To fulfill this role, diatoms as other living organisms must find in their environment good conditions, including www.selleckchem.com/products/ABT-263.html the right range of macro- and microelements. Among the mandatory microelements required for cell functioning, zinc (Zn) occupies a particular place because it acts as a structural component [2] and as functional component of numerous enzymes, in some gene transcription regulators [3] and as a cofactor in zinc-finger protein involved in mitosis regulation [4] (for review, see [5]). As for other nutrient, Zn should be present within a definite range to allow optimum cell functioning and growth. In Zn-deficient conditions, diatoms cannot develop whereas when Zn is present in excess, crucial processes are inhibited partially or totally (growth: [6�C8], photosynthesis: [9, 10]) while the oxidative stress develops [11�C13].

Because the optimal range of Zn concentrations depends on diatom species, this type of algae is used as bioindicators [14].Physiological and biochemical studies have demonstrated that the capacity to tolerate Zn is linked to the ability to establish defense mechanisms (for reviews see [5, 15]). Among these mechanisms, Zn chelation seems to be major. Zn ions can be chelated by exopolysaccharides as in the diatom Skeletonema costatum [16] or in the cytoplasm by phytochelatins, which are cysteine-rich pseudopeptides. Phytochelatins are synthesized by addition of glutathione units (��-Glu-Cys-Gly) through the catalytic action of phytochelatin synthase (PCS), a ��-glutamyl cysteine transpeptidase [17].

The aim of this study was to compare the effect of an increase of Zn ion concentration on the growth, photosynthetic process, and responses to metal stress of four diatom species. Amphora acutiuscula and Nitzschia palea were harvested and isolated from the South-East Vietnamese coast, at the Can Gio site, which is confronted by pollution from the Mekong River, and two other diatom species (A. coffeaeformis and Entomoneis paludosa) isolated from the French Atlantic coast. N. palea often develops in polluted waters [18], and A. coffeaeformis has been shown to be a tolerant species to UV [19, 20] and Cu [10] but sensitive to Cd [14].2. Materials and Methods2.1. Culture ConditionsAmphora acutiuscula K��tzing and Nitzschia palea (K��tzing) Smith were collected at the Can Gio coastal site in South East Vietnam (latitude: 10��40��09���; longitude: 107��00��59���), whereas Dacomitinib A. coffeaeformis (Agardh) K��tzing and Entomoneis paludosa (W. Smith) Reimer were collected on the French Atlantic coast and were obtained from the Nantes Culture Collection (strains UTC58 and NCC18.2, resp.). Each taxon was axenically cultured in artificial seawater (ASW) prepared from Millipore ultrapure water according to Harrison et al. [21].