Nanostructures and Nanobacteria

Nanobacteria (also spelled nannobacteria) are small ovoid or spherical structures ranging from 50 to 200 nm in size that have been observed by electron microscopy in association with clays and carbonate minerals as well as medically important urinary calculi and arterial plaque. In at least one study, nano-sized structures within a meteorite were presented as potential evidence of extraterrestrial life. Three major hypotheses have been developed to explain nanobacteria: (1) they represent an artifact of specimen preparation for microscopy, (2) they represent independent or previously unrecognized life forms, and (3) they represent nano-sized structures (nanostructures) arising from conventional microorganisms such as bacteria and archaea. In this chapter, we discuss experimental evidence that addresses these three hypotheses, propose studies that investigate the contribution of nanostructures (nanobacteria) to mineral formation, and suggest a possible contribution of nanostructures to chemical evolution.