Universidad Austral de Chile - Tesis Electrónicas UACh ...

SUMMARY
American Foulbrood (A.F) is one of the most harmful disease that affects the bees of
the Apis mellifera L. species. It not only kills the infected larvae, but also is potentially
lethal for the colonies. This disease is highly contagious, because it is facilitated by the
exchange between the material of the beehive and the bee colonies.
The objective of the present study was, to isolate and identify to the species level,
strains belonging to the genus Bacillus, isolated from honey samples and beehive
material. The strains were evaluated as antagonists against Paenibacillus larvae ATCC
25745 and a field strain, causative agent of the A.F. The identification was performed
by sequencing the 16S rRNA gene. For this purpose the gene of each strain was
amplified and cloned in the plasmid pGEMT-Easy. The plasmid containing the gene
was sent abroad for sequencing, wich was done for the eight Bacillus strains. The
sequences obtained were compared with the database to find their identity.
No strains belonging to the species P. larvae were identified among the Bacillus, the
species were identified as B. cereus, B. subtilis and B. pumilus. Of the eight strains
identified, three were checked against the two P. larvae strain, individually and as a
mixture. Such antagonism tests revealed an inhibition of the strain 87 (B. pumilus) when
faced with the strains 95 (B. subtilis) and 97 (B. pumilus). These two Bacillus strains
showed the highest antagonistic activity against P. larvae ATCC 25745 and P. larvae
field strain. These species are harmless to the apiary and humans, thus have a great
potential like biocontroler compounds for the inhibition of the pathogen.
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