Witches Butter Nostoc commune


Witches Butter Nostoc commune

Discovered on urban garage block. 9th January 2013. © Peter Hillman

Witches Butter Nostoc commune

Discovered on urban garage block. 9th January 2013. © Peter Hillman

Witches Butter Nostoc commune

Discovered on urban garage block. 9th January 2013. © Peter Hillman

Witches Butter Nostoc commune

Discovered on urban garage block. 9th January 2013. © Peter Hillman

Family Nostocaceae

Also known as Star Jelly or Mare’s Eggs, this was once classed as an alga, and now a cyanobacterium (photosynthetic bacterium) which has no nuclei or internal membrane systems. It is bluish-green, olive-green or brown in colour, and it forms a gelatinous mass with other colonies close by. When wet it has the appearance of a slippery convoluted blob, and when dry it shrivels and becomes wrinkled and unsightly. Cyanobacteria created the conditions in the Earth’s early atmosphere that aided the evolution of the higher oxygen-using organisms that came after them. They are also very important contributors to the planetary biosphere’s current carbon and nitrogen levels.

Witches Butter can fix nitrogen from the atmosphere and can therefore live in locations where no nitrogenous compounds are available from the substrate. It does not have chloroplasts but contains photosynthetic pigments in the cytoplasm of the cells. It also contains pigments that absorb long and medium wavelength ultraviolet radiation, which enables it to survive in places with high levels of radiation. To multiply, it forms two new cells when they divide by binary fission.

Witches Butter is very adaptable to different habitats and environments and is a very successful species. It is able to survive in extreme conditions of cold and dryness, and is both a terrestrial and freshwater species. It can remain dormant for an extended period of time and revive when conditions improve and water becomes available. The desiccated colony is resistant to heat and to repeated patterns of freezing and thawing. It can be found growing on man-made structures like roofs and pavings in urban environments, on gravels and amongst mosses. It is particularly associated with limestone, coral and other calcium-carbonate-based rocks. Also found in parks, fields, gardens and lawns, where it can suddenly appear after rain as if from nowhere, giving the impression it had just fallen from the sky, as if from a shooting star. A common and widespread species.


Field notes: Is it a fungus? Is it an algae? When I first came across this strange toffee coloured, jellied mass covering the entire roof of a garage complex, I had no idea what it was. At first I thought it was an algae, especially as most of it appeared to be thriving in pools of stagnent water, and then finally decided it must be some species of jellied fungus. I was also reminded of an old movie called The Blob starring Steve McQueen, but I was wrong on all accounts. After some Google investigations I discovered to my utter surprise that it was in fact a bacteria, a cyanobacterium, to be precise.