ISSN:
1432-072X
Keywords:
Anabaena
;
Heterocyst
;
Phycobiliproteins
;
Phycocyanin
;
Allophycocyanin
;
Hydrogen
;
Nitrogenase activity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract A comparative study has been made on the pigment composition and nitrogenase activity of whole filaments and isolated beterocysts from a mutant strain of Anabaena CA. The whole cell absorption spectra of intact filaments and isolated heterocysts showed close resemblance especially between 550–700 nm region. On a quantitative basis the chlorophyll a content was found almost equal between the vegetative cell and heterocyst but the c-phycocyanin content in the heterocyst was about 1/2 that of the vegetative cell. The purification of the phycobiliprotein on DEAE-cellulose showed the presence of c-phycocyanin (γmax 615 nm) and allophycocyanin (γmax 645 nm, shoulder 620 nm). Isolated heterocysts under H2 showed acetylene reduction rates of 57 nmol C2H4/mg dry wt·min (342 μmol C2H4/mg chl a·h), whereas intact filaments reduced at the rate of 18 nmol C2H4/mg dry wt·min (108 μmol C2H4/mg chl a·h). This rate accounts for 30% recovery of nitrogenase activity in isolated heterocysts compared to whole filaments. The activity was strictly light dependent and was linear under H2 for more than 3 h. Addition of as little as 5% H2 under argon stimulated the C2H2 reductionseveral fold. The acetylene reduction (nitrogenase activity) also showed tolerance to 5% added O2 either under H2 or argon. The results suggest that the heterocyst of Anabaena CA-V is different in some characteristics (viz., higher endogenous C2H2 reduction rate, prolonged activity and higher levels of phycobiliproteins) than those reported in other Anabaena species.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00413520
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