Induction and Differentiation of Heterocysts in the Filamentous Cyanobacterium Cylindrospermum licheniforme

Abstract

The fragmentation of Cylindrospermum licheniforme filaments resulted in the induction of a synchronous round of heterocyst differentiation. Young heterocysts (proheterocysts) appeared 12 to 15 h after fragmentation, and 12 to 15% of the cells became heterocysts within 24 h. NH,Cl or NaNO, prevented the formation of new heterocysts, while differentiation was stimulated twofold by the absence of atmospheric N,. The sequence of appearance of heterocyst-specific characteristics was observed following filament fragmentation. Nitrogenase activity increased rapidly between 13 and 26 h, paralleling the increase in heterocyst frequency. Glycolipids unique to the heterocyst envelope were also synthesized between 13 and 26 h, and activities of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase increased after 10 h and 90 h respectively. Aged medium induced sporulation in intact filaments within 1 d, but sporulation could occur no earlier than 2 d after filament fragmentation, indicating that the induction of sporulation requires the presence of mature (but not necessarily functional) heterocysts.

Synchronous Akinete Germination and Heterocyst Differentiation in Anabaena PCC 7937 and Nostoc PCC 6720

“…In this case the intercellular zone of inhibition attributable to each heterocyst is reduced to the minimum. The increase of heterocyst frequency after filament fragmentation (Van de Water & Simon, 1982;Juttner, 1983) is in support of this theory. Unfortunately, unicellular cultures are not readily obtained from filamentous cyanobacteria.…”

“…Various treatments, such as low concentrations of rifampicin and 7-azatryptophan, increase this proportion, but the modes of action of these compounds are unknown (Mitchison & Wilcox, 1973;Stacey et al, 1979;Wolk & Quine, 1975). A purely physical approach, fragmentation of filaments before heterocyst induction, also yields high heterocyst frequencies (10-15%) ( Van de Water & Simon, 1982;Juttner, 1983). This communication describes the isolation and characterization of isolates of Anabaena PCC 7937 and Nostoc PCC 6720 yielding a transient heterocyst frequency of up to 30-38% upon germination of the akinetes in the absence of combined nitrogen.…”

Heterocyst Differentiation in Cylindrospermum licheniforme: Studies on the Role of Transcription

“…An axenic isolate of Cylindrospermum licheniforme Kiitz., derived from strain B 1828 of the University of Texas culture collection (UTEX) (Fisher & Wolk, 1976) was grown in the nitrogen-free medium of Allen & Arnon (1955) diluted 16-fold (AA/l6). Growth conditions and procedures for heterocyst induction were as described by Van de Water & Simon (1982).…”

“…In the first round of differentiation, new proheterocysts appear after 9-12 h and reach a maximum number at 15 h. Mature heterocysts form after 15 & 1 h, and 12-1 5 %of all cells in the culture become morphologically mature heterocysts with characteristic pore plugs within 26 h. The sequence in which several heterocyst-specific traits appear following filament fragmentation has been characterized. For example, nitrogenase activity increases in parallel with the mature heterocyst frequency between 15 and 26 h ( Van de Water & Simon, 1982).…”

“…the heterocysts are located at the ends of the filaments. When cultures of this organism growing in nitrogen-free medium are briefly sonicated, existing heterocysts are detached and the filaments are broken into fragments of 3-5 cells long whose terminal cells differentiate synchronously ( Van de Water & Simon, 1982). In the first round of differentiation, new proheterocysts appear after 9-12 h and reach a maximum number at 15 h. Mature heterocysts form after 15 & 1 h, and 12-1 5 %of all cells in the culture become morphologically mature heterocysts with characteristic pore plugs within 26 h. The sequence in which several heterocyst-specific traits appear following filament fragmentation has been characterized.…”