Siegel S M, Roberts K, Nathan H, Daly O
Science. 1967 Jun 2;156(3779):1231-4. doi: 10.1126/science.156.3779.1231.
A living, ammonia-obligate, umbellate form, similar to the Precambrian microfossil Kakabekia umbellata Barghoorn, has been isolated from two soil specimens collected at Harlech, Wales. This organism is amenable to culture on agar and in broth. The two soil specimens are similar in that they differ from a typical clay loam in high content of carbon, hydrogen, and organic nitrogen and low levels of sodium, potassium, and titanium. In all other constituents, such as calcium, magnesium, and iron, they are quite dissimilar. Kakabekia-like forms can be grown in glucose-anmonia media with the latter as the sole source of nitrogen, but they can also be grown on peptone and silicate in glucose-free media. Ammonia is necessary, and growth is always slow without glucose. The fission process was not observed, but the enlargement and differentiation of a preumbellate structure into its "mature" form, followed by disintegration (senescence) of this stage, was seem. An ontogeny is proposed in which the stalk and basal bulb of the complete umbellate structure are assumed to be part of the reproductive appartus.
