Isolation of signal molecules that induce protease production in haloalkaliphilic archaea

ROBERTO PAGGI; ROSANA DE CASTRO

Tucumán

Congreso; Reunión Anual de la SAIB; 2009

SAIB

Bacteria can communicate through a signaling pathway mediated by molecules secreted during growth, denoted as quorum sensing (QS). Little is known on the role of QS in extreme environments, and this mechanism has not been confirmed in Archaea. The alkaliphilic haloarchaeon Natrialba magadii secretes a serine protease (NEP) as the cells enter the stationary phase. We have shown that early production of NEP is induced by cell-free spent medium from stationary phase cultures suggesting the occurrence of a QS-like mechanism in N. magadii. To further explore this possibility, the aim of this work was to isolate the “signal molecule” present in stationary phase cultures of N. magadii. Signal molecules were purified by: 1. Ethyl acetate extraction (EA); 2. Reverse phase chromatography. Flow-through (FL) and fractions eluted with 5, 30, 60 and 100 % (v/v) methanol were assayed. These fractions were added to low density cultures of N. magadii and then samples were removed to measure cell growth and protease activity. Fresh medium was used as control. Early induction of protease activity was observed in cultures assayed with EA extracts, and FL/30% methanol relative to control cultures while the duplication times were similar. These data suggest a hydrophobic nature of the signal molecule; however, conditions need to be optimized to improve reproducibility