Photorhabdus laumondii is a well-known bacterium with a complex life cycle involving mutualism with nematodes of the genus Heterorhabditis and pathogenicity towards insect hosts. It provides an excellent model for studying the diverse roles of lectins, saccharide-binding proteins, in both symbiosis and pathogenicity. This study focuses on the seven-bladed β-propeller lectins of P. laumondii (PLLs), examining their biochemical properties (structure and saccharide specificity) and biological functions (gene expression, interactions with the nematode symbiont, and the host immune system response). Structural analyses revealed diverse oligomeric states among PLLs and a unique organisation of binding sites not described outside the PLL lectin family. Lectins exhibited high specificity for fucosylated and O-methylated saccharides with a significant avidity effect for multivalent ligands. Gene expression analysis across bacterial growth phases revealed that PLLs are predominantly expressed during the exponential phase. Interaction studies with the host immune system demonstrated that PLL5 uniquely induced melanisation in Galleria mellonella hemolymph. Furthermore, PLL2, PLL3, and PLL5 interfered with reactive oxygen species production in human blood cells, indicating their potential role in modulating host immune responses. Biofilm formation assays and binding studies with nematode life stages showed no significant involvement of PLLs in nematode colonization. Our findings highlight the primary role of PLLs in Photorhabdus pathogenicity rather than in symbiosis and offer valuable insight into the fascinating dynamics within the Photorhabdus-nematode-insect triparted system.

• Klíčová slova
• Photorhabdus, glycan array, lectin, nematode, structure-function study,
• MeSH
• bakteriální proteiny * chemie   metabolismus   genetika   MeSH
• hlístice * mikrobiologie   MeSH
• lektiny * chemie   metabolismus   genetika   MeSH
• lidé MeSH
• Photorhabdus * metabolismus   chemie   genetika   MeSH
• symbióza MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální proteiny * MeSH
• lektiny * MeSH

Entomopathogenic nematodes (EPNs) are efficient insect parasites, that are known for their mutualistic relationship with entomopathogenic bacteria and their use in biocontrol. EPNs produce bioactive molecules referred to as excreted/secreted products (ESPs), which have come to the forefront in recent years because of their role in the process of host invasion and the modulation of its immune response. In the present study, we confirmed the production of ESPs in the EPN Heterorhabditis bacteriophora, and investigated their role in the modulation of the phenoloxidase cascade, one of the key components of the insect immune system. ESPs were isolated from 14- and 21-day-old infective juveniles of H. bacteriophora, which were found to be more virulent than newly emerged nematodes, as was confirmed by mortality assays using Galleria mellonella larvae. The isolated ESPs were further purified and screened for the phenoloxidase-inhibiting activity. In these products, a 38 kDa fraction of peptides was identified as the main candidate source of phenoloxidase-inhibiting compounds. This fraction was further analyzed by mass spectrometry and the de novo sequencing approach. Six peptide sequences were identified in this active ESP fraction, including proteins involved in ubiquitination and the regulation of a Toll pathway, for which a role in the regulation of insect immune response has been proposed in previous studies.

• Klíčová slova
• Galleria mellonella, Heterorhabditis bacteriophora, excreted/secreted products, immunity, melanization, phenoloxidase, virulence,
• Publikační typ
• časopisecké články MeSH

The Photorhabdus species is a Gram-negative bacteria of the family Morganellaceae that is known for its mutualistic relationship with Heterorhabditis nematodes and pathogenicity toward insects. This study is focused on the characterization of the recombinant lectin PLL3 with an origin in P. laumondii subsp. laumondii. PLL3 belongs to the PLL family of lectins with a seven-bladed β-propeller fold. The binding properties of PLL3 were tested by hemagglutination assay, glycan array, isothermal titration calorimetry, and surface plasmon resonance, and its structure was determined by X-ray crystallography. Obtained data revealed that PLL3 binds similar carbohydrates to those that the other PLL family members bind, with some differences in the binding properties. PLL3 exhibited the highest affinity toward l-fucose and its derivatives but was also able to interact with O-methylated glycans and other ligands. Unlike the other members of this family, PLL3 was discovered to be a monomer, which might correspond to a weaker avidity effect compared to homologous lectins. Based on the similarity to the related lectins and their proposed biological function, PLL3 might accompany them during the interaction of P. laumondii with both the nematode partner and the insect host.

• Klíčová slova
• O-methylated saccharides, Photorhabdus, l-fucose, lectin,
• MeSH
• bakteriální proteiny chemie   genetika   metabolismus   MeSH
• fruktosa metabolismus   MeSH
• kalorimetrie MeSH
• krystalografie rentgenová MeSH
• lektiny chemie   genetika   metabolismus   MeSH
• Photorhabdus metabolismus   MeSH
• povrchová plasmonová rezonance MeSH
• rekombinantní proteiny chemie   metabolismus   MeSH
• sekundární struktura proteinů MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální proteiny MeSH
• fruktosa MeSH
• lektiny MeSH
• rekombinantní proteiny MeSH

A recently described bangle lectin (PHL) from the bacterium Photorhabdus asymbiotica was identified as a mainly fucose-binding protein that could play an important role in the host-pathogen interaction and in the modulation of host immune response. Structural studies showed that PHL is a homo-dimer that contains up to seven L-fucose-specific binding sites per monomer. For these reasons, potential ligands of the PHL lectin: α-L-fucopyranosyl-containing mono-, di-, tetra-, hexa- and dodecavalent ligands were tested. Two types of polyvalent structures were investigated - calix[4]arenes and dendrimers. The shared feature of all these structures was a C-glycosidic bond instead of the more common but physiologically unstable O-glycosidic bond. The inhibition potential of the tested structures was assessed using different techniques - hemagglutination, surface plasmon resonance, isothermal titration calorimetry, and cell cross-linking. All the ligands proved to be better than free L-fucose. The most active hexavalent dendrimer exhibited affinity three orders of magnitude higher than that of standard L-fucose. To determine the binding mode of some ligands, crystal complex PHL/fucosides 2 - 4 were prepared and studied using X-ray crystallography. The electron density in complexes proved the presence of the compounds in 6 out of 7 fucose-binding sites.

• MeSH
• antibakteriální látky chemie   farmakologie   terapeutické užití   MeSH
• bakteriální infekce farmakoterapie   mikrobiologie   MeSH
• bakteriální proteiny antagonisté a inhibitory   chemie   izolace a purifikace   metabolismus   MeSH
• dendrimery chemie   farmakologie   terapeutické užití   MeSH
• erytrocyty MeSH
• fukosa analogy a deriváty   farmakologie   terapeutické užití   MeSH
• hemaglutinace účinky léků   MeSH
• interakce hostitele a patogenu účinky léků   MeSH
• krystalografie rentgenová MeSH
• lektiny antagonisté a inhibitory   chemie   izolace a purifikace   metabolismus   MeSH
• lidé MeSH
• ligandy MeSH
• molekulární modely MeSH
• Photorhabdus metabolismus   MeSH
• povrchová plasmonová rezonance MeSH
• rekombinantní proteiny chemie   izolace a purifikace   metabolismus   MeSH
• vazebná místa MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antibakteriální látky MeSH
• bakteriální proteiny MeSH
• dendrimery MeSH
• fucose-binding lectin MeSH Prohlížeč
• fukosa MeSH
• lektiny MeSH
• ligandy MeSH
• rekombinantní proteiny MeSH

It has been known for many years that in temperate climates the European honey bee, Apis mellifera, exists in the form of two distinct populations within the year, short-living summer bees and long-living winter bees. However, there is only limited knowledge about the basic biochemical markers of winter and summer populations as yet. Nevertheless, the distinction between these two kinds of bees is becoming increasingly important as it can help beekeepers to estimate proportion of long-living bees in hives and therefore in part predict success of overwintering. To identify markers of winter generations, we employed the continuous long-term monitoring of a single honey bee colony for almost two years, which included measurements of physiological and immunological parameters. The results showed that the total concentration of proteins, the level of vitellogenin, and the antibacterial activity of haemolymph are the best three of all followed parameters that are related to honey bee longevity and can therefore be used as its markers.

• Klíčová slova
• honey bee, immunity, longevity, physiology, seasonal changes,
• Publikační typ
• časopisecké články MeSH