Spatial patterns of microbial diversity and activity in an aged creosote-contaminated site

Restoration of polluted sites via in situ bioremediation relies heavily on the indigenous microbes and their activities. Spatial heterogeneity of microbial populations, contaminants and soil chemical parameters on such sites is a major hurdle in optimizing and implementing an appropriate bioremediation regime. We performed a grid-based sampling of an aged creosote-contaminated site followed by geostatistical modelling to illustrate the spatial patterns of microbial diversity and activity and to relate these patterns to the distribution of pollutants. Spatial distribution of bacterial groups unveiled patterns of niche differentiation regulated by patchy distribution of pollutants and an east-to-west pH gradient at the studied site. Proteobacteria clearly dominated in the hot spots of creosote pollution, whereas the abundance of Actinobacteria, TM7 and Planctomycetes was considerably reduced from the hot spots. The pH preferences of proteobacterial groups dominating in pollution could be recognized by examining the order and family-level responses. Acidobacterial classes came across as generalists in hydrocarbon pollution whose spatial distribution seemed to be regulated solely by the pH gradient. Although the community evenness decreased in the heavily polluted zones, basal respiration and fluorescein diacetate hydrolysis rates were higher, indicating the adaptation of specific indigenous microbial populations to hydrocarbon pollution. Combining the information from the kriged maps of microbial and soil chemistry data provided a comprehensive understanding of the long-term impacts of creosote pollution on the subsurface microbial communities. This study also highlighted the prospect of interpreting taxa-specific spatial patterns and applying them as indicators or proxies for monitoring polluted sites

Cross-tolerance to abiotic stresses in halophytes: Application for phytoremediation of organic pollutants

International audienceHalopytes are plants able to tolerate high salt concentrations but no clear definition was retained for them. In literature, there are more studies that showed salt-enhanced tolerance to other abiotic stresses compared to investigations that found enhanced salt tolerance by other abiotic stresses in halophytes. The phenomenon by which a plant resistance to a stress induces resistance to another is referred to as cross-tolerance. In this work, we reviewed cross-tolerance in halophytes at the physiological, biochemical, and molecular levels. A special attention was accorded to the cross-tolerance between salinity and organic pollutants that could allow halophytes a higher potential of xenobiotic phytoremediation in comparison with glycophytes

Monitoring of microbial hydrocarbon remediation in the soil

Bioremediation of hydrocarbon pollutants is advantageous owing to the cost-effectiveness of the technology and the ubiquity of hydrocarbon-degrading microorganisms in the soil. Soil microbial diversity is affected by hydrocarbon perturbation, thus selective enrichment of hydrocarbon utilizers occurs. Hydrocarbons interact with the soil matrix and soil microorganisms determining the fate of the contaminants relative to their chemical nature and microbial degradative capabilities, respectively. Provided the polluted soil has requisite values for environmental factors that influence microbial activities and there are no inhibitors of microbial metabolism, there is a good chance that there will be a viable and active population of hydrocarbon-utilizing microorganisms in the soil. Microbial methods for monitoring bioremediation of hydrocarbons include chemical, biochemical and microbiological molecular indices that measure rates of microbial activities to show that in the end the target goal of pollutant reduction to a safe and permissible level has been achieved. Enumeration and characterization of hydrocarbon degraders, use of micro titer plate-based most probable number technique, community level physiological profiling, phospholipid fatty acid analysis, 16S rRNA- and other nucleic acid-based molecular fingerprinting techniques, metagenomics, microarray analysis, respirometry and gas chromatography are some of the methods employed in bio-monitoring of hydrocarbon remediation as presented in this review

Integrated control and related technology of assistive devices

Assistive devices are now available that allow persons with severe physical disabilities to complete tasks independently. When the user has severe physical limitations, it may be advantageous to have an integrated control system where a single control interface (e.g., joystick, head switches, voice recognition system, keypad) is used to operate two or more assistive devices (e.g., power wheelchairs, augmentative communication devices, computers, environmental control units, and other devices that are controlled electronically). The advantages of integrated control are that persons with limited motor control can access several devices with one access site without assistance, and the user does not need to learn a different operating mechanism for each device. The purpose of this review is to convey the depth and breadth of the research that has been conducted on integrated control systems, as well as to provide some insights into future directions. We reviewed research works pertaining to communication and environmental control, computer access, and wheelchair guidance systems. Information gathered in this study will help people become fully aware of the status of contemporary integrated control technology in order to increase the quality of life of people who use electronic assistive devices. © 2003 RESNA

Investigation of the performance of an ergonomic handrim as a pain-relieving intervention for manual wheelchair users

Manual wheelchair users commonly experience pain in their hands and wrists associated with the repetitive stress of propulsion. The objective of this research was to examine the effect of an ergonomic wheelchair handrim as an intervention designed to reduce pain in the hands and wrists and improve functional outcomes for manual wheelchair users. Three studies were conducted to achieve this objective. In the first study 10 individuals with paraplegia underwent a biomechanical analysis before and after a 2-week practice period with a Natural-Fit (NF) prototype ergonomic handrim. The biomechanical results showed that grip moments were reduced with the NF handrim prototype as compared with the subjects' current handrim (p <.1). Other biomechanical findings were mixed. In the second study, 46 manual wheelchair users who replaced their standard handrim with the commercially available NF handrim completed a questionnaire of retrospective measures of symptom severity. Average duration of use of the NF was 6 months. When asked to compare propelling with the NF to propelling with their prior handrims, 85% of respondents reported less pain in their hands and 80% reported less pain in their wrists. The third study was a replication and extension of Study 2: 82 manual wheelchair users who replaced their standard handrim with the NF completed retrospective symptom severity and functional status scales after using the NF for an average of 9 months. Results again confirmed that using the NF led to a reduction in the severity of symptoms and to improved functional outcomes. © 2006 Taylor & Francis Group, LLC