regarding the concentration values and the degree of response.

Extraction, partial characterization and susceptibility to Hg2+ of acid phosphatase from the microalgae Pseudokirchneriella subcapitata.

Pseudokirchneriella subcapitata is a unicellular green algae widely distributed in freshwater and soils. Due to its cosmopolitan characteristic, its use is recommended by national and international protocols in ecotoxicity studies. The alteration of phosphatase activities by agriculture pollutants like heavy metals has been extensively used as a biomarker in risk assessment and biomonitoring. In this study, we compared the extraction of acid phosphatase from P. subcapitata by different procedures and we studied the stability, substrates specificity, kinetics and the effect of Hg2+ in the crude extract. The freezing and thawing technique associated with probe sonication was the most suitable method of extraction. The enzyme was stable when frozen at -20ºC for at least six months, showed an optimum pH of 5 and a Km value of 0.27 mM for p-nitrophenylphosphate (pNPP) as substrate. Some natural organic substrates were cleaved by a similar extent as the synthetic substrate pNPP. Short term exposure (24 hours) to Hg2+ had little effect but inhibition of the specific activity was observed after 7 days with EC50 (concentration of Hg2+ that promotes 50% decrease of specific activity) value of 12.63 μM Hg2+ .

Effect of copper on the activation of the acid phosphatase from the green algae Pseudokirchneriella subcapitata.

The in vitro activation effect of copper on the acid phosphatase of the green algae Pseudokirch- neriella subcapitata (formely Selenastrum capricor- nutum) under preincubation condition. Apparent Michaelis constant values of 1.21 and 0.37 mM, and activation energy values of 26.8 and 13.6 kJ mol -1 were determined in the absence and in the presence of 0.2 mM Cu2?, respectively. The dissociation constant value for Cu2? binding to the enzyme was determined to be 22.04 lM. The decrease of the apparent Michaelis constant (Km) and activation energy values in the presence of Cu2? correlates well with its activating effect on the acid phosphatase activity. This propriety could be used as a sensitive bioindicator for copper in environmental samples.

Effect of sewage sludge metals on Daphnia similis acid phosphatase.

2009

In vitro effects of metals on the acid phosphatase from the microalgae Pseudokirchneriella subcapitata.

2008

Influence of Pseudomonas putida AF7 inoculation on soil enzymes.

There has been some concern about the environmental impact of microbial agents. Pseudomonas may be used as bioremediator and as biopesticide. In this study, we report the use of soil enzyme assays as biological indicator of possible negative effects in soil functioning after the P. putida AF7 inoculation. For that, P. putida AF7 was originally isolated from the rizosphere of rice and was inoculated on three soil types: Rhodic Hapludox (RH), Typic Hapludox (TH); and Arenic Hapludult (AH). The acid phosphatase, b-glucosidase and protease enzymes activities were measured for three period of evaluation (7, 14 and 21 days). In general, the enzymatic activities pre- sented variation among the tested soils. The highest activities of b-glucosidase and acid phosphatase were observed in the RH and AH soils, while the protease activity was higher in the TH soil. Also, the soil charac- teristics were measured for each plot. The activity of enzymes from the carbon cycle was positively correlated with the N and the P and the enzyme from the nitrogen cycle was negatively correlated with N and C.org. The presented data indicate that soil biochemical properties can be an useful tool for use as an indicator of soil perturba- tions by microbial inoculation in a risk assessment.

Influence of Pseudomonas putida AF7 inoculation on soil enzymes.

Pseudomonas may use as bioremediator and as biopesticide. The use of soil enzymatic assays as biological indicator of possible negative effects in soil functioning was evaluated after P.putida AF7 inoculation. For that, AF7 was originally isolated from the rizosphere of rice and was inoculated on three soils: Rhodic Hapludox (RH), Typic Hapludox (TH); and Arenic Hapludult (AH). Soil characteristics were measured in each plot. Acid phosphatase, ?-glucosidase and protease activities were measured at 7, 14 and 21 days. The enzyme activity waved during the experimental period but there is a significant reduction of ?-glucosidase activity in RH soil on day 14. Corg was positively correlated to the activities of ?-glucosidase and protease. The presented data indicate that soil biochemical properties may be useful as indicator of soil perturbations.

Fosfatase ácida e alcalina em solo sob manejo do sistema integração lavoura pecuária e floresta.

2016