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Chapter 2 : Moshe Benziman and the Discovery of Cyclic Di-GMP
Category: Microbial Genetics and Molecular Biology
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The story of cyclic dimeric GMP (c-di-GMP), the subject of this chapter, now recognized as a universal bacterial second messenger. A cellulose molecule is a homopolymer of D-glucose residues linked in β-1,4-glucosidic bonds. The nature of the immediate precursor of cellulose, UDP-glucose, has been identified, and the biochemical pathways leading to its formation have been established. The work of Moshe Benziman, his students, and his colleagues, who studied cellulose biosynthesis in a relatively simple bacterial model, made a major contribution toward a better understanding of cellulose biosynthesis. The complexity of the plant cell wall biogenesis makes studies of the cellulose biosynthesis in plants a very difficult task and prompted the search for a more convenient experimental model. A series of experiments was aimed at pinpointing the cellulose biosynthesis pathway and identifying the immediate precursor of cellulose. The discovery of the GTP-mediated activation of cellulose synthase provided the platform for an important advance, solubilization of the high-activity enzyme system while preserving its capability to respond to the GTP-mediated regulatory mechanism. The finding that the regulatory protein, necessary for activation of the Gluconacetobacter xylinus cellulose synthase, was actually a diguanylate cyclase (cyclic Di-GMP (c-di-GMP) synthase, DGC) constituted a key step toward characterization of the enzymes involved in biosynthesis and hydrolysis of c-di-GMP. The discovery of c-di-GMP presented a tempting platform to study molecular pathways possibly connected to this nucleotide, not only in other bacteria but also in eukaryotic systems.
Moshe Benziman in a 1996 photograph.
(A) Dorit Amikam as a visiting scientist in Moshe Benziman’s laboratory in 1987. (B) Moshe Benziman with his favorite pipe.
Cellulose pellicle formed by a static culture of G. xylinus after 24 h at 30°C (reprinted from reference 67 with permission).
A model for regulation of cellulose biosynthesis in G. xylinus by c-di-GMP (reprinted from reference 67 with permission).
Organization of cdg operons in G. xylinus (reprinted from reference 79 with permission).
Domain architectures of DGC1 and PDE-A1. Graphical representations in the SMART database ( 51 ) of the domain structure of the dgcl and pdeA1 gene products (GenBank accession no. AF052517; UniProt entries O87374 and O87373, respectively).