The Effect of Plasmids and Other Biomolecules on the Effectiveness of Antibiofilm Agents - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 157

Fig. 1 Plasmid pET28
map. This plasmid harbours
(1) a pMB1 origin of
replication (Ori), (2) a
repressor for the lac
promoter ( lac I), (3) a
transcriptional promoter
from the T7 phage
(T7 promoter), (4) an
affinity purification tag
(HIS-Tag), (5) a T7
transcriptional terminator
(T7 terminator), and (6) a
kanamycin resistance gene
(Kan)

Fig. 2 Plasmid pUC8 map.
This plasmid harbours (1) a
mutated pMB1 origin of
replication (Ori), (2) a
lactose promoter [P(Lac
promoter)], (3) an
α -complementation site for

blue/white screening, (4) a
β -lactamase promoter [P

(Bla)], and (5) an ampicillin
resistance gene (Amp)

resistance gene and a fragment of the lacZ gene for -complementation. When a

gene is cloned in this plasmid using the existing multiple cloning site, it disrupts the
lacZ fragment. When this recombinant plasmid containing the cloned gene is
transformed into suitable host cells, the colonies can be readily selected through a
procedure called “blue/white” screening.

α

1.2 Physiological Effects of the Presence of Plasmids

Plasmid presence can have a variety of effects on host physiology. Some investi-
gations have considered plasmids as “cellular parasites” (Diaz Ricci and Hern ´ ndez
2000 ) since it was recognised that the introduction and expression of foreign DNA
in a host organism often changes the metabolism of that organism as a consequence
of the “metabolic burden” (Glick 1995 ). The term “metabolic burden” (sometimes
also called “metabolic load” or “metabolic drain”) is defined as the amount of host
cell resources (raw materials and energy) that is required to maintain and express
foreign DNA (Glick 1995 ). Concerning the physiological alterations at culture
level, several studies with E. coli have shown that plasmid-bearing cells exhibited