Biomedical Engineering Reference
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Fig. 3
Schematic
representation of the flow
cell system used to study the
effect of non-conjugative
plasmids on the biofilm-
forming and resistance
capacity of
E. coli
strains
1995
; Ow et al.
2006
; Wang et al.
2006
). A detrimental effect of the metabolic
burden was a reduced cellular viability in plasmid-bearing cells, an outcome
previously mentioned by Diaz Ricci and Hern
´
ndez (
2000
), possibly as a result
of the stress suffered by these cells. An increase in glucose metabolism in
transformed cells may have been accompanied by the increase in ATP and fermen-
tation by-products, and this accumulation of end-products caused metabolic stress
(Diaz Ricci et al.
1991
,
1992
). As it is known that several stress conditions favour
biofilm formation, the conjugation of the above-mentioned stress factors may have
stimulated biofilm formation by the transformed strains as thicker biofilms were
obtained in these cases (Teod´sio et al.
2012
).
Biofilm susceptibility experiments were performed using a quaternary ammo-
nium compound—BDMDAC—that was circulated in the system (Fig.
3
) at the
same flow conditions used for biofilm formation (Teod´sio et al.
2012
). The tested
biocide treatment was not sufficient for complete biofilm removal. It seems that the
biofilms formed by the non-transformed strain were more resistant to this treatment,
although the total number of cells was relatively constant for all tested strains
during the treatment (Teod
´
sio et al.
2012
). In a previous study (Sim˜es
et al.
2005a
), the same concentration of a quaternary ammonium compound was
also ineffective in removal of
Pseudomonas
biofilms. Sim˜es et al. (
2005a
) dem-
onstrated that the presence of BAC increased biofilm mechanical stability. On the
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