Biological role of PLL and PHL – lectins produced by entomopathogenic bacteria Photorhabdus luminescens and Photorhabdus asymbiotica
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| Year of publication | 2018 |
| Type | Conference abstract |
| MU Faculty or unit | |
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| Description | Photorhabdus is a genus of gram-negative bacteria which is known for its symbiotic relationship with entomopathogenic nematodes of the genus Heterorhabditis. Both bacteria and nematodes produce variety of toxins, proteases and other compounds which make them highly pathogenic for a wide range of insects. In our work we focused on lectins produced by bacteria P. luminescens and P. asymbiotica. Both species are known as highly virulent entomopathogens, but the latter is also able to cause serious and difficultly treatable infections in humans. Recently, we have identified two sequentially similar lectins designated as PLL and PHL in the genome of P. luminescens and P. asymbiotica, respectively. Recombinant forms of these lectins share high affinity towards L-fucose and both bind to the surface of red blood cells and haemocytes of Galleria mellonella. PLL agglutinates haemocytes and red blood cells A, whereas only red blood cells O were effectively agglutinated by PHL. Although we did not observe any damage on cells treated with lectins, neither the lectins were toxic to G. mellonella upon injection, PHL was found to be interfering with humoral immunity in both insect and human. PHL is recognised by immune system which reacts by increased melanisation in insects and increased production of reactive oxygen species in human blood observed in vitro. Interestingly, PHL inhibited production of reactive oxygen species elicited by neutrophil activators and decreased antimicrobial activity both in human blood and insect haemolymph. Despite many similarities, we show that the role of PLL and PHL is distinct. It is important to note that besides the involvement of studied lectins in infection and suppression of host immune system, they could also play role in symbiosis with nematodes or mediate interactions within bacterial population. This work was supported by grants no. 17-03253S and 18-18964S from the Czech Science Foundation. Photorhabdus is a genus of gram-negative bacteria which is known for its symbiotic relationship with entomopathogenic nematodes of the genus Heterorhabditis. Both bacteria and nematodes produce variety of toxins, proteases and other compounds which make them highly pathogenic for a wide range of insects. In our work we focused on lectins produced by bacteria P. luminescens and P. asymbiotica. Both species are known as highly virulent entomopathogens, but the latter is also able to cause serious and difficultly treatable infections in humans. Recently, we have identified two sequentially similar lectins designated as PLL and PHL in the genome of P. luminescens and P. asymbiotica, respectively. Recombinant forms of these lectins share high affinity towards L-fucose and both bind to the surface of red blood cells and haemocytes of Galleria mellonella. PLL agglutinates haemocytes and red blood cells A, whereas only red blood cells O were effectively agglutinated by PHL. Although we did not observe any damage on cells treated with lectins, neither the lectins were toxic to G. mellonella upon injection, PHL was found to be interfering with humoral immunity in both insect and human. PHL is recognised by immune system which reacts by increased melanisation in insects and increased production of reactive oxygen species in human blood observed in vitro. Interestingly, PHL inhibited production of reactive oxygen species elicited by neutrophil activators and decreased antimicrobial activity both in human blood and insect haemolymph. Despite many similarities, we show that the role of PLL and PHL is distinct. It is important to note that besides the involvement of studied lectins in infection and suppression of host immune system, they could also play role in symbiosis with nematodes or mediate interactions within bacterial population. This work was supported by grants no. 17-03253S and 18-18964S from the Czech Science Foundation. |
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