Tag: Poster 85

Force Matching Sense: An Ipsilateral Shoulder Study Investigating the Effect of Torque and Elevation Angle

Presenter: Katya Trousset

Faculty Mentor: Andrew Karduna, David Phillips

Presentation Type: Poster 85

Primary Research Area: Science

Major: Human Physiology

Force matching sense (FMS), or the ability to reproduce a desired force one or more times, is one of three subdivisions that define proprioception. Unlike the other two, joint position sense (JPS) and kinesthesia, FMS is not associated with joint motion (Riemann & Lephart, 2002a). Previous research has found that JPS becomes more accurate as shoulder elevation and external load increases (D. Suprak, Osternig, & Karduna, 2005). The goal of the present study was to investigate how torque and shoulder abduction angle contribute to accuracy of FMS in an ipsilateral remembered force matching task. FMS was tested on the dominant arm of 12 subjects (6 males, 6 females) at three angles (50, 70, and 90 degrees of elevation in the scapular plane), and at 20, 40, and 60 percent above subject baseline torque. It was found that there was no significant change in error due to abduction angle (p > 0.05), but force reproduction error decreased as torque load increased (p < 0.05). From these findings, it appears that FMS does not follow the same pattern as JPS when reproducing a target at different angles, suggesting that these two components must be considered separately when assessing proprioception.

Experimental Evolution of a Bacterial Symbiont to its Host’s Environment

Presenter(s): Helena Klein − Biology

Faculty Mentor(s): Karen Guillemin, Cathy Robinson

Poster 85

Research Area: Natural/Physical Science

Funding: META Grant

The bacteria that live in our guts, and those of other vertebrates, affect our health in a myriad of ways, from aiding in digestion to training our immune system. However, how bacteria first colonize the gut is little-understood. In particular, environment seems to play an important role in host colonization, especially in aquatic organisms. I proposed investigating environmental adaptation to find novel mechanisms for host colonization. I hypothesized that adaptation of a bacterial symbiont to its host’s environment increases host colonization. I tested this hypothesis via experimental evolution by serially passaging a strain of Aeromonas veronii, a zebrafish gut isolate, in fish-conditioned water to quickly and non-specifically find new genes that could affect host colonization. Surprisingly, I found that while the evolved strains grew to higher population densities in the water than the ancestor, these strains had variable gut colonization fitness. In fact, one strain had significantly reduced gut colonization fitness. Genome sequencing revealed that this strain had mutations affecting motility and Type I secretion system membrane protein genes. I recreated the latter mutation in the wildtype bacterial strain and found that it increased Aeromonas fitness in fish water, however gut colonization was comparable to the wildtype. This suggests that other mutations in the evolved isolate, presumably those in the motility genes, are responsible for the reduced host colonization. Future work will further investigate motility mutations among others. This work contributes to our understanding of host colonization dynamics and can lead to the development of probiotics to improve human health.