Multivalency plays a major role in biological processes and particularly in the relationship between pathogenic microorganisms and their host that involves protein–glycan recognition. These interactions occur during the first steps of infection, for specific recognition between host and bacteria, but also at different stages of the immune response. The search for high-affinity ligands for studying such interactions involves the combination of carbohydrate head groups with different scaffolds and linkers generating multivalent glycocompounds with controlled spatial and topology parameters. By interfering with pathogen adhesion, such glycocompounds including glycopolymers, glycoclusters, glycodendrimers and glyconanoparticles have the potential to improve or replace antibiotic treatments that are now subverted by resistance. Multivalent glycoconjugates have also been used for stimulating the innate and adaptive immune systems, for example with carbohydrate-based vaccines. Bacteria present on their surfaces natural multivalent glycoconjugates such as lipopolysaccharides and S-layers that can also be exploited or targeted in anti-infectious strategies.

The steps involved in the biosynthesis of the ADP- l - glycero -β- d - manno- heptose (ADP- l -β- d -heptose) precursor of the inner core lipopolysaccharide (LPS) have not been completely elucidated. In this work, we have purified the enzymes involved in catalyzing the intermediate steps leading to the synthesis of ADP- d -β- d -heptose and have biochemically characterized the reaction products by high-performance anion-exchange chromatography. We have also constructed a deletion in a novel gene, gmhB (formerly yaeD ), which results in the formation of an altered LPS core. This mutation confirms that the GmhB protein is required for the formation of ADP- d -β- d -heptose. Our results demonstrate that the synthesis of ADP- d -β- d -heptose in Escherichia coli requires three proteins, GmhA (sedoheptulose 7-phosphate isomerase), HldE (bifunctional d -β- d -heptose 7-phosphate kinase/ d -β- d -heptose 1-phosphate adenylyltransferase), and GmhB ( d , d -heptose 1,7-bisphosphate phosphatase), as well as ATP and the ketose phosphate precursor sedoheptulose 7-phosphate. A previously characterized epimerase, formerly named WaaD (RfaD) and now renamed HldD, completes the pathway to form the ADP- l -β- d -heptose precursor utilized in the assembly of inner core LPS.

A novel barophilic, hyperthermophilic, anaerobic sulfur-metabolizing archaeon, strain MPT(T = type strain), was isolated from a hydrothermal vent site (Snakepit) on the Mid-Atlantic Ridge (depth, 3550 m). Enrichments and isolation were done under 40 MPa hydrostatic pressure at 95°C. Strain MPTwas barophilic at 75, 80, 85, 90, 95 and 98°C, and was an obligate barophile between 95 and 100°C (T max). For growth above 95°C a pressure of 15·0-17·5 MPa was required. The strain grew at 48-95°C under atmospheric pressure. The optimal temperature for growth was 85°C at both high (40 MPa) and low (0·3 MPa) pressures. The growth rate was twofold higher at 85°C under in situ hydrostatic pressure compared to at low pressure. Strain MPTcells were motile, coccoid, 0·8-2·0 μm in diameter and covered by a hexagonal S-layer lattice. The optimum pH and NaCI concentration for growth at low pressure were 7·0 and 20-30 gl-1, respectively. The new isolate was an obligate heterotroph and utilized yeast extract, beef extract and peptone for growth. Growth was optimal in the presence of elemental sulfur. Rifampicin and chloramphenicol inhibited growth. The core lipids consisted of a major archaeol and a complex lipid pattern consisting of a major phospholipid. The DNA G+C content was 37·1 mol%. Sequencing of the 16S rRNA gene revealed that strain MPTbelonged to the genus Thermococcus and it is proposed that this isolate should be designated as a new species, Thermococcus barophilus.