Immune tolerance to an intestine-adapted bacteria, Chryseobacterium sp., injected into the hemocoel of Protaetia brevitarsis seulensis

Abstract

To explore the interaction of gut microbes and the host immune system, bacteria were isolated from the gut of Protaetia brevitarsis seulensis larvae. Chryseobacterium sp., Bacillus subtilis, Arthrobacter arilaitensis, Bacillus amyloliquefaciens, Bacillus megaterium, and Lysinibacillus xylanilyticus were cultured in vitro, identified, and injected in the hemocoel of P. brevitarsis seulensis larvae, respectively. There were no significant changes in phagocytosis-associated lysosomal formation or pathogen-related autophagosome in immune cells (granulocytes) from Chryseobacterium sp.-challenged larvae. Next, we examined changes in the transcription of innate immune genes such as peptidoglycan recognition proteins and antimicrobial peptides following infection with Chryseobacterium sp. PGRP-1 and -2 transcripts, which may be associated with melanization generated by prophenoloxidase (PPO), were either highly or moderately expressed at 24 h post-infection with Chryseobacterium sp. However, PGRP-SC2 transcripts, which code for bactericidal amidases, were expressed at low levels. With respect to antimicrobial peptides, only coleoptericin was moderately expressed in Chryseobacterium sp.-challenged larvae, suggesting maintenance of an optimum number of Chryseobacterium sp. All examined genes were expressed at significantly higher levels in larvae challenged with a pathogenic bacterium. Our data demonstrated that gut-inhabiting bacteria, the Chryseobacterium sp., induced a weaker immune response than other pathogenic bacteria, E. coli K12.

Bacteria from the Midgut of Common Cockchafer (Melolontha melolontha L.) Larvae Exhibiting Antagonistic Activity Against Bacterial Symbionts of Entomopathogenic Nematodes: Isolation and Molecular Identification

“…bacteria have been isolated from the gut of another member of the Scarabaeidae family, i.e., Protaetia brevitarsis seulensis [40]. Furthermore, the antibacterial activities of bacteria from the genera Chryseobacterium [45] and Citrobacter have been described before [46,47]; however, their interactions with the symbiotic bacteria of entomopathogenic nematode, have not been reported so far, as in the case of Pseudomonas or Serratia.…”

Hemocyte Morphology and Cellular Immune Response in Termite (Reticulitermes speratus)

“…Among these, hemocytes usually responsible for immune responses in insects can be classified into two types: granulocytes and plasmatocytes ( Salt 1970 , Gupta 1979 ). The morphological characteristics of granulocytes and plasmatocytes are based on observation of lobopodia-like or fan-like structures around the cell membrane ( Fig 1C and D ) ( Kwon et al 2014 , Hwang et al 2015 , Lee et al 2016 ). Cells exhibiting pseudopods and extracellular traps around the cell membrane during culture were considered to be attached to the culture slides.…”

“…Figure 3B and B-1 shows typical granulocytes harboring various types of granule in the cytoplasm and lobopodia-like or fan-like structures around the cell membrane. The shape and function of insect granulocytes have been studied extensively; these cells are recognized as one of the most important immune cells in insects ( Gupta 1979 , Kwon et al 2014 , Cho 2016 , Lee et al 2016 ). Plasmatocytes exhibited a typical spindle shape with lobopodia-like or fan-like structures around the cell membrane ( Fig.…”

“…Cell-mediated defense is provided by immune-activated hemocytes. Immune-activated hemocytes fight foreign pathogens such as bacteria, fungi, and parasites through the processes of phagocytosis, encapsulation, and nodulation ( Salt 1970 , Kwon et al 2014 , Lee et al 2016 ). Therefore, to examine cellular immune responses in insects, it is important to identify the types and characteristics of hemocytes.…”

Hemocyte-hemocyte adhesion by granulocytes is associated with cellular immunity in the cricket, Gryllus bimaculatus

“…However, most insects do not have all seven types. For example, in the case of the fly and the mosquito, only three types of hemocytes have been described, while in many species of Coleoptera there are at least five types of hemocytes 2,8–10 . Furthermore, even in insects with many types of hemocytes, only a few types are thought to be key players in cellular immunity.…”