Surprising Effects of Rocking Motion on Leishmania tarentolae Behavior in Culture and Implications for Cell Stress

Leishmania are an understudied genus of parasitic protozoans causing significant health problems for people, particularly in tropical climates. To better understand the growth of Leishmania and potential drug sensitivity implications, the effects of motion on cells grown in vitro were probed. Using a stock Leishmania tarentolae cell culture, cells were placed in 10 mL of a Brain–Heart Infusion medium in either a non-moving (static) environment or on a flat platform of one of two lab rockers (set at a minimal speed) in a dark environment for 13 days. Also, the addition of 0.5 M of L-Proline was evaluated. Microscopy, cell clumping, cell viability, and secreted acid phosphatase (SAP) activity data were collected. Results show that a constant slow rocking motion changed cell growth, clumping behavior, and detectable SAP activity relative to the no-motion cultures, but this change was dependent on which rocker was used, indicating a complexity in the growth of these cells in culture. Thus, continuous motion affects the stresses placed on the cells during a growth curve under some conditions. The implications of this study lead to questions about the effects of motion on the efficacy of pharmaceutical testing in vitro. Further study of the effects of motion on Leishmania is important.