Intracellular
accumulation of c-di-GMP and its regulation on self-flocculation of the
bacterial cells from Zymomonas mobilis
Kai Li, Juan Xia, Chen-Guang
Liu*, Feng-Wu Bai11*Corresponding
authors. E-mails:
cg.liu@sjtu.edu.cn (C.
G. Liu) and
fwbai@sjtu.edu.cn (F. W.
Bai)
State Key Laboratory of Microbial Metabolism, Joint International
Research Laboratory of Metabolic & Developmental Sciences, School of
Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai
200240, China.
Abstract:Zymomonas mobilis is an emerging chassis engineered to produce
bulk products because of its glycolysis through the Entner-Doudoroff
pathway, with less ATP produced for lower biomass accumulation and
higher yields with targeted products.
When
self-flocculated, the bacterial
cells are more productive and tolerant to stresses for high product
titers, but this morphology needs to be controlled properly to avoid
internal mass transfer limitations associated with strong flocculation.
In this study, we explored the regulation of cyclic diguanosine
monophosphate (c-di-GMP) on self-flocculation of bacterial cells through
cellulose biosynthesis. While ZMO1365 and ZMO0919, with GGDEF domains
for diguanylate cyclase activities, catalyze c-di-GMP biosynthesis,
ZMO1487, with an EAL domain for phosphodiesterase activity, catalyzes
c-di-GMP degradation, but ZMO1055
and ZMO0401 contain dual domains with phosphodiesterase activities.
Since c-di-GMP is synthesized from GTP, the intracellular accumulation
of this signal molecule by deactivating the activity of
phosphodiesterase is preferred for activating cellulose biosynthesis to
flocculate bacterial cells, since such a strategy exerts less
perturbation on intracellular processes regulated by GTP. These
discoveries are significant not only for engineering
unicellular Z. mobilis strains with a self-flocculating
morphology to boost production but also for understanding the mechanism
underlying c-di-GMP biosynthesis and degradation in the bacterium.
Keywords: Zymomonas mobilis ; chassis; self-flocculation;
c-di-GMP; microbial cell factories; industrial production