Time dependent influx and efflux of phenol by immobilized microbial consortium

Phenol, like many other organic solvents, is toxic to micro-organisms even at low concentrations. However, some micro-organisms can withstand this toxicity to a certain concentration. To observe the uptake mechanism of phenol, bacteria were isolatedfrom a petroleum refinery effluent and identified. Study was carried out to understand the effect of varying sub-lethal concentrations of phenol, on all the isolated individual bacterial cultures. Out of the bacteria isolated, Serratia liquefaciens was found to tolerate phenol concentration up to 1500 mg l^-1. A microbial consortium of the isolated bacteriawas formulated and immobilized. Individual cultures were also immobilized and uptake of phenol by the immobilized micro-organisms was observed in a nutrient-rich and nutrient-stressed medium containing phenol as a sole source of carbon. A time-dependent uptake of phenol was exhibited by the micro-organismsin nutrient-stressed medium, after which a sudden increase in phenol concentration occurred in the extracellular medium, till it reached back to the initial concentration. This was attributedto an active efflux mechanism adopted by the micro-organisms to withstand the toxic shock.     

Non-mosaic trisomy 20 presenting at 21 weeks' gestation as a thoraco-abdominal mass

Non-mosaic trisomy 20 is rare in fetuses surviving beyond the first trimester. We report a case of a fetus with non-mosaic trisomy 20 in amniotic fluid cultures obtained during the prenatal evaluation of an unusual thoraco-abdominal mass which was found at autopsy to be pulmonary sequestration. Gross inspection and autopsy of the fetus revealed multiple anomalies. Copyright © 2001 John Wiley & Sons, Ltd.     

Application of adaptive cluster sampling to low-density populations of freshwater mussels

Freshwater mussels appear to be promising candidates for adaptive cluster sampling because they are benthic macroinvertebrates that cluster spatially and are frequently found at low densities. We applied adaptive cluster sampling to estimate density of freshwater mussels at 24 sites along the Cacapon River, WV, where a preliminary timed search indicated that mussels were present at low density. Adaptive cluster sampling increased yield of individual mussels and detection of uncommon species; however, it did not improve precision of density estimates. Because finding uncommon species, collecting individuals of those species, and estimating their densities are important conservation activities, additional research is warranted on application of adaptive cluster sampling to freshwater mussels. However, at this time we do not recommend routine application of adaptive cluster sampling to freshwater mussel populations. The ultimate, and currently unanswered, question is how to tell when adaptive cluster sampling should be used, i.e., when is a population sufficiently rare and clustered for adaptive cluster sampling to be efficient and practical? A cost-effective procedure needs to be developed to identify biological populations for which adaptive cluster sampling is appropriate.     

Fetal translocation between chromosomes 2, 18, and 21 resolved by fish

An apparently balanced t(2q;21q) translocation was discovered in fetal blood and amniocytes of a 22-week fetus, monitored because of ultrasonographic evidence of a heart disease. FISH (fluorescence in situ hybridization) analysis disclosed a complex translocation between chromosomes 2q, 18q, and 21q, which was inherited from the healthy mother. This observation corroborates the usefulness of molecular cytogenetic techniques in raising the quality of prenatal diagnosis and detecting subtle rearrangements not resolved by standard cytogenetics.     

Characterization and diurnal variation of size-resolved inorganic water-soluble ions at a rural background site

Water-soluble inorganic ions in aerosol samples have been studied. The sample collection took place during summer in 2003 at a European background site which is operating within the framework of the European Monitoring and Evaluation Program. Gent type PM10 stacked filter unit (SFU) samplers were operated in parallel on a day and night basis to collect particles in separate coarse (2.0-10 microm) and fine (<2.0 microm) size fractions. Particulate masses were measured gravimetrically; the filters from one of the SFU samplers were analyzed by particle-induced X-ray emission spectrometry (PIXE) and instrumental neutron activation analysis (INAA). Filters from the other SFU sampler were analyzed by ion chromatography (IC) for major inorganic anions (MSA-, NO2(-), NO3(-), Cl-, Br-, SO4(2-), oxalate) and cations (Na+, K+, NH4(+), Mg2+, Ca2+). The water-soluble inorganic ions measured were responsible for 44% and 16% of the total fine and coarse particulate mass, respectively. In the fine size fraction, the main ionic components were SO4(2-) and NH4(+) accounting for about 90% of fine ionic mass. In the coarse fraction the main ionic components were Ca2+ and NO3(-), followed by SO4(2-). Significant day and night difference in the mass concentrations was observed only for fine NO3(-). The molar ratios of fine NH4(+) to SO4(2-) indicated their complete neutralization to (NH4)2SO4. According to the cation-to-anion ratios the coarse particles were alkaline, while the fine particles were slightly acidic or neutral. By comparing the corresponding concentrations obtained from PIXE/INAA and IC, we determined the water-extractable part of the individual species. We also investigated the effect of long-range transported air masses on the local air concentrations, and we found that the air quality of this background monitoring station was affected by regional pollution sources.     

Evaluation of metabisulfite and a commercial steel wool for removing chromium(VI) from wastewater

Efficiency of metabisulfite and a commercial steel wool as reducing agents in the removal of Cr(VI) from wastewaters was evaluated. Chromium(VI) was converted to Cr(III), precipitated with NaOH, and removed by filtration. A reduction of more than 1.0 × 10⁵ and 4.0 × 10⁵ fold in total Cr and the Cr(VI) concentrations, respectively, was observed by employing steel wool masses as low as 0.4420 g to 30-mL solutions of wastewater. Chromium(III) hydroxide obtained after the treatment was recycled and used as marker in cattle nutrition studies. The liquid residue obtained after the treatment was reused as precipitation agent replacing NaOH.     

Nitrate controls methyl mercury production in a streambed bioreactor

Organic carbon bioreactors provide low-cost, passive treatment of a variety of environmental contaminants but can have undesirable side effects in some cases. This study examines the production of methyl mercury (MeHg) in a streambed bioreactor consisting of 40 m3 of wood chips and designed to treat nitrate (NO?) in an agricultural drainage ditch in southern Ontario (Avon site). The reactor provides 30 to 100% removal of NO?-N concentrations of 0.6 to 4.4 mg L(-1), but sulfate (SO?(2-)) reducing conditions develop when NO? removal is complete. Sulfate reducing conditions are known to stimulation the production of MeHg in natural wetlands. Over one seasonal cycle, effluent MeHg ranged from 0.01 to 0.76 ng L(-1) and total Hg ranged from 1.3 to 3.4 ng L(-1). During all sampling events when reducing conditions were only sufficient to promote NO?(-) reduction (or denitrification) ( = 5, late fall 2009, winter 2010), MeHg concentrations decreased in the reactor and it was a net sink for MeHg (mean flux of -5.1 μg m(-2) yr(-1)). During all sampling events when SO?(2-) reducing conditions were present ( = 6, early fall 2009, spring 2010), MeHg concentrations increased in the reactor and it was a strong source of MeHg to the stream (mean flux of 15.2 μg m(-2) yr(-1)). Total Hg was consistently removed in the reactor (10 of 11 sampling events) and was correlated to the total suspended sediment load ( r2 = 0.69), which was removed in the reactor by physical filtration. This study shows that organic carbon bioreactors can be a strong source of MeHg production when SO?(2-) reducing conditions develop; however, maintaining NO?-N concentrations > 0.5 mg L suppresses the production of MeHg.     

C and N Content in Density Fractions of Whole Soil and Soil Size Fraction Under Cacao Agroforestry Systems and Natural Forest in Bahia,Brazil

Agroforestry systems (AFSs) have an important role in capturing above and below ground soil carbon and play a dominant role in mitigation of atmospheric CO₂. Attempts has been made here to identify soil organic matter fractions in the cacao-AFSs that have different susceptibility to microbial decomposition and further represent the basis of understanding soil C dynamics. The objective of this study was to characterize the organic matter density fractions and soil size fractions in soils of two types of cacao agroforestry systems and to compare with an adjacent natural forest in Bahia, Brazil. The land-use systems studied were: (1) a 30-year-old stand of natural forest with cacao (cacao cabruca), (2) a 30-year-old stand of cacao with Erythrina glauca as shade trees (cacao + erythrina), and (3) an adjacent natural forest without cacao. Soil samples were collected from 0-10 cm depth layer in reddish-yellow Oxisols. Soil samples was separated by wet sieving into five fraction-size classes (>2000 μm, 1000–2000 μm, 250–1000 μm, 53–250 μm, and <53 μm). C and N accumulated in to the light (free- and intra-aggregate density fractions) and heavy fractions of whole soil and soil size fraction were determined. Soil size fraction obtained in cacao AFS soils consisted mainly (65 %) of mega-aggregates (>2000 μm) mixed with macroaggregates (32–34%), and microaggregates (1–1.3%). Soil organic carbon (SOC) and total N content increased with increasing soil size fraction in all land-use systems. Organic C-to-total N ratio was higher in the macroaggregate than in the microaggregate. In general, in natural forest and cacao cabruca the contribution of C and N in the light and heavy fractions was similar. However, in cacao + erythrina the heavy fraction was the most common and contributed 67% of C and 63% of N. Finding of this study shows that the majority of C and N in all three systems studied are found in macroaggregates, particularly in the 250–1000 μm size aggregate class. The heavy fraction was the most common organic matter fraction in these soils. Thus, in mature cacao AFS on highly weathered soils the main mechanisms of C stabilization could be the physical protection within macroaggregate structures thereby minimizing the impact of conversion of forest to cacao AFS.