ON THE CULTURE OF A MICROORGANISM SIMILAR TO THE PRECAMBRIAN MICROFOSSIL KAKABEKIA UMBELLATA BARGHOORN IN NH ₃ -RICH ATMOSPHERES

Preservation records of micro-organisms: evidence of the tenacity of life

“…The most famous case of this was the discovery of Kakabekia-like forms of bacteria from ammonia-rich soil samples from Harlech, Wales. These micro-organism:; did not fit any modern day category but were morphologically similar to Kakabekia unabellata Barghorn, which has been identified as a Precambrian microfossil (Siegel & Guimarro, 1966;Siegel & Siegel, 1968).…”

“…We would expect many survivors in recent strata, virtually none in old ones '. The alternative approach was that taken by Becquerel(1950), who extrapolated survival time versus temperature data to estimate that at absolute zero micro-organisms could survive for millions or billions of years (Sneath, 1962). Assenov (1 982) extrapolated data obtained at high temperatures (which are used for sterilization) to show that the energy of excitation must limit the extreme duration of anabiosis to 1O4-1O5 years.…”

“…Perhaps the most significant and ground-breaking analysis was created by Sneath (1962Sneath ( , 1964, who used data from the preservation of micro-organisms in herbarium soil to estimate a deathrate in stored micro-organisms. This represents the extrapolation of data from survival times at constant temperature.…”

Acid‐base regulation during ammonium assimilation in Hydrodictyon africanum

“…The intracellular (cytoplasmic) ammonium concentration, which must be exceeded before toxicity is observed, is very high in some organisms (e.g. Siegel & Giumarro, 1966;Siegel et aL, 1967;Siegel, Nathan, & Roberts, 1968;Sayeed & Kenny, 1978;Hoddinott, Reid & Ingledew, 1978;Raven, 1980), A problem in all considerations of toxicity and metabolism of ammonium is that it is not clear whether the active species is NH3 or NH^, Work on other phototrophs which attempts to distinguish between NH3 and NH^*^ as the major species crossing the plasmalemma includes that of Barr, Koh & Ryan (1974) and of Loppert (1979), in addition to the work of Walker et al ( 1979a) and Walker et al (1979b) on Chara corallina which was discussed in the Introduction. Barr et al (1974) showed that the ammonium distribution between the vacuole of Nitella elavata and the bathing medium could be explained in terms of vacuolar and external pH values and passive NH3 transport, with i' NH3 ^^^ ^^^ plasmalemma plus tonoplast of 4,4,10"^ cm s-', With the relatively high (2,5-14 mmol m^^) concentrations of NH3 in the bathing medium in these experiments, it is likely that diffusive NH3 entry could supply both assimilatory and storage demands for ammonia; any NH^ uniporter present in the plasmalemma would presumably be subject to feedback inhibition under these conditions (cf.…”

A Living Organism Morphologically Comparable to the Precambrian Genus Kakabekia

“…1, right) in a culture from a soil sample obtained at the base of the walls of Harlech Castle, Wales, located on a bluff overlooking the Irish Sea. This sample had been cultured under experimental atmospheres containing ammonia as part of a search for ammonia-tolerant bacteria and fungi (Siegel and Giumarro, 1965). The significance of this finding 1 Received for publication 13 November 1967.…”