Oxytetracycline effect on the structure of bacterioplankton in microcosm / Efeito da oxitetraciclina na estrutura do bacterioplâncton no microcosmo

Resíduos de medicamentos são frequentemente encontrados em matrizes ambientais. A classe dos antimicrobianos é uma das que causa grande preocupação devido aos potenciais efeitos negativos sobre a comunidade microbiana que desempenha papel crucial nos processos, dinâmica e estabilidade dos ecossistemas. O objetivo deste trabalho foi avaliar os aspectos ecológicos da ação do antimicrobiano oxitetraciclina (OTC) sobre a densidade e diversidade bacterianas de um sistema de água doce. Foram desenvolvidos experimentos em microcosmos, em triplicata, totalizando 18 microcosmos-tratamento contendo água do ambiente com 2 mg L-1 de oxitetraciclina e 18 microcosmos controle contend apenas água do ambiente. O conteúdo dos microcosmos foi analizado em 1, 5, 10, 20, 45 e 70 dias. O decaimento da OTC e as mudanças nas variáveis abióticas e bióticas foram verificadas em cada dia de amostagem. O tempo de meia-vida da OTC nas condições experimentais estabelecidas foi de 3,8 dias (R2 = 98%). O valores de nitrogênio total (NT) e carbono orgânico dissolvido (COD) foram significativamente diferentes entre os microcosmos controle e tratamento. A densidade bacteriana foi significativamente diferente entre os microcosmos controle e tratamento, estando entre 1,57x103 e 3,48x105 células por mL de água nos microcosmos-controle e entre 1,17x105 e 2,19x105 células por mL de água nos microcosmos-tratamento. A densidade bacteriana apresentou correlação negativa ao COD. No microcosmos-tratamento, a densidade bacteriana esteve negativamente correlacionada à OTC. Em relação à diversidade bacteriana, valores similares foram encontrados entre controle e tratamento nos tempos de análise T1 e T70, mas em T20 foi observado maior diversidade nas amostras dos microcosmos-tratamento. Os resultados demonstraram que para as condições estabelecidas, a OTC pode mediar a coexistencia de espécies, controlando bactérias com maior potencial competitivo, aumentando a diversidade bacteriana por consequencia.

Screening of Marine-derived Fungi Isolated from the sponge Didemnun ligulum for Biodegradation of Pentachlorophenol

Contamination by pesticides employed in agriculture has caused serious environmental harm. Pentachlorophenol (PCP) is a phenolic organochlorine compound and a dangerous pollutant which was banned from Brazil since 1985; however, there are still many contaminated areas. This pesticide is a serious problem because it has high toxicity and persistence at the environment due to its resistance to biotic and abiotic degradation. The use of microorganisms as degrading agents is considered an efficient method to reduce the adverse effects of environmental contaminants. It is noteworthy that fungi from marine environment are adapted to extreme conditions, including high chlorine concentrations, and can produce unique enzymes with interesting properties. Therefore, marine-derived fungi have an excellent enzymatic potential for the biotransformation of xenobiotics such as organochlorine pesticides. In this work, fifteen fungi strains isolated from a marine invertebrate, the ascidian Didemnun ligulum, were evaluated according to their ability to grow in solid culture media (3% malt extract agar) in the presence of different concentrations (10, 25, 30, 40, and 50 mg L–1) of PCP. Among the tested strains, nine could grow in at least one concentration, and Trichoderma harzianum CBMAI 1677 showed optimal growth at the higher evaluated concentration (50 mg L–1), showing toxicity resistance and suggesting its potential for biodegradation of PCP. In a later work, it was observed that T. harzianum CBMAI 1677 was able to degrade PCP. These results confirmed the efficiency of marine-derived fungi to biodegrade persistent compounds and could enable the development of bioremediation methodologies using these microorganism

Aerobic biodegradation of butanol and diesel oil blends

This work aimed to evaluate the aerobic biodegradation of butanol/diesel oil blends (5, 10, 15, 20%, v/v) in comparison to the biodiesel/diesel oil blend (20%, v/v). Respirometric experiments simulating the contamination of natural environments (soil and water from a river) were carried out in biometer flasks (250 mL) used to measure microbial carbon dioxide (CO2) production. The automated turbidimeter Bioscreen C was used to follow the growth of Pseudomonas aeruginosa LBI on butanol/diesel oil blends. A redox indicator (2,6-dichlorophenol indophenol - DCPIP) test was used to evaluate the capability of four inocula to biodegrade the blends with 20% (v/v). The experiment which simulated the soil contamination demonstrated that butanol is less biodegradable than diesel oil, and for this reason the increase in the portion of butanol in the  butanol/diesel blend from 5 to 20% had negative effects on biodegradation. While in soil the biodiesel/diesel blend was more easily biodegraded than the butanol/diesel blend, in water this order was the inverse. The insoluble fuels (diesel and biodiesel) were poorly biodegraded in water and the biodegradation of the butanol/diesel blend was favored by the water solubilization of the butanol, which enhances the bioavailability of this compound. On the other hand, initial concentrations of butanol in the water higher than 10 mL L-1 inhibited the cell growth of the tested microorganisms. Thus, butanol toxicity presumably had a significant effect on the degree of biodegradation of the fuel blends.Key words: Butanol, biodiesel, diesel, biodegradation, blends, soil, water

Effects of fire stress to soil protozoan abundance and richness in a Brazilian savanna

Protozoans are important components of the aquatic and terrestrial food webs. Since they are voracious bacterial predators in terrestrial habitats, they can consequently affect soil fertility. Considering that fire is a common and frequent event in agricultural and natural soils, especially in cerrado areas, this work aimed evaluating the effects of fire on protozoan communities occurring in a soil with cerrado vegetation. It was conducted 16 samplings (from august/2011 to august/2012) at a location exposed to a fire event (Burned) and one not exposed (Control). The “Non-Flooded Petri Dish” technique used to evaluate the protozoan cryptic diversity of the samples. Qualitative and quantitative analyses of the active soil protozoans were also done. It was used the Canonic Correspondence analysis (CCA), Jaccard indexes, the Bray-Curtis similarity coefficient, Shannon indexes and Kruskal-Wallis test for data analysis. It was found 102 morphospecies, distributed into 12 protozoan taxonomical groups. From the total, only 32 morphospecies, distributed into 9 taxonomical groups, were active. The CCA evidenced that the significant variables by the Monte Carlo test, that showed association with the biological data were: mean air temperature, mean relative humidity of the air, coarse sand, medium sand, fine sand and clay. The Jaccard index and Bray-Curtis test showed that the Control (C) and Burned (Q) areas are similar. The value chosen to delimit the clusters were respectively 0,25 and 0,60. The Shannon index gave the same results for the two areas. This index and the BrayCurtis test consider both richness and abundance, but the Jaccard index considers only richness. The KruskalWallis test showed a significant difference between the two areas in only 2 samplings. With the other 14 sampling there was no difference. Protozoan densities did not change at the first three weeks from the fire event, then, the populations starts to reduce. Subsequently, three months after the fire, at more favorable conditions, the protozoan populations increased again. After this phase, three and a half months after the fire, protozoan densities reduced and the densities stayed similar in both regions. The fire did not caused changes in the protozoan community structure, but only caused density reduction. Probably the fire did not affect directly this community, but indirectly, intensifying soil drought. We concluded that these protozoan populations are adapted to the effects of fire

Optimized culture and growth curves of two ciliated protozoan strains of Paramecium caudatum Ehrenberg, 1833 to use in ecotoxicologycal assays

Protozoans are microbial eukaryotes known to be ideal for aquatic ecotoxicological testing. Therefore, aiming to evaluate their possible use in standardized ecotoxicity assays we determined the best cultivation conditions and growth curves for two strains of the ciliated protozoan Paramecium caudatum Ehenberg 1833. One strain (PC1) was isolated from the Monjolinho reservoir-SP (22° 01’ S and 47° 53’ W) where the mean dissolved O2 is 5.205 mgL-1, pH 6.43 and electrical conductivity 34.75 μS cm-1. The other strain (PC2) from the Óleo lagoon in Jataí Ecological Station- SP (21° 36’ S and 47° 49’ W), with mean dissolved of 4,42 mgL-1, pH 4.90 and electrical conductivity 10.96 μS cm-1. The higher mean cellular biovolume and density obtained were used to evaluate different cultivation parameters such as temperature, pH, light exposition, stirring regimen and cultivation flask size. Considering protozoan densities and cell biovolume, the best culture conditions for PC1 strain was pH 9.0 at 30 °C and for PC2 was pH 7.0 at 27.5 °C. For both strains and evaluated parameters (biovolume and density), the bottle size did not interfered in the results and absence of light resulted in better ones. Concerning agitation, for PC2, there was no significant difference for this parameter and for PC1 in the absence of shaking we obtained better results. Therefore we decided to make the tests in the absence of light and without shaking. Regarding cell biovolume, the best condition was pH 9.0 at 25 ° C for the PC1 strain and pH 8.0 at 20 ° C for PC2 strain. The generation time calculated in a 96 hours growth curve was 8.35 hours for PC1 and 7.6 hours for PC2. In the end of the experiment, the number of generations (n) and maximum population (N) were higher for PC2 than for PC1 and were, 11.02 and 10.78, respectively, for n values and 7548 and 6400 for N ones. The growth strategies of the two strains were quite different but both were considered suitable for laboratorial growth and use for ecotoxicity tests in standardized conditions