Nostoc pruniforme

Mare's eggs
Scientific classification
Domain:	Bacteria
Phylum:	Cyanobacteria
Class:	Cyanophyceae
Order:	Nostocales
Family:	Nostocaceae
Genus:	Nostoc
Species:	N. pruniforme
Binomial name
Nostoc pruniforme C.Agardh ex Bornet & Flahault

Nostoc pruniforme (Mare's eggs) are a species of cyanobacterium. These freshwater bacteria grow in colonies which take the form of dark green, gelatinous spheres with a smooth surface like a plum. It is common and widely distributed both geographically and ecologically in oligotrophic and mesotrophic freshwaters in temperate and sub-Arctic regions.^[1]

In temperate lakes, N. pruniforme appears to grow in diameter from ~0·2 cm in late spring to 2–3 cm in midsummer and it can rapidly die off, supposedly because of attacks by viruses or bacteria at high summer temperatures (K. Sand-Jensen, unpubl. data). In contrast, in a cold (4 °C), nutrient-poor spring in Oregon, USA, N. pruniforme reached a handball size of 15–17 cm in diameter and weighed 2.6 kg after sustained slow growth for 9–14 years.^[2] Very large colonies are also found in cold transparent lakes in Greenland (K. Sand-Jensen, unpubl. data). In addition to their larger size and persistence, they differ from Danish temperate specimens by having a more solid surface and a denser gel.