Biomedical Engineering Reference
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Fig. 2
Fluorescent microscopy images of
E. faecalis
T9 (
a
),
B. subtilis
subsp.
natto
(
b
), and
E. coli
XL10 (
c
) transconjugants expressing GFP
nutrients increased IncP plasmid invasion and regular disturbance of the spatial
organization in the biofilm strongly improved plasmid invasiveness
(Fox
et al.
2008
).
Arends and coworkers also used a dual fluorescence approach differing from that
described above in the way that two differently labeled plasmids, a mobilizable
GFP-labeled plasmid based on the transfer region of broad-host-range Inc18 plas-
mid pIP501 and a RFP-labeled non-mobilizable plasmid, were used (Arends
et al.
2012
; Arends, Schiwon, and Grohmann, unpublished data). Donors and
transconjugants were distinguished by using fluorescence microscopy: donors
exhibited green and red fluorescence (GFP and RFP), whereas recipients, which
had acquired the mobilizable plasmid, showed only green fluorescence. Using this
approach conjugative transfer among distinct Gram-positive bacteria and from the
Gram-positive
E. faecalis
to the Gram-negative
E. coli
could be visualized (Fig.
2
).
A similar approach was applied for monitoring conjugative plasmid transfer among
Gram-positive bacteria using GFP-labeled mobilizable plasmid, CFPopt-labeled
non-mobilizable plasmid, and YFP-labeled conjugative plasmid (P. Modrie and
J. Mahillon, unpublished results).
6 Conclusions and Perspectives
HGT mediated via all three major modes, conjugation, transduction, and transfor-
mation occurs efficiently in planktonic cultures and in microbial biofilms. A general
feature is that HGT occurs with higher frequencies in biofilm mode. HGT enables
bacteria to obtain and maintain the extraordinary plasticity of their genomes and is
an important mechanism for the enormous adaptability of bacteria to changing
environmental conditions.
Many questions concerning the trigger of HGT in different environments still
remain unanswered. In their recent review on GEIs, Juhas and coworkers suggested
that we are unwittingly, by changing the conditions for bacteria in hospitals—via
antibiotic stress—and in the environment—via pollution—generating selective
conditions which promote the success of self-transferable and stress-responsive
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