Phytoplankton occurrence and dynamics in rivers are mainly shaped by hydrophysical conditions and nutrient availability. Phytoplankton main structuring factors have been poorly studied in West African rivers, and this study was undertaken to identify these conditions in two tropical rivers that vary in size and human impact. For this, environmental variables and phytoplankton monthly samples we...

The one-dimensional pattern of heterocyst in the model cyanobacterium Anabaena sp. PCC 7120 is coordinated by the transcription factor HetR and PatS peptide. Here we report the complex structures of HetR binding to DNA, and its hood domain (HetRHood) binding to a PatS-derived hexapeptide (PatS6) at 2.80 and 2.10 Å, respectively. The intertwined HetR dimer possesses a couple of novel HTH motifs,...

Filaments of the blue-green alga Anabaena variabilis permeabilized by dimethylsulfoxide (DMSO) produce increased amounts of 5-aminolevulinate in the presence of levulinic acid. The metabolic activity of the filaments remains unperturbed in the presence of up to 7.5% (v/v) DMSO. Studies utilizing DMSO-permeabilized filaments confirm that 5-aminolevulinate is synthesized preferably from glutamate...

RECENT work, particularly that of De (1939), has shown that some blue-green algae are capable of utilizing the free nitrogen of the atmosphere in the synthesis of cell material. Much further work will be necessary, however, before the importance of nitrogen fixation by these organisms in nature can be estimated, our knowledge both of the distribution of the property within the group of the Myxo...

patA expression is induced 3 to 6 h after nitrogen step-down. We establish that the transcription of patA is under the positive control of NtcA. The patA promoter region shows two conserved NtcA-binding boxes. These NtcA-binding sites and their interaction with NtcA are key elements for patA expression in heterocysts.

Brownian motion with drift is constructed on the real line as the almost sure limit of a sequence of random walks. Central to the construction is an embedded varying environment branching process, which encodes the sample path behaviour of the limiting diiusion. We show how a single small time bound on the normed limit of the branching process leads to diierent small and large time bounds on th...

The cyanobacterium Anabaena flos-aquae and many other phytoplankton species have a complex life cycle that includes a resting stage (akinete). We present a new agent-based (also known as individual-based) model of Anabaena that includes the formation and behavior of akinetes. The model is part of a coupled Eulerian– Lagrangian model and can reproduce the main features of the observed seasonal a...

We have determined that the type II restriction enzyme . Ava II , isolated from Anabaena variabilis, recognizes and cuts the sequence 5' G-1GTCC 3' 3 CCAG+G 5' The eight Ava II sites of pBR322 have been mapped, as well as a unique site for Ava