Detection and characterization of the novel bacteriocin entomocin 9, and safety evaluation of its producer, Bacillus thuringiensis ssp. entomocidus HD9.
OBJECTIVE
To identify and characterize new bacteriocins from a collection of 41 strains belonging to 27 subspecies of Bacillus thuringiensis, and to evaluate the safety of the producers.


RESULTS
Bacillus thuringiensis ssp. entomocidus HD9 produced in the culture supernatant an antimicrobial activity against Gram-positive bacteria including Listeria monocytogenes, one of four pathogenic Pseudomonas aeruginosa and several fungi. Production of the antibacterial activity, named entomocin 9, started during mid-logarithmic growth reaching its maximum at the early stationary phase. Entomocin 9 retained more than 72% of activity after incubation for 20 min at 121 degrees C. Activity was lost after proteinase K treatment, it was stable in a pH range between 3 and 9, and resistant to lyophilization. After partial purification with ammonium sulphate precipitation followed by gel-filtration and anion-exchange chromatography, an active protein of ca 12.4 kDa was isolated. The mode of action of entomocin 9 was bactericidal and caused cell lysis of growing cells. Despite the presence of a range of virulence related genes, including haemolysin BL, nonhaemolytic enterotoxin, cytotoxin K and several hydrolytic activities, B. thuringiensis HD9 was not toxic against Vero cells.


CONCLUSIONS
Entomocin 9 is a novel heat-stable, bacteriocin produced by B. thuringiensis HD9. The absence of toxicity against Vero cells suggests the suitability of strain HD9 for a safe application in antimicrobial treatments.


CONCLUSIONS
New finding on entomocin 9 would make B. thuringiensis attractive in biotechnological applications as an antimicrobial agent in agriculture and food industry.
Cherif
A
A
Laboratoire de Microbiologie, Département de Biologie, Faculté des Sciences de Tunis, Campus Universitaire, Tunis, Tunisia. ameur.cherif@fst.rnu.tn
Chehimi
S
S
Limem
F
F
Hansen
B M
BM
Hendriksen
N B
NB
Daffonchio
D
D
Boudabous
A
A
D000818:Animals; D001409:Bacillus cereus / Q000235:genetics; D001413:Bacillus thuringiensis / Q000378:metabolism / Q000472:pathogenicity*; D001430:Bacteriocins / Q000096:biosynthesis / Q000302:isolation & purification* / Q000494:pharmacology; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D005612:Freeze Drying; D005798:Genes, Bacterial; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D014709:Vero Cells; D014774:Virulence
D001430:Bacteriocins; C481310:entomocin 9, Bacillus thuringiensis