Field and cultivated Microcoleus chthonoplastes: The search for clues to its prevalence in marine microbial mats

Abstract

The cyanobacterial species ``Microcoleus chthonoplastes'' is defined by the presence of many typically oscillatorian filaments with tapered, conically shaped terminal cells within a common sheath both in the botanical (Geitler 1932) and, more recently in the bacteriological literature (Castenholz 1988). The significant and often dominant ecological role of Microcoleus species in the formation and stabilization of intertidal and hypersaline microbial mat systems around the world is well recognized. However, it is not known if geographically disjunct populations referred to as ``Microcoleus chthonoplastes'' on the basis of gross morphological traits alone constitute a close genetic unit, or are in fact examples of evolutionary convergence driven by the adaptive advantages of a ``microcoleus-like'' morphology in benthic marine environments. What adaptive advantages this morphology may confer has been difficult to ascertain since these features, most notably the defining features of bundle formation, and presence of conically-shaped terminal cells, are not observed in currently available cultures.