A midgut lysate of the Riptortus pedestris has antibacterial activity against LPS O-antigen-deficient Burkholderia mutants.
Riptortus pedestris, a common pest in soybean fields, harbors a symbiont Burkholderia in a specialized posterior midgut region of insects. Every generation of second nymphs acquires new Burkholderia cells from the environment. We compared in vitro cultured Burkholderia with newly in vivo colonized Burkholderia in the host midgut using biochemical approaches. The bacterial cell envelope of in vitro cultured and in vivo Burkholderia differed in structure, as in vivo bacteria lacked lipopolysaccharide (LPS) O-antigen. The LPS O-antigen deficient bacteria had a reduced colonization rate in the host midgut compared with that of the wild-type Burkholderia. To determine why LPS O-antigen-deficient bacteria are less able to colonize the host midgut, we examined in vitro survival rates of three LPS O-antigen-deficient Burkholderia mutants and lysates of five different midgut regions. The LPS O-antigen-deficient mutants were highly susceptible when cultured with the lysate of a specific first midgut region (M1), indicating that the M1 lysate contains unidentified substance(s) capable of killing LPS O-antigen-deficient mutants. We identified a 17 kDa protein from the M1 lysate, which was enriched in the active fractions. The N-terminal sequence of the protein was determined to be a soybean Kunitz-type trypsin inhibitor. These data suggest that the 17 kDa protein, which was originated from a main soybean source of the R. pedestris host, has antibacterial activity against the LPS O-antigen deficient (rough-type) Burkholderia.
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan 46241, South Korea.
Ho Am
HA
Jang
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan 46241, South Korea.
Eun Sil
ES
Seo
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan 46241, South Korea.
Min Young
MY
Seong
Global Research Laboratory of Insect Symbiosis, College of Pharmacy, Pusan National University, Busan 46241, South Korea. Electronic address: brlee@pusan.ac.kr.
Bok Luel
BL
Lee
D000818:Animals; D000900:Anti-Bacterial Agents / Q000276:immunology*; D019117:Burkholderia / Q000235:genetics / Q000276:immunology*; D019121:Burkholderia Infections / Q000235:genetics / Q000276:immunology*; D002457:Cell Extracts / Q000276:immunology*; D002478:Cells, Cultured; D041981:Gastrointestinal Tract / Q000276:immunology*; D020062:Heteroptera / Q000276:immunology*; D054884:Host-Pathogen Interactions; D019476:Insect Proteins / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology; D009154:Mutation / Q000235:genetics; D019081:O Antigens / Q000235:genetics; D013559:Symbiosis; D014361:Trypsin Inhibitors / Q000276:immunology*
D000900:Anti-Bacterial Agents; D002457:Cell Extracts; D019476:Insect Proteins; D008070:Lipopolysaccharides; D019081:O Antigens; D014361:Trypsin Inhibitors
Burkholderia; Lipopolysaccharide; O-antigen; Riptortus; Symbiosis