Original paper

Adherence of hormogonia to substrata is mediated by polysaccharides produced by necridic cells

Hernández-Mariné, Mariona; Roldán, Mònica


In most filamentous cyanobacteria the hormogonia are a transient non-growth state that serves in the short-distance dispersal, attachment and subsequent establishment of biofilms. The mechanisms involved in their adhesion are complex, including nonspecific interactions, properties determined by the organisms and the environmental conditions. The aim of this study was to further our knowledge of the formation of the mucilaginous substances that mediate in the firsts steps of the hormogonium attachment processes. Intact-live biofilms, from aerophytic dim habitats, were processed for Transmission Electron Microscopy and Confocal Scanning Laser Microscopy (CSLM) with and without fluorescent labelling for DNA and polysaccharidic substances. Those biofilms were mainly built by Leptolyngbya spp. and Scytonema spp. In the above filamentous cyanobacteria the first visible aspect of hormogonia differentiation was the formation of cells that help trichome breakage, called necridia. The investigation revealed changes in such cells. At the beginning they presented higher pigment fluorescence than the neighbour cells without change in size. While changing to a characteristic cupping glass shape the CSLM revealed the loss of pigment fluorescence and the increased production of intracellular polysaccharides. Trichome breakage and hormogonia liberation were caused by the disintegration of such necridia, that at their final step only presented a strong polysaccharidic fluorescence. The immediate neighbours, that became the newly formed hormogonium, retain those cupping glass polysaccharidic fluorescent remains of necridia attached at one or both tips. These polysaccharidic pads seemed to act as glue-like attachment mechanism at the onset of hormogonia adhesion to substrata. We can then postulate that colonization of habitats and plant infection by filamentous cyanobacteria is efficient because hormogonia and their sticky tip are involved. However more studies are needed to understand the significance of necridia remains and their contribution to the formation of biofilms.


adhesionattachmentbiofilmscatacombsconfocal scanning laser microscopycslmcon-acyanobacteriaepshoechst 33258hormogoniahypogean environmentsleptolyngbyapolysaccharidesscytonema