a b s t r a c tIt is well known that microorganisms well-adapted to survival in extreme ecosystems could be considered as new sources of biomolecules that have biotechnological importance. On French Polynesian atolls, microbial mats are developing in water ponds exposed to fluctuations in physical and chemical parameters. In these microbial mats, which are called "kopara" by the inhabitants, bacteria coexist with cyanobacteria, and a synergistic relationship may exist between these two types of living microorganisms. A large number of cyanobacteria and bacteria have been isolated from different mats. Under laboratory conditions, these microorganisms were shown to produce various exopolymers, including exopolysaccharides and poly-␤-hydroxyalkanoates, along with pigments for further commercial developments. This manuscript gives an overview of substances isolated and characterized from these bacteria and cyanobacteria and discusses their potential applications in biotechnology.

Isethionic acid (2-hydroxyethane sulfonic acid) and floridoside (2-O-alpha-D-galactopyranosylglycerol) were extracted from the red alga, Grateloupia turuturu, and tested for anti-settlement activity against cyprid larvae of the tropical barnacle, Balanus amphitrite and for their toxicity to nauplius larvae. Isethionic acid was active for anti-settlement but had the disadvantage of being toxic to nauplius larvae. Floridoside was a potent inhibitor of cyprid settlement at non-toxic concentrations to nauplii (0.01 mg ml(-1)).

Aims:  The objective of the present work was to describe a new deep‐sea, aerobic, mesophilic and heterotrophic bacterium, referenced as strain AT1214, able to produce polyhydroxyalkanoates (PHAs) under laboratory conditions. This bacterium was isolated from a shrimp collected nearby a hydrothermal vent located on the Mid‐Atlantic Ridge. Methods and Results:  This micro‐organism, on the basis of the phenotypical features and genotypic investigations, can be clearly assigned to the Halomonas genus and the name of Halomonas profundus is proposed. Optimal growth occurred between 32 and 37°C at a pH between 8 and 9 and at ionic strength between 20 and 30 g l−1 of sea salts. The G + C content of DNA was 58·6%. This bacterium produced PHAs of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) from different carbon sources. Conclusions:  The bacterium H. profundus produces PHA of 3HB and 3HV monomers from different carbon sources. Significance and Impact of the Study:  PHAs share physical and material properties that suggest them for application in various areas, and are considered as an alternative to nonbiodegradable plastics produced from fossil oils. In this study, we describe a new bacteria isolated from a deep‐sea hydrothermal vent with the capability to produce polyesters of biotechnological interest.

A bacterium isolated from microbial mats located on a polynesian atoll produced a high molecular weight (3,000 kDa) and highly sulphated exopolysaccharide. Previous studies showed that the chemical structure of this EPS consisted of neutral sugars, uronic acids, and high proportions of acetate and sulphate groups. The copper- and iron-binding ability of the purified pre-treated native EPS was investigated. Results showed that this EPS had a very high affinity for both copper (9.84 mmol g(-1) EPS) and ferrous iron (6.9 mmol g(-1) EPS). Amazingly, this EPS did not show any affinity for either ferric ions or selenium salts. This finding is one of the first steps in assessing the biotechnological potential of this polysaccharide.