Differential transfer dynamics of pAW63 plasmid among members of the Bacillus cereus group in food microcosms.
OBJECTIVE
To assess the dynamics of plasmid transfer between Bacillus thuringiensis and B. cereus in various food microcosms using the B. thuringiensis pAW63 and Staphylococcus aureus pUB110 plasmids as models.


RESULTS
The conjugative behaviour of pAW63, which resembles the B. anthracis virulence plasmid pXO2, and the mobilization of pUB110 were investigated using kinetics studies performed in reference LB (lysogeny broth) medium, full-cream and skimmed milks, soya milk and rice milk. Transfers of pAW63 and pUB110 were found to occur in the five tested media, with higher frequencies observed in food matrices, most notably in full-cream milk, skimmed milk and soya milk, where the mean transfer frequencies reached 10(-3) transconjugants per recipient cell. The most notable observations were that the higher transfer frequencies obtained in foodstuffs compared to those observed in LB were because of an earlier onset of conjugation in combination with a higher transfer rate and/or a longer mating period.


CONCLUSIONS
These results indicate that not only the potential for plasmid transfer but also the overall timing of conjugation is affected by each of these food matrices.


CONCLUSIONS
This new approach to study plasmid transfer provides insights for a better understanding of conjugation in food microcosms from both animal and vegetable origins among members of the B. cereus group.
Modrie
P
P
Laboratory of Food and Environmental Microbiology, Université catholique de Louvain, Croix du Sud 2/12, Louvain-la-Neuve, Belgium.
Beuls
E
E
Laboratory of Food and Environmental Microbiology, Université catholique de Louvain, Croix du Sud 2/12, Louvain-la-Neuve, Belgium.
Mahillon
J
J
Laboratory of Food and Environmental Microbiology, Université catholique de Louvain, Croix du Sud 2/12, Louvain-la-Neuve, Belgium.
D000818:Animals; D001409:Bacillus cereus / Q000235:genetics*; D001413:Bacillus thuringiensis / Q000235:genetics*; D003227:Conjugation, Genetic; D003470:Culture Media; D005516:Food Microbiology; D008892:Milk / Q000382:microbiology; D012275:Oryza / Q000382:microbiology; D010957:Plasmids / Q000235:genetics*; D013025:Glycine max / Q000382:microbiology
D003470:Culture Media