''Kakabekia'' is a genus of

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

. ''Kakabekia umbellata'' was first found in the 1.88 billion year old Gunflint Chert, and in 1966, a living member of the genus, ''Kakabekia barghoorniana'' was discovered in Wales - it is also found around the world, typically at 1000-2000m elevations. The roughly 2 billion year interval between these species has led some to call it the “oldest living fossil”.

Anatomy

''Kakabekia umbellata'', as described by Barghoorn and Tyler in 1965 has an umbellate “mantle”, a stalk-like “stipe” and a “bulb” attached to it. Morphology of ''K. barhoorniana'' differs; it has a round structure with radial segmentation. They have a (possibly siliceous) ring around this structure. Feulgen-positive material (DNA) was seen in “clots” in ''K. barghooriniana'' cytoplasms, placing them in the Prokaryotes.

Distribution

''Kakabekia umbellata'' is known from the Gunflint chert of

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. ''K. barghoorniana'' was first discovered in a soil sample cultured in ammonia from Harlech Castle, Wales in 1968. Further research found ''K. b.'' in Iceland and Alaska, as well as other locations in Wales.

Metabolism

''Kakabekia'' has an unusual metabolism. While it has no need for oxygen in its growth, it is not inhibited by it, like

Clostridium ''Clostridium'' is a genus of anaerobic, Gram-positive bacteria. Species of ''Clostridium'' inhabit soils and the intestinal tract of animals, including humans. This genus includes several significant human pathogens, including the causative ag ...

. This, and the fact that it has some of the oxygen-utilising enzymes, suggest that it is a transition stage of oxygen-utilisation. ''Kakabekia barghoorni'' can only be grown in ammonia-rich conditions. This may reflect ancient atmosphere composition.

Ontogeny

Barghoorn and Tyler propose an ontogeny where, starting from a

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

, the stipe is grown which then produced the umbellate "mantle". In 1967, Licari and Cloud noted that many fossil " Huroniosporas" (a

wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...

containing spore-like beings) have holes or "apertures" in them, suggesting a detachment point from ''Kakabekia'' stipes. However, based on observations of living ''K. barghoorniana'', Siegel et al. came to a very different conclusion. They found that the spore-like bodies would grow into a larger, spherical organism, encircled by the ring described above. Then, divisions form radiating from the center, and a stipe grows and releases a spore. After about 10 days, the organism degenerates and dies (senescence).

References

External links

AlgaeBase
{{Taxonbar, from=Q16976713 Prehistoric life Fossil algae