Section Abstracts: Biology with Microbiology and Molecular Biology
Virginia Journal of Science
Biology with M icrobiology and M olecular Biology SHIGA TOXIN PATHOGENESIS IN THE GASTROINTESTINAL TRACT. Abigail J. Lenz & Andrew J. Fabich. Dept. of Biology & Chemistry, Liberty Univ., Lynchburg, VA 24515. Enterohemorrhagic Escherichia coli (EHEC) is a gram negative bacteria that is the leading cause of infectious kidney failure worldwide; a primary mechanism of EHEC infection is Shiga toxin (stx), which is carried by Golgi phosphoprotein 4 (GPP130) and binds globotriaosylceramide (Gb3) receptors on the endothelial cell surface, initiating a cascade that ultimately leads to apoptosis. Citrobacter rodentium genetically engineered with stx (CR) has successfully been used in mice to model the effects of EHEC in humans. W e show that competition drives the pathogenic effects of CR infection. ENTRAINM ENT OF SYNTHETIC GENE OSCILLATORS BY A NOSIY STIM ULUS. N. C. Butzin, P. L. Hochendoner, C. T. Ogle, P. Hill & W . M ather, Dept. of Physics, Virginia Tech, Blacksburg, VA. M odulation of biological oscillations by external stimuli lies at the root of many phenomena, including maintenance of circadian rhythms, propagation of neural signals, and somatogenesis. W hile it is well established that regular periodic modulation can entrain an oscillator, a curious phenomenon is that a noisy (rugged) modulation can also robustly entrain oscillations. This latter scenario may describe, for instance, the effect of irregular weather patterns on circadian rhythms, or why irregular neural stimuli can still reliably transmit information. A synthetic biology approach has already proven useful in understanding the entrainment of oscillators by periodic signaling, which can mimic the response of a number of noisy oscillating systems: cell cycles, NF-kB response, etc. W e similarly seek to use synthetic biology as a platform to understand how aperiodic signals can strongly correlate the behavior of cells. This study should lead to a deeper understanding of how fluctuations in our environment and even within our body may promote substantial synchrony between our cells. W e investigate experimentally and theoretically the entrainment of an ensemble of synthetic gene oscillators by a noisy stimulus. Stochastic simulations suggested that a synthetic gene oscillator would be strongly entrained by two aperiodic signals: telegraph noise and phase noise. This simulation-based prediction was tested by a combination of microfluidic and microscopy using a real synthetic circuit in Escherichia coli. W e use delayed feedback models to analyze these cells. W e show that cells are entrained by two noisy signals: telegraph and phase noise. Cells are entrained when either signal period or amplitudes are varied. EFFECT OF CONVERTING TO ORGANIC TURKEY REARING PRACTICES ON ANTIBIOTIC RESISTANCE OF ENTEROCOCCI FROM USED LITTER. Steven G. M cBride, Lindsey Toothman, Pradeep Vasudevan & Joanna B. M ott. Dept. of Biol., James M adison Univ., Harrisonburg VA. 22807. Conventional turkey production employs antimicrobial compounds for prophylaxis, treatment, and growth promotion. Conversely, organically raised turkeys are not administered antimicrobial compounds. Increasing public interest in organic and antibiotic free foods has led to a growing
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market for their production. In this study the prevalence of antibiotic resistance in
Enterococcus spp. isolated from the turkey litter of adult tom turkeys after they were
sent to market, was compared before and after the farm transitioned to organic rearing
practices. Enterococcus spp. were isolated on m-EI agar and identified to species
phenotypically. Susceptibility to 12 antimicrobial compounds was determined using the
Kirby-Bauer disc diffusion technique. The proportions of resistant bacteria were
compared using chi-square test and Fischer?s exact test. Isolates from the litter of
organic birds differed in species composition and resistance profiles from those isolated
from the conventionally farmed litter. Isolates from organic litter exhibited a reduction
in the percentage of isolates resistant to gentamicin (- 47%), tetracycline (- 42%), and
doxycycline (- 25%). These results suggest that changing to organic rearing practices
affects the antibiotic resistance of bacteria in turkey litter.
EFFECTS OF SYNTHETHETIC ANDROGEN ON P21 EXPRESSION IN M CF-7
CELLS. Tawany C. Almeida & Rosemary Barra, Department of Biological Sciences,
University of M ary W ashington, Fredericksburg, VA 22401. In the United States,
breast cancer is the most prevalent form of cancer in women and is second only to lung
and bronchial cancer as the leading cause of cancer death. A number of factors have
been identified that increase the risk of developing breast cancer, including specific
gene expression, age, estrogen exposure, and obesity. It has also been demonstrated
by both in vivo and in vitro studies, that some breast cancer cells express both
androgen and estrogen receptors. These studies sugges (...truncated)