A model of the phototactic reaction chain of the cyanobacterium Anabaena variabilis

Photomovement in Motile Microorganisms—ii

“…, 1986). As reported recently, lo2 seems to play an important role in photooxidative death (Nultsch, 1985a;Nultsch and Schuchart, 1985;Schuchart and Nultsch, 1984 and references therein). Quenching '02 by NaN3 or other '02 quenchers does not only prevent the photooxidative death, but also changes the phototactic reaction sign from negative to positive (see above).…”

“…Obviously the '0' or one of its volatile reaction products generated in photosynthesis diffuses through the plasma membrane and is removed by the gas stream. Likewise the water soluble crocetin and water solubilized carotenoid preparations such as pcarotene, canthaxanthin and the C3,,-ester ethyl-papo-8'-carotenoate, all potent '02 quenchers, are effective in shifting the transition point to higher fluence rates, although they are not taken up by the cells (Nultsch and Schuchart, 1985). Other '02 quenchers, such as DABCO (= 1,4-diazabicyclo[2.2.2]octane) were also active in changing the reaction sign, but most of them, especially the furan derivatives, such as DMF, are cytotoxic in the concentrations used in in v i m experiments.…”

“…2) by Nultsch and Schuchart (1985). According to this model, the photoreceptor pigments, probably chlorophyll a and the phycobiliproteins, are located in the thylakoid membranes arranged in the periphery of the cells.…”

“…The arrows outside the trichomes symbolize the motive force on both flanks, leading to forward or backward movement. The photoreceptor molecules P are located in the thylakoids and in the phycobilisomes, respectively (Nultsch and Schuchart, 1985).…”

“…Since Porphyridium cells are motionless in the dark, oxidative phosphorylation apparently does not serve as an energy source of movement. Light initiates photokinetic movement with an optimum at 10 000 Ix (Nultsch et al, 1979a). The action spectrum (Fig.…”