Landscape characteristics shape surface soil microbiomes in the Chihuahuan Desert.

Introduction: Soil microbial communities, including biological soil crust microbiomes, play key roles in water, carbon and nitrogen cycling, biological weathering, and other nutrient releasing processes of desert ecosystems. However, our knowledge of microbial distribution patterns and ecological drivers is still poor, especially so for the Chihuahuan Desert.

Methods: This project investigated the effects of trampling disturbance on surface soil microbiomes, explored community composition and structure, and related patterns to abiotic and biotic landscape characteristics within the Chihuahuan Desert biome.

Environmental filtering structures fungal endophyte communities in tree bark.

The factors that control the assembly and composition of endophyte communities across plant hosts remains poorly understood. This is especially true for endophyte communities inhabiting inner tree bark, one of the least studied components of the plant microbiome. Here, we test the hypothesis that bark of different tree species acts as an environmental filter structuring endophyte communities, as well as the alternative hypothesis, that bark acts as a passive reservoir that accumulates a diverse assemblage of spores and latent fungal life stages.

Anthropogenic N deposition alters soil organic matter biochemistry and microbial communities on decaying fine roots.

Fine root litter is a primary source of soil organic matter (SOM), which is a globally important pool of C that is responsive to climate change. We previously established that ~20 years of experimental nitrogen (N) deposition has slowed fine root decay and increased the storage of soil carbon (C; +18%) across a widespread northern hardwood forest ecosystem. However, the microbial mechanisms that have directly slowed fine root decay are unknown.

A new generation of zirconia supported metal oxide catalysts for converting low grade renewable feedstocks to biodiesel.

A new class of zirconia supported mixed metal oxides (ZnO-TiO(2)-Nd(2)O(3)/ZrO(2) and ZnO-SiO(2)-Yb(2)O(3)/ZrO(2)) has demonstrated the ability to convert low quality, high free fatty acid (FFA) bio-oils into biodiesel. Pelletized catalysts of ZrO(2) supported metal oxides were prepared via a sol-gel process and tested in continuous flow packed bed reactors for up to 6 months. In a single pass, while operating at mild to moderate reaction conditions, 195 °C and 300 psi, these catalysts can perform simultaneous esterification and transesterification reactions on feedstock of 33% FFA and 67% soybean oil to achieve FAME yields higher than 90%.

Continuous microalgae cultivation in a photobioreactor.

New biomass sources for alternative fuels has become a subject of increasing importance as the nation strives to resolve the economic and strategic impacts of limited fossil fuel resources on our national security, environment, and global climate. Algae are among the most promising non-food-crop-based biomass feedstocks. However, there are currently no commercially viable microalgae-based production systems for biofuel production that have been developed, as limitations include less-than optimal oil content, growth rates, and cultivation techniques.

Nanoscale investigation on E. coli adhesion to modified silicone surfaces.

Bacterial infection is a major challenge in biomaterials development. The adhesion of microorganisms to the material surface is the first step in infectious conditions and this quickly leads to the formation of biofilms on a material surface. A unique attribute of atomic force microscopy (AFM) is that it reveals not only the morphology of cells and the surface roughness of the substrate, but it can also quantify the adhesion force between bacteria and surfaces.

Culture of microalgae Chlorella minutissima for biodiesel feedstock production.

Microalgae are among the most promising of non-food based biomass fuel feedstock alternatives. Algal biofuels production is challenged by limited oil content, growth rate, and economical cultivation. To develop the optimum cultivation conditions for increasing biofuels feedstock production, the effect of light source, light intensity, photoperiod, and nitrogen starvation on the growth rate, cell density, and lipid content of Chlorella minutissima were studied.

Performance of heterogeneous ZrO2 supported metaloxide catalysts for brown grease esterification and sulfur removal.

In order to achieve a viable biodiesel industry, new catalyst technology is needed which can process a variety of less expensive waste oils, such as yellow grease and brown grease. However, for these catalysts to be effective for biodiesel production using these feedstocks, they must be able to tolerate higher concentrations of free fatty acids (FFA), water, and sulfur. We have developed a class of zirconia supported metaloxide catalysts that achieve high FAME yields through esterification of FFAs while simultaneously performing desulfurization and de-metallization functions.

Effect of nutrients on growth and lipid accumulation in the green algae Dunaliella tertiolecta.

Production of biofuel from algae is dependent on the microalgal biomass production rate and lipid content. Both biomass production and lipid accumulation are limited by several factors, of which nutrients play a key role. In this research, the marine microalgae Dunaliella tertiolecta was used as a model organism and a profile of its nutritional requirements was determined.

Competitive transesterification of soybean oil with mixed methanol/ethanol over heterogeneous catalysts.

Methylesters and ethylesters of fatty acids were synthesized using homogeneous CH(3)ONa and CH(3)CH(2)ONa, anion exchanged resin, and CaO-La(2)O(3) catalysts. Methanol, ethanol, and methanol/ethanol mixtures were used as the alcohol feed for transesterification of soybean oil. With a homogeneous catalyst (CH(3)ONa) there was essentially no difference in conversion rates between methanolysis and ethanolysis in batch reactions.

Influence of silicone surface roughness and hydrophobicity on adhesion and colonization of Staphylococcus epidermidis.

Bacterial adhesion and colonization are complicated processes that depend on many factors, including surface chemistry, hydrophobicity, and surface roughness. The contribution of each of these factors has not been fully elucidated because most previous studies used different polymeric surfaces to achieve differences in properties. The objective of this study was to modify hydrophobicity and roughness on one polymeric surface, eliminating the confounding contribution of surface chemistry.

Patterned immobilization of antibodies in mechanically induced cracks.

A new approach of chemically immobilizing antibody within a pattern based on thin-film cracking is presented. An adjustable pattern width is achieved with resolutions varied from nano- to microscale by using loading stress on thin-film coated elastomer substrate in both one and two dimensions. By introduction of solution or chemical vapor deposition approaches, antibodies were covalently immobilized in the channels.

Functionalization of AlN surface and effect of spacer density on Escherichia coli pili-antibody molecular recognition.

The immobilization of antibodies to sensor surfaces is critical in biochemical sensor development. In this study, Jeffamine spacers were employed to tether Escherichia coli K99 pilus antibody to AlN/sapphire surfaces which may allow the antibody to freely reorient and potentially improving the antigen capture efficiency. Spacer density was one of the key parameters to be optimized in studying its effect on the immobilization of antibody.

The effect of self-assembled layers on the release behavior of rifampicin-loaded silicone.

Providing a long period of sustained antibiotic release is one of the important challenges in the development of clinical shunts for long-term implantation. A cast-molding approach was used to load rifampicin into the silicone precursor before curing. Sustained in vitro release from rifampicin-loaded silicone for upwards of 110 days at a level of approximately 2-4 microg/cm2 per day was achieved.

Investigation of spacer length effect on immobilized Escherichia coli pili-antibody molecular recognition by AFM.

The immobilization of antibodies to sensor surfaces is critical in biochemical sensor development. In this study, Poly(ethylene glycol) (PEG) and Jeffamine spacers were employed to tether Escherichia coli K99 pilus antibody to silicon wafer surfaces for the purpose of improving the orientation of antibody as well as reducing the steric hindrance. To illustrate the effect of spacer length, a variety of linear polymers were used to covalently attach the antibodies to silicon surfaces.

Stability of and inflammatory response to silicon coated with a fluoroalkyl self-assembled monolayer in the central nervous system.

A self-assembled monolayer (SAM) of fluoroalkyl silane (FAS) (CF(3)(CF(2))(5)(CH(2))(2)SiCl(3)) was deposited on the surface of silicon wafers, aiming to enhance its stability and to reduce the inflammatory response in the central nervous system. Following implantation of the FAS SAM coated silicon in rat brains, the FAS SAM coating failed to reduce the inflammatory response of silicon, because it could not prevent the corrosion of the underlying silicon. The corrosion was hindered for the initial 10 days by the FAS SAM coating, but there was nearly no difference when compared to the uncoated silicon when the implantation periods were extended to 28 and 90 days.

Effect of surface modification of siliconeon Staphylococcus epidermidis adhesion and colonization.

Cerebrospinal fluid (CSF) shunts for the treatment of hydrocephalus are generally made of silicone rubber. The growth of bacterial colonies on the silicone surface leads to frequent CSF shunt complications. A systematic study of the effect of the surface modification of silicone on Staphylococcus epidermidis adhesion and colonization was performed for different incubation times by means of colony counting and scanning electron microscopy (SEM).

Effect of surface proteins on Staphylococcus epidermidis adhesion and colonization on silicone.

Shunt infections are one of the most serious complications in shunt implant surgery. Previous studies have suggested that cerebrospinal fluid (CSF) proteins could affect bacterial adhesion and subsequent shunt infection. A systematic study using immobilized protein on the surface of silane-modified silicone was conducted to determine how these modifications influenced Staphylococcus epidermidis adhesion and colonization.

Nanoscale investigation on adhesion of E. coli to surface modified silicone using atomic force microscopy.

Bacterial adhesion on biomaterial surfaces is the initial step in establishing infections and leads to the formation of biofilms. In this study, silicone was modified with different biopolymers and silanes, including: heparin, hyaluronan, and self-assembled octadecyltrichlorosilane (OTS), and fluoroalkylsilane (FAS). The aim was to provide a stable and bacteria-resistant surface by varying the degree of hydrophobicity and the surface structure.

Immobilization of polysaccharides on a fluorinated silicon surface.

A self-assembled monolayer (SAM) of fluoroalkyl silane (FAS) was deposited on a silicon surface by chemical vapor deposition (CVD) at room temperature under 1.01x10(5)Pa nitrogen. Using this new approach, the quality and reproducibility of the SAM are better than those prepared either in solution or by vapor phase deposition, and the deposition process is simpler.

Effect of cast molded rifampicin/silicone on Staphylococcus epidermidis biofilm formation.

Infection is one of the most common catheter-related complications, especially in shunt systems used to treat hydrocephalus. Staphylococcus epidermidis is directly related to biomaterial infections owing to its ability to form a biofilm on implanted materials. In this study, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to investigate the effect of the antibiotic rifampicin on the colonization and growth of S.

In vitro haemocompatibility and stability of two types of heparin-immobilized silicon surfaces.

Heparin was covalently immobilized onto a silicon surface by two different methods, carbodiimide-based immobilization and photo-immobilization. In the former method, a (3-aminopropyl) trimethoxysilane (APTMS) self-assembled monolayer (SAM) or multilayer was first coated onto the silicon surface as the bridging layer, and heparin was then attached to the surface in the presence of water-soluble carbodiimide. In the latter method, an octadecyltrichlorosilane (OTS) SAM was coated on the silicon surface as the bridging layer, and heparin was modified by attaching photosensitive aryl azide groups.

In vitro stability study of organosilane self-assemble monolayers and multilayers.

The stability of self-assembled monolayers (SAMs) and multilayers formed on silicon surface by amino-terminated silanes and SAMs formed by alkyl and glycidyl terminated silanes were investigated in vitro with saline solution at 37 degrees C for up to 10 days. FTIR and XPS results indicated that amino-terminated SAMs and multilayers are very unstable if the alkyl chain is short ((CH2)3), while stable if the alkyl chain is long ((CH2)11). On the other hand, alkyl-terminated SAMs are very stable regardless of the alkyl chain length, and glycidyl terminated SAM retained approximately 77% of the organosilane molecules after 10 days.

Feasibility of a photosynthetic artificial lung.

The success of extracorporeal membrane oxygenation (ECMO) for the treatment of acute respiratory failure has led to consideration of the development of a more portable, and perhaps even implantable, artificial lung. The authors suggest a bioregenerative life support system that includes a photo-synthetic organism that can remove CO2 and produce O2 in the presence of an energy source. To build a model of such a photosynthetic artificial lung, the photosynthetic capability of a high temperature strain of the algae Chlorella pyrenoidosa was maximized at a cell density of 25 million cells/ml to serve as the O2 producer and CO2 remover.

Survival of composite chondrocutaneous grafts by vessel implantation: a study in the rabbit ear model.

Composite chondrocutaneous graft reconstruction or reattachment has limited applicability, is traditionally restricted to small segmental losses, and is dependent on the status of the recipient bed and graft periphery for successful revascularization. Surgical enhancement of composite graft survival was experimentally investigated in the rabbit ear model through transposition and appositional placement of an adjacent vascular pedicle. Fluorescein-derived surface-survival determinations, microangiographic vessel-counting methods, and histologic analysis were used to study the effects of vascular augmentation, pedicle design variations, and angiogenic substance in sixty 8-cm2, full-thickness auricular grafts.