Intermountain Growth Curve of Mannheimia haemolytica

Overview

Mannheimia haemolytica is a bacteria involved in respiratory infections in ruminant species, often working in tandem with other bacteria to cause co-infections. Pneumonic mannheimosis is caused by one of these co -infections, with Mycoplasma ovipneumoniae functioning as a predisposing agent, and Mannheimia haemolytica acting as the secondary, symptomatic infectant. This infection has caused a high mortality rate in Rocky Mountain bighorn sheep, and currently has no treatment or preventative. From preliminary observations, I hypothesized that the bacteria’s growth phase would spike on the lower half of eight hours post inoculation. I began by isolating a singular colony of Mannheimia haemolytica and placing it in a broth media, which was placed in an incubator shaker for eight hours. Each hour, two samples were taken to measure the optical density and make dilutions for blood agar streak plates. I observed the growth phase of the bacteria and saw a spike in both the optical density and colony forming units of t he samples between hour three and four, with the optical density rising from 0.085 to 0.279 and the colony forming units spiking from 1.12E±09 to 5.57E±09. These results confirmed my expectation of Mannheimia haemolytica's growth phase spike occurring in the first half of an eight hour timeframe, and suggests that further experimentation with this bacteria should be performed between hours three and four after inoculation for more easily measurable results. Moving forward with the knowledge gained from research, preventative and treatment options will be experimented on within this timeframe. Methylene Blue Film Fabrication for Piezoelectric PFAS Detection Jordan Chong Davidson Academy, Reno, NV Mentor M. Rashed Khan, University of Nevada, Reno Per- and polyfluoroalkyl substances (PFAS), nicknamed “forever chemicals,” are widespread contaminants in water. Current methods of detecting PFAS are expensive and burdensome, so new low-cost detection methods are in high demand. Certain new methods incorporate the active properties of the low-cost chemical methylene blue (C16H18ClN3S), but these methods are limited in sensitivity due to their colorimetric basis. To improve upon previous implementations, this project incorporates methylene blue in a distinct mass -based mechanism that allows for PFAS sensing at higher sensitivity and similar cost. The active technology is a quartz chip that vibrates when an electric current is applied (a phenomenon called piezoelectricity). This chip is coated in a thin film of methylene blue, which binds PFAS molecules; as PFAS accumulates on the film, the resul ting change in mass alters the chip’s vibrational properties, allowing nanogram -level detection. Using calibrated water solutions, a detection model is obtained that would allow PFAS sensing in unknown water samples, and the model’s performance is tested o n real tap water samples spiked with PFAS. This innovation has the potential to aid PFAS -affected communities by facilitating water safety measurements, and may be modified to sense other contaminants.