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Lubbock, TX, United States

Moore-Kucera J.,Texas Tech University | Cox S.B.,Research and Testing Laboratory LLC | Peyron M.,Western Washington University | Bailes G.,Western Washington University | And 5 more authors.
Applied Microbiology and Biotechnology | Year: 2014

Plastics are used widely as agricultural mulches to suppress weeds and retain soil moisture. Disposal of conventional plastic mulches requires physical removal for disposal in a landfill or incineration. Biodegradable plastic mulches that could be tilled into the soil at the end of a growing season represent an attractive alternative to conventional plastic mulches. In this study, three commercially available mulches labeled as "biodegradable" and one experimental, potentially biodegradable mulch were used during a tomato growing season, and then buried in field soil at three locations for approximately 6 months, as would occur typically in an agricultural setting. Degradation after 6 months in soil was minimal for all but the cellulosic mulch. After removal of mulches from soil, fungi were isolated from the mulch surfaces and tested for their ability to colonize and degrade the same mulches in pure culture. The majority of culturable soil fungi that colonized biodegradable mulches were within the family Trichocomaceae (which includes beneficial, pathogenic, and mycotoxigenic species of Aspergillus and Penicillium). These isolates were phylogenetically similar to fungi previously reported to degrade both conventional and biodegradable plastics. Under pure culture conditions, only a subset of fungal isolates achieved detectable mulch degradation. No isolate substantially degraded any mulch. Additionally, DNA was extracted from bulk soil surrounding buried mulches and ribosomal DNA was used to assess the soil microbial community. Soil microbial community structure was significantly affected by geographical location, but not by mulch treatments. © 2014 Springer-Verlag.

Erickson R.A.,Texas Tech University | Erickson R.A.,U.S. Geological Survey | Cox S.B.,Texas Tech University | Cox S.B.,Research and Testing Laboratory LLC | And 5 more authors.
Ecological Modelling | Year: 2014

Population models have emerged as a powerful tool to better understand the ecological effects of toxicant exposure. Currently, most ecotoxicology population models are deterministic and fail to account for natural variability in biological processes and uncertainty in parameter estimates. We developed, parameterized, and analyzed a Daphnia population model with three different levels of demographic stochasticity to examine how a pesticide, pendimethalin, affects population dynamics. We conducted laboratory studies to generate the data used for the modeling process. The simplest model only included parameter uncertainty and variability. The second model included daily stochastic fecundities. The third model included stochastic fecundities and stochastic mortalities. Of the three models, the second model with stochastic fecundity best described our laboratory test system. All three models were used to test hypotheses about how pesticides would affect population dynamics. We found that pendimethalin either decreased the baseline juvenile survivorship rate or the carrying capacity. We could differentiate the two test effects with our system. Our findings demonstrate how stochastic population models may provide insight into pesticide exposure. © 2013 Elsevier B.V.

Erickson R.A.,Texas Tech University | Hayhoe K.,Texas Tech University | Presley S.M.,Texas Tech University | Allen L.J.S.,Texas Tech University | And 3 more authors.
Environmental Research Letters | Year: 2012

Shifts in temperature and precipitation patterns caused by global climate change may have profound impacts on the ecology of certain infectious diseases. We examine the potential impacts of climate change on the transmission and maintenance dynamics of dengue, a resurging mosquito-vectored infectious disease. In particular, we project changes in dengue season length for three cities: Atlanta, GA; Chicago, IL and Lubbock, TX. These cities are located on the edges of the range of the Asian tiger mosquito within the United States of America and were chosen as test cases. We use a disease model that explicitly incorporates mosquito population dynamics and high-resolution climate projections. Based on projected changes under the Special Report on Emissions Scenarios (SRES) A1fi (higher) and B1 (lower) emission scenarios as simulated by four global climate models, we found that the projected warming shortened mosquito lifespan, which in turn decreased the potential dengue season. These results illustrate the difficulty in predicting how climate change may alter complex systems. © 2012 IOP Publishing Ltd.

Mutlu E.A.,Rush University Medical Center | Keshavarzian A.,Rush University Medical Center | Keshavarzian A.,Rush University | Keshavarzian A.,University Utrecht | And 17 more authors.
PLoS Pathogens | Year: 2014

HIV progression is characterized by immune activation and microbial translocation. One factor that may be contributing to HIV progression could be a dysbiotic microbiome. We therefore hypothesized that the GI mucosal microbiome is altered in HIV patients and this alteration correlates with immune activation in HIV. 121 specimens were collected from 21 HIV positive and 22 control human subjects during colonoscopy. The composition of the lower gastrointestinal tract mucosal and luminal bacterial microbiome was characterized using 16S rDNA pyrosequencing and was correlated to clinical parameters as well as immune activation and circulating bacterial products in HIV patients on ART. The composition of the HIV microbiome was significantly different than that of controls; it was less diverse in the right colon and terminal ileum, and was characterized by loss of bacterial taxa that are typically considered commensals. In HIV samples, there was a gain of some pathogenic bacterial taxa. This is the first report characterizing the terminal ileal and colonic mucosal microbiome in HIV patients with next generation sequencing. Limitations include use of HIV-infected subjects on HAART therapy. © 2014 Mutlu et al.

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