Anabaena is a genus of filamentous, un-branched Cyanobacteria consisting of bead-like cells and enlarged spores or heterocysts.

Anabaena are a genus of Blue-green Algae or Cyanobacteria.
Specifically, Anabaena are known for their nitrogen-fixing abilities.
These prokaryotic cells are not true algae (which are eukaryotic) but also aren't truly bacterial cells as they produce energy via photosynthesis.
Genus: Anabaena. Species: not specified