An improved silver stain for the visualization of lipopolysaccharides on polyacrylamide gels

Analysis of the antigenic and immunogenic properties of the native rabies virus glycoprotein purified by Lens culinaris lectin affinity chromatography

Rabies virus glycoprotein (RABV-G) is responsible for the recognition of specific cell surface receptors and induces the production of neutralizing antibodies (VNA). Since RABV-G is a glycoprotein, this work aimed to evaluate Lens culinaris (LCA) chromatography as a simple and effective purification method. The purity and identification of the protein obtained were analyzed by SDS-PAGE, ELISA and lectin-binding assay. The antigenic properties of the purified RABV-G were evaluated by direct ELISA using human serum samples from individuals who had received rabies pre-exposure vaccination. For the immunogenicity study, Swiss Webster mice were immunized with purified RABV-G and the specific antibodies were measured by direct ELISA and RFFIT. As results, it was observed that the purified protein reveled a molecular mass of 55 kDa and the presence of carbohydrate; additionally, it was recognized by anti-rabies virus glycoprotein monoclonal antibody. Purified RABV-G induced high VNA titers (>50.0 IU/ml) in vivo, as detected by RFFIT, as well as RABV-G specific IgG1 (0.8 mean OD±SD) and IgG2a (0.3 mean OD±SD) antibodies, with a predominance of IgG1 (p< 0.001). In addition, it was observed that RABV-G was efficient in selectively detecting anti- RABV-G IgG in the sera of vaccinated individuals compared to the negative control. Therefore, LCA chromatography was efficient in preserving the native properties of RABV-G that are essential in inducing an adequate humoral immune response. In addition, the purified RABV-G presented analytical potential as an ELISA reagent.

The GE296_RS03820 and GE296_RS03830 genes are involved in capsular polysaccharide biosynthesis in Riemerella anatipestifer

Riemerella anatipestifer is a pathogenic bacterium that causes duck serositis and meningitis, leading to significant harm to the duck industry. To escape from the host immune system, the meningitis-causing bacteria must survive and multiply in the bloodstream, relying on specific virulence factors such as capsules. Therefore, it is essential to study the genes involved in capsule biosynthesis in R. anatipestifer. In this study, we successfully constructed gene deletion mutants Δ3820 and Δ3830, targeting the GE296_RS03820 and GE296_RS03830 genes, respectively, using the RA-LZ01 strain as the parental strain. The growth kinetics analysis revealed that these two genes contribute to bacterial growth. Transmission and scanning electron microscopy (TEM and SEM) and silver staining showed that Δ3820 and Δ3830 produced the altered capsules and compounds of capsular polysaccharides (CPSs). Serum resistance test showed the mutants also exhibited reduced C3b deposition and decreased resistance serum killing. In vivo, Δ3820 and Δ3830 exhibited markedly declining capacity to cross the blood-brain barrier, compared to RA-LZ01. These findings indicate that the GE296_RS03820 and GE296_RS03830 genes are involved in CPSs biosynthesis and play a key role in the pathogenicity of R. anatipestifer. Furthermore, Δ3820 and Δ3830 mutants presented a tendency toward higher survival rates from RA-LZ01 challenge in vivo. Additionally, sera from ducklings immunized with the mutants showed cross-immunoreactivity with different serotypes of R. anatipestifer, including 1, 2, 7 and 10. Western blot and SDS-PAGE assays revealed that the altered CPSs of Δ3820 and Δ3830 resulted in the exposure of some conserved proteins playing the key role in the cross-immunoreactivity. Our study clearly demonstrated that the GE296_RS03820 and GE296_RS03830 genes are involved in CPS biosynthesis in R. anatipestifer and the capsule is a target for attenuation in vaccine development.

A Simple and Rapid Microscale Method for Isolating Bacterial Lipopolysaccharides

Bacterial endotoxins (lipopolysaccharides (LPSs)) are important mediators of inflammatory processes induced by Gram-negative microorganisms. LPSs are the key inducers of septic shock due to a Gram-negative bacterial infection; thus, the structure and functions of LPSs are of specific interest. Often, highly purified bacterial endotoxins must be isolated from small amounts of biological material. Each of the currently available methods for LPS extraction has certain limitations. Herein, we describe a rapid and simple microscale method for extracting LPSs. The method consists of the following steps: ultrasonic destruction of the bacterial material, LPS extraction via heating, LPS purification with organic solvents, and treatment with proteinase K. LPSs that were extracted by using this method contained less than 2-3% protein and 1% total nucleic acid. We also demonstrated the structural integrity of the O-antigen and lipid A via the sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) methods, respectively. We demonstrated the ability of the extracted LPSs to induce typical secretion of cytokines and chemokines by primary macrophages. Overall, this method may be used to isolate purified LPSs with preserved structures of both the O-antigen and lipid A and unchanged functional activity from small amounts of bacterial biomass.

The effect of lipopolysaccharide from uropathogenic Escherichia coli on the immune system, testis tissue, and spermatozoa of BALB/c mice

Objective

Uropathogenic Escherichia coli is known to cause urinary tract infections, and the endotoxin (lipopolysaccharide [LPS]) of this bacterium may cause deficiencies of sperm quality and morphology. In the present study, the effects of LPS on mouse sperm were studied, and the levels of interleukin (IL)-17A and possible changes in testis tissue were evaluated.

Methods

LPS of uropathogenic E. coli was extracted using the methanol-chloroform method, followed confirmation using sodium dodecyl sulfate-polyacrylamide electrophoresis. Purified LPS (100 µg/kg) or phosphate-buffered saline was injected intraperitoneally into BALB/c mice for 7 days consecutively in the test and control groups, mice were sacrificed on days 3, 7, and 42 after the first injection. Blood was tested for levels of IL-17A using the enzyme-linked immunosorbent assay method. Testis tissue and sperm were collected from each mouse and were studied according to standard protocols.

Results

The mean sperm count and motility significantly decreased (p=0.03) at 3, 7, and 42 days after the injections. The level of IL-17A in the test groups increased, but not significantly (p=0.8, p=0.11, and p=0.15, respectively). Microscopic studies showed no obvious changes in the morphology of the testis tissue; however, significant changes were observed in the cellular parenchyma on day 42.

Conclusion

LPS can stimulate the immune system to produce proinflammatory cytokines, resulting in an immune response in the testis and ultimately leading to deficiency in sperm parameters and testis tissue damage. In addition, the presence of LPS could significantly impair sperm parameters, as shown by the finding of decreased motility.

Methionine and Tryptophan Play Different Modulatory Roles in the European Seabass (Dicentrarchus labrax) Innate Immune Response and Apoptosis Signaling-An In Vitro Study

The range of metabolic pathways that are dependent on a proper supply of specific amino acids (AA) unveils their importance in the support of health. AA play central roles in key pathways vital for immune support and individual AA supplementation has shown to be able to modulate fish immunity. In vitro trials are important tools to evaluate the immunomodulatory role of AA, and the present study was conceived to evaluate methionine and tryptophan roles in immune-related mechanisms aiming to understand their effects in leucocyte functioning and AA pathways. For that purpose, head-kidney leucocytes were isolated and a primary cell culture established. The effect of methionine or tryptophan surplus on cell viability was assessed. Medium L-15 10% FBS without AA addition (0.5mM of L-methionine, 0.1 mM of L-tryptophan) was used as control. To that, L-methionine or L-tryptophan were supplemented at 1 and 2 times (M1x or M2x, and T1x or T2x). Nitric oxide, ATP, total antioxidant capacity, and immune-related genes were evaluated in response to lipopolysaccharides extracted from Photobacterium damselae subsp. piscicida or UV-inactivated bacteria). Moreover, caspase 3 activity and apoptosis-related genes were evaluated in response to the apoptosis-inducing protein, AIP56. Distinct roles in leucocytes' immune response were observed, with contrasting outcomes in the modulation of individual pathways. Methionine surplus improved cell viability, polyamine production, and methionine-related genes expression in response to an inflammatory agent. Also, methionine supplementation lowered signals of apoptosis by AIP56, presenting lower caspase 3 activity and higher il1β and nf-κb expression. Cells cultured in tryptophan supplemented medium presented signals of an attenuated inflammatory response, with decreased ATP and enhanced expression of anti-inflammatory and catabolism-related genes in macrophages. In response to AIP56, leucocytes cultured in a tryptophan-rich medium presented lower resilience to the toxin, higher caspase 3 activity and expression of caspase 8, and lower expression of several genes, including nf-κb and p65. This study showed the ability of methionine surplus to improve leucocytes' response to an inflammatory agent and to lower signals of apoptosis by AIP56 induction, while tryptophan attenuated several cellular signals of the inflammatory response to UV-inactivated bacteria and lowered leucocyte resilience to AIP56.

Glycated albumin based photonic crystal sensors for detection of lipopolysaccharides and discrimination of Gram-negative bacteria

We present two types of two-dimensional (2D) photonic crystals (PC) hydrogel sensors based on glycated albumin (G-alb) as a proof-of-concept for utilizing recognition between G-alb and bacterial cell surface lipopolysaccharides (LPS) to detect and discriminate Gram-negative bacteria. The G-alb functionalized PC-G-alb hydrogel provides recognition of different LPS via hydrogen bonding and can discriminate different Gram-negative bacteria based on their LPS types. The hydrogel delivered LOD of 0.87 ng mL^-1 for E.coli LPS, 153 CFU mL^-1 for E.coli, 1.22 ng mL^-1 for P.aeruginosa LPS and 225 CFU mL^-1 for P.aeruginosa. On the other hand, LPS bioimprinted hydrogel (PC-G-alb-LPS_imp) provides selective recognition of E.coli LPS with LOD 0.76 ng mL^-1 and for E.coli 58 CFU mL^-1, via generation of flexible specific cavities for E.coli and its LPS. The two hydrogels showed remarkable recoveries for both LPS and Gram-negative bacteria in the relevant samples of milk, orange juice, river water, and serum with a short response time of 6-12 min. In the binding process, the hydrogels shrink, and 2D PC particle spacing decreases with diffraction shift from green to blue. The diffraction shifts can be visually observed, measured through Debye's diffraction ring diameter by a laser pointer or determined from a spectrometer.

Changes in physiology and virulence during the selection of resistant Yersinia ruckeri mutants under subinhibitory cefotaxime concentrations

Bacterial antibiotic resistance is one of the main healthcare problems currently. Apart from reducing antibiotic efficacy, it has awakened the interest of scientists due to its association with bacterial fitness and virulence. Interestingly, antibiotic resistance can be a source of both increased fitness and decreased fitness, even though the molecular basis of these relationships remains unknown. The aim of this work is to define the effects of sub-MIC concentrations of cefotaxime, an antibiotic extensively used in clinical practice, on the physiology and virulence of Yersinia ruckeri and to determine the importance of these sub-MIC concentrations for the selection of antibiotic-resistant mutants in the aquatic environment. Results indicated that exposure to sub-MIC concentrations of cefotaxime selected Y. ruckeri populations with irreversible alterations in the physiology, such as slow growth, aggregation in liquid cultures and modification of the colony morphology. These bacteria also displayed changes in the OMPs and LPS profiles and a full attenuation of virulence. An overexpression of the envelope stress regulator RpoE was also detected after exposure to the antibiotic. In conclusion, exposure to cefotaxime selected, at high frequency, Y. ruckeri strains that survive the antibiotic stress at the expense of a fitness cost and the loss of virulence.

Colorimetric detection and typing of E. coli lipopolysaccharides based on a dual aptamer-functionalized gold nanoparticle probe

A rapid method for identification and typing of lipopolysaccharides (LPS) was developed by utilizing the different binding affinities between two kinds of gold nanoparticles (AuNPs) functionalized with two aptamers. Aptamers against ethanolamine and E. coli O111:B4 LPS were used to functionalize the AuNPs. The AuNPs functionalized with ethanolamine aptamer can bind to ethanolamine and are termed general probe (G-probe). The G-probe can recognize any type of LPS because ethanolamine is a component of every type of LPS. This causes a sandwich-mediated aggregation of the AuNPs and a color change from red to blue. The AuNPs functionalized with aptamer against the LPS of E. coli O111:B4 specifically bind to O111:B4 LPS and are termed specific probe (S-probe). By using these two probes, a logic typing method was developed. It can detect LPS in concentrations between 2.5 and 20 μg·mL^-1 and with a 1 μg·mL^-1 detection limit. In the authors' perception, the use of a dual aptamer-based colorimetric method has a large potential in terms of selective detection of microorganisms. Graphical abstract Two aptamer functionalized AuNP probes, G-probe and S-probe, were prepared for LPS typing and detecting. E. coli O111:B4 LPS was easily distinguished from O55:B5 LPS according to the signal output configurations (On & On Vs On & Off) of a general probe (G-probe) and a specific probe (S-probe).

Rapid and simple purification of elastin-like polypeptides directly from whole cells and cell lysates by organic solvent extraction

Elastin-like polypeptides (ELP) are a well-known class of proteins that are being increasingly utilized in a variety of biomedical applications, due to their beneficial physicochemical properties. A unifying feature of ELP is their demonstration of a sequence tunable inverse transition temperature (Tt) that enables purification using a simple, straightforward process called inverse transition cycling (ITC). Despite the utility of ITC, the process is inherently limited to ELP with an experimentally accessible Tt. Since the underlying basis for the ELP Tt is related to its high overall hydrophobicity, we anticipated that ELP would be excellent candidates for purification by organic extraction. We report the first method for rapidly purifying ELP directly from whole E. coli cells or clarified lysates using pure organic solvents and solvent mixtures, followed by aqueous back extraction. Our results show that small ELP and a large ELP-fusion protein can be isolated in high yield from whole cells or cell lysates with greater than 95% purity in less than 30 min and with very low levels of LPS and DNA contamination.

Cell Based-Green Fluorescent Biosensor Using Cytotoxic Pathway for Bacterial Lipopolysaccharide Recognition

Lipopolysaccharide (LPS), a characteristic component of the outer membrane of Gram-negative bacteria, can be used as an effective biomarker to detect bacterial contamination. Here, we reported a 293/hTLR4A-MD2-CD14 cell-based fluorescent biosensor to detect and identify LPS, which is carried out in a 96-well microplate which is nondestructive, user-friendly, and highly efficient. The promoter sequence of the critical signaling pathway gene ZC3H12A (encoding MCPIP1 protein) and enhanced green fluorescence protein (EGFP) were combined to construct a recombinant plasmid, which was transferred into 293/hTLR4A-MD2-CD14 cells through lipid-mediated, DNA-transfection way. LPS was able to bind to TLR4 and coreceptors-induced signaling pathway could result in green fluorescent protein expression. Results show that stable transfected 293/hTLR4A-MD2-CD14 cells with LPS treatment could be directly and continually observed under a high content screening imaging system. The novel cell-based biosensor detects LPS at low concentration, along with the detection limit of 0.075 μg/mL. The cell-based biosensor was evaluated by differentiating Gram-negative and Gram-positive bacteria and detecting LPS in fruit juices as well. This proposed fluorescent biosensor has potential in sensing LPS optically in foodstuff and biological products, as well as bacteria identification, contributing to the control of foodborne diseases and ensurance of public food safety with its high throughput detection way.

Amino acids as modulators of the European seabass, Dicentrarchus labrax, innate immune response: an in vitro approach

Teleost innate immune system is a most developed and powerful system in which fish highly rely throughout their lives. Conditions in aquaculture farms are particularly prone to disease, thus, health and welfare ensuring strategies are an urgent call to which nutrition is gradually becoming a most regarded achievement tool. This study intended to evaluate different amino acids' effect on immune-related mechanisms as well as their potential as enhancers of European seabass, Dicentrarchus labrax, leucocyte functioning. To achieve these goals, primary cultures of head-kidney leucocytes were established and kept in amino acid (glutamine, arginine, tryptophan or methionine) supplemented culture media in two doses. The effects of amino acids treatments were then evaluated after stimulation with either Vibrio anguillarum or Vibrio anguillarum lipopolysaccharides by measuring nitric oxide production, extracellular respiratory burst, ATP and arginase activities, and expression of immune-related genes. Glutamine, arginine and tryptophan showed to be particularly relevant regarding cell energy dynamics; arginine and tryptophan supplementation also resulted in down-regulation of important immune-related genes. Immune responses in cells treated with methionine were generally enhanced but further studies, particularly those of enzymes activity, are essential to complement gene expression results and to better understand this nutrient's immune role in fish.

Specific surface glycan decorations enable antimicrobial peptide resistance in plant-beneficial pseudomonads with insect-pathogenic properties

Some plant-beneficial pseudomonads can invade and kill pest insects in addition to their ability to protect plants from phytopathogens. We explored the genetic basis of O-polysaccharide (O-PS, O-antigen) biosynthesis in the representative insecticidal strains Pseudomonas protegens CHA0 and Pseudomonas chlororaphis PCL1391 and investigated its role in insect pathogenicity. Both strains produce two distinct forms of O-PS, but differ in the organization of their O-PS biosynthesis clusters. Biosynthesis of the dominant O-PS in both strains depends on a gene cluster similar to the O-specific antigen (OSA) cluster of Pseudomonas aeruginosa. In CHA0 and other P. protegens strains, the OSA cluster is extensively reduced and new clusters were acquired, resulting in high diversity of O-PS structures, possibly reflecting adaptation to different hosts. CHA0 mutants lacking the short OSA form of O-PS were significantly impaired in insect virulence in Galleria injection and Plutella feeding assays. CHA0, PCL1391, and other insecticidal pseudomonads exhibited high resistance to antimicrobial peptides, including cecropins that are central to insect immune defense. Resistance of both model strains depended on the dominant OSA-type O-PS. Our results suggest that O-antigen is essential for successful insect infection and illustrate, for the first time, its importance in resistance of Pseudomonas to antimicrobial peptides.

Purification of the exopolysaccharide produced by Alteromonas infernus: identification of endotoxins and effective process to remove them

Alteromonas infernus bacterium isolated from deep-sea hydrothermal vents can produce by fermentation a high molecular weight exopolysaccharide (EPS) called GY785. This EPS described as a new source of glycosaminoglycan-like molecule presents a great potential for pharmaceutical and biotechnological applications. However, this unusual EPS is secreted by a Gram-negative bacterium and can be therefore contaminated by endotoxins, in particular the lipopolysaccharides (LPS). Biochemical and chemical analyses of the LPS extracted from A. infernus membranes have shown the lack of the typical LPS architecture since 3-deoxy-D-manno-oct-2-ulopyranosonic acid (Kdo), glucosamine (GlcN), and phosphorylated monosaccharides were not present. Unlike for other Gram-negative bacteria, the results revealed that the outer membrane of A. infernus bacterium is most likely composed of peculiar glycolipids. Furthermore, the presence of these glycolipids was also detected in the EPS batches produced by fermentation. Different purification and chemical detoxification methods were evaluated to efficiently purify the EPS. Only the method based on a differential solubility of EPS and glycolipids in deoxycholate detergent showed the highest decrease in the endotoxin content. In contrast to the other tested methods, this new protocol can provide an effective method for obtaining endotoxin-free EPS without any important modification of its molecular weight, monosaccharide composition, and sulfate content.

Synergistic Interaction Between Phage Therapy and Antibiotics Clears Pseudomonas Aeruginosa Infection in Endocarditis and Reduces Virulence

Background.

Increasing antibiotic resistance warrants therapeutic alternatives. Here we investigated the efficacy of bacteriophage-therapy (phage) alone or combined with antibiotics against experimental endocarditis (EE) due to Pseudomonas aeruginosa, an archetype of difficult-to-treat infection.

Methods.

In vitro fibrin clots and rats with aortic EE were treated with an antipseudomonas phage cocktail alone or combined with ciprofloxacin. Phage pharmacology, therapeutic efficacy, and resistance were determined.

Results.

In vitro, single-dose phage therapy killed 7 log colony-forming units (CFUs)/g of fibrin clots in 6 hours. Phage-resistant mutants regrew after 24 hours but were prevented by combination with ciprofloxacin (2.5 × minimum inhibitory concentration). In vivo, single-dose phage therapy killed 2.5 log CFUs/g of vegetations in 6 hours (P < .001 vs untreated controls) and was comparable with ciprofloxacin monotherapy. Moreover, phage/ciprofloxacin combinations were highly synergistic, killing >6 log CFUs/g of vegetations in 6 hours and successfully treating 64% (n = 7/11) of rats. Phage-resistant mutants emerged in vitro but not in vivo, most likely because resistant mutations affected bacterial surface determinants important for infectivity (eg, the pilT and galU genes involved in pilus motility and LPS formation).

Conclusions.

Single-dose phage therapy was active against P. aeruginosa EE and highly synergistic with ciprofloxacin. Phage-resistant mutants had impaired infectivity. Phage-therapy alone or combined with antibiotics merits further clinical consideration.

Tenacibaculosis induction in the Senegalese sole (Solea senegalensis) and studies of Tenacibaculum maritimum survival against host mucus and plasma

Tenacibaculum maritimum, the aetiological agent for marine tenacibaculosis, is one of the most significant pathogens that threaten Senegalese sole, Solea senegalensis (Kaup), aquaculture. Because no immersion challenge with T. maritimum has been reported previously for this flatfish species, this study aimed to optimize bacterial yields as well as to establish a challenge model for tenacibaculosis induction. Several approaches were performed to optimize bacterial culture conditions, including treatment with non-ionic surfactants, detergents, cellulase hydrolysis and strong shaking. A prolonged bath challenge was performed for 24 h under two different temperatures, 16 and 23 °C. Moreover, mucus and plasma bactericidal activities against T. maritimum were also assessed. Culturing bacteria with strong shaking and continuous shaking provided suitable culture conditions to obtain higher bacterial yields without aggregation and fluctuation, contrary to most other treatments that showed a huge amount of bacterial aggregates. A prolonged bath method for 24 h, without skin or gill scarification, was considered suitable for disease induction with high mortality rates. Moreover, data regarding mucus and plasma bactericidal activities suggested that there is a lack of host innate immune response against T. maritimum or that this particular pathogen presents evading strategies against Senegalese sole.

A rapid and visual aptasensor for Lipopolysaccharides detection based on the bulb-like triplex turn-on switch coupled with HCR-HRP nanostructures

For previously reported aptasensor, the sensitivity and selectivity of aptamers to targets were often suppressed due to the reporter label of single-stranded molecular beacon or hindrance of the duplex DNA strand displacement. To solve the affinity declining of aptamers showed in traditional way and realize on-site rapid detection of Lipopolysaccharides (LPS), we developed an ingenious structure-switching aptasensor based on the bulb-like triplex turn-on switch (BTTS) as the effective molecular recognition and signal transduction element and streptavidin-horseradish peroxidase modified hybridization chain reaction (HCR-HRP) nanocomposites as the signal amplifier and signal report element. In the presence of LPS, the bulb-like LPS-aptamer (BLA) and LPS formed the LPS/aptamer complex, while the BTTS disassembled and liberated the dissociative bridge probes (BP) to achieve molecular recognition and signal transduction. Immobilized BP, captured by immobilized capture probes (CP), triggered hybridization chain reactions (HCR) to amplify the switching signal, and the HCR products were then modified with streptavidin-horseradish peroxidase (SA-HRP) to form HCR-HRP nanostructures to output colorimetric signals. In less than four hours, the proposed biosensor showed a detection limit of 50pg/mL of LPS quantitatively with the portable spectrophotometer and the observation limit of 20ng/mL semi-quantitatively with the naked eye, opening up new opportunities for LPS detection in future clinical diagnosis, food security and environment monitoring.

Highly sensitive detection of lipopolysaccharides using an aptasensor based on hybridization chain reaction

Lipopolysaccharides (LPS), integral components of the outer membrane of all gram-negative bacteria, are closely associated with foodborne diseases such as fever, diarrhea and hypotension, and thus, the early and sensitive detection of LPS is necessary. In this study, an aptasensor assay based on hybridization chain reaction (HCR) was developed to detect LPS. Briefly, two complementary stable species of biotinylated DNA hairpins coexisted in solution until the introduction of a detection probe triggered a hybridization chain reaction cascade. The DNA conjugates specifically reacted with the LPS, which were captured by the ethanolamine aptamer attached to the reaction well surface. After optimizing the key reaction conditions, such as the reaction time of HCR, the amount of the capture probe and detection probes, the increase in the LPS concentration was readily measured by the optical density value, and a relatively low detection limit (1.73 ng/mL) was obtained, with a linear response range of 1–10⁵ng/mL. The approach presented herein introduced the use of an aptasensor for LPS discrimination and HCR for signal amplification, offering a promising option for detecting LPS.

The core and O-polysaccharide structure of the Caulobacter crescentus lipopolysaccharide

Here we describe the analysis of the structure of the lipopolysaccharide (LPS) from Caulobacter crescentus strain JS1025, a derivative of C. crescentus CB15 NA1000 with an engineered amber mutation in rsaA, leading to the loss of the protein S-layer and gene CCNA_00471 encoding a putative GDP-L-fucose synthase. LPS was isolated using an aqueous membrane disruption method. Polysaccharide and core oligosaccharide were produced by mild acid hydrolysis and analyzed by nuclear magnetic resonance spectroscopy and chemical methods. Spectra revealed the presence of two polysaccharides, one of them, a rhamnan, could be removed using periodate oxidation. Another polymer, built from 4-amino-4-deoxy-D-rhamnose (perosamine), mannose, and 3-O-methyl-glucose, should be the O-chain of the LPS according to genetic data. The attribution of the rhamnan as a part of LPS or a separate polymer was not possible.