Biomedical subjects

Raina M Maier

Publications and source records attributed to Raina M Maier.

At least 19 recordsLinked to original sources

PubMed2007

Phytostabilization potential of quailbush for mine tailings: growth, metal accumulation, and microbial community changes.

Abandoned mine tailings sites in semiarid regions remain unvegetated for extended periods of time and are subject to eolian dispersion and water erosion. This study examines the potential phytostabilization of a lead-zinc mine tailings site using a native, drought-tolerant halophyte, quailbush [Atriplex lentiformis (Torr.) S. Wats.]. In a greenhouse study germination, growth, and metal uptake was evaluated in two compost-amended mine tailings samples, K4 (pH 3) and K6 (pH 6) at 75, 85, 90, 95, and 100% mine tailings, and two controls, off-site and compost. Microbial community changes were monitored by performing MPN analysis of iron- and sulfur-oxidizing bacteria as well as heterotrophic plate counts. Results demonstrate that germination is not a good indicator for phytostabilization since it was only inhibited in the unamended K4 treatment. Plant growth was significantly reduced in 95 and 100% mine tailings, while growth in 75, 85, and 90% treatments was similar to the off-site control. Quailbush accumulated elevated levels of the nutrient metals Na, K, Mn, and Zn in the shoot tissues; however, metal accumulation was generally below the domestic animal toxicity limit. Initially, autotrophic population estimates were four to six logs higher than heterotrophic counts, indicating extremely stressed conditions. However, post-harvest, heterotrophic bacterial counts increased to normal levels (approximately 10(6) CFU g-1 dry tailings) and dominated the rhizosphere. Therefore, with compost amendment, quailbush has good potential as a native species candidate for phytostabilization of mine tailings in semiarid environments.

Atriplex↗

PubMed2006

Culturable microbial diversity and the impact of tourism in Kartchner Caverns, Arizona.

Kartchner Caverns in Benson, AZ, was opened for tourism in 1999 after a careful development protocol that was designed to maintain predevelopment conditions. As a part of an ongoing effort to determine the impact of humans on this limestone cave, samples were collected from cave rock surfaces along the cave trail traveled daily by tour groups (200,000 visitors year-1) and compared to samples taken from areas designated as having medium (30-40 visitors year-1) and low (2-3 visitors year-1) levels of human exposure. Samples were also taken from fiberglass moldings installed during cave development. Culturable bacteria were recovered from these samples and 90 unique isolates were identified by using 16S rRNA polymerase chain reaction and sequencing. Diversity generally decreased as human impact increased leading to the isolation of 32, 27, and 22 strains from the low, medium, and high impact areas, respectively. The degree of human impact was also reflected in the phylogeny of the isolates recovered. Although most isolates fell into one of three phyla: Actinobacteria, Firmicutes, or Proteobacteria, the Proteobacteria were most abundant along the cave trail (77% of the isolates), while Firmicutes predominated in the low (66%) and medium (52%) impact areas. Although the abundance of Proteobacteria along the cave trail seems to include microbes of environmental rather than of anthropogenic origin, it is likely that their presence is a consequence of increased organic matter availability due to lint and other organics brought in by cave visitors. Monitoring of the cave is still in progress to determine whether these bacterial community changes may impact the future development of cave formations.

Actinobacteria↗

PubMed2006

Determination of the acid dissociation constant of the biosurfactant monorhamnolipid in aqueous solution by potentiometric and spectroscopic methods.

The acid dissociation constant in water for a monorhamnolipid mixture extracted from Pseudomonas aeruginosa ATCC 9027 has been determined using potentiometry and two spectroscopic approaches at concentrations below and above the critical micelle concentration (cmc). Potentiometric titrations resulted in pKa values ranging from 4.28 +/- 0.16 to 5.50 +/- 0.06 depending on concentration. 1H NMR spectrochemical titrations at concentrations below the cmc revealed a pKa value of 4.39 +/- 0.06. ATR-FT-IR spectrochemical titrations on solutions well above the cmc gave a pKa value of 4.84 +/- 0.05. The value of 4.28 for the free rhamnolipid molecule for concentrations below the cmc differs markedly from that reported previously. However, the pKa of 5.50 for surface-adsorbed and solution aggregates correlates closely to that previously reported. Differences in these pKa values are rationalized in terms of the pH- and concentration-dependent aggregation behavior of rhamnolipids in aqueous solution.

Absorption↗

PubMed2006

Bacterial community structure in the hyperarid core of the Atacama Desert, Chile.

Soils from the hyperarid Atacama Desert of northern Chile were sampled along an east-west elevational transect (23.75 to 24.70 degrees S) through the driest sector to compare the relative structure of bacterial communities. Analysis of denaturing gradient gel electrophoresis (DGGE) profiles from each of the samples revealed that microbial communities from the extreme hyperarid core of the desert clustered separately from all of the remaining communities. Bands sequenced from DGGE profiles of two samples taken at a 22-month interval from this core region revealed the presence of similar populations dominated by bacteria from the Gemmatimonadetes and Planctomycetes phyla.

Bacteria↗

PubMed2006

Effect of clays, metal oxides, and organic matter on rhamnolipid biosurfactant sorption by soil.

Rhamnolipids produced by Pseudomonas aeruginosa have been proposed as soil washing agents for enhanced removal of metal and organic contaminants from soil. A potential limitation for the application of rhamnolipids is sorption by soil matrix components. The objective of this study is to empirically determine the contribution of representative soil constituents (clays, metal oxides, and organic matter) to sorption of the rhamnolipid form most efficient at metal complexation (monorhamnolipid). Sorption studies show that monorhamnolipid (R1) sorption is concentration dependent. At low R1 concentrations that are relevant for enhancing organic contaminant biodegradation, R1 sorption followed the order: hematite (Fe(2)O(3))>kaolinite>MnO(2) approximately illite approximately Ca-montmorillonite>gibbsite (Al(OH)(3))>humic acid-coated silica. At high R1 concentrations, relevant for use in complexation/removal of metals or organics, R1 sorption followed the order: illite>>humic acid-coated silica>Ca-montmorillonite>hematite>MnO(2)>gibbsite approximately kaolinite. These results allowed prediction of R1 sorption by a series of six soils. Finally, a comparison of R1 and R2 (dirhamnolipid) shows that the R1 form sorbs more strongly alone than when in a mixture of both the R1 and R2 forms. The information presented can be used to estimate, on an individual soil basis, the extent of rhamnolipid sorption. This is important for determining: (1) whether rhamnolipid addition is a feasible remediation option and (2) the amount of rhamnolipid required to efficiently remove the contaminant.

Adsorption↗

PubMed2005

Real-time, in situ monitoring of bioactive zone dynamics in heterogeneous systems.

Successful implementation of in situ bioremediation is contingent upon understanding how physicochemical and microbial factors affect the formation and dynamics of microbially active regions known as bioactive zones (BAZs). This study demonstrates how a novel fiber optic detection system can be used to test hypotheses concerning real-time, in situ BAZ formation and dynamics. This study focuses on naphthalene transport in saturated porous media containing defined physicochemical and microbial heterogeneities. Biological activity was measured using a lux reporter bacterium, Pseudomonas putida RB1353, that bioluminesces during naphthalene catabolism. Results show that the presence of defined heterogeneities drives the development of BAZs at material-property interfaces where the confluence of naphthalene, dissolved oxygen, and sufficient microbial density is optimal. Thus, despite successful transport of P. putida RB1353 into a sterile low-permeability region containing substrate, BAZ formation in this region was limited by local physicochemical conditions (e.g., naphthalene and dissolved oxygen bioavailability). In another instance, transport of P. putida RB1353 occurred against advective flow, resulting in BAZ formation upgradient of inoculated regions. Defined systems such as this can be used as a basis for predicting localization of activity in complex subsurface systems.

Biodegradation, Environmental↗

PubMed2005

Influence of hydroxypropyl-beta-cyclodextrin (HPCD) on the bioavailability and biodegradation of pyrene.

It is well known that the limited aqueous solubilities of polycyclic aromatic hydrocarbons (PAH) often reduce their bioavailability to bacterial populations. The objective of this study was to test the impact of a solubility-enhancement reagent, hydroxypropyl-beta-cyclodextrin (HPCD), on the bioavailability and biodegradation of pyrene. No measurable loss of pyrene occurred for the control vials throughout the first 22 weeks of the experiment, indicating the absence of mass loss via abiotic transformation and volatilization. The vials containing pyrene and the degrader isolate (Burkholderia CRE 7), but no HPCD, also exhibited no measurable loss of pyrene throughout the experiment. Conversely, biodegradation of pyrene appears to have been initiated after approximately 15 weeks for the vials containing 10(4) mg l(-1) HPCD. By the end of the experiment, approximately 14% (w/w) of the pyrene was biodegraded in the presence of HPCD. These results indicate that HPCD may be useful for enhancing the bioavailability and biodegradation of pyrene and other PAHs.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2005

Biodegradation during contaminant transport in porous media: 7. Impact of multiple-degrader community dynamics.

The biodegradation and transport of phenanthrene in porous media containing multiple populations of phenanthrene degraders is examined with a series of miscible-displacement experiments. A long-term experiment was conducted with a soil containing an indigenous microbial community comprised of 25 identified phenanthrene-degrading isolates. The rate and magnitude of phenanthrene biodegradation oscillated throughout the six-month experiment. This behavior, at least in part, is attributed to multiple-population dynamics associated with the indigenous community of phenanthrene degraders, the composition of which changed during the experiment. This hypothesis is supported by the results of experiments conducted using sterilized porous media that were inoculated with selected isolates obtained from the indigenous soil community. The results of experiments conducted with sterilized soil inoculated with isolate A exhibited an initial extended period of steady phenanthrene effluent concentrations, followed by a uniform decline. The results of experiments conducted using sterilized sand for single-isolate systems with one of three selected isolates and for systems of two-isolate combinations, indicate the existence of apparent synergistic and antagonistic interactions among the isolates. For example, phenanthrene biodegradation was relatively extensive and occurred without a lag phase for isolate A alone. However, biodegradation was constrained when isolate A and B were combined, indicating an antagonistic interaction. Conversely, whereas extensive lag phases were exhibited by both isolates B and C for the single-isolate experiments, there was minimal lag when isolates B and C were combined, indicating a synergistic interaction.

Benzoates↗

PubMed2004

The influence of system complexity on bacterial transport in saturated porous media.

A series of miscible-displacement column experiments were conducted under saturated flow conditions to systematically investigate the influence of physical and biological complexity on bacterial activity and fate in the presence and absence of a non-sorbing growth substrate, salicylate. Bacterial elution was monitored for three different systems; System I--a sterilized, inoculated, well-sorted sand, System II--a sterilized, inoculated, heterogeneous loamy sand (Hayhook), and System III--two different unsterilized loamy sands (Hayhook and Vinton) each with their associated indigenous microbial community. Results show that System I behaved ideally with respect to both cell and substrate transport, wherein: (1) growth occurred in response to substrate addition, (2) cell elution increased in response to the substrate pulse, and (3) breakthrough curves were reproducible for both substrate and cell elution. In contrast, System II showed ideal behavior with respect to substrate transport but showed variable behavior for cell transport. Further, there was no measurable growth in response to substrate addition and no increase in cell elution during the salicylate pulse. System III exhibited non-ideal behavior for both substrate and cell transport. Of particular interest is the fact that the indigenous communities of the two soils behaved differently. Specifically, for the Hayhook soil, an increased elution response was observed for the heterotrophic population while the salicylate-degrading community was preferentially retained in the column. In contrast for the Vinton soil, the substrate pulse did not elicit an elution response from either the heterotrophic or salicylate-degrading community from the culturable, indigenous Vinton microorganisms. For Systems II and III, the observed variability appears to be associated with the biological component of the system, since sterile controls were reproducible. This type of systematic study is critical for understanding cell and substrate transport behavior in complex, heterogeneous systems, and illustrates the potential uncertainty associated with measurements in such systems.

Absorption↗

PubMed2004

Structure and characterization of flavolipids, a novel class of biosurfactants produced by Flavobacterium sp. strain MTN11.

Herein we report the structure and selected properties of a new class of biosurfactants that we have named the flavolipids. The flavolipids exhibit a unique polar moiety that features citric acid and two cadaverine molecules. Flavolipids were produced by a soil isolate, Flavobacterium sp. strain MTN11 (accession number AY162137), during growth in mineral salts medium, with 2% glucose as the sole carbon and energy source. MTN11 produced a mixture of at least 37 flavolipids ranging from 584 to 686 in molecular weight (MW). The structure of the major component (23%; MW = 668) was determined to be 4-[[5-(7-methyl-(E)-2-octenoylhydroxyamino)pentyl]amino]-2-[2-[[5-(7-methyl-(E)-2-octenoylhydroxyamino)pentyl]amino]-2-oxoethyl]-2-hydroxy-4-oxobutanoic acid. The partially purified flavolipid mixture isolated from strain MTN11 exhibited a critical micelle concentration of 300 mg/liter and reduced surface tension to 26.0 mN/m, indicating strong surfactant activity. The flavolipid mixture was a strong and stable emulsifier even at concentrations as low as 19 mg/liter. It was also an effective solubilizing agent, and in a biodegradation study, it enhanced hexadecane mineralization by two isolates, MTN11 (100-fold) and Pseudomonas aeruginosa ATCC 9027 (2.5-fold), over an 8-day period. The flavolipid-cadmium stability constant was measured to be 3.61, which is comparable to that for organic ligands such as oxalic acid and acetic acid. In summary, the flavolipids represent a new class of biosurfactants that have potential for use in a variety of biotechnological and industrial applications.

Alkanes↗

PubMed2003

Comparative electrochemical inactivation of bacteria and bacteriophage.

Electric fields and currents have been shown to be capable of disinfecting drinking water and reducing the numbers of bacteria and yeast in food. However, little research has been conducted regarding the effectiveness of electric fields and currents in the inactivation of viruses. The objective of this study was to compare the ability of bacteria and bacteriophage to survive exposure to direct electric current in an electrochemical cell, where they would be subject to irreversible membrane permeabilization processes, direct oxidation of cellular/viral constituents by electric current, and disinfection by electrochemically generated oxidants. Suspensions of the bacteria Escherichia coli and Pseudomonas aeruginosa and bacteriophage MS2 and PRD1 at both high (approximately 1 x 10(6)CFU or PFU/mL) and low (approximately 1 x 10(3)CFU or PFU/mL) population densities were exposed to currents ranging from 25 to 350 mA in 5s pulses. Post-exposure plaque counts of the bacteriophage were proportionally higher than bacterial culturable counts at corresponding current exposures. E. coli and MS2 were then exposed to 5 mA for 20 min at both high and low population densities. The inactivation rate of E. coli was 2.1-4.3 times greater than that of MS2. Both bacteria and bacteriophage were more resistant to exposure to direct current at higher population densities. Also, amelioration of inactivation within the electrochemical cell by the reducing agent glutathione indicates the major mechanism of inactivation in the electrochemical cell is disinfection by electrochemically generated oxidants. The implications of these results are that technologies relying upon direct current to reduce the numbers of microbes in food and water may not be sufficient to reduce the numbers of potentially pathogenic viruses and ensure the safety of the treated food or water.

Bacteriophages↗

PubMed2003

Biosurfactants: evolution and diversity in bacteria.

In summary, biosurfactants are an example of a class of microbial natural products that has coevolved among many genera. But whereas the biosurfactants produced in the bacterial and archaeal domains are convergent in function (suggesting that they are very important), they have developed in parallel with respect to genotype and phenotype (the surfactants are not related genetically or in terms of molecular structure). Because of this parallel evolution, currently available molecular screening techniques are of little use for the discovery of new biosurfactants. Development of such techniques will continue to be problematic because there is no relationship between the surfactants produced by different microbial genera and even species. Yet, the potential for application of biosurfactants and other natural products is great due to growing demand for biodegradable and environmentally friendly analogues for synthetic chemicals.

Archaea↗

PubMed2003

Issues underlying use of biosensors to measure metal bioavailability.

Heavy metal-mediated toxicity in the environment is dependent on bioavailable metal concentrations both internal and external to microbial cells. Both internal and external metal bioavailability are influenced by multiple factors in the soil environment. External factors include pH, redox potential, ionic strength, organic matter and clay content. The internal bioavailable metal concentration is dependent on both the aforementioned external factors, as well as metal uptake and efflux activities that are specific for each microorganism. The metal-specific biosensors discussed in this article can be used to measure internal metal bioavailability.

Biological Assay↗

PubMed2003

The influence of substrate and electron acceptor availability on bioactive zone dynamics in porous media.

Two approaches were used to investigate the influence of dissolved oxygen (DO) and substrate availability on the formation and dynamics of "bioactive zones" in a water-saturated porous medium. A bioactive zone is defined as a region where a microbial community is sufficiently active to metabolize bioavailable substrates. In the first approach, microbial activity was characterized by monitoring the spatial and temporal variability of DO and aqueous substrate (salicylate and naphthalene) concentrations during miscible-displacement experiments. In the second approach, microbial activity was monitored using multiple fiber optics emplaced in the porous medium to detect luminescence produced by Pseudomonas putida RB1353, a bioluminescent reporter organism that produces light when salicylate (an intermediate of naphthalene degradation) is present. The results of both approaches show that the location and size of the bioactive zones were influenced by in situ DO and substrate availability. When DO was not a limiting factor (i.e., lower substrate input concentrations), the bioactive zone encompassed the entire column, with the majority of the microbial activity occurring between the inlet and midpoint. However, as the availability of DO became limiting for the higher substrate input experiments, the size of the bioactive zone shrank and was ultimately limited to the proximity of the column inlet.

Biodegradation, Environmental↗

PubMed2003

Temporal change in culturable phenanthrene degraders in response to long-term exposure to phenanthrene in a soil column system.

Widespread environmental contamination by polycyclic aromatic hydrocarbons (PAH) has led to increased interest in the use of natural attenuation as a clean-up strategy. However, few bioremediation studies have investigated the behaviour of the indigenous PAH-degrading community after long-term exposure to a PAH. In this study, a column packed with sandy loam soil was exposed to a solution saturated with phenanthrene ( approximately 1.2 mg l-1) for a 6-month period to examine the temporal response of the indigenous phenanthrene-degrading community. Initial soil, effluent, and final soil samples were collected and analysed for phenanthrene concentration and culturable phenanthrene degraders. Phenanthrene-degrading isolates were grouped by colony morphology. For each unique group, 16S rDNA polymerase chain reaction was performed, and then sequencing analysis was used to identify the isolate at the genus level. Twenty-five phenanthrene-degrading isolates, potentially representing 19 genera, were obtained from this analysis. Of these, eight genera have not been reported previously to degrade phenanthrene, including Afipia, Janthinobacterium, Leptothrix, Massilia, Methylobacterium, Rhizobium, Sinorhizobium and Thiobacillus. Results indicate that the dominant phenanthrene-degrading population changed over the course of this 6-month experiment. Specifically, the isolates obtained initially from the soil were not subsequently found in either effluent samples or the soil at the end of the experiment. Furthermore, several isolates that were found in the soil at the end of the experiment were not observed in the soil initially or in the effluent samples. This study confirms earlier findings indicating that a diverse community participates in phenanthrene degradation in the environment, and also suggests that the composition of this community is temporally variable.

Bacteria↗

PubMed2003

Effect of temperature, pH, and initial cell number on luxCDABE and nah gene expression during naphthalene and salicylate catabolism in the bioreporter organism Pseudomonas putida RB1353.

One limitation of employing lux bioreporters to monitor in situ microbial gene expression in dynamic, laboratory-scale systems is the confounding variability in the luminescent responses. For example, despite careful control of oxygen tension, growth stage, and cell number, luminescence from Pseudomonas putida RB1353, a naphthalene-degrading lux bioreporter, varied by more than sevenfold during saturated flow column experiments in our laboratory. Therefore, this study was conducted to determine what additional factors influence the luminescent response. Specifically, this study investigated the impact of temperature, pH, and initial cell number (variations within an order of magnitude) on the peak luminescence of P. putida RB1353 and the maximum degradation rate (V(max)) during salicylate and naphthalene catabolism. Statistical analyses based on general linear models indicated that under constant oxygen tension, temperature and pH accounted for 98.1% of the variability in luminescence during salicylate catabolism and 94.2 and 49.5% of the variability in V(max) during salicylate and naphthalene catabolism, respectively. Temperature, pH, and initial substrate concentration accounted for 99.9% of the variability in luminescence during naphthalene catabolism. Initial cell number, within an order of magnitude, did not have a significant influence on either peak luminescence or V(max) during salicylate and naphthalene catabolism. Over the ranges of temperature and pH evaluated, peak luminescence varied by more than 4 orders of magnitude. The minimum parameter deviation required to alter lux gene expression during salicylate and naphthalene catabolism was a change in temperature of 1 degrees C, a change in pH of 0.2, or a change in initial cell number of 1 order of magnitude. Results from this study indicate that there is a need for careful characterization of the impact of environmental conditions on both the expression of the reporter and catabolic genes and the activities of the gene products. For example, even though lux gene expression was occurring at approximately 35 degrees C, the luciferase enzyme was inactive. Furthermore, this study demonstrates that with careful characterization and standardization of measurement conditions, the attainment of a reproducible luminescent response and an understanding of the response are feasible.

Aldehyde Oxidoreductases↗

PubMed2003

Distribution of biosurfactant-producing bacteria in undisturbed and contaminated arid Southwestern soils.

Biosurfactants are a unique class of compounds that have been shown to have a variety of potential applications in the remediation of organic- and metal-contaminated sites, in the enhanced transport of bacteria, in enhanced oil recovery, as cosmetic additives, and in biological control. However, little is known about the distribution of biosurfactant-producing bacteria in the environment. The goal of this study was to determine how common culturable surfactant-producing bacteria are in undisturbed and contaminated sites. A series of 20 contaminated (i.e., with metals and/or hydrocarbons) and undisturbed soils were collected and plated on R(2)A agar. The 1,305 colonies obtained were screened for biosurfactant production in mineral salts medium containing 2% glucose. Forty-five of the isolates were positive for biosurfactant production, representing most of the soils tested. The 45 isolates were grouped by using repetitive extragenic palindromic (REP)-PCR analysis, which yielded 16 unique isolates. Phylogenetic relationships were determined by comparing the 16S rRNA gene sequence of each unique isolate with known sequences, revealing one new biosurfactant-producing microbe, a Flavobacterium sp. Sequencing results indicated only 10 unique isolates (in comparison to the REP analysis, which indicated 16 unique isolates). Surface tension results demonstrated that isolates that were similar according to sequence analysis but unique according to REP analysis in fact produced different surfactant mixtures under identical growth conditions. These results suggest that the 16S rRNA gene database commonly used for determining phylogenetic relationships may miss diversity in microbial products (e.g., biosurfactants and antibiotics) that are made by closely related isolates. In summary, biosurfactant-producing microorganisms were found in most soils even by using a relatively limited screening assay. Distribution was dependent on soil conditions, with gram-positive biosurfactant-producing isolates tending to be from heavy metal-contaminated or uncontaminated soils and gram-negative isolates tending to be from hydrocarbon-contaminated or cocontaminated soils.

Arizona↗

PubMed2003

Impact of metals on the biodegradation of organic pollutants.

Forty percent of hazardous waste sites in the United States are co-contaminated with organic and metal pollutants. Data from both aerobic and anaerobic systems demonstrate that biodegradation of the organic component can be reduced by metal toxicity. Metal bioavailability, determined primarily by medium composition/soil type and pH, governs the extent to which metals affect biodegradation. Failure to consider bioavailability rather than total metal likely accounts for much of the enormous variability among reports of inhibitory concentrations of metals. Metals appear to affect organic biodegradation through impacting both the physiology and ecology of organic degrading microorganisms. Recent approaches to increasing organic biodegradation in the presence of metals involve reduction of metal bioavailability and include the use of metal-resistant bacteria, treatment additives, and clay minerals. The addition of divalent cations and adjustment of pH are additional strategies currently under investigation.

Biodegradation, Environmental↗