Diatoms
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DIATOMS
Important factors controlling and/or inducing biofilm detachment include the activity of matrix-degrading enzymes, microbially generated gas bubbles, nutrient levels, microbial growth status, availability of multivalent crosslinking cations, fluid shear stress, and contact attrition (Hunt et al., 2004). In addition, there is increasing evidence that bacterial biofilms may actively regulate dispersion processes using cell-to-cell signaling (quorum-sensing). Dissolution of the biofilm matrix and release of bacteria are hypothesized to be triggered when a signal molecule, i.e., an excreted bacterial metabolite, accumulates to a threshold concentration (Hunt et al., 2004; Waters and Bassler, 2005).
Bibliography Bryers, J. D., 1988. Modeling biofilm accumulation. In Bazin, M. J., and Prosser, J. I. (eds.), Physiological Models in Microbiology. Boca Raton, FL: CRC Press, Vol. 2, pp. 109–144. Hunt, S. M., Werner, E. M., Huang, B., Hamilton, M. A., Stewart, P. S., 2004. Hypothesis for the role of nutrient starvation in biofilm detachment. Applied and Environmental Microbiology, 70, 7418–7425. Stewart, P. S., 1993. A model of biofilm detachment. Biotechnology and Bioengineering, 41, 111–117. Toutain, C. M., Caiazza, N. C., O’Toole, G. A., 2004. Molecular basis of biofilm development by Pseudomonads. In Ghannoum, M., and O’Toole, G. A. (eds.), Microbial Biofilms. Washington, DC: ASM, pp. 43–63. Waters, C. M., and Bassler, B. L., 2005. Quorum sensing: cell-tocell communication in bacteria. Annual Reviews of Cell and Developmental Biology, 21, 319–346.
Cross-references Biofilms Extracellular Polymeric Substances (EPS)
DIATOMS Nicole Brinkmann1, Thomas Friedl1, Kathrin I. Mohr1,2 1 University of Göttingen, Göttingen, Germany 2 Helmholtz Centre for Infection Research, Braunschweig, Germany
Synonyms Bacillariophyta Definition Diatoms (Chromalveolates supergroup, photosynthetic Stramenopiles, Bacillariophyta) are unicellular or colonial eukaryotic algae with unique cell walls composed of amorphous silica and consisting of two parts. The diatoms (Bacillariophyta) represent an extremely diverse and successful lineage of photosynthetic Stramenopiles (Chromalveolates) with cell walls composed of amorphous silica and consisting of two parts,
termed frustules, as their most striking feature. The diatoms are of unicellular organization, but some form colonies. The diatom plastids are derived from red algal secondary symbiosis and are golden brown due to the high concentration of the carotenoid fucoxanthin. Diatoms are exceedingly abundant and thought to be the most important group of eukaryotic phytoplankton, responsible for approximately 40% of marine primary productivity (Falkowski et al., 1998). Their high abundance coupled with the resistance of diatom frustules to dissolution in normal waters has resulted in massive sedimentary accumulation and a significant fossil record.
Cell structure Frustule: The diatom frustule is a highly patterned external wall composed of amorphous silica [(SiO2)n(H2O)]. Silica is often plent
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