The Cellular Slime Molds

Animal cells also produce lectins.24 105 185 193 The amebas of the cellular slime mold Dictyostelium synthesize a classical lectin called discoidin I that binds GalNAc or Gal. It is absent from cells until they... 

Early studies revealed that the 3, 5 -cyclic phosphate diesterase is present in all mammalian tissues (38, 33, 36), being most active in cerebral cortex (36, 37). It has also been identified in extracts of liver fluke (Fasciola hepatica), the common earthworm (Lumbricus terrestris), and fly larvae (36) and it has been studied in marine organisms (38), the cellular slime mold Dictyostelium discovdeum (39, AO), and in E. coli (Al). The enzyme has been partially purified from beef heart (30), dog heart, (A8) and bovine brain (37, A3). No highly purified preparations have yet been obtained and most studies have been performed with relatively crude preparations. 

The cellular slime mold Dictyostelium purpureum K1001 contains AB0022A (2255), a novel antibacterial dibenzofuran, the structure of which was confirmed by total synthesis (2038). The lichen Lecanora cinereocarnea has yielded several new dibenzofurans, including three chlorinated analogues (2256-2258) (2039), and Lecanora iseana contains 2259 and 2260 (2040). The first naturally occurring polybrominated dibenzofuran, corallinafuran (2261), is present in a crustose coralline red alga that also contains corallinaether (1913) cited earlier (1769). 

The enzyme activity was from the cellular slime mold Dictyostelium mi-nutum. 

Bonner, J.T. 1%7. The Cellular Slime Molds. Princeton Univ. Press, Princeton, NJ. 

Schaap, P. M. Wang. 1984. The possible involvement of oscillatory cAMP signaling in multi-cellular morphogenesis of the cellular slime molds. Dev. Biol. 105 470-8. 

The biosynthesis of trehalose has also been studied during various stages of development, especially in the cellular slime-mold Dictyostelium... 

Chemotaxis, i.e., the oriented movement of freely motile and free living amoebae, and in particular of the cellular slime molds, has been analyzed in great detail (see Chapter 5). Like other organisms, Dic-tyostelium and other Acrasiales react preferentially to compounds which signal the presence of prey bacteria, or of other cells of their species. 

Rogers MJ, Ji XH, Russell RGG, Blackburn GM, Williamson MP, Bayless AV, Ebetino FH, Watts DJ (1994) Incorporation of bisphosphonates into adenine-nucleotides by amebas of the cellular slime-mold dictyostelium-discoideum. Biochem J 303 303-311... 

Morandini P, Offer J, Traynor D, Nayler O, Neu-haus D, Taylor GW, Kay RR (1995) The proximal pathway of metabolism of the chlorinated signal molecule differentiation-inducing factor-I (dif-1) in the cellular slime-mold Diotyostelium. Biochem J 306 735-743... 

One example of pattern formation in complex systems occurs in the life cycle of the cellular slime mold Dictyostelium discoideum. Figure 20.2 describes the life cycle of this species. Beginning as isolated amebas at the unicellular stage (a), they move in the surrounding medium, feed on such nutrients such as bacteria and proliferate by cell division. Globally speaking, they constitute a uniform system, inasmuch as their density (number of cells per square centimeter) is essentially constant. Suppose now that the amebas are starved in the laboratory this is induced deliberately, in Nature it may happen because of... 

Figure 20.2 Life cycle of the cellular slime mold Dictyostelium discoideum (Courtesy A. Goldbeter)...

Over the past 40 years, numerous modeling studies have focused on the cellular slime mold Dictyostelium discoideum. This is because D. discoideum provides an experimentally accessible and relatively simple system for studying key developmental processes like chemotaxis, cell sorting, and complex pattern formation. Early studies adopted continuous models [77-80]. More recent studies used elegant hybrid approaches that combined CA models and partial differential equations to model 2D and 3D problems involving aggregation and self-organization ofD. discoideum [81-84]. 

All these polyenoic fatly acids were of the all-cis configuration, although monoenoic fatty acids of the trans configuration have been detected in algae (Klenk et al., 1963). It will be noted that, with the exception of some fatty acids of the cellular slime mold Dictyostelium discoideum, these polyenoic fatty acids all have double bonds in the methylene-interrupted sequence. 

The biosynthesis of polyenoic fatty acids by the cellular slime mold Dictyostelium discoideum merits separate discussion. This protist has a unique system based on carboxyl-directed A and A desaturation which, coupled with two-carbon addition, is capable of synthesizing fatty acids unknown in other protists (Davidoff and Kom, 1963a). Saturated fatty acids are synthesized by two-carbon addition, and successive desaturation steps produce 16 1(9) and 16 2(5,9) from palmitic acid, and 18 1(9) and 18 2(5,9) from stearic acid. 16 1(9) is also converted to 18 1(11) by two-carbon addition, giving 18 2(5,11) on desaturation. 

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