Karen K. Bernd

Whole-cell flagellum-based motility studied using back focal plane interferometry in a laser trap transducer

The biflagellated alga Chlamydomonas reinhardtii undergoes light-directed motility by controlling the beating patterns of its flagella. The molecular mechanisms of this control system are debated. To help understand the process we are using a laser trap transducer to capture single, swimming Chlamydomonas by their contractile vacuole - the organelle that allows them to regulate cell volume. Trapping the cell by this organelle enables us to accurately and reproducibly measure the swimming force, beat frequencies and waveforms generated by the flagella. This is a unique approach to understanding the motor mechanisms and regulation of flagella in intact cells.

Dichloroacetate Decreases Cell Health and Activates Oxidative Stress Defense Pathways in Rat Alveolar Type II Pneumocytes

Dichloroacetate (DCA) is a water purification byproduct that is known to be hepatotoxic and hepatocarcinogenic and to induce peripheral neuropathy and damage macrophages. This study characterizes the effects of the haloacetate on lung cells by exposing rat alveolar type II (L2) cells to 0–24 mM DCA for 6–24 hours. Increasing DCA concentration and the combination of increasing DCA concentration plus longer exposures decrease measures of cellular health. Length of exposure has no effect on oxidative stress biomarkers, glutathione, SOD, or CAT. Increasing DCA concentration alone does not affect total glutathione or its redox ratio but does increase activity in the SOD/CAT oxidative stress defense pathway. These data suggest that alveolar type II cells rely on SOD and CAT more than glutathione to combat DCA-induced stress.

“STOP: Can You Drink That Water?” Microbiology, Chemistry, & Advocacy in an Inquiry-Based Water Quality Curriculum for 8th Graders

Abstract For many middle school students, connections between their lives and concepts like chemical reactivity, microbial contamination, and experimental sampling are not obvious. They may also feel that, even if there were connections, understanding the monitoring and quality of natural resources is something for grownups and beyond their responsibility. This curriculum highlights connections. Students characterize bacteria in a local untreated water source and investigate the mechanism, effectiveness, and byproducts of chlorine bleach as a water treatment. Working in groups, they use different growth and treatment conditions to characterize samples, thus collectively obtaining a more complete description of the system. The North Carolina 8th Grade Standard Course of Study Objectives were used during curricular development, and alignment to Next Generation Science Standards performance expectations is provided. Teacher-guided discussions, demonstrations, experimentation, and database investigation engage students as they develop informed and critical opinions about water quality and water treatment methods. The final activity connects scientific investigation to advocacy and civic engagement.