Following a discussion of the problems involved in the creation of the larger taxonomic units among the bacteria, an outline has been presented for a more rational approach.
The final arrangement proposed can best be presented in the form of the following Key to the divisions, classes, and orders of the kingdom Monera, composed of microorganisms without true nuclei, plastids, and sexual reproduction.
A. Organisms photosynthetic with the evolution of oxygen and possessing the typical green plant chlorophylls, phycocyanin and sometimes phycoerythrin, and colorless, non-photosynthetic counterparts, clearly recognizable as such.
Division I Myxophyta.
B. Organisms not so characterized.
Division II Schizomycetae.
I. Unicellular or mycelial organisms with rigid cell walls. Motility, when present, by means of flagella. Endospores, cysts, or conidia may be formed.
Class 1 Eubacteriae.
a. Organisms photosynthetic, but not producing oxygen. Order 1. Rhodobacteriales.
b. Non-photosynthetic organisms.
Order 2. Eubacteriales.
2. Mycelial organisms.
Order 3. Actinomycetales.
II. Unicellular rod-shaped organisms, without rigid cell walls. Always creeping motility. Microcysts and fruiting bodies may be formed.
Class 2. Myxobacteriae.
One order Myxobacteriales.
III. Unicellular, spiral organisms without rigid cell walls. Motility by means of an elastic axial filament or modified fibrillar membrane.
Class 3. Spirochaetae.
One order Spirochaetales.
IV. For organisms not falling into the previous classes see Appendix in text.