Information Technology Reference
In-Depth Information
microorganisms, including bacteria. Communication mediated by homoserine
lactones can widely be seen in various Gram-negative bacteria. The mechanism
of this behavior was well characterized in
Vibrio fischeri
, due to their biolumi-
nescent activity mediated by homoserine lactones [6]. It has been shown that
bacterial information transfer can be engineered as an extension of
Escherichia
coli
into which the
lux
genes of
Vibrio fischeri
are transformed [9]. The commu-
nication abilities of bacteria therefore allow us to build microbial information
processors for cellular computing.
PHEROMONE-INDUCED CONJUGATION AND PLASMID
TRANSFER OF
ENTEROCOCCUS FAECALIS
Communication mechanisms in Gram-positive bacteria are not yet well un-
derstood. One of the exceptions to this is the conjugative plasmid transfer
system in
Enterococcus faecalis
[3, 4, 10].
E. faecalis
conjugate in response to
a pheromone is released by other cells (Figure 6.1). Pheromones are seven- or
eight-residue amino peptides produced in
E. faecalis
(Table 6.1). In the case of
cPD1, the pheromone is produced by truncation of a 22-residue precursor that is
the signal peptide of a lipoprotein. Pheromones are secreted to the outside of the
cell and received by other
E. faecalis
cells that carry the conjugative plasmid.
The pheromones activate transcription of plasmid genes that encode particular
cell-surface adhesion molecules. Expression of the adhesion molecules on the
cell surface induces cell aggregation in
E. faecalis
. Once cell aggregation oc-
curs, the plasmid is transferred from cell to cell, one cell acting as the donor
and another as the recipient during conjugative plasmid transfer.
Figure 6.1
Pheromone-induced conjugative plasmid transfer in
E. faecalis
.
