What season suits you best? Seasonal light changes and cyanobacterial competition.

GUADALUPE CASCALLARES; PABLO M GLEISER

Carlos Paz

Congreso; XIII Latin American Workshop on Nonlinear Phenomena; 2013

Nearly all living organisms, including some bacterial species, exhibit biological processes with a period of about 24 h called circadian rhythms. These rhythms allow living organisms to anticipate the daily alternation of light and darkness. Experiments carried out by Woele et al. (1998-2004) have shown the adaptative value of circadian clocks in Cyanobacteria. In these experiments a wild type cyanobacterial strain (with a 24h circadian rhythm) and a mutant strain (with a longer or shorter period) grow in competition. The external light dark cycle was changed in dierent experiments in order to match the circadian period of the dierent strains. They found that the strain whose circadian period matches the light-dark has a larger tness. As a consequence the initial population of one strain grows while the other decays. These experiments were made under xed light and dark intervals. However, in Nature this relationship is not constant, and it changes according to the season. Therefore, seasonal changes in light could aect the competition between dierent strains. Using a theoretical model proposed by Gonze et al. (2002), which takes into account cell growth, secretion of a cell growth inhibitor and the existence of a light-sensitive circadian oscillator, we analyze how modulation of light can change the survival of the dierent cyanobacterial strains. Our results show that there is a clear shift in the competition due to the modulation of light, which could be experimentally veried.