Copyright (c) 2012 All rights reserved. http://works.bepress.com/kevin_feris Recent documents in Kevin P. Feris en-us Thu, 19 Jan 2012 10:35:10 PST 3600 http://works.bepress.com/kevin_feris/10 http://works.bepress.com/kevin_feris/10 Fri, 16 Sep 2011 09:24:11 PDT We used a combination of sampling and statistical approaches to investigate the relative influence of metals, soil acidity, and organic matter on a suite of analogous plant and microbial community parameters in floodplain soils contaminated by mine wastes in the early twentieth century. We compared the sensitivity of plant and microbial communities to environmental variables and to one another using constrained ordination analyses. Environmental factors accounted for a larger percentage of the total variance in microbial communities (56.2%) than plant communities (22.0%). We also investigated biological and geochemical changes that occurred along a short transect (64 cm) that spanned a transition from productive grassland to an area of barren wasteland representing a total functional collapse of the grassland/soil ecosystem. Along this small-scale transect we quantified geochemical parameters and biological parameters in two soil layers, an upper layer (0–10 cm) and a lower layer (10–20 cm). Results from the short transect indicated that soil respiration was not a strong indicator of underlying metal concentrations, but soil acidity was correlated in the upper and lower layers. PLFA profiles changed with distance along the gradient in the upper, but not the lower layer. Implications for remediation of contaminated floodplain soils are discussed.

]]> Philip W. Ramsey et al. http://works.bepress.com/kevin_feris/9 http://works.bepress.com/kevin_feris/9 Fri, 17 Jun 2011 16:27:02 PDT Nanoscale materials can have cytotoxic effects. Here we present the first combined empirical and theoretical investigation of the influence of electrostatic attraction on nanoparticle cytotoxicity. Modeling electrostatic interactions between cells and 13 nm spheres of zinc oxide nanoparticles provided insight into empirically determined variations of the minimum inhibitory concentrations between four differently charged isogenic strains of Pseudomonas aeruginosa PAO1. We conclude that controlling the electrostatic attraction between nanoparticles and their cellular targets may permit the modulation of nanoparticle cytotoxicity.

]]> Kevin Feris http://works.bepress.com/kevin_feris/8 http://works.bepress.com/kevin_feris/8 Wed, 15 Jun 2011 15:16:43 PDT Fluorescein isothiocyanate (FITC)-encapsulated SiO₂ core-shell particles with a nanoscale ZnO finishing layer have been synthesized for the first time as multifunctional "smart" nanostructures. Detailed characterization studies confirmed the formation of an outer ZnO layer on the SiO₂–FITC core. These ~200 nm sized particles showed promise toward cell imaging and cellular uptake studies using the bacterium Escherichia coli and Jurkat cancer cells, respectively. The FITC encapsulated ZnO particles demonstrated excellent selectivity in preferentially killing Jurkat cancer cells with minimal toxicity to normal primary immune cells (18% and 75% viability remaining, respectively, after exposure to 60 μg/ml) and inhibited the growth of both gram-positive and gram-negative bacteria at concentrations ≥250–500 μg/ml (for Staphylococcus aureus and Escherichia coli, respectively). These results indicate that the novel FITC encapsulated multifunctional particles with nanoscale ZnO surface layer can be used as smart nanostructures for particle tracking, cell imaging, antibacterial treatments and cancer therapy.

]]> Hua Wang et al. http://works.bepress.com/kevin_feris/7 http://works.bepress.com/kevin_feris/7 Wed, 15 Jun 2011 15:16:40 PDT Accurate natural resource damage assessment necessitates monitoring organisms or communities that respond most sensitively to contaminants. Observational studies have demonstrated a correlation between fluvial heavy metal deposition and hyporheic microbial community structure. To establish a causal relationship between sediment metal content and the structure of colonizing bacterial communities, we performed a controlled field experiment. River sediments of 1.75−2.36 mm in diameter with five different contaminant concentrations were collected from an environmental metal contamination gradient. Sediments were sterilized and then recolonized by incubation in the hyporheic zone of an uncontaminated river (i.e., a common garden experiment was performed). A significant correlation between hyporheic microbial community structure and heavy metal contamination (R² = 0.81) was observed. The abundance of two phylogenetic groups was highly correlated with the level of heavy metal contamination (Group I, R² = 0.96; Group III, R² = 0.96, most closely affiliated with the α- and γ-proteobacteria, respectively). Microbial community structural responses were detected at metal concentrations an order of magnitude lower than those previously reported to impact benthic macroinvertebrate communities. We conclude that hyporheic microbial communities could offer the most sensitive method for assessing natural resource damage in lotic ecosystems in response to fluvial heavy metal deposition.

]]> Kevin P. Feris et al. http://works.bepress.com/kevin_feris/6 http://works.bepress.com/kevin_feris/6 Tue, 24 May 2011 09:45:46 PDT A novel microcalorimetric approach was used to analyze the responses of a metal-tolerant soil bacterium (Pseudomonas putida strain KT2440) to metal resistance gene deletions in cadmium-amended media. As hypothesized, under cadmium stress, the wild-type strain benefited from the resistance genes by entering the exponential growth phase earlier than two knockout strains. In the absence of cadmium, strain KT1, carrying a deletion in the main component (czcA1) of a Cd/Zn chemiosmotic efflux transporter (CzcCBA1), grew more efficiently than the wild type and released 700 kJ (per mole of biomass carbon) less heat than the wild-type strain, showing the energetic cost of maintaining CzcCBA1 in the absence of cadmium. A second mutant strain (KT4) carrying a different gene deletion, cadA2, which encodes the main Cd/Pb efflux transporter (a P-type ATPase), did not survive beyond moderate cadmium concentrations and exhibited a decreased growth yield in the absence of cadmium. Therefore, CadA2 plays an essential role in cadmium resistance and perhaps serves an additional function. The results of this study provide direct evidence that heavy metal cation efflux mechanisms facilitate shorter lag phases in the presence of metals and that the maintenance and expression of tolerance genes carry quantifiable energetic costs and benefits.

]]> Sean M. Gibbons et al. http://works.bepress.com/kevin_feris/5 http://works.bepress.com/kevin_feris/5 Fri, 16 Jan 2009 07:38:38 PST Abstract Nanoparticles are increasingly being recognized for their potential utility in biological applications including nanomedicine. Here we examine the response of normal human cells to ZnO nanoparticles under different signaling environments and compare it to the response of cancerous cells. ZnO nanoparticles exhibit a strong preferential ability to kill cancerous T cells (∼28–35 ×) compared to normal cells. Interestingly, the activation state of the cell contributes toward nanoparticle toxicity, as resting T cells display a relative resistance while cells stimulated through the T cell receptor and CD28 costimulatory pathway show greater toxicity in direct relation to the level of activation. Mechanisms of toxicity appear to involve the generation of reactive oxygen species, with cancerous T cells producing higher inducible levels than normal T cells. In addition, nanoparticles were found to induce apoptosis and the inhibition of reactive oxygen species was found to be protective against nanoparticle induced cell death. The novel findings of cell selective toxicity, towards potential disease causing cells, indicate a potential utility of ZnO nanoparticles in the treatment of cancer and/or autoimmunity.

]]> Cory Hanley et al. Research Publications and Presentations http://works.bepress.com/kevin_feris/4 http://works.bepress.com/kevin_feris/4 Fri, 16 Jan 2009 07:38:33 PST We report on the toxicity of ZnO nanoparticles (NPs) to gram-negative and gram-positive bacterial systems, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and primary human immune cells. ZnO NP (~13 nm) showed complete inhibition of E. coli growth at concentrations 3.4 mM, whereas growth of S. aureus was completely inhibited for 1 mM. Parallel experiments using flow cytometry based assays clearly demonstrated that growth inhibitory properties of ZnO NP were accompanied by a corresponding loss of cell viability. Identical ZnO NP had minimal effects on primary human T cell viability at concentrations toxic to both gram-negative and gram-positive bacteria. Collectively, these experiments demonstrate selectivity in the toxic nature of ZnO NP to different bacterial systems and human T lymphocytes. Developing selective toxicity to biological systems and controlling it by NP design could lead to biomedical and antibacterial applications.

]]> K. M. Reddy et al. Research Publications and Presentations http://works.bepress.com/kevin_feris/3 http://works.bepress.com/kevin_feris/3 Fri, 16 Jan 2009 07:38:29 PST Ethanol (EtOH) is a commonly used fuel oxygenate in reformulated gasoline and is an alternative fuel and fuel supplement. Effects of EtOH release on aquifer microbial ecology and geochemistry have not been well characterized in situ. We performed a controlled field release of petroleum constituents (benzene (B), toluene (T), o-xylene (o-X) at ∼1–3 mg/L each) with and without EtOH (∼500 mg/L). Mixed linear modeling (MLM) assessed effects on the microbial ecology of a naturally sulfidic aquifer and how the microbial community affected B, T, and o-X plume lengths and aquifer geochemistry. Changes in microbial community structure were determined by quantitative polymerase chain reaction (qPCR) targeting Bacteria, Archaea, and sulfate reducing bacteria (SRB); SRB were enumerated using a novel qPCR method targeting the adenosine-5′-phosphosulfate reductase gene. Bacterial and SRB densities increased with and without EtOH-amendment (1−8 orders of magnitude). Significant increases in Archaeal species richness; Archaeal cell densities (3–6 orders of magnitude); B, T, and o-X plume lengths; depletion of sulfate; and induction of methanogenic conditions were only observed with EtOH-amendment. MLM supported the conclusion that EtOH-amendment altered microbial community structure and function, which in turn lowered the aquifer redox state and led to a reduction in bioattenuation rates of B, T, and o-X.

]]> Kevin Feris Research Publications and Presentations http://works.bepress.com/kevin_feris/2 http://works.bepress.com/kevin_feris/2 Fri, 16 Jan 2009 07:38:25 PST Interest in the relationships between soil microbial communities and ecosystem functions is growing with increasing recognition of the key roles microorganisms play in a variety of ecosystems. With a wealth of microbial methods now available, selecting the most appropriate method can be daunting, especially to those new to the field of microbial ecology. In this review, we highlight those methods currently used and most applicable to ecological studies, including assays to study various aspects of the carbon and nitrogen cycles (e.g., pool dilution, acetylene reduction, enzyme analyses, among others), methods to assess microbial community composition (e.g., phospholipid fatty acid analysis (PLFA), denaturing gradient gel electrophoresis (DGGE), terminal restriction fragment length polymorphism analysis (TRFLP), quantitative polymerase chain reaction (qPCR)) and methods to directly link community structure to function (e.g., stable isotope probing (SIP)). In our discussion of these methods, we describe the information each method provides, as well as some of their strengths and weaknesses. Using a case study, we illustrate how these methods can be applied to investigate relationships between microbial communities and the processes they perform in wetland ecosystems. We end our discussion with a series of questions to consider prior to designing experiments, in the hope that these questions will help guide ecologists in selecting the most appropriate method(s) for their research.

]]> Rebecca E. Drenovsky et al. Research Publications and Presentations