Growth, structure, and classification of Selenomonas

Abstract

The morphologically distinct microorganism Selenomonas (family Spirillaceae) exhibits a 'crescent moon' shape with a characteristic tuft of flagella situated in the middle of the concave side of the cell. Apart from aspects of classification, other fundamentally biological questions arise, such as the behavior of the concavely placed flagellar tuft during cell division. Another problematic area concerns the nucleus of selenomonads. The chromatin bodies of Selenomonas are in close proximity to the flagellar tuft. In many cases it appeared that the flagella may even originate within the nuclear area. Thus, the unusual type of flagellation, the mention in Bergey's Manual that the flagella are tapered, and the possibility of the flagella originating in a nuclear region all contribute to the fundamental classification of the selenomonads. This review emphasizes aspects of classification, growth, and structure of S. ruminantium and S. sputigena, with some marginal studies of S. palpitans, for purposes of comparison.