Transport of Potential Microbial Source Tracking Markers in Sandy Material

ABSTRACT TRANSPORT OF POTENTIAL MICROBIAL SOURCE TRACKING MARKERS IN SANDY MATERIALS by Jennifer J. Johanson The University of Wisconsin-Milwaukee 2016 Under the Supervision of Professor Shangping Xu Groundwater, a primary source of drinking water for nearly half the people in the United States, can be contaminated by pathogenic bacteria from fecal materials causing outbreaks of waterborne illness. Therefore, early identification of the presence of fecal contamination in groundwater can help prevent such outbreaks, and determining whether bacteria originate from human or animal feces can narrow down the location of potential pollution sources, allowing timely remediation and reduced potential for future outbreaks. Pathogens are found in relatively low concentration in feces leading to difficulties in their detection in groundwater samples. In addition, a wide variety of pathogenic bacteria and viruses may exist in feces making it costly to analyze groundwater directly for all potential pathogens. As a result, groundwater samples are routinely analyzed for non-pathogenic fecal indicator bacteria (FIB), which are used as a proxy for the potential contamination by fecal pathogens. An ideal FIB would be abundant in the source material, easy and inexpensive to analyze, mobile in the subsurface so that it does not lag behind the pathogens, and host-specific to help identify the contaminant source. Bacteria which can be identified as originating selectively from human vs nonhuman sources (animals) are especially helpful in determining the source of contamination when multiple potential sources are present. Escherichia coli (E. coli) has long been used as a FIB due to its abundance in fecal matter. However E. coli is found in many different hosts, which limits its use for source identification. Recent research has focused on identifying microbial source tracking (MST) bacteria which have markers that are specific to human or animal hosts, and these host-specific markers can be critical in early source identification efforts. This potential for MST is especially promising if combined with the other characteristics of an ideal FIB, such as abundance and mobility in the subsurface. This research focuses on evaluating the subsurface mobility of two bacteria, Enterococcus faecium (E. faecium) and Bacteriodes fragilis (B. fragilis), in order to better understand their potential use as source-tracking FIB. These bacteria are both abundant in fecal matter and they have shown promise as having human-specific markers. We performed column experiments to compare their subsurface transport through sandy material. Bacteria with relatively high attachment to sand have lower mobility in groundwater and may therefore be less effective as early tracers of fecal contamination The first part of our research compares two strains of E. faecium; one with and one without Enterococcal surface protein (Esp), a marker which recent research has linked to human sources, to evaluate whether the presence of Esp affects bacterial attachment to sand. The results indicate that in water with neutral pH (~7.2) the presence of Esp is linked to increased attachment to sand, thereby reducing the mobility of the Esp positive E. faecium. Because indicator bacteria should have relatively high mobility, this increased attachment potentially decreases the usefulness of Esp for MST. The results are consistent with calculations using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory of colloidal attachment, which predicts that attachment in bacteria with Esp should be greater than in those without Esp due to the presence of a higher energy barrier for the bacteria without Esp. The second part of this research compares the transport of the common aerobic fecal indicator bacteria E. coli, which has had limited success in source tracking, to the much more abundant anaerobic B. fragilis, which has shown promise as a potential MST bacteria. The results indicate that in water with neutral pH and low total ionic strength conditions, both E. coli and B. fragilis have similar attachment to sand, but at high ionic strength, such as may be found in areas near the source of contamination, the B. fragilis has lower attachment (and thus potentially higher mobility) than E. coli. The XDLVO calculations indicate a secondary energy minimum exists at higher ionic strength for both bacteria. This secondary minimum, which is absent at low ionic strength, occurs at a distance of 1 to 20 nm from the sand surface and appears to be the result of compression of the electrostatic double layer. The depth of this energy minimum is greater for E. coli than for B. fragilis, leading to greater attachment in the E. coli than the B. fragilis

Low levels of amyloid-beta and its transporters in neonatal rats with and without hydrocephalus

<p>Abstract</p> <p>Background</p> <p>Previous studies in aging animals have shown that amyloid-beta protein (Aβ) accumulates and its transporters, low-density lipoprotein receptor-related protein-1 (LRP-1) and the receptor for advanced glycation end products (RAGE) are impaired during hydrocephalus. Furthermore, correlations between astrocytes and Aβ have been found in human cases of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD). Because hydrocephalus occurs frequently in children, we evaluated the expression of Aβ and its transporters and reactive astrocytosis in animals with neonatal hydrocephalus.</p> <p>Methods</p> <p>Hydrocephalus was induced in neonatal rats by intracisternal kaolin injections on post-natal day one, and severe ventriculomegaly developed over a three week period. MRI was performed on post-kaolin days 10 and 21 to document ventriculomegaly. Animals were sacrificed on post-kaolin day 21. For an age-related comparison, tissue was used from previous studies when hydrocephalus was induced in a group of adult animals at either 6 months or 12 months of age. Tissue was processed for immunohistochemistry to visualize LRP-1, RAGE, Aβ, and glial fibrillary acidic protein (GFAP) and with quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify expression of LRP-1, RAGE, and GFAP.</p> <p>Results</p> <p>When 21-day post-kaolin neonatal hydrocephalic animals were compared to adult (6–12 month old) hydrocephalic animals, immunohistochemistry demonstrated levels of Aβ, RAGE, and LRP-1 that were substantially lower in the younger animals; in contrast, GFAP levels were elevated in both young and old hydrocephalic animals. When the neonatal hydrocephalic animals were compared to age-matched controls, qRT-PCR demonstrated no significant changes in Aβ, LRP-1 and RAGE. However, immunohistochemistry showed very small increases or decreases in individual proteins. Furthermore, qRT-PCR indicated statistically significant increases in GFAP.</p> <p>Conclusion</p> <p>Neonatal rats with and without hydrocephalus had low expression of Aβ and its transporters when compared to adult rats with hydrocephalus. No statistical differences were observed in Aβ and its transporters between the control and hydrocephalic neonatal animals.</p

Reward-Related Dorsal Striatal Activity Differences between Former and Current Cocaine Dependent Individuals during an Interactive Competitive Game

Cocaine addiction is characterized by impulsivity, impaired social relationships, and abnormal mesocorticolimbic reward processing, but their interrelationships relative to stages of cocaine addiction are unclear. We assessed blood-oxygenation-level dependent (BOLD) signal in ventral and dorsal striatum during functional magnetic resonance imaging (fMRI) in current (CCD; n = 30) and former (FCD; n = 28) cocaine dependent subjects as well as healthy control (HC; n = 31) subjects while playing an interactive competitive Domino game involving risk-taking and reward/punishment processing. Out-of-scanner impulsivity-related measures were also collected. Although both FCD and CCD subjects scored significantly higher on impulsivity-related measures than did HC subjects, only FCD subjects had differences in striatal activation, specifically showing hypoactivation during their response to gains versus losses in right dorsal caudate, a brain region linked to habituation, cocaine craving and addiction maintenance. Right caudate activity in FCD subjects also correlated negatively with impulsivity-related measures of self-reported compulsivity and sensitivity to reward. These findings suggest that remitted cocaine dependence is associated with striatal dysfunction during social reward processing in a manner linked to compulsivity and reward sensitivity measures. Future research should investigate the extent to which such differences might reflect underlying vulnerabilities linked to cocaine-using propensities (e.g., relapses)

Shedding light on plant litter decomposition: Advances, implications and new directions in understanding the role of photodegradation

Litter decomposition contributes to one of the largest fluxes of carbon (C) in the terrestrial biosphere and is a primary control on nutrient cycling. The inability of models using climate and litter chemistry to predict decomposition in dry environments has stimulated investigation of non-traditional drivers of decomposition, including photodegradation, the abiotic decomposition of organic matter via exposure to solar radiation. Recent work in this developing field shows that photodegradation may substantially influence terrestrial C fluxes, including abiotic production of carbon dioxide, carbon monoxide and methane, especially in arid and semi-arid regions. Research has also produced contradictory results regarding controls on photodegradation. Here we summarize the state of knowledge about the role of photodegradation in litter decomposition and C cycling and investigate drivers of photodegradation across experiments using a meta-analysis. Overall, increasing litter exposure to solar radiation increased mass loss by 23% with large variation in photodegradation rates among and within ecosystems. This variation was tied to both litter and environmental characteristics. Photodegradation increased with litter C to nitrogen (N) ratio, but not with lignin content, suggesting that we do not yet fully understand the underlying mechanisms. Photodegradation also increased with factors that increased solar radiation exposure (latitude and litter area to mass ratio) and decreased with mean annual precipitation. The impact of photodegradation on C (and potentially N) cycling fundamentally reshapes our thinking of decomposition as a solely biological process and requires that we define the mechanisms driving photodegradation before we can accurately represent photodegradation in global C and N models. © 2012 US Government