title: Identification and Characterization of Bacillus cereus SW7-1 in Bombyx mori (Lepidoptera: Bombycidae).
abstract: The bacterial diseases of silkworms cause significant reductions in sericulture and result in huge economic loss. This study aimed to identify and characterize a pathogen from diseased silkworm. SW7-1, a pathogenic bacterial strain, was isolated from the diseased silkworm. The strain was identified on the basis of its bacteriological properties and 16S rRNA gene sequence. The colony was round, slightly convex, opaque, dry, and milky on a nutrient agar medium, the colony also exhibited jagged edges. SW7-1 was Gram-positive, without parasporal crystal, and 0.8-1.2 by 2.6-3.4 µm in length, resembling long rods with rounded ends. The strain was positive to most of the physiological biochemical tests used in this study. The strain could utilize glucose, sucrose, and maltose. The results of its 16S rRNA gene sequence analysis revealed that SW7-1 shared the highest sequence identity (>99%) with Bacillus cereus strain 14. The bacterial strain was highly susceptible to gentamycin, streptomycin, erythromycin, norfloxacin, and ofloxacin and moderately susceptible to tetracycline and rifampicin. It exhibited resistance to other antibiotics. SW7-1 had hemolytic activity and could produce extracellular casease, lipase, and amylase. SW7-1 could reproduce septicemia-like symptoms with high mortality rate when re-fed to healthy silkworm. .The median lethal concentration (LC50) was 5.45 × 10(4) cfu/ml. Thus, SW7-1 was identified as B. cereus, which is a pathogen for silkworm and human infections are possible.
authors.affiliation: College of Biotechnology, Southwest University, Chongqing 400716, China State Key Laboratory of Silkworm Genome Biology, Chongqing 400716, China.
authors.forename: Guan-Nan
authors.initials: GN
authors.lastname: Li
authors.affiliation: College of Food Science, Southwest University, Chongqing 400716, China.
authors.forename: Xue-Juan
authors.initials: XJ
authors.lastname: Xia
authors.affiliation: College of Biotechnology, Southwest University, Chongqing 400716, China State Key Laboratory of Silkworm Genome Biology, Chongqing 400716, China.
authors.forename: Huan-Huan
authors.initials: HH
authors.lastname: Zhao
authors.affiliation: College of Biotechnology, Southwest University, Chongqing 400716, China State Key Laboratory of Silkworm Genome Biology, Chongqing 400716, China.
authors.forename: Parfait
authors.initials: P
authors.lastname: Sendegeya
authors.affiliation: College of Biotechnology, Southwest University, Chongqing 400716, China State Key Laboratory of Silkworm Genome Biology, Chongqing 400716, China zhuy@swu.edu.cn.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001409:Bacillus cereus / Q000187:drug effects / Q000302:isolation & purification* / Q000378:metabolism / Q000472:pathogenicity*; D012831:Bombyx / Q000382:microbiology*; D050260:Carbohydrate Metabolism; D004269:DNA, Bacterial / Q000235:genetics; D007814:Larva / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: Bacillus cereus; characterization; identification; pathogen; silkworm (Bombyx mori)