ORIGINAL ARTICLE Effect of incubation temperature on growth parameters of Pseudoalteromonas antarctica NF 3 and its production of extracellular polymeric substances  M. Nevot, V. Deroncele ´ , Mª J. Montes and E. Mercade Department of Microbiology, University of Barcelona, Barcelona, Spain Introduction Pseudoalteromonas antarctica NF 3 is an Antarctic cold- adapted bacterium that produces abundant extracellular polymeric substances (EPS) (Bozal et al. 1994; Nevot et al. 2006a). It has been suggested that P. antarctica EPS could provide a protective barrier around the bacterium based on its ability to coat liposomes and protect them against several surfactants (de la Maza et al. 1997; Co ´ cera et al. 2001). Other interesting properties found for this bacterial EPS, such as its ability to change ice crystal structure (Rubinsky, personal communication) or con- tribute to in vitro wound healing, have stimulated its use in the cosmetics and pharmaceutical industries (Parente et al. 2002). In Antarctic marine bacteria, several factors affect growth and EPS production, with temperature being one of the most important (Mancuso Nichols et al. 2005a). Pseudoalteromonas antarctica NF 3 has been defined as a psychrotolerant bacterium, but the influence of tempera- ture on growth parameters and the temperature depen- dence of EPS production have not yet been studied. One useful way to evaluate bacterial behaviour under different temperatures is to examine the three parameters that characterize the three phases of bacterial growth: the lag time (k) as a measure of the lag phase, the maximum growth rate (l) for the exponential growth phase and the maximum population density (A) for the stationary phase. These three parameters can be estimated by the re-parameterized Gompertz equation for bacterial growth. This primary mathematical model fits well the growth of various bacterial species under a variety of culture condi- tions (Zwietering et al. 1990; Shi and Xia 2003; Lu et al. 2005). Secondary growth mathematical models, the Keywords Antarctica, arrhenius model, exopolymer, pseudoalteromonas, square root model, temperature. Correspondence Elena Mercade, Departament de Microbiologia i Parasitologia Sanita ` ries, Facultat de Farma ` cia, Universitat de Barcelona, Avd. Joan XXIII s ⁄ n, E-08028 Barcelona, Spain. E-mail: mmercade@ub.edu  This work is dedicated to the memory of Jesu ´ s Guinea Sa ´ nchez who died on 29 September 2006, with sorrow, respect and gratitude. 2007 ⁄ 0775: received 17 May 2007, revised 17 December 2007 and accepted 19 Decem- ber 2007 doi:10.1111/j.1365-2672.2008.03769.x Abstract Aim: To evaluate the effect of temperature on growth parameters and on extra- cellular polymeric substance (EPS) production for Pseudoalteromonas antarctica NF 3 . Methods and Results: For this purpose, three growth parameters, lag time (k), maximum growth rate (l) and maximum population density (A), were calcu- lated with the predictive Gompertz model. To evaluate the variations in l with respect to temperature, the secondary Arrhenius and the square root models were used. Below the optimal growth temperature (17Æ5°C), the growth of P. antarctica was separated into two domains at the critical temperature of 12°C. Within the suboptimal domain (12–17Æ5°C), the temperature characteristic was the lowest (5Æ29 kcal mol )1 ). Growth population densities were maintained over the entire physiological portion assayed (5–17Æ5°C). Higher crude EPS production was found at temperatures included in the cold domain (5–12°C). Conclusions: All calculated parameters revealed an optimal adaptation of this strain to cold temperatures. Significance and Impact of the Study: The knowledge of the influence of tem- perature on growth parameters of P. antarctica NF 3 and on EPS production could improve the production of this extracellular polymeric substance that is currently being used in the cosmetic and pharmaceutical industries. Journal of Applied Microbiology ISSN 1364-5072 ª 2008 The Authors Journal compilation ª 2008 The Society for Applied Microbiology, Journal of Applied Microbiology 105 (2008) 255–263 255