Microbiology

Bacterial Wood

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Science  30 Mar 2001:
Vol. 291, Issue 5513, pp. 2517
DOI: 10.1126/science.291.5513.2517b

The presence of cellulose biosynthetic genes in Escherichia coli has remained mysterious. Certainly, the common laboratory strain E. coli K-12 produces no cellulose, but this strain cannot be taken as the prototypical bacterium. Zogaj et al. have looked carefully at nonpathogenic strains of enterobacteria, including Salmonella, Pseudomonas and Klebsiella, and have detected the production of cellulose.

Cellulose is the most abundant natural polymer and is the intrinsic structural component of plants. Bacteria produce cellulose for physical protection and, in species such as Agrobacterium and Rhizobium, for adhesion to host cells. When Salmonella typhimurium enters stationary phase a distinct multicellular form, rdar, develops under the control of the agfD gene. Simultaneously, at least two extracellular matrix components are generated, one being thin, aggregative fimbriae and the other now identified as cellulose. Together, these form a hydrophobic network encasing tightly packed cells within an inert matrix, which probably is important for the survival of commensal organisms in harsh environments. As the biosynthetic genes in the species examined by Zogaj et al. form a module with surprisingly homologous sequences, it seems likely that they constitute a laterally transferred unit between cohabiting biofilm residents. — CA

Mol. Microbiol.39, 1452 (2001).

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