8 / 21
Page 54
Notes:
allied
academies
Microbiology: Current Research 2017 | Volume 1, Issue 2
Joint Conference
GLOBAL APPLIED MICROBIOLOGY CONFERENCE
MICROBIAL & BIOCHEMICAL RESEARCH AND TECHNOLOGIES
October 18-19, 2017
Toronto, Canada
International Congress on
&
Peptidoglycan (PG) synthesis interruption in
∆mrcB
mutant disturbs the bacterial envelope assembly
and induces the ECA biosynthesis in
Escherichia coli cells
Fatiha Dilmi
1, 2
, Khadidja Senouci-Rezkallah
1
, Lakhdar Belabid
1
1
Université Mustapha Stambouli de Mascara, Algeria
2
University of Mostaganem, Algeria
T
he envelope of Gram-negative bacterium is especially
complex and contains two membranes with a thin layer
of peptidoglycan (PG) exoskeleton sandwiched in between
them. These structures play a key role in maintaining cellular
integrity and offer protection from external abuses. Most
of our best antibiotics such as penicillin and vancomycin
block the biosynthesis of the bacterial envelope and cause
cell lysis. Indeed, bacterial envelope biogenesis is one
of the best sources of bacterial targets for antibacterial
development, because it involves factors that are unique
to bacteria and are important for bacterial physiology. In
order to determine the role of PG synthesis in envelope
biogenesis,
E. coli
WT cells and
ΔelyC
and
∆mrcB
mutants
were grown in LB medium 37°C and 22°C. After that, the
hydroxyl radical level was measured by the Flow cytometry
(FACS). RNA extraction and purification was achieved and
transcriptional analysis by RT-PCR was performed. Then,
murA, mrcB and uppS
genes expression was measured. Our
results were shown that these genes were overexpressed
at low temperature in WT cells, and highly expressed in
ΔelyC
and
∆mrcB
mutants. These results show the role of
PG and/or ECA synthesis at low temperature. We, therefore
observed that the ECA biosynthesis genes was expressed in
the WT cells of
E. coli
at low temperature 22°C, and more
expressed in
ΔelyC
and
∆mrcB
mutants associated with the
overexpression
of uppS
gene. In addition, uppS gene was too
up-regulated at 37°C and 22°C in
ΔelyC
and
∆mrcB
mutants.
So, in the absence of PG synthesis, the lipid carrier Und-P
can be produced for the cell wall or more precisely ECA or
another polysaccharides biosynthesis. Our results confirm
that the cells lacking either of these PBPs are viable, but the
simultaneous inactivation of both factors results in rapid
lysis and cell death. In addition, the overexpression of ECA
biosynthetic cluster,
mrcB
and
uppS
genes in
ΔelyC
mutant
confirms the competition between the PG and ECA synthetic
pathways for the lipid carrier Und-P. Taken together, these
findings suggest that
∆mrcB
mutant can increase the ECA
biosynthesis in the absence of PG synthesis. These results
reveal the role of PBP1b protein in the envelope biogenesis
correlated with ECA biosynthesis.
Speaker Biography
Khadidja Senouci-Rezkallah received the License (DEA) degree from Mustapha
Stambouli University, Biology department, Mascara, Algeria in 2005, Master’s degree
in Microbiology and Biochemistry from Aix-Marseilles III University, Faculty of Saint-
JeromeMarseille, France. After that, she received her PhD degree fromAix-Marseille III,
Faculty of Saint-JeromeMarseille, France. The area of her research is microbiology and
molecular biology on physiological and molecular characterization of acid tolerance
response of
Bacillus cereus
. From 2009 to 2013, she worked as Assistant Professor-
Researcher at Mascara University, Algeria. She worked on the characterization of the
response to acid and heat stress in bacteria responsible to food-borne illness (
E. coli
,
Stapylococcus aureus
and
B. subtilis
).
e:
khadidja.senouci@icloud.com