Structures of polysaccharides and oligosaccharides of some Gram-negative marine Proteobacteria

Extraction and characterization of an exopolysaccharide from a marine bacterium

The marine bacterial exopolysaccharides (EPS) have transfigured the biotech sector with their myriad applications and prospects. This work was carried out to characterize and analyze the functional and biochemical properties of an EPS (EPS-DR3A) produced by a marine bacterium, Pseudoalteromonas sp. YU16-DR3A. The bacterium was cultured in Zobell marine broth for the production of EPS. The extracted EPS designated as EPS-DR3A was composed of 69% carbohydrates and 7.6% proteins with a molecular weight of 20 kDa. FT-IR spectra showed the presence of different functional groups. The monosaccharide analysis performed using GC-MS showed the presence of fucose, erythrotetrose, ribose, and glucose as monomers. EPS-DR3A showed excellent emulsifying activity against the tested hydrocarbons and food oils with stable emulsions. Rheological analysis of EPS-DR3A revealed the pseudoplastic behavior. The EPS-DR3A displayed good thermal stability with a degradation temperature of 249 °C and a melting point at 322 °C. Further, it had the ability to scavenge DPPH and nitric oxide free radicals with good total antioxidant activity. The in vitro biocompatibility study of EPS-DR3A showed high degree of biocompatibility with human dermal fibroblast cells at the tested concentrations. Taken together, the findings such as thermostability, emulsifying activity, pseudoplasticity, antioxidant activity, and biocompatibility of EPS-DR3A make this biomolecule an important candidate for a wide range of biomedical applications.

Extracellular polymeric substances with metal adsorption capacity produced by Pseudoalteromonas sp. MER144 from Antarctic seawater

The EPS-producing Pseudoalteromonas sp. MER144 was selected among 606 isolates from Antarctic seawater due to its evident slimy appearance on agar plates. The production of EPSs was enhanced by a step-by-step approach varying the carbon source, substrate and NaCl concentrations, temperature, and pH. Optimal conditions for the EPS production resulted at temperature of 4 °C and pH 7, with addition of 2% sucrose (w/v) and 3% NaCl (w/v). EPSs produced under optimal conditions were chemically characterized, resulting in a moderate carbohydrate content (35%), uronic acids (14%), and proteins (12%). Monosaccharide composition was estimated to be Glu:Man:GluN:Ara:GluA:GalA:Gal (1:0.36:0.26:0.06:0.06:0.05:0.03), while the estimated molecular weight was about 250 kDa. The addition of sucrose in the culture medium, by stimulating the EPS production, allowed MER144 to tolerate higher concentrations of mercury and cadmium. This finding was probably dependent on the presence of uronic acids and sulfate groups, which can bind cations, in the extracted EPSs. Monitoring EPS production under optimal conditions at different concentrations of mercury and cadmium revealed that EPS amounts increased at increasing heavy metal concentrations, indicating an adaptation to the stress conditions tested.

Structures and gene clusters of the O-specific polysaccharides of the lipopolysaccharides of Escherichia coli O69 and O146 containing glycolactilic acids: ether conjugates of D-GlcNAc and D-Glc with (R)- and (S)-lactic acid

Based on the O-specific polysaccharides of the lipopolysaccharides (O-polysaccharides, O-antigens), strains of a clonal species Escherichia coli are classified into 184 O serogroups. In this work, structures of the O-polysaccharides of E. coli O69 and O146 were elucidated and gene clusters for their biosynthesis were characterized. The O-polysaccharides were released from the lipopolysaccharides by mild acid hydrolysis and studied by sugar analysis and one- and two-dimensional ¹H and ¹³C NMR spectroscopy before and after O-deacetylation. The O146 polysaccharide was also studied by Smith degradation. The O69 and O146 polysaccharides were found to contain ether conjugates of monosaccharides with lactic acid called glycolactilic acids: 2-acetamido-2-deoxy-4-O-[(R)-1-carboxyethyl]-D-glucose (D-GlcNAc4Rlac) and 3-O-[(S)-1-carboxyethyl]-D-glucose (D-Glc3Slac), respectively. Structures of the pentasaccharide repeats of the O-polysaccharides were established, and that of E. coli O69 was found to differ in the presence of D-GlcNAc4Rlac from the structure reported for this bacterium earlier (Erbing C, Kenne L, Lindberg B. 1977. Carbohydr Res. 56:371-376). The O-antigen gene clusters of E. coli O69 and O146 between conserved genes galF and gnd were analyzed taking into account the O-polysaccharide structures established, and functions of putative genes for synthesis of D-Glc3Slac and D-GlcNAc4Rlac and for glycosyltransferases were assigned based on homology with O-antigen biosynthesis genes of other enteric bacteria. It was found that in E. coli and Shigella spp. predicted enolpyruvate reductases of the biosynthesis pathway of glycolactilic acids, LarR and LarS, which catalyze formation of conjugates with (R)- or (S)-lactic acid, respectively, are distinguished by sequence homology and size.

Characterization, Anti-Inflammatory and Antiproliferative Activities of Natural and Sulfonated Exo-Polysaccharides from Streptococcus thermophilus ASCC 1275

Exo-polysaccharides (EPS) isolated from Streptococcus thermophilus ASCC 1275 were sulfated (31%). High-performance liquid chromatography identified that EPS was composed of mannose (30.19%), galactose (20.10%), glucose (18.05%), glucosamine (16.04%), galactosamine (9.06%), glucuronic acid (3.55%), and ribose (3.01%). Pro-/anti-inflammatory cytokine secretion ratios (IL-1β/IL-10, IL-6/IL-10, and TNF-α/IL-10) of lipopolysaccharide stimulated RAW 264.7 macrophages were significantly decreased by EPS and S.EPS treatments in a dose dependent manner. Furthermore, anti-inflammatory activities of S.EPS improved 49.3% and 24.0% than those of EPS before or after LPS treatment. The reactive oxygen species were inhibited by EPS and S.EPS by 49.6% and 55.1% at 50 μg/mL, respectively. Inhibition activities of S.EPS on nitric oxide production were 12.9% and 55.4% higher than those of EPS at 10 and 50 μg/mL. Additionally, S.EPS exhibited stronger antiproliferative activity on Caco-2 and HepG2 cells. Our results indicated that anti-inflammatory and antiproliferative activities of EPS were significantly (P < 0.01) improved by sulfonation.

The O-specific polysaccharide from the marine bacterium Pseudoalteromonas agarivorans KMM 255(T)

The O-specific polysaccharide was isolated from the lipopolysaccharide of a marine bacterium Pseudoalteromonas agarivorans KMM 255(T) and studied by chemical methods along with (1)H and (13)C NMR spectroscopies. The following new structure of the O-specific polysaccharide from P. agarivorans KMM 255(T) containing 2-acetamido-2-deoxy-D-glucose (D-GlcNAc), D-glucose (D-Glc), D-glucuronic acid (D-GlcA) and two residues of D-galactose (D-Gal) was established: Formula: see text].

Structural Investigation of the Oligosaccharide Portion Isolated from the Lipooligosaccharide of the Permafrost Psychrophile Psychrobacter arcticus 273-4

Psychrophilic microorganisms have successfully colonized all permanently cold environments from the deep sea to mountain and polar regions. The ability of an organism to survive and grow in cryoenviroments depends on a number of adaptive strategies aimed at maintaining vital cellular functions at subzero temperatures, which include the structural modifications of the membrane. To understand the role of the membrane in the adaptation, it is necessary to characterize the cell-wall components, such as the lipopolysaccharides, that represent the major constituent of the outer membrane. The aim of this study was to investigate the structure of the carbohydrate backbone of the lipooligosaccharide (LOS) isolated from the cold-adapted Psychrobacter arcticus 273-4. The strain, isolated from a 20,000-to-30,000-year-old continuously frozen permafrost in Siberia, was cultivated at 4 °C. The LOS was isolated from dry cells and analyzed by means of chemical methods. In particular, it was degraded either by mild acid hydrolysis or by hydrazinolysis and investigated in detail by ¹H and ¹³C NMR spectroscopy and by ESI FT-ICR mass spectrometry. The oligosaccharide was characterized by the substitution of the heptose residue, usually linked to Kdo in the inner core, with a glucose, and for the unusual presence of N-acetylmuramic acid.

Exopolysaccharides produced by marine bacteria and their applications as glycosaminoglycan-like molecules

Although polysaccharides are ubiquitous and the most abundant renewable bio-components, their studies, covered by the glycochemistry and glycobiology fields, remain a challenge due to their high molecular diversity and complexity. Polysaccharides are industrially used in food products; human therapeutics fall into a more recent research field and pharmaceutical industry is looking for more and more molecules with enhanced activities. Glycosaminoglycans (GAGs) found in animal tissues play a critical role in cellular physiological and pathological processes as they bind many cellular components. Therefore, they present a great potential for the design and preparation of therapeutic drugs. On the other hand, microorganisms producing exopolysaccharides (EPS) are renewable resources meeting well the actual industrial demand. In particular, the diversity of marine microorganisms is still largely unexplored offering great opportunities to discover high value products such as new molecules and biocatalysts. EPS-producing bacteria from the marine environment will be reviewed with a focus on marine-derived EPS from bacteria isolated from deep-sea hydrothermal vents. Information on chemical and structural features, putative pathways of biosynthesis, novel strategies for chemical and enzymatic modifications and potentialities in the biomedical field will be provided. An integrated approach should be used to increase the basic knowledge on these compounds and their applications; new clean environmentally friendly processes for the production of carbohydrate bioactive compounds should also be proposed for a sustainable industry.

Gram-negative marine bacteria: structural features of lipopolysaccharides and their relevance for economically important diseases

Gram-negative marine bacteria can thrive in harsh oceanic conditions, partly because of the structural diversity of the cell wall and its components, particularly lipopolysaccharide (LPS). LPS is composed of three main parts, an O-antigen, lipid A, and a core region, all of which display immense structural variations among different bacterial species. These components not only provide cell integrity but also elicit an immune response in the host, which ranges from other marine organisms to humans. Toll-like receptor 4 and its homologs are the dedicated receptors that detect LPS and trigger the immune system to respond, often causing a wide variety of inflammatory diseases and even death. This review describes the structural organization of selected LPSes and their association with economically important diseases in marine organisms. In addition, the potential therapeutic use of LPS as an immune adjuvant in different diseases is highlighted.

Thermodynamic characterization of proton-ionizable functional groups on the cell surfaces of ammonia-oxidizing bacteria and archaea

The ammonia-oxidizing archaeon Nitrosopumilus maritimus strain SCM1 (strain SCM1), a representative of the Thaumarchaeota archaeal phylum, can sustain high specific rates of ammonia oxidation at ammonia concentrations too low to sustain metabolism by ammonia-oxidizing bacteria (AOB). One structural and biochemical difference between N. maritimus and AOB that might be related to the oligotrophic adaptation of strain SCM1 is the cell surface. A proteinaceous surface layer (S-layer) comprises the outermost boundary of the strain SCM1 cell envelope, as opposed to the lipopolysaccharide coat of Gram-negative AOB. In this work, we compared the surface reactivities of two archaea having an S-layer (strain SCM1 and Sulfolobus acidocaldarius) with those of four representative AOB (Nitrosospira briensis, Nitrosomonas europaea, Nitrosolobus multiformis, and Nitrosococcus oceani) using potentiometric and calorimetric titrations to evaluate differences in proton-ionizable surface sites. Strain SCM1 and S. acidocaldarius have a wider range of proton buffering (approximately pH 10-3.5) than the AOB (approximately pH 10-4), under the conditions investigated. Thermodynamic parameters describing proton-ionizable sites (acidity constants, enthalpies, and entropies of protonation) are consistent with these archaea having proton-ionizable amino acid side chains containing carboxyl, imidazole, thiol, hydroxyl, and amine functional groups. Phosphorous-bearing acidic functional groups, which might also be present, could be masked by imidazole and thiol functional groups. Parameters for the AOB are consistent with surface structures containing anionic oxygen ligands (carboxyl- and phosphorous-bearing acidic functional groups), thiols, and amines. In addition, our results showed that strain SCM1 has more reactive surface sites than the AOB and a high concentration of sites consistent with aspartic and/or glutamic acid. Because these alternative boundary layers mediate interaction with the local external environment, these data provide the basis for further comparisons of the thermodynamic behavior of surface reactivity toward essential nutrients.

Campylobacter jejuni strain discrimination and temperature-dependent glycome expression profiling by lectin microarray

Gram-negative Campylobacter jejuni is the leading cause of bacterial gastroenteritis in humans worldwide and the most frequently identified infectious trigger in patients developing Guillain-Barré syndrome (GBS). While C. jejuni is pathogenic in humans, it is a commensal in avian hosts. Bacterial cell surface carbohydrates are important virulence factors and play roles in adherence, colonisation and infection. The mechanisms leading to infection or persistent colonisation of C. jejuni are not well understood but host temperature may provide an important stimulus for specific adaptation. Thus, examination of the modulation of the total surface glycome of C. jejuni in response to temperature may help shed light on commensal and pathogenic mechanisms for this species. C. jejuni strains 81116 and 81-176 were cultured at 37 and 42°C to simulate human and avian host conditions, respectively, and whole cells were profiled on lectin microarrays constructed to include a wide range of binding specificities. C. jejuni 81116 profiles indicated that the previously characterised lipopolysaccharide (LPS)-like molecule and N-linked glycans were the predominantly recognised cell surface structures while capsular polysaccharide (CPS), lipooligosaccharides (LOS) and N-linked glycosylation were best recognised for strain 81-176 at 37°C. The profiles of both strains varied and were distinguishable at both temperatures. At the higher temperature, reduced dominance of the LPS-like structure was associated with strain 81116 and a change in the relative distribution of CPS and LOS structures was indicated for strain 81-176. This change in LOS molecular mass species distribution between temperatures was confirmed by SDS-PAGE analysis. Additionally, opposite behaviour of certain lectins was noted between the plate agglutination assay and the microarray platform. Insights into the important glycosylation involved in C. jejuni host cell tropism at different growth temperatures were gained using the lectin microarray platform.

Structure of the O-Specific polysaccharide from Shewanella japonica KMM 3601 containing 5,7-Diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-talo-non-2-ulosonic acid

Structure of the O-specific polysaccharide chain of the lipopolysaccharide (LPS) of Shewanella japonica KMM 3601 was elucidated. The initial and O-deacylated LPS as well as a trisaccharide representing the O-deacetylated repeating unit of the O-specific polysaccharide were studied by sugar analysis along with 1H and 13C NMR spectroscopy. The polysaccharide was found to contain a rare higher sugar, 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-talo-non-2-ulosonic acid (a derivative of 4-epilegionaminic acid, 4eLeg). The following structure of the trisaccharide repeating unit was established: →4)-α-4eLegp5Ac7Ac-(2→4)-β-D-GlcpA3Ac-(1→3)-β-D-GalpNAc-(1→.

Giant DNA virus mimivirus encodes pathway for biosynthesis of unusual sugar 4-amino-4,6-dideoxy-D-glucose (Viosamine)

Mimivirus is one the largest DNA virus identified so far, infecting several Acanthamoeba species. Analysis of its genome revealed the presence of a nine-gene cluster containing genes potentially involved in glycan formation. All of these genes are co-expressed at late stages of infection, suggesting their role in the formation of the long fibers covering the viral surface. Among them, we identified the L136 gene as a pyridoxal phosphate-dependent sugar aminotransferase. This enzyme was shown to catalyze the formation of UDP-4-amino-4,6-dideoxy-D-glucose (UDP-viosamine) from UDP-4-keto-6-deoxy-D-glucose, a key compound involved also in the biosynthesis of L-rhamnose. This finding further supports the hypothesis that Mimivirus encodes a glycosylation system that is completely independent of the amoebal host. Viosamine, together with rhamnose, (N-acetyl)glucosamine, and glucose, was found as a major component of the viral glycans. Most of the sugars were associated with the fibers, confirming a capsular-like nature of the viral surface. Phylogenetic analysis clearly indicated that L136 was not a recent acquisition from bacteria through horizontal gene transfer, but it was acquired very early during evolution. Implications for the origin of the glycosylation machinery in giant DNA virus are also discussed.

Heparin-like entities from marine organisms

Polysaccharides are ubiquitous in animals and plant cells where they play a significant role in a number of physiological situations e.g. hydration, mechanical properties of cell walls and ionic regulation. This review concentrates on heparin-like entities from marine procaryotes and eukaryotes. Carbohydrates from marine prokaryotes offer a significant structural chemodiversity with novel material and biological properties. Cyanobacteria are Gram-negative photosynthetic prokaryotes considered as a rich source of novel molecules, and marine bacteria are a rich source of polysaccharides with novel structures, which may be a good starting point from which to synthesise heparinoid molecules. For example, some sulphated polysaccharides have been isolated from gamma-proteobacteria such as Alteromonas and Pseudoalteromonas sp. In contrast to marine bacteria, all marine algae contain sulphated wall polysaccharides, whereas such polymers are not found in terrestrial plants. In their native form, or after chemical modifications, a range of polysaccharides isolated from marine organisms have been described that have anticoagulant, anti-thrombotic, anti-tumour, anti-proliferative, anti-viral or anti-inflammatory activities.In spite of the enormous potential of sulphated oligosaccharides from marine sources, their technical and pharmaceutical usage is still limited because of the high complexity of these molecules. Thus, the production of tailor-made oligo- and polysaccharidic structures by biocatalysis is also a growing field of interest in biotechnology.

The structural diversity of carbohydrate antigens of selected gram-negative marine bacteria

Marine microorganisms have evolved for millions of years to survive in the environments characterized by one or more extreme physical or chemical parameters, e.g., high pressure, low temperature or high salinity. Marine bacteria have the ability to produce a range of biologically active molecules, such as antibiotics, toxins and antitoxins, antitumor and antimicrobial agents, and as a result, they have been a topic of research interest for many years. Among these biologically active molecules, the carbohydrate antigens, lipopolysaccharides (LPSs, O-antigens) found in cell walls of gram-negative marine bacteria, show great potential as candidates in the development of drugs to prevent septic shock due to their low virulence. The structural diversity of LPSs is thought to be a reflection of the ability for these bacteria to adapt to an array of habitats, protecting the cell from being compromised by exposure to harsh environmental stress factors. Over the last few years, the variety of structures of core oligosaccharides and O-specific polysaccharides from LPSs of marine microrganisms has been discovered. In this review, we discuss the most recently encountered structures that have been identified from bacteria belonging to the genera Aeromonas, Alteromonas, Idiomarina, Microbulbifer, Pseudoalteromonas, Plesiomonas and Shewanella of the Gammaproteobacteria phylum; Sulfitobacter and Loktanella of the Alphaproteobactera phylum and to the genera Arenibacter, Cellulophaga, Chryseobacterium, Flavobacterium, Flexibacter of the Cytophaga-Flavobacterium-Bacteroides phylum. Particular attention is paid to the particular chemical features of the LPSs, such as the monosaccharide type, non-sugar substituents and phosphate groups, together with some of the typifying traits of LPSs obtained from marine bacteria. A possible correlation is then made between such features and the environmental adaptations undertaken by marine bacteria.

Influence of arsenate adsorption to ferrihydrite, goethite, and boehmite on the kinetics of arsenate reduction by Shewanella putrefaciens strain CN-32

The kinetics of As(V) reduction by Shewanella putrefaciens strain CN-32 was investigated in suspensions of 0.2, 2, or 20 g L(-1) ferrihydrite, goethite, or boehmite at low As (10 μM) and lactate (25 μM) concentrations. Experimental data were compared with model predictions based on independently determined sorption isotherms and rates of As(V) desorption, As(III) adsorption, and microbial reduction of dissolved As(V), respectively. The low lactate concentration was chosen to prevent significant Fe(III) reduction, but still allowing complete As(V) reduction. Reduction of dissolved As(V) followed first-order kinetics with a 3 h half-life of As(V). Addition of mineral sorbents resulted in pronounced decreases in reduction rates (32-1540 h As(V) half-life). The magnitude of this effect increased with increasing sorbent concentration and sorption capacity (goethite < boehmite < ferrihydrite). The model consistently underestimated the concentrations of dissolved As(V) and the rates of microbial As(V) reduction after addition of S. putrefaciens (∼5 × 10(9) cells mL(-1)), suggesting that attachment of S. putrefaciens cells to oxide mineral surfaces promoted As(V) desorption and thereby facilitated As(V) reduction. The interplay between As(V) sorption to mineral surfaces and bacterially induced desorption may thus be critical in controlling the kinetics of As reduction and release in reducing soils and sediments.

Occurrence of L-iduronic acid and putative D-glucuronyl C5-epimerases in prokaryotes

Glycosaminoglycans (GAGs) are polysaccharides that are typically present in a wide diversity of animal tissue. Most common GAGs are well-characterized and pharmaceutical applications exist for many of these compounds, e.g. heparin and hyaluronan. In addition, also bacterial glycosaminoglycan-like structures exist. Some of these bacterial GAGs have been characterized, but until now no bacterial GAG has been found that possesses the modifications that are characteristic for many of the animal GAGs such as sulfation and C5-epimerization. Nevertheless, the latter conversion may also occur in bacterial and archaeal GAGs, as some prokaryotic polysaccharides have been demonstrated to contain L-iduronic acid. However, experimental evidence for the enzymatic synthesis of L-iduronic acid in prokaryotes is as yet lacking. We therefore performed an in silico screen for D-glucuronyl C5-epimerases in prokaryotes. Multiple candidate C5-epimerases were found, suggesting that many more microorganisms are likely to exist possessing an L-iduronic acid residue as constituent of their cell wall polysaccharides.

Uronic acids in oligosaccharide and glycoconjugate synthesis

This chapter describes the assembly of uronic acid containing oligosaccharides and glycoconjugates. Two strategies are available to access these target molecules, namely a pre-glycosylation oxidation approach, in which uronic acid building blocks are used, and a post-glycosylation oxidation strategy, which employs an oxidation step after the assembly of the oligosaccharide chain. Because uronic acid building blocks are generally considered to be less reactive than their non-oxidized counterparts, the latter approach has found most application in carbohydrate synthesis. With the aid of selected examples of recent syntheses of biologically relevant oligosaccharides and glycoconjugates, the reactivity of different uronic acid building blocks is evaluated. From these examples it is apparent that the generally assumed low reactivity of uronic acids does not a priori rule out an efficient assembly of these target compounds. Besides influencing the reactivity of a given pyranoside, the C-5 carboxylic acid function can also have a profound effect on the stereochemical course of a glycosylation reaction, which can be exploited in the stereoselective formation of glycosidic bonds.

Emulsifying and metal ion binding activity of a glycoprotein exopolymer produced by Pseudoalteromonas sp. strain TG12

In this study, we describe the isolation and characterization of a new exopolymer that exhibits high emulsifying activities against a range of oil substrates and demonstrates a differential capacity to desorb various mono-, di-, and trivalent metal species from marine sediment under nonionic and seawater ionic-strength conditions. This polymer, PE12, was produced by a new isolate, Pseudoalteromonas sp. strain TG12 (accession number EF685033), during growth in a modified Zobell's 2216 medium amended with 1% glucose. Chemical and chromatographic analysis showed it to be a high-molecular-mass (>2,000 kDa) glycoprotein composed of carbohydrate (32.3%) and protein (8.2%). PE12 was notable in that it contained xylose as the major sugar component at unusually high levels (27.7%) not previously reported for a Pseudoalteromonas exopolymer. The polymer was shown to desorb various metal species from marine sediment-a function putatively conferred by its high content of uronic acids (28.7%). Seawater ionic strength (simulated using 0.6 M NaCl), however, caused a significant reduction in PE12's ability to desorb the sediment-adsorbed metals. These results demonstrate the importance of electrolytes, a physical parameter intrinsic of seawater, in influencing the interaction of microbial exopolymers with metal ions. In summary, PE12 may represent a new class of Pseudoalteromonas exopolymer with a potential for use in biotechnological applications as an emulsifying or metal-chelating agent. In addition to the biotechnological potential of these findings, the ecological aspects of this and related bacterial exopolymers in marine environments are also discussed.

A lectin microarray approach for the rapid analysis of bacterial glycans

Rapid evaluation of microbial cell-surface carbohydrates is essential to understanding the mechanisms by which bacteria use glycans to establish pathogenic or symbiotic relationships. Microbial glycan analysis is complicated both by the vast diversity of possible carbohydrate structures and by their dynamic nature. Bacteria can rapidly alter their glycan coats by switching the genes that are involved on and off in a phase-variable manner. Currently, there is a lack of appropriate tools for studying dynamic carbohydrate alterations. Here, we present a lectin microarray protocol for the high-throughput evaluation of cell-surface microbial sugars. The binding patterns of fluorescent bacteria to these arrays provide a simple means to fingerprint bacteria based on their surface carbohydrates. In addition, this method provides a rapid, parallel evaluation of glycans from multiple bacterial samples, allowing dynamic changes in carbohydrate structures to be studied. The entire procedure takes approximately 12 h but the printing of the microarray can be performed in advance.

Molecular structure of endotoxins from Gram-negative marine bacteria: an update

Marine bacteria are microrganisms that have adapted, through millions of years, to survival in environments often characterized by one or more extreme physical or chemical parameters, namely pressure, temperature and salinity. The main interest in the research on marine bacteria is due to their ability to produce several biologically active molecules, such as antibiotics, toxins and antitoxins, antitumor and antimicrobial agents. Nonetheless, lipopolysaccharides (LPSs), or their portions, from Gram-negative marine bacteria, have often shown low virulence, and represent potential candidates in the development of drugs to prevent septic shock. Besides, the molecular architecture of such molecules is related to the possibility of thriving in marine habitats, shielding the cell from the disrupting action of natural stress factors. Over the last few years, the depiction of a variety of structures of lipids A, core oligosaccharides and O-specific polysaccharides from LPSs of marine microrganisms has been given. In particular, here we will examine the most recently encountered structures for bacteria belonging to the genera Shewanella, Pseudoalteromonas and Alteromonas, of the gamma-Proteobacteria phylum, and to the genera Flavobacterium, Cellulophaga, Arenibacter and Chryseobacterium, of the Cytophaga-Flavobacterium-Bacteroides phylum. Particular attention will be paid to the chemical features expressed by these structures (characteristic monosaccharides, non-glycidic appendages, phosphate groups), to the typifying traits of LPSs from marine bacteria and to the possible correlation existing between such features and the adaptation, over years, of bacteria to marine environments.

Isolation and structural characterization of a novel polysaccharide prepared from Arca subcrenata Lischke

A water-soluble polysaccharide was isolated from Arca subcrenata Lischke (named ASLP) by hot-water extraction, anion-exchange, and gel-permeation chromatography. The average molecular weight of ASLP was estimated to be 3500 Da. The structural characterization of ASLP was performed by sugar composition analysis, methylation analysis, and partial acidic hydrolysis. Further analysis of ASLP was carried out by UV, FT-IR and NMR spectroscopies (1D, COSY, and HSQC, respectively). Our data suggests that ASLP is an alpha-(1-->4)-D-glucan, with an alpha-(1-->6)-D-glucan at the C-6 position every fourth residue along the main chain. The branch chain has three glucose residues. The possible structure, determined on the basis of structural analyses results, was also determined. Preliminary in vitro tests revealed that ASLP can stimulate mouse spleen lymphocyte proliferation and its branches are extremely important for its immunological activity.

An antarctic psychrotrophic bacterium Halomonas sp. ANT-3b, growing on n-hexadecane, produces a new emulsyfying glycolipid

A bacterial strain ANT-3b was isolated at the sea-ice seawater interface from Terra Nova Bay station, Ross Sea, Antarctica. It was isolated on mineral medium supplemented with 2% diesel fuel as a sole carbon and energy source and grown routinely on 2% n-hexadecane. Analysis of 16S rRNA gene sequence indicates that the strain has 99.8% sequence similarity with Halomonas neptunia. The strain ANT-3b was grown in mineral medium supplemented with n-hexadecane between 4 and 20 degrees C, but not at 30 degrees C. The maximum degradation rate of the n-alkane was measured at 15 degrees C, with 5.6+/-1.7 mg O2 microg(-1) protein d(-1). The strain ANT-3b produced emulsifying compounds when grown on n-hexadecane, but not on mineral medium supplemented with D-fructose. A preliminary characterisation of the emulsifier was carried out. The lipid moiety contained a mixture of fatty acids with a following composition in molar ratio: caprylic acid 18.85, myristic acid 1.0, palmitic acid 9.68, palmitoleic acid 5.69 and oleic acid 1.26. The polysaccharide moiety also contained a mixture of sugars with the following molar ratio: mannose 1.71, galactose 1.00 and glucose 2.96. The molecular weight of the glycolipid component determined by gel permeation chromatography was in the 18 kDa range and contained smaller fragments, possibly oligomeric contaminants. Transmission electron microscopy showed contact between the glycolipid secreted by the strain and n-hexadecane broken down to nanodroplets at the water interface, to form a material with mesophase (liquid crystal) organisation.

Structure of the O-specific polysaccharide from Shewanella japonica type strain KMM 3299T containing the rare amino sugar Fuc4NAc

An acidic O-specific polysaccharide (PS) of the agar-digesting bacterium Shewanella japonica with the type strain KMM 3299(T) was obtained by mild acid hydrolysis of the lipopolysaccharide. The polysaccharide was studied by component analysis, methylation analysis, (1)H and (13)C NMR spectroscopy, including 2D NMR experiments. The PS was determined to have the following structure involving three unusual amino sugars:

The structure of the O-polysaccharide of the Pseudoalteromonas rubra ATCC 29570T lipopolysaccharide containing a keto sugar

The structure of the phenol-soluble polysaccharide from Pseudoalteromonas rubra type strain ATCC 29570T has been elucidated using 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, gNOESY, ROESY, 1H,13C gHMQC and gHMBC experiments. It is concluded that the trisaccharide repeating unit of the polysaccharide has the following structure: [carbohydrate structure: see text] where Sug is 2-acetamido-2,6-dideoxy-D-xylo-hexos-4-ulose, Am is acetimidoyl and Acyl is a malic acid residue, which is O-acetylated in approximately 70% of the units.

The O-chain structure from the LPS of marine halophilic bacterium Pseudoalteromonas carrageenovora-type strain IAM 12662T

The O-chain polysaccharide of the lipopolysaccharide from the halophilic marine bacterium Pseudoalteromonas carrageenovora IAM 12662T was characterized. The structure was studied by means of chemical analysis and 2D NMR spectroscopy of the de-O-acylated lipopolysaccharide and shown to be the following:Col is colitose, 3,6-di-deoxy-L-xylo-hexose.

Structure of an acidic polysaccharide from the marine bacterium Pseudoalteromonas aliena type strain KMM 3562T containing two residues of l-serine in the repeating unit

The structure of an acidic polysaccharide from Pseudoalteromonas aliena type strain KMM 3562(T) has been elucidated. The polysaccharide was studied by component analysis, (1)H and (13)C NMR spectroscopy, including 2D NMR experiments. A (1)H, (13)C band-selective constant-time heteronuclear multiple-bond connectivity experiment was used to determine amide linkages, between serine and uronic acid (UA) residues, via (3)J(H,C) correlations between Ser-alphaH and UA-C-6. It was found that the polysaccharide consists of pentasaccharide repeating units with the following structure: [carbohydrate structure]; see text.

The complete structure of the lipooligosaccharide from the halophilic bacterium Pseudoalteromonas issachenkonii KMM 3549T

Novel lipooligosaccharide components were isolated and identified from the lipooligosaccharide fraction of the halophilic marine bacterium Pseudoalteromonas issachenkonii type strain KMM 3549T. The complete structure was achieved by chemical analysis, 2D NMR spectroscopy and MALDI mass spectrometry as the following: [carbohydrate formula see text] All sugars are d-pyranoses. Hep is L-glycero-D-manno-heptose, Kdo is 3-deoxy-D-manno-oct-2-ulosonic acid, P is phosphate, residues and substituents in italic are not stoichiometrically linked. In addition, by MALDI mass spectrometry of the intact LOS, the lipid A moiety was also identified as a mixture of penta-, tetra- and triacylated species.

Structure of an acidic O-specific polysaccharide from marine bacterium Shewanella fidelis KMM 3582T containing Nε-[(S)-1-carboxyethyl]-Nα-(d-galacturonoyl)-l-lysine

The O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of the marine bacterium Shewanella fidelis type strain KMM 3582T and studied by sugar analysis along with 1H and 13C NMR spectroscopy including one-dimensional NOE in difference mode and two-dimensional experiments. The polysaccharide was found to consist of linear tetrasaccharide repeating units containing Nepsilon-[(S)-1-carboxyethyl]-Nalpha-(D-galacturonoyl)-L-lysine and having the following structure: [See text.] The amide of D-galacturonic acid with Nepsilon-[(S)-1-carboxyethyl]-L-lysine ('alaninolysine', 2S,8S-AlaLys) was found for the first time in nature as a component of the O-specific polysaccharide of Providencia rustigianii O14 (Carbohydr. Res. 2003, 338, 1009-1016).

Structure of the O-polysaccharide of Idiomarina zobellii KMM 231T containing two unusual amino sugars with the free amino group, 4-amino-4,6-dideoxy-d-glucose and 2-amino-2-deoxy-l-guluronic acid

Mild acid degradation of the lipopolysaccharide of the bacterium Idiomarina zobellii, type strain KMM 231T, with aq 2% HOAc at 100 degrees C, yielded an oligosaccharide, which represents one repeating unit of the O-polysaccharide. A polysaccharide was obtained by mild base degradation of the lipopolysaccharide. The following structure of the O-polysaccharide was elucidated by 1H and 13C NMR spectroscopy of the oligosaccharide and base-degraded lipopolysaccharide, including COSY, TOCSY, ROESY, 1H, 13C HSQC, HSQC-TOCSY and HMBC experiments: [-->3)-alpha-D-Quip4N-(1-->4)-alpha-D-GlcpA-(1-->6)-alpha-D-GlcpNAc-(1-->4)-alpha-L-GulpNA-(1-->3)-beta-D-FucpNAc-(1-->] The O-polysaccharide is distinguished by the presence of two unusual amino sugars, 4-amino-4,6-dideoxy-D-glucose (D-Qui4N) and 2-amino-2-deoxy-L-guluronic acid (L-GulNA), both having the free amino group. The unexpectedly high acid lability of the glycosidic linkage of 2-acetamido-2,6-dideoxy-D-galactose (D-FucNAc) could be associated with the presence of a free amino group adjacent to the site of attachment of FucNAc to Qui4N.