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In the past few decades, researchers have been examining natural microbial communities with a variety of culture-independent methods. These methods have also been applied to the study of microbial communities impacted by anthropogenic activity. Microbial communities are of interest because of their innate metabolic activities that can be exploited for a variety of beneficial purposes, such as the remediation of harmful pollutants. This manuscript reviews three widely used culture-independent methods as applied to the field of bioremediation (sequencing of rDNA clone libraries, terminal restriction fragment length polymorphism, and microarrays). These techniques are economically feasible and appropriate for undergraduate researchers. Each technique is briefly explained before case studies of their successful applications in bioremediation are reviewed. Drawbacks of each method are also presented. The advancement of microbial community analysis techniques in the future is discussed.
The allelopathic compounds secreted into the soil by Brassica nigra (L.) W. D. J. Koch (black mustard) serve to reduce seed germination rates and plant fitness in nearby species. As such, B. nigra shares in an amensalistic relationship with most of the species within range of its allelopathic interference. However, Cucurbita foetidissima (buffalo gourd) is a native species in southern California that has managed to persist within and around areas invaded by B. nigra. We hypothesized that increased proximity to B. nigra would negatively impact C. foetidissima fitness and alter life history strategies. We found that C. foetidissima growing in close proximity to B. nigra had smaller fruit volume, a lower number of seeds per fruit, lower dry seed weight, a higher number of seeds per cubic centimeter, and a higher number of seeds per gram of fruit than C. cucurbita that grew outside of the allelopathic range of B. nigra. The reproductive strategy of C. cucurbita also appeared to change from K-selection to r-selection in the presence of allelochemicals.
Stress has been a subject of intense research over the past few decades. Any holistic understanding of stress requires an interdisciplinary approach. In particular, psychosocial stress studies must include both sociocultural and biochemical variables in their design. In this experiment, a competitive binding immunoassay was used to quantify cortisol samples before and after an exam in undergraduate university students (n = 29). Multiple variables potentially relating to cortisol production and psychosocial stress reactions were assessed using a pre-exam questionnaire. This questionnaire also included a question regarding perceived preparedness before and after the exam. It was hypothesized that a rise in cortisol (signifying a stress response) would correlate with negative change between predicted preparedness for an exam and retrospect preparedness. Out of 29 students, 10 exhibited a rise in cortisol. Of those 10, 9 noted a decrease in confidence after the exam. A contingency table was used to organize data for a Chi2 analysis. It was found that a rise in cortisol was significantly correlated with a negative change in confidence (p < 0.05). Future studies should investigate the roles of corticosteroid binding globulin and other possible variables in salivary cortisol measurement as well as any effects of group study on pre-exam salivary cortisol levels.
While there is currently no research linking skin infections to improperly sanitized yoga mats, there are many investigations concerning athletes and infectious disease outbreaks due to contact with athletic equipment, particularly at the high school or college level. The yoga community has developed a number of essential-oil based cleaning products that are advertised as “all-natural” or “organic” and antibacterial or antifungal. In order to test the effectiveness of these agents, two commercially available products were chosen and a third was produced in the laboratory to simulate the popular “Do It Yourself” recipes. The antibacterial effectiveness of these products was tested against Staphylococcus aureus and compared to the antibacterial properties of Lysol® using disk diffusion assays. Based on the lack of established disinfectant chemicals in the “all natural” cleaners, we hypothesized that these cleaning products would not be as effective in controlling the growth of S. aureus as Lysol. The three natural cleaning products appear to be minimally effective against S. aureus, even at high concentrations. Surprisingly, when tested independently, select ingredients of the cleaning products exhibit high levels of effectiveness.