''Petalonema alatum'' is a cyanobacterium. It was first described and drawn by the Scottish author

Dugald Carmichael Dugald Carmichael (born 1772 in Stronacraoibh, Lismore Island, died 1827 in Appin) was a Scottish botanist and officer in the 72nd Highlanders. He is known as the "Father of Marine Botany". The plant genus ''Carmichaelia'' is named after him. He ...

under the taxonomic name ''Oscillatoria allata'' in 1826. In 1833, Miles Joseph Berkeley re-published it under its current name ''Petalonema alatum''. ''P. alatum'' produces a slime-like mucopolysaccharide in the form of interlocking slime funnels. The structure looks like a quill under the light microscope, which is where the species gets its name "alatum", meaning quill. These slime envelopes are up to 270 μm wide in diameter and are therefore visible by the naked eye as filiform formations ("''nema''" = floss). The habitats for this filamentous cyanobacterium are mainly wet limestone walls and creates together with other bacteria, microalgae, bryophytes and micromycets gray or gray-brown biofilms. Populations of ''P. alatum'' have specialized cells - yellow heterocytes to bind atmospheric nitrogen which are in colour contrast to vegetative blue-green/turquoise cells in filamentous

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

References

{{Taxonbar, from=Q13538183 Nostocales Bacteria described in 1826