Four samples from different farms and municipalities in the
Belém area were selected to perform cloning and sequencing. The
fragments amplified by RT-PCR were cloned using the Invitrogen
TOPO TA Cloning Kit, according to the manufacturer’s protocol.
Approximately 5 L of the plasmid preparations containing the
inserted amplicons were used to transform competent E. coli DH5
cells by heat shock, and the transformed cells were plated on
Luria-Bertani medium (LB) plates containing ampicillin
(100 g/mL) plus IPTG (0.1 mM) and X-Gal (20 g/mL). The
recombinant colonies were identified based on the white color of
the colonies and then transferred to liquid LB medium containing
ampicillin (100 g/mL) and incubated at 37
◦
C for 12 h at 250 rpm.
The presence of recombinant colonies containing the target fragment was confirmed by PCR using the primers RD6F and RD6R.
These PCR products were purified for nucleotide sequencing using
the QIAquick@
PCR Purification Kit, following the protocol provided
by the manufacturer.
The nucleotide sequences were determined by sequencing with
the Big Dye Terminator Kit (Applied Biosystems) using the same
primers as those used for RT-PCR. Sequencing was conducted on
an ABI PRISM 3100 automatic sequencer (Applied Biosystems).