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ResumeUn clone de cyanobacterie chroococcale (Aphanothece sp.) isole des salines de Santa Pola (Espagne) a ete etudie d'un point de vue morphologique et ultrastructural. De plus, outre la chlorophylle a, la phycocyanine et Pallophycocyanine, une analyse par HPLC a permis de separer 10 caroteno'ides: myxoxanthophylles, nostoxanthine, caloxanthine, zeaxanthine, cryptoxanthine, echinenone, epoxydes de ß-carotene et ß-carotene. Ce dernier pigment forme ä lui seul 70-80% de la masse totale des caroteno'ides.Uimpact de la salinite (de 0,6 M ä 3 M de NaCl), de la temperature (de 25 °C ä 40 °C) et leur interaction sur la croissance de cette chroococcale ont ete etudies. C'est une algue eurytherme et halotolerante, s'adaptant rapidement aux stress causes par ces 2 facteurs. La croissance est relativement lente, le temps minimum de generation observe est de 29,7 h et a ete obtenu pour une salinite de 2 M et une temperature de 40 °C; on a observe une etroite interdependance entre ces deux facteurs. Salinite et temporature n'ont pas engendre de variations importantes ni dans la composition pigmentaire (chl a et caroteno'ides varient de fa?on identique), ni dans la taille des cellules (correlation hautement significative entre longueur et largeur). On observe des variations importantes dans la concentration protoinique et glucidique des cellules, mais sans relation previsible avec la temperature et la salinite.Cette souche pourrait presenter un interet en aquiculture intensive de par sa richesse en proteines et polysaccharides. Abstract Interaction of Salinity and Temperature on Morphology, Growth and Cell Composition of a Halotolerant Cyanobacterium (Aphanothece sp.)A strain of Aphanothece sp., a chroococcalian cyanobacterium, was isolated from Santa Pola Salt Marsh (Spain) and studies were carried out concerning its morphological and ultrastructural aspects. In addition to the following light-harvesting pigments, chlorophyll a, phycocyanin and allophycocyanin, ten algal carotenoids were identified by HPLC: mixoxanthophylls, nostoxanthin, caloxanthin, zeaxanthin, cryptoxanthin, echinenone, several derivatives of ß-earotene containing epoxidic functions and ß-carotene. The latter pigment accounted for 70 to 80% of total carotenoids. 318 Berland et al: Interaction salinite-temperature sur Aphanothece sp.The effect of salinity (0,6 to 3 M NaCl) on the growth of this alga was investigated at different temperatures (25 °C to 40 °C). The results indicate that this cyanobacteria is an eurythermal and halotolerant organism exhibiting rapid adaptation to salinity and temperature changes. Aphanothece sp. showed a low relative growth rate with a minimum doubling time of 29.7 h at 2 M NaCl and 40 °C. No significant influence of the different salt concentations and temperatures on pigmentation (similar changes in chla and carotenoid contents) and cell size (highly significant correlation between length and breadth) was found in Aphanothece sp. Variations in carbohydrate and protein cell contents showed no evident relationship to salinity...

Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (20–40 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 2–3 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats.Key words: microbial mats, cyanobacteria, bacterial pigments, French Polynesia atolls, exopolymers.

Microbial mats that develop in shallow brackish and hyposaline ponds in the rims of two French polynesian atolls (Rangiroa and Tetiaroa) were intensively investigated during the past three years. Comparative assessment of these mats (called kopara in polynesian language) showed remarkable similarities in their composition and structure. Due to the lack of iron, the color of the cyanobacterial pigments produced remained visible through the entire depth of the mats (20-40 cm depth), with alternate green, purple, and pink layers. Profiles of oxygen, sulfide, pH, and redox showed the anoxia of all mats from a depth of 2-3 mm. Analyses of bacterial pigments and bacterial lipids showed that all mats consisted of stratified layers of cyanobacteria (mainly Phormidium, Schizothrix, Scytonema) and purple and green phototrophic bacteria. The purple and green phototrophic bacteria cohabit with sulfate reducers (Desulfovibrio and Desulfobacter) and other heterotrophic bacteria. The microscopic bacterial determination emphasized the influence of salinity on the bacterial diversity, with higher diversity at low salinity, mainly for purple nonsulfur bacteria. Analyses of organic material and of exopolymers were also undertaken. Difference and similarities between mats from geomorphological, microbiological, and chemical points of view are discussed to provide multicriteria of classification of mats.