Applied Microbiology and Microbial Biotechnology

G.I. LUCCHESI; A.S. LIFFOURRENA; P.S. BOERIS; M.A. SALVANO

Current Research, Technology and Education Topics

Formatex

Lugar: Badajoz; Año: 2010; p. 1297 - 1303

Quaternary ammonium compounds (QACs) are commercially available chemicals commonly used in a variety of products such as cosmetics, antiseptic solutions, textile finishes, and fabric softeners. Released into the environment, the biodegradability of QACs may be limited by their antimicrobial activity. However some species of bacteria, notably strains of Pseudomonas, have high resistance to QACs and are thought to be responsible for biodegradation in activated sludge. Here, we show how tetradecyltrimethylammonium bromide (TTAB), a representative of QACs, might be degraded by P. putida A ATCC 12633. We also establish that the response to TTAB involves changes in the membrane phospholipids composition. P. putida A ATCC 12633 uses TTAB as a sole carbon, nitrogen, and energy source. The TTAB degradation is initiated by N-dealkylation catalyzed by a monooxygenase activity resulting in the formation of tetradecylalkanal and trimethylamine (TMA). The TMA produced is used by P. putida A ATCC 12633 as a nitrogen source through trimethylamine monooxygenase activity and is also accumulated inside the cell, decreasing the bacterial growth an effect counteracted by the addition of AlCl3. In the presence of 0.1 mM AlCl3, the intracellular concentration of free TMA is decreased by the formation of an Al3+:TMA complex, and the TTAB is fully consumed without accumulation of undesirable compounds. On the other hand, in P. putida A ATCC 12633, the adaptative response and resistance to the bactericidal activity of TTAB involves an initial mechanism, producing changes at membrane levels involving specific variations in the content of phosphatidic acid, phosphatidylglycerol, and cardiolipin. These modifications indicate that these phospholipids are involved in cellular responses to QACs, utilizing principally phosphatidic acid to neutralize the high positive charge density given for the ammonium quaternary moiety from TTAB. Also, when P. putida are grown with TTAB in the presence of AlCl3, phosphatidylcholine increased. This indicate that this particular phospholipid may be involved in the bacteria response to binding Al3+ and allowing us to formulate a physiological role of phosphatidylcholine as a temporary reservoir of available Al3+.