and assayed as described previously (Tsujii et al. 1996). In
brief, 100 ll supernatant of SE strain was added in 50 mM
phosphate buffer at pH 6.7 and incubated at 37C for
30 min. The enzymatic reaction was initiated by adding
0.5 mM p-nitrophenyl-N-acetyl-b-D-glucosaminide and
incubated for 1 h at 37C. The reaction was stopped by
adding three volumes of 1 M Na2CO3. Enzymatic activity
was quantified by measuring the absorption at 405 nm and
compared with standard curve of p-nitrophenol. One unit of
hydrolase activity is defined as amount of enzyme converting
1.0 lmole of p-nitrophenyl-N-acetyl-b-D-glucosaminide
to p-nitrophenol per min under the assay conditions.
With regard to AHL-lactonases, primers from the literature
(Lee et al. 2002) were used to screen for the presence
of aiiA homologue gene. Genomic DNA was isolated from
B. thuringiensis using the standard method described by
Sambrook and Russell (2001). The aiiA homolog gene was
amplified using chromosomal DNA as a template and the
oligonucleotide primers AIF (50
-TAAATGTAAAGGTGGATACATAATGACAGT-30
) and AIR (50
-AGCTCATGACTTTTTGCACTATATATA-30
). The PCR conditions
involved denaturation at 94C for 3 min followed by 28
cycles at 94C for 30 s, 50C for 30 s, and 72C for 1 min
with PCR Master Mix (MBI, Fermentas).
Stat