Observations With the Electron Microscope on the Fine Structure of the Nuclei of Two Spherical Bacteria

A B S T R A C TThe fine structure of an unencapsulated strain of Diplococcus pneumoniae is described. A striking feature of thcsc bacteria is an intracytoplasmic m e m b r a n e system which appears to be an extension of septa of dividing bactcria. The possible function of these structures and their relationship to the plasma m e m b r a n e and other types of intracytoplasmic membranes found in pncumococcus is discussed. I N T R O D U C T I O NO u r main interest in the fine structure of Diplococcus pneumoniae stems from the fact that these bacteria readily undergo genetic transformation. Prior to undertaking electron microscope studies on this process, the fine structure of pneumococcal cells in thin sections was examined. During the preliminary stage of these studies on a transformable strain, we observed some unique membranous structures which, to the best of our knowledge, have not previously been described in bacteria. M A T E R I A L S A N D M E T H O D SUnencapsulated strains of Diplocoecus pneumoniae R6, R1, and some nutritional mutants derived from R6 were used in these studies. These strains were derived from Diplovoceus pneumoniae R36A (1) which has been used as a laboratory strain for over 20 years. Forty-ml batches of bacteria were grown in a modified Adams-Roe medium (2) (medium A) or in a semisynthetic medium (3) (medium B) at 37°C in 25 x 150 mm tubes, without aeration. Small inocula (105 cells/ml) of cells from the exponential phase of growth were used and the cultures were harvested in the late exponential phase. In these media, stationary phase cultures undergo spontaneous autolysis, the first recognizable stage of which is a quantitative conversion of the cocci to fragile spherical bodies of fairly uniform size which are deficient in their cell walls. Throughout this paper, such preparations will be referred to as "spheroplasts."The bacteria were fixed and stained according to the method of Ryter and Kellenberger (4), embedded in cross-linked methacrylate, and sectioned with a Porter-Blum mlcrotome using a diamond knife. The sections were stained with lead according to the method of Karnovsky (5) (method B) and were examined in the RCA electron microscopes models 2B, 3F, or in the Siemens Elmiskop I. R E S U L T SThe nuclear region of pneumococcus resembles that of other bacteria prepared by the method of Ryter and Kellenberger (4). It is located centrally in the cell, is devoid of a nuclear membrane, and has a density lower than that of the surrounding cytoplasm (Fig. 1). The nuclear region is filled with more or less tightly packed uniform fibrils 25 to 30 A wide (Fig. 2).Differences in the internal structure of the nuclear region could be observed from one experiment to another or even in adjacent cells within the same section, in spite of the fact that the preparative procedure was the same throughout.These variations were essentially of three types: variation in the degree of interpenetration of the nuclear region and the cytoplasm which ranged 453 on

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“…A similar orientation of the nuclear fibrils after the Ryter-Kellenberger procedure has been observed in other bacteria (9)(10)(11).…”

Section: R E S U L T Ssupporting

confidence: 81%

THE FINE STRUCTURE OF DIPLOCOCCUS PNEUMONIAE

Tomasz

Jamieson

Ottolenghi

1964

The Journal of Cell Biology

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“…1). A ropelike appearance, such as that found in a small coccus by van Iterson and Robinow (1961), is also seen in some of our micrographs (Fig. 1 and 8).…”

Section: Pmsupporting

confidence: 81%

FINE STRUCTURE OF LISTERIA MONOCYTOGENES

Edwards

Stevens

1963

J Bacteriol

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AND Roy W. STE-VENS. Fine structure of Listeria monocytogenes. J. Bacteriol. 86:414-428. 1963.-Cells of Listeria monocytogenes, at different stages of growth, were fixed with osmium tetroxide and treated with MATERIALS AND METHODS L. monocytogenes Pirie 1940, strain 6057, was employed in this study. The culture was examined for morphological and staining characteristics prior to transfer to Tryptone (Difco; 1 % Tryptone, 0.5% sodium chloride, pH 7 to 7.2) and Tryptose (Difco; 2% Tryptose, 0.2 % glucose, 0.25% sodium hypophosphate, pH 7.5) broth or agar (2 % agar added to broths when solid medium 414

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“…15 and 24). A ropelike appearance first described by van Iterson and Robinow (1961) is demonstrated in Fig. 24.…”

Section: Resultsmentioning

confidence: 65%

MICROMORPHOLOGY OF DERMATOPHILUS CONGOLENSIS

Gordon

Edwards

1963

J Bacteriol

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Gordon, Morris A. (Division of Laboratories and Research, New York State Department of Health, Albany), and Mercedes R. Edwards . Micromorphology of Dermatophilus congolensis . J. Bacteriol. 86: 1101–1115. 1963.—As seen in electron micrographs of thin sections, Dermatophilus congolensis is a holocarpic actinomycete that fragments, after formation of septa in several planes, into Sarcina -like packets and then into individual cocci. Release of coccal forms from the filaments and packets is by dissolution of a capsular matrix, which is a product of degradation of the cell wall. The plasmalemma is a “unit membrane.” Regularly occurring plasmalemmosomes (“onion bodies”) of uniform structure are apparently related to septum formation. A typical bacterial nucleoid is seen in most sections, and ribosomes are scattered throughout the cytoplasm. Specimens for electron microscopy were prepared by a modification of Kellenberger's method.

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Observations With the Electron Microscope on the Fine Structure of the Nuclei of Two Spherical Bacteria

Cited by 38 publications

References 15 publications

THE FINE STRUCTURE OF DIPLOCOCCUS PNEUMONIAE

THE FINE STRUCTURE OF DIPLOCOCCUS PNEUMONIAE

FINE STRUCTURE OF LISTERIA MONOCYTOGENES

MICROMORPHOLOGY OF DERMATOPHILUS CONGOLENSIS

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