Role of sphingomyelinase in infectious diseases caused by Bacillus cereus.
Bacillus cereus (B. cereus) is a pathogen in opportunistic infections. Here we show that Bacillus cereus sphingomyelinase (Bc-SMase) is a virulence factor for septicemia. Clinical isolates produced large amounts of Bc-SMase, grew in vivo, and caused death among mice, but ATCC strains isolated from soil did not. A transformant of the ATCC strain carrying a recombinant plasmid containing the Bc-SMase gene grew in vivo, but that with the gene for E53A, which has little enzymatic activity, did not. Administration of an anti-Bc-SMase antibody and immunization against Bc-SMase prevented death caused by the clinical isolates, showing that Bc-SMase plays an important role in the diseases caused by B. cereus. Treatment of mouse macrophages with Bc-SMase resulted in a reduction in the generation of H(2)O(2) and phagocytosis of macrophages induced by peptidoglycan (PGN), but no effect on the release of TNF-α and little release of LDH under our experimental conditions. Confocal laser microscopy showed that the treatment of mouse macrophages with Bc-SMase resulted in the formation of ceramide-rich domains. A photobleaching analysis suggested that the cells treated with Bc-SMase exhibited a reduction in membrane fluidity. The results suggest that Bc-SMase is essential for the hydrolysis of SM in membranes, leading to a reduction in phagocytosis.
Department of Microbiology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, Japan.
Masataka
M
Oda
Manabu
M
Hashimoto
Masaya
M
Takahashi
Yuka
Y
Ohmae
Soshi
S
Seike
Ryoko
R
Kato
Aoi
A
Fujita
Hideaki
H
Tsuge
Masahiro
M
Nagahama
Sadayuki
S
Ochi
Teppei
T
Sasahara
Shunji
S
Hayashi
Yoshikazu
Y
Hirai
Jun
J
Sakurai
D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology* / Q000494:pharmacology; D001409:Bacillus cereus / Q000201:enzymology* / Q000254:growth & development / Q000276:immunology*; D001483:Base Sequence; D002855:Chromatography, Thin Layer; D006861:Hydrogen Peroxide / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010587:Phagocytosis / Q000187:drug effects; D038761:Photobleaching; D011401:Promoter Regions, Genetic / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D018805:Sepsis / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000907:Antibodies, Bacterial; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D006861:Hydrogen Peroxide; D013108:Sphingomyelin Phosphodiesterase