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Full-Text Articles in Life Sciences
A Second Nitrogenase In Vegetative Cells Of A Heterocyst-Forming Cyanobacterium, T Thiel, E M. Lyons, J C. Erker, A Ernst
A Second Nitrogenase In Vegetative Cells Of A Heterocyst-Forming Cyanobacterium, T Thiel, E M. Lyons, J C. Erker, A Ernst
Teresa Thiel
In many filamentous cyanobacteria nitrogen fixation occurs in differentiated cells called heterocysts. Filamentous strains that do not form heterocysts may fix nitrogen in vegetative cells, primarily under anaerobic conditions. We describe here two functional Mo-dependent nitrogenases in a single organism, the cyanobacterium Anabaena variabilis. Using a lacZ reporter with a fluorescent beta-galactoside substrate for in situ localization of gene expression, we have shown that the two clusters of nif genes are expressed independently. One nitrogenase functions only in heterocysts under either aerobic or anaerobic growth conditions, whereas the second nitrogenase functions only under anaerobic conditions in vegetative cells and heterocysts. …
Pollination Of The Crown Imperial Fritillaria Imperialis By Great Tits Parus Major, Winfried S. Peters, Michael Pirl, Gerhard Gottsberger, Dieter Stefan Peters
Pollination Of The Crown Imperial Fritillaria Imperialis By Great Tits Parus Major, Winfried S. Peters, Michael Pirl, Gerhard Gottsberger, Dieter Stefan Peters
Winfried S. Peters
Visitations of flowers of the Crown Imperial by Great Tits at two different locations in Hessen, Germany, in 1990 and 1993 are described. The observations prove that flowers were visited because of the nectar; most likely pollination occurs during this visits. Similar reports from Europe are discussed. The significance of specific interactions including ecological generalists such as the Great Tit is considered in the context of the phylogenetic reconstruction of the development of co-adaptive syndroms.