Transfer frequencies indicated that the mating mechanism
was active within colony biofilms and SL-biofilms
(Figure 5). For chamber slide SL-biofilms, an average
transfer frequency of 2.90 × 10-6 was measured and is
within the range reported in Mevarech and Werczberger’s
1985 study in which mating was first discovered
through co-filtering cells on nitrocellulose filters [56].
The transfer frequency for a shaking culture control was
low as expected, and mating was not quantifiable in
uni-culture biofilms of either H53 or H98 cells (as there
is no available source for transfer of the gene required
for growth on the selective medium).