Re: Nannobacteria: Surely Not Figments, But What Under Heaven Are They?
(naturalSCIENCE Article of March 4, 1997)
From: Dave LaChance
Date: Fri, 04 Dec 1998 10:03:47 -0500
Subject: Robert Folk's Article on Nannobacteria
Nannobacteria: A novel life form?
Robert Folk's March 4, 1997 article and comments on it have led me to conclude that though the term nannobacteria may be a misnomer, the objects in question may be an intermediary form of life between viruses and bacteria.
Like viruses, nannobacteria may lack a cell wall, but could have also evolved the capability of secreting a porous "shell" around themselves. Such a "shell" would be readily fossilized, and could have served as a foundation for evolving cell walls. Further, by being porous, the organisms would have continuous access to saline fluids to support their internal machinery, and the "shell" could be dispensed with after cell walls evolved. Given the fact that nannobacteria are reportedly abundant in travertines, limestones and dolomites, my first speculation would be that such "shells" would be composed of calcium carbonate, possibly in the form of aragonite.
A Comment on Dave LaChance's Theory
In an evolutionary sense, the concept of a life form intermediate between viruses and the types of unicellular organisms with which we are familiar is implausible, because viruses are parasitic on cells whose metabolic and biosynthetic machinery they co-opt in order to reproduce themselves. Viruses are most unlikely, therefore, to be in any sense ancestors of cells. On the other hand, the notion of an organism intermediate in complexity between a virus and typical cell raises an interesting question.
Either life on Earth arrived from elsewhere (panspermia), an idea that appeals to few evolutionists, or it evolved from a chance aggregation of relatively simple inorganic constituents. If the latter assumption is correct, the earliest ancestors of cellular organisms must have been much simpler than cells of the type with which we are familiar. As Stuart Kauffman discusses in At Home in the Universe they would have lacked not only nucleic acids, but also proteins. They would have consisted in little more than some kind of a vesicle enclosing a collection of small molecules (including, perhaps, oligopeptides, which not only form spontaneously in solution, but can have significant catalytic properties), in which each molecule's formation is catalyzed by some other molecule in the organization.
If this was how life on Earth began, the question arises: where are our earliest cellular ancestors? Replaced, perhaps, by later and better adapted forms. But is it not possible that in some ecological niche early cellular forms still thrive? And if that is so, then the argument that the so-called nan(n)obacteria observed by Robert Folk and others are too small to contain the necessary components of a cellular life, for example ribosomes and Danielli membranes, is not necessarily valid. Something much smaller might function effectively as a self-perpetuating chemical system of the kind envisaged by Kauffman.
This, of course, is mere speculation, but the outcome of ongoing studies of the nano-scale forms associated with mineral formation that Folk and others have reported will surely be awaited by many with the greatest interest.