Lipopolysaccharides of Pantoea agglomerans 7604 and 8674 with structurally related O-polysaccharide chains: Chemical identification and biological properties

Timber-colonizing gram-negative bacteria as potential causative agents of respiratory diseases in woodworkers

Occurrence

Gram-negative bacteria occur commonly in the inner tissues of stored coniferous and deciduous timber, showing a marked variation in numbers. The greatest maximal numbers are found in the sapwood of coniferous timber. The common constituents of the Gram-negative biota are potentially pathogenic species of Enterobacteriaceae family of the genera Rahnella, Pantoea, Enterobacter, and Klebsiella. The air of wood-processing facilities is polluted with the wood-borne Gram-negative bacteria and produced by them endotoxin, as demonstrated worldwide by numerous studies.

Effects

There are three potential pathways of the pathogenic impact of wood-borne Gram-negative bacteria on exposed woodworkers: allergic, immunotoxic, and infectious. Allergic impact has been underestimated for a long time with relation to Gram-negative bacteria. Hopefully, the recent demonstration of the first documented case of hypersensitivity pneumonitis (HP) in woodworkers caused by Pantoea agglomerans which developed in extremely large quantities in birch sapwood, would speed up finding of new wood-related cases of HP caused by Gram-negative bacteria. The second pathway is associated with endotoxin, exerting strong immunotoxic (excessively immunostimulative) action. It has been demonstrated that endotoxin is released into wood dust in the form of nano-sized microvesicles, by peeling off the outer membrane of bacteria. Endotoxin microvesicles are easily inhaled by humans together with dust because of small dimensions and aerodynamic shape. Afterwards, they cause a nonspecific activation of lung macrophages, which release numerous inflammatory mediators causing an inflammatory lung reaction, chest tightness, fever, gas exchange disorders, and bronchospasm, without radiographic changes. The resulting disease is known as “Organic Dust Toxic Syndrome” or “toxic pneumonitis.” The potential third pathway of pathogenic impact is infection. The suspected species is Klebsiella pneumoniae that may occur commonly in wood dust; however, until now this pathway has not been confirmed.

Conclusion

Summarizing, Gram-negative bacteria-inhabiting timber should be considered, besides filamentous fungi and actinobacteria, as important risk factors of occupational disease in woodworkers that could be either HP with allergenic background or toxic pneumonitis elicited by endotoxin.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-021-01829-1.

Lipopolysaccharide of Pantoea agglomerans 7460: O-specific polysaccharide and lipid A structures and biological activity

Lipopolysaccharide (LPS) was isolated from Pantoea agglomerans 7460 cells by phenol-water extraction. Mild acid degradation allowed to separate OPS and lipid A. Lipid A was analyzed by negative-ion mode ESI MS and found to consist mainly of hexaacylated derivative containing biphosphorylated GlcN disaccharide, four 14:0 (3-OH), 18:0 and 12:0 fatty acids. The structure of the O-specific polysaccharide was established by chemical, NMR and computational methods: The LPS of Р. agglomerans 7460 showed low level of toxicity and pyrogenicity to compare with LPS of E. coli O55:B5 and pyrogenal, respectively. The ability of the modified (succinylated) LPS, which have lost its toxicity, to block the toxic effects of native LPS has been shown.

Structure of O-Polysaccharide and Lipid A of Pantoea Agglomerans 8488

The Pantoea agglomerans 8488 lipopolysaccharide (LPS) was isolated, purified and characterized by monosaccharide and fatty acid analysis. The O-polysaccharide and lipid A components of the LPS were separated by mild acid degradation. Lipid A was studied by electrospray ionization mass spectrometry (ESI-MS) and found to consist of hexa-, penta-, tetra- and tri-acylated species. Two-dimensional nuclear magnetic resonance (NMR) spectroscopy revealed the following structure of the O-polysaccharide repeating unit →3)-α-L-Rhap-(1→6)-α-D-Manp-(1→3)-α-L-Fucp-(1→3)-β-D-GlcNAcp-(1→. The LPS showed a low level of toxicity, was not pyrogenic, and reduced the adhesiveness index of microorganisms to 2.12, which was twofold less than the control. LPS modified by complex compounds of germanium (IV) and tin (IV) were obtained. It was found that six LPS samples modified by Sn compounds and two LPS samples modified by Ge compounds lost their toxic activity when administered to mice in a dose of LD50 (105 µg/mice or 5 mg/kg). However, none of the modified LPS samples changed their serological activity in an Ouchterlony double immunodiffusion test in agar.

A comparative study on the structures of Grifola frondosa polysaccharides obtained by different decolourization methods and their in vitro antioxidant activities

Decolourization of polysaccharides is one of the crucial procedures that affects their structure, which is closely related to their bioactivity. Here, Grifola frondosa polysaccharide (GFP) was decolourized with H2O2 and AB-8 macroporous resin. Then, two main fractions, named DGFP and SGFP, were obtained by purification with Sepharose CL-4B. The molecular weights of these two polysaccharides were determined to be 6.306 × 106 (±0.410%) Da and 1.174 × 107 (±0.299%) Da by HPSEC. Monosaccharide analysis indicated that DGFP was composed of glucose, mannose, and galactose (32.20 : 1.00 : 1.75), while SGFP consisted entirely of glucose. Despite a backbone →4)-α-Glcp-(1→ in two polysaccharides, reducing ends Rα →3)-α-Glcp and Rβ →4)-β-Glcp were observed in DGFP by 1D/2D NMR. The results suggested that decolourization with low concentrations of H2O2 might alter the structure of GFP and generate new reducing ends. In vitro antioxidant results implied that DGFP exhibited a higher ability to scavenge DPPH and hydroxyl radicals and reduced the over-generated ROS levels in a concentration-dependent manner. These results suggested that the antioxidant effects of GFP could be activated by decolourization with H2O2. Therefore, DGFP might be a more promising natural antioxidant than SGFP.

Pantoea agglomerans P1a lipopolysaccharide: Structure of the O-specific polysaccharide and lipid A and biological activity

O-specific polysaccharide and lipid A were obtained from the lipopolysaccharide from new strain of Рantoea agglomerans P1a by mild acid hydrolysis. It was found that the major form of lipid A presented by tetraacylated derivative containing biphosphorylated GlcN disaccharide, three 14:0 (3-OH) and 12:0 residues. The structure of the O-specific polysaccharide was established by chemical, NMR and computational methods: →3)-α-D-Manp-(1 → 4)-β-D-Fucp-(1 → 4)-ɑ-D-Fucp-(1→The LPS of Р. agglomerans P1a showed low level of toxicity and pyrogenicity to compare with LPS of E. coli O55:B5 and pyrogenal (respectively).