Prosthecomicrobium and Ancalomicrobium : New Prosthecate Freshwater Bacteria

Abstract

Direct microscopic examination of natural freshwater samples reveals a variety of small microorganisms having elaborate cellular appendages. Several strains were isolated from crude cultures containing low concentrations of organic nutrients. All of the isolates are procaryotic. They are aerobic chemoorgano-trophs that require vitamins for growth. Because they cannot be assigned to any of the existing bacterial genera, 2 new genera are proposed: Ancalomicrobium for organisms which have several long appendages and reproduce by budding; Prosthecomicrobium for organisms which have many short appendages tapering toward a blunt tip and reproduce by binary fission. Gas vacuoles were found in strains of each genus. The term prostheca proposed for the rigid appendages of procaryotic cells bounded by the cell wall, is defined to include the structures on these new bacteria, as well as the stalks of the caulobacters and the hyphae of the hyphomicrobia.