Feb 24, 2017

Phenotypic elasticity of epithelial/mesenchymal hybrids

Jena Meyer '17

Cellular plasticity shown in wound healing and cancer metastasis, is demonstrated by Epithelial-to-Mesenchymal Transition (EMT) and its reverse process Mesenchymal-to-Epithelial Transition (MET). In the process of transforming into mesenchymal cells, epithelial cells gain migratory abilities as they lose their cell adhesion characteristics--these traits can be expressed partially or completely. Those cells who complete the process of EMT and become phenotypically mesenchymal, are not known for their tendency to migrate as individual cells. On the other hand, cells who have only partially undergone EMT have both epithelial and mesenchymal characteristics have been termed hybrid E/M cells. These hybrid E/Ms have been found to collectively migrate in wound healing, and in the formation of tumor clusters. It was previously assumed that the hybrid E/M phenotype was 'metastable', and now phenotypic stability factors (PSFs) like OVOL and GRHL2 have been found to strongly influence the EMT process and stabilize the hybrid E/M phenotype. Lung cancer cells were able to maintain a stable hybrid E/M phenotype for a significant period of time and collectively migrate--shown by the knockdown of PSFs OVOL and GRHL2. Results indicate the likelihood of the hybrid E/M phenotype not needing to be 'metastable', and strengthens the association between partial EMT and aggressive tumor progression.

Phenotypic Characterization of Sinorhizobium sp. HM007-10 Bacteriophage HMSP-1

Mady Couves '17

Nitrogen fixing bacteria inhabit the soil and form a symbiotic relationship with legume plants. Sinorhizobium are capable of converting N2 to an accessible form legumes can absorb, ammonia. Nitrogen-fixing symbioses can be affected by several factors, including environmental conditions, nutrient availability, and competition with other microbes. Bacteriophages are viruses that infect bacteria, and limit the survival of these organisms in soils. Bacteriophages are capable of disrupting symbioses and diminishing the nitrogen-fixing capabilities of legume crops. The goals of this project were to investigate the abundance of bacteriophages in the genomes of nitrogen-fixing bacteria and to isolate and characterize bacteriophages from the rhizosphere of legumes. Bioinformatics analyses were utilized to identify bacteriophages the genomes of rhizobia. The results showed that bacteriophages were abundant in Mesorhizobium (96%), Bradyrhizobium (75%) and Sinorhizobium (70%) of the species analyzed. Subsequently, we attempted to isolate and characterize bacteriophages from the roots of legumes. A bacteriophage (HMSP-1) was isolated from the rhizosphere of alfalfa. This virus has a titer of 7.56 x 108 pfu/ml and infects strains of the genus Sinorhizobium. Host range analyses showed 15 of the 41 strains were hosts for the virus, which suggests a narrow host range. Electron microscopy revealed a phage morphology consisting of a polyhedral head of 60 nm and tail of 100 nm; these traits are characteristics of phages of the Myoviridae family. A one step growth was performed to assess the time scale and the number of viruses released per infected cell (burst size). The results suggest a latent period (no detectable virus) of approximately 160 minutes that led to an exponential increase of phage particles for 120 min. The burst size of the phage was calculated as 40 p.f.u. per infected cell. Experiments are in progress to determine the size and complete genome sequence of phage HMSP-1.