Aims: The objective of the present work was to describe an aerobic, mesophilic and heterotrophic marine bacterium, designated HYD657, able to produce an exopolysaccharide (EPS). It was isolated from a East Pacific Rise deep‐sea hydrothermal vent polychaete annelid. 
Methods and Results: This micro‐organism, on the basis of the phenotypical features and genotypic investigations, can be clearly assigned to the Alteromonas macleodii species and the name A. macleodii subsp. fijiensis biovar deepsane is proposed. Optimal growth occurs between 30 and 35°C, at pH between 6˙5 and 7˙5 and at ionic strengths between 20 and 40 g l−1 NaCl. The G + C content of DNA was 46˙5%. This bacterium excreted, under laboratory conditions, an EPS consisting of glucose, galactose, rhamnose, fucose and mannose as neutral sugars along with glucuronic and galacturonic acids and a diacidic hexose identified as a 3‐0‐(1 carboxyethyl)‐d‐glucuronic acid. Its average molecular mass was 1˙6 × 106 Da. 
Conclusions: The bacterium HYD657, for which the name A. macleodii subsp. fijiensis biovar deepsane is proposed, produces an unusual EPS in specific medium. 
Significance and Impact of the Study: Due to its interesting biological activities, applications have been found in cosmetics. Its probable contribution to the filamentous microbial mat in the Alvinella pompejana microenvironment can be also mentioned.

The heterotrophic and mesophilic marine bacterium HYD-1545 was isolated on a metal-amended medium from the dorsal integument of the hydrothermal vent polychaete Alvinella pompejana. This strain, which can be assigned to the genus Alteromonas on the basis of its G+C content and phenotypical features, produced large amounts of an acidic polysaccharide in batch cultures. The polysaccharide was excreted during the stationary phase of growth and contained glucose, galactose, glucuronic acid, galacturonic acid, and 4,6-O-(1-carboxyethilidene)-galactose as major components. This polysaccharide was a polyelectrolyte, and the viscosity of its solutions depended on the ionic strength. The decrease in viscosity with increasing NaCl concentrations and the effect of Ca21 in decreasing the viscosity at low Ca2+ concentrations support a model in which the polysaccharide carries anionic groups. However, an unusual behavior was observed at higher concentrations and could be related to intermolecular interactions involving Ca2+ ions.

Pili have been isolated from Neisseria gonorrhoeae by controlled homogenization followed by selective disaggregation in sucrose and purification by CsCl density gradient centrifugation. Pili from six gonococcal strains had buoyant densities of 1-30 to 1-31 g ml-l on CsCl. The pili were immunologically distinct when tested with rabbit antisera to purified pili. The amino acid composition of pilin from strains ~9 and 201 was very similar, consisting of 208 and 2 I 2 amino acid residues respectively giving molecular weights of 22 600 and 22352. The pili contained a high proportion (46 %) of non-polar amino acids. Further analysis of strain ~9 pili revealed the presence of I to 2 phosphate groups and I to 2 hexose groups per pilin subunit; no amino sugars were detected. Pili from strain ~9 were resolved into two bands by equilibrium density gradient centrifugation or column isoelectric focusing, suggesting the presence of more than one kind of pilus.

Abstract. Specimens of alvinellid polychaetes (Alvinella pompejana Desbruy6res andLaubier, 1980 and A. caudata Desbruy6res andLaubier, 1986) and their tubes were sampled from deep-sea hydrothermal vents at 13°N from the manned submersible "Nautile" during the "Hydronaut" cruise (October to November 1987) on the East Pacific Rise. Samples were subjected to bacterial analysis aboard the mother ship "Nadir" to detect bacteria involved in the nitrogen and sulphur cycles, in non-specific heterotrophic processes, and displaying resistance to selected heavy metals. Cultures were incubated at different temperatures under atmospheric and "in situ" (250 atm) pressures. Bacterial growth was observed in enrichment cultures for most metabolic types screened. Heavy-metalresistant bacteria were also detected in many samples. No filamentous bacterial form was observed in the cultures. The results demonstrate a high metabolic diversity in episymbiotic flora, indicating that the worm (A. pompejana or A. caudata), its tube and its epiflora represent a complex micro-ecosystem.