Some Morphological Characteristics of Nodule Bacteria as Shown by the Electron Microscope. II

Abstract

A few species of legume nodule bacteria have been studied by means of the electron microscope in an attempt to discover distinct morphological differences within the genus (Appleman, Barnes, and Sears, 1942). It is the purpose of this paper to present a more detailed study of the morphology of the soybean and sweet clover nodule bacteria, particularly with reference to localized fat areas and nuclear contents, in which classical cytological reagents and specific chemical solvents were used.In order to show differences in cell structure under the electron microscope it is often necessary to alter the density of the cellular components so that a specific region is rendered more or less opaque than the surrounding area. For this

Biochemical and Symbiotic Properties of the Rhizobia 1

“…Binucleate and multinucleate cells are described. Bodies suggestive of nuclei are described by Baylor et al (39). According to them the presence of a lipoidal nuclear membrane is inferred and a nuclear pattern is substantiated in soybean rhizobia by the microchemical techniques of Knaysi and Mudd (180) and Mirsky and Pollister (236).…”

“…Two forms of banded soybean rhizobia are described: one of these contains dense, dumbbell shaped configurations; the other is characterized by multiple vacuolation between dense poles. Neither granulation nor vacuolation attributable to dissolved nucleoprotein is observed in sweet clover rhizobia (39). Electron micrographs have failed to show localized fat globules in these cells, despite the ease with which they are identified in stained preparations with light microscopy (205).…”

“…The thick outer slime layer surrounding the celLs has provided the major technical difficulty. Some success in its elimination is afforded by frequent transfer of cultures in Laird's medium 5, a carbohydrate free, mineral salts yeast extract medium (31,39,195).…”

Demonstration, with the Electron Microscope, of a Nucleus in Bacillus mycoides Grown in a Nitrogen-free Medium

“…On the basis of these observations, Knaysi and Mudd concluded that bacteria contain nuclear material which, de-pending on conditions yet unknown but probably related to environment and development, may be diffuse in the protoplasm or may be partly or totally differentiated into a nucleus. Baylor, Appleman, Sears, and Clark (1945) studied the internal structure of Rhizobium leguminosarum with and without previous treatment with various solvents and nuclear stains. Untreated cells and cells stained with Heidenhain's hematoxylin contained poorly visible opaque bodies.…”