Isolation and 16S DNA characterization of soil microorganisms from tropical soils capable of utilizing the herbicides hexazinone and tebuthiuron

Six non-fermentative bacteria were isolated from Colombian (South America) and Hawaiian (USA) soils after enrichment with minimal medium supplemented with two herbicides, hexazinone (Hex) and tebuthiuron (Teb). Microscopic examination and physiological tests were followed by partial 16S DNA sequence analysis, using the first 527 bp of the 16S rRNA gene for bacterial identification. The isolated microorganisms (and in brackets, the herbicide that each degraded) were identified as: from Colombia. Methylobacterium organophilum [Teb], Paenibacillus pabuli [Teb], and Micrmbacterium foliorum [Hex]; and from Hawaii, Methylobacterium radiotolerans [Teb], Paenibacillus illinoisensis [Hex], and Rhodococcus equi [Hex]. The findings further explain how these herbicides, which have potential for illicit coca (Erythroxylum sp.) control, dissipate following their application to tropical soils.     

Measurement of 13C/12C of chloroacetic acids by gas chromatography/combustion/isotope ratio mass spectrometry

This paper describes a novel analytical methodology using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) to measure the 13C/12C ratios of chloroacetic acids (CAAs). CAAs are a major class of environmental pollutants that are widely distributed throughout the world, often at relatively high concentrations, and are of concern due to their toxic effects, particularly on plants. The 13C/12C of CAA reagents was measured by IRMS subsequent to offline combustion. Aqueous solutions of these CAAs were derivatized to the corresponding methyl chloroacetates (MCAAs) with acidic methanol with a known isotopic composition, extracted into pentane, and analyzed by GC/C/IRMS. Measured 13C/12C ratios of derivatized MCAAs were in agreement with calculated values within 1 per thousand for monochloroacetic acid and trichloroacetic acid and within 2 per thousand for dichloroacetic acid, suggesting that methylation and other analytical methodology steps do not isotopically fractionate derivatized MCAAs. 13C/12C ratios of reagent CAAs from different sources had varying isotopic signatures suggesting differences in source carbon and/or production methods. Our results underscore the potential of stable isotopes to serve as tracers of environmental sources of CAAs.     

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m³ FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NO_x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NO_x and simplified ambient surrogate–NO_x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO_x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO_x levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.     

Environmental exposure to PCBs and cancer incidence in eastern Slovakia

In a population-based cross-sectional study, we compared serum levels of 15 polychlorinated biphenyl (PCB) congeners and three organochlorine pesticides in residents of two districts in eastern Slovakia, one with extensive environmental contamination from a former PCB production site (Michalovce) and the other matched on geography but with low (background) levels (Svidnik). The age-adjusted geometric means for sum of 15 measured PCB congeners were statistically significantly higher in subjects from the Michalovce district for both sexes: 3327.6 versus 1331.4 ng/g of lipid in males, 2751.8 versus 992.2 ng/g of lipid in females. Levels of DDE and DDT were also significantly higher, although the absolute differences were less pronounced. There was no substantial difference in HCB levels between the districts. We also conducted an ecologic study to compare cancer incidence occurring in these same two districts from 1985 through 1994. We calculated standardized incidence ratios (SIRs) and 95% confidence intervals for each district using indirect standardization and rates from eastern Slovakia. Among males from Michalovce (exposed), but not Svidnik (unexposed), there was an excess of cancer of the tongue (SIR=1.46; 1.06-1.96), stomach (SIR=1.15; 1.00-1.32), lung (SIR=1.14; 1.04-1.24), testis (SIR=1.40; 0.97-1.97), and kidney (SIR=1.23; 0.98-1.52), and lower than expected incidence of prostate cancer (SIR=0.83; 0.69-0.97); in contrast, there was an excess of peritoneal (SIR=3.05; 1.11-6.63) and laryngeal cancer (SIR=1.43; 0.99-1.98) in Svidnik not observed Michalovce. Among females from Michalovce, but not Svidnik, there was an excess of cancer of the lip (SIR=2.54; 1.53-3.96), stomach (SIR=1.22; 1.02-1.44), and lung (SIR=1.17; 0.94-1.45); in contrast, there was an excess of kidney (SIR=1.61; 1.03-2.40) and thyroid (SIR=1.97; 1.12-3.20) cancer in Svidnik not observed in Michalovce. Taken together, these results raise the possibility that high environmental exposure to organochlorines in the Michalovce district may be associated with higher rates of certain cancers, particularly stomach and lung cancer.     

Illuminating reactive microbial transport in saturated porous media: demonstration of a visualization method and conceptual transport model

We demonstrate a method to study reactive microbial transport in saturated translucent porous media using the bacteria Pseudomonas fluorescens 5RL genetically engineered to carry a plasmid with bioluminescence genes inducible by salicylate. Induced bacteria were injected into a cryolite grain filled chamber saturated with a sterile non-growth-promoting (phosphorus limited) chemical mixture containing salicylate as an aromatic hydrocarbon analogue. The amount of light produced by the bacteria serves as an estimator of the relative efficiency of aerobic biodegradation since bioluminescence is dependent on both salicylate and oxygen but only consumes oxygen. Bioluminescence was captured with a digital camera and analyzed to study the evolving spatial pattern of the bulk oxygen consuming reactions. As fluid flow transported the bacteria through the chamber, bioluminescence was observed to initially increase until an oxygen depletion zone developed behind the advective front. Bacterial transport was modeled with the advection dispersion equation and oxygen concentration was modeled assuming bacterial consumption via Monod kinetics with consideration of additional effects of rate-limited mass transfer from residual gas bubbles. Consistent with previous measurements, bioluminescence was considered proportional to oxygen consumed. Using the observed bioluminescence, model parameters were fit that were consistent with literature values and produced results in good agreement with the experimental data. These findings demonstrate potential for using this method to investigate the complex spatial and temporal dynamics of reactive microbial transport in saturated porous media.     

Conservation Genetics of North American Freshwater Mussels Amblema and Megalonaias

Freshwater bivalves are among the most endangered groups of organisms in North America. Efforts to protect the declining mussel fauna are confounded by ambiguities associated with recognition of distinct evolutionary entities or species. This, in part, is due to the paucity of reliable morphological characters for differentiating taxa. We have employed allozymes and DNA sequence data to search for diagnosably distinct evolutionary entities within two problematic genera of unionid mussels, Amblema and Megalonaias. Within the genus Amblema three species are recognized based on our DNA sequence data for the mitochondrial 16S rRNA and allozyme data (Amblema neislerii, A. plicata, and A. elliotti). Only one taxonomically distinct entity is recognized within the genus Megalonaias—M. nervosa. Megalonaias boykiniana of the Apalachicolan Region is not diagnosable and does not warrant specific taxonomic status. Interestingly, Megalonaias from west of the Mississippi River, including the Mississippi, exhibited an allozyme and mtDNA haplotype frequency shift suggestive of an east-west dichotomy. The results of this study eliminate one subspecies of Amblema and increase the range of A. plicata. This should not affect the conservation status of "currently stable" assigned to A. plicata by Williams et al. (1993). The conservation status of A. elliotti needs to be reexamined because its distribution appears to be limited to the Coosa River System in Alabama and Georgia.     

Quantifying the efficiency of soil sampling designs: A multivariate approach

The objective of this paper is to quantify and compare the loss functions of the standard two-stage design and its composite sample alternative in the context of multivariate soil sampling. The loss function is defined (conceptually) as the ratio of cost over information and measures design inefficiency. The efficiency of the design is the reciprocal of the loss function. The focus of this paper is twofold: (a) we define a measure of multivariate information using the Kullback–Leibler distance, and (b) we derive the variance-covariance structure for two soil sampling designs: a standard two-stage design and its composite sample counterpart. Randomness in the mass of soil samples is taken into account in both designs. A pilot study in Slovenia is used to demonstrate the calculations of the loss function and to compare the efficiency of the two designs. The results show that the composite sample design is more efficient than the two-stage design. The efficiency ratio is 1.3 for pH, 2.0 for C, 2.1 for N, and 2.5 for CEC. The multivariate efficiency ratio is 2.3. These ratios primarily reflect cost ratios; influence of the information is small.     

The behavioral response of female Nuttall's White-crowned Sparrows to male song of natal and alien dialects

Summary Female Nuttall's White-crowned Sparrows (Zonotrichia leucophrys nuttalli) were tested in a laboratory experiment to determine their response to stimulation by songs from their natal dialect (Clear) and by songs from three different alien dialects (Fig. 1). The greatest number of copulation solicitation displays and amount of locomotor activity were caused by songs of the subject's natal dialect (Clear); the next most potent stimulus was the contiguously adjacent dialect (Buzzy); the least effective stimuli were songs from a dialect 25 km distant (McClure), representing the same non-migratory subspecies, and a dialect 1,900 km distant (Sand Creek), representing a migratory montane subspecies of White-crowned Sparrow (Figs. 2–4).These results constitute a test of a deduction made from the assortative mating theory and suggest that female White-crowned Sparrows find male song of their natal dialect sexually more stimulating. Thus, speculating about the natural circumstances, females given an unrestricted choice would be expected to mate with males from their natal dialect region.     

Malaria infection and host behavior: a comparative study of Neotropical primates

Parasites are ubiquitous in populations of free-ranging animals and impact host fitness, but virtually nothing is known about the factors that influence patterns of disease risk across species and the effectiveness of behavioral defenses to reduce this risk. We investigated the correlates of malaria infection (prevalence) in Neotropical primates using data from the literature, focusing on host traits involving group size, body mass, and sleeping behavior. Malaria is spread to these monkeys through anopheline mosquitoes that search for hosts at night using olfactory cues. In comparative tests that used two different phylogenetic trees, we confirmed that malaria prevalence increases with group size in Neotropical primates, as suggested by a previous non-phylogenetic analysis. These results are consistent with the hypothesis that larger groups experience increased risk of attack by mosquitoes, and counter to the hypothesis that primates benefit from the encounter-dilution effect of avoiding actively-seeking insects by living in larger groups. In contrast to non-phylogenetic tests, body mass was significant in fewer phylogeny-based analyses, and primarily when group size was included as a covariate. We also found statistical support for the hypothesis that sleeping in closed microhabitats, such as tree holes or tangles of vegetation, reduces the risk of malaria infection by containing the host cues used by mosquitoes to locate hosts. Due to the small number of evolutionary transitions in sleeping behavior in this group of primates, however, this result is considered preliminary until repeated with a larger sample size. In summary, risk of infection with malaria and other vector-borne diseases are likely to act as a cost of living in groups, rather than a benefit, and sleeping site selection may provide benefits by reducing rates of attack by malaria vectors.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.