- Email: [email protected]
Observations upon the resting nucleus of the typhoid bacterium
OBSERVATIONS UPON THE RESTING NUCLEU OF THE TYPHOID BACTERIUM K. A. BISSET Department
of Bacteriology,
University
of 3irminghm
Received March 8, 1950
INTRODUCTION
THE form of the nucleus of young, vegetative cells of bacteria is now we11 known. The information upon the subject has been fully discussed by karski (4) in an admirable review, and in a monograph (2) by the author of this paper. It has been suggested by the author (1, 2), that this vegetative nucleus, with its rod-shaped chromosomes, or chromosome complexes, is in A vesicular nucleus is found in tbe a semipermanent mitotic condition. microcyst stage, which is adopted by resting cultures of almost all bacteria, as well as in the better known spore of Bacillaceae and microcyst of Myxobacteria. This microcyst is spherical or oval in shape, and its morphology is very typical, so that the genera of the otherwise morphologically ~nd~sting~isbab~e Bacteriaceae may thus be distinguished (3). The microcyst of Salmonella typhi is especially large, and the structure of the nucleus can readily be discerned by both electron and photomicroscopy.
METHODS
A strain of S. @phi was used in which the maturation of the microcyst was very rapid, being complete after two or three days. Preparations were stained by the HCl-Giemsa technique. Wet smears were fixed in osmic acid vapour, stained and mounted in water. The degree of acid-hydrolysis required to reveal the nuclear structures of the resting cells was considerably less than was required by the corresponding vegetative cells. This was due, presumably, to their lower nueleotide content. (For techniques see (2)). Preparations for electron microscopy were thoroughly washed in saline and then in distilled water. This method was successful in reducing the opacity of the cells to the electron beam by the removal of surface mucus. Metallic shadowing was no& employed.
474
K. A. Bisset
OBSERVATIONS
With the microscope the resting cell of S. typhi was clearly seen to possess vesicular structure, a nuclear a large, central nucleus, with a well-marked membrane and an eccentric chromatin granule occupying about pne third of the total volume of the nucleus (Figs. 1 & 2). This vesicular appearance was also seen quite clearly by the electron microscope (Fig. 3), but the details of the structure of the nucleus were not so well shown, despite the better definition of the electron microscope. The unavoidable desiccation of the material, in preparation for the vacuum chamber, was presumably responsible for this defect. The lower cell in The two, transverse nuclear elements Fig. 3 is in the vegetative condition. can be distinguished? alth,ough their outline,is not as distinct as in the resting cells. SUMMARY
By the electron and light-microscopes the resting shown to possess a well-marked vesicular structure, brane and an eccentric granule.
nucleus of S. typhi is with a nuclear mem-
REFERENCES 1. 2. 3. 4.
BISSET, K. A., J. Hyg., Camb., 47, 182 (1949). __ The Cytology ‘and Life-History of Bacteria, Edinburgh, F J. Gen. Microbial. (In press, 1950). I:, PIEKARSKI, G., Erg. Hyg. B&t. Imm., 26, 333 (1949).
1950.
Observations upon fhe resting nucleus
47%
Fig. 1.
Fig. 1. S . typhi. Microcysts, stained by acid-Giemsa, Fig. 2. 7 ‘he same as 1, without outlining. x 5,000. (The electron Newton).
micrograph
the main structures
was made with the kind assistance
outlined.
x 7,500.
of Miss C. M. F. Hale and Mr. 6. @.
476
K. A. Bisset
Fig. 3. Above, microcyst showing Fig. 3. Electron micrograph. x 16,000. cell showing chromosomal nucleus.
vesicular
ndcleus;
below,
vegetative
of Bacteriology,
University
of 3irminghm
Received March 8, 1950
INTRODUCTION
THE form of the nucleus of young, vegetative cells of bacteria is now we11 known. The information upon the subject has been fully discussed by karski (4) in an admirable review, and in a monograph (2) by the author of this paper. It has been suggested by the author (1, 2), that this vegetative nucleus, with its rod-shaped chromosomes, or chromosome complexes, is in A vesicular nucleus is found in tbe a semipermanent mitotic condition. microcyst stage, which is adopted by resting cultures of almost all bacteria, as well as in the better known spore of Bacillaceae and microcyst of Myxobacteria. This microcyst is spherical or oval in shape, and its morphology is very typical, so that the genera of the otherwise morphologically ~nd~sting~isbab~e Bacteriaceae may thus be distinguished (3). The microcyst of Salmonella typhi is especially large, and the structure of the nucleus can readily be discerned by both electron and photomicroscopy.
METHODS
A strain of S. @phi was used in which the maturation of the microcyst was very rapid, being complete after two or three days. Preparations were stained by the HCl-Giemsa technique. Wet smears were fixed in osmic acid vapour, stained and mounted in water. The degree of acid-hydrolysis required to reveal the nuclear structures of the resting cells was considerably less than was required by the corresponding vegetative cells. This was due, presumably, to their lower nueleotide content. (For techniques see (2)). Preparations for electron microscopy were thoroughly washed in saline and then in distilled water. This method was successful in reducing the opacity of the cells to the electron beam by the removal of surface mucus. Metallic shadowing was no& employed.
474
K. A. Bisset
OBSERVATIONS
With the microscope the resting cell of S. typhi was clearly seen to possess vesicular structure, a nuclear a large, central nucleus, with a well-marked membrane and an eccentric chromatin granule occupying about pne third of the total volume of the nucleus (Figs. 1 & 2). This vesicular appearance was also seen quite clearly by the electron microscope (Fig. 3), but the details of the structure of the nucleus were not so well shown, despite the better definition of the electron microscope. The unavoidable desiccation of the material, in preparation for the vacuum chamber, was presumably responsible for this defect. The lower cell in The two, transverse nuclear elements Fig. 3 is in the vegetative condition. can be distinguished? alth,ough their outline,is not as distinct as in the resting cells. SUMMARY
By the electron and light-microscopes the resting shown to possess a well-marked vesicular structure, brane and an eccentric granule.
nucleus of S. typhi is with a nuclear mem-
REFERENCES 1. 2. 3. 4.
BISSET, K. A., J. Hyg., Camb., 47, 182 (1949). __ The Cytology ‘and Life-History of Bacteria, Edinburgh, F J. Gen. Microbial. (In press, 1950). I:, PIEKARSKI, G., Erg. Hyg. B&t. Imm., 26, 333 (1949).
1950.
Observations upon fhe resting nucleus
47%
Fig. 1.
Fig. 1. S . typhi. Microcysts, stained by acid-Giemsa, Fig. 2. 7 ‘he same as 1, without outlining. x 5,000. (The electron Newton).
micrograph
the main structures
was made with the kind assistance
outlined.
x 7,500.
of Miss C. M. F. Hale and Mr. 6. @.
476
K. A. Bisset
Fig. 3. Above, microcyst showing Fig. 3. Electron micrograph. x 16,000. cell showing chromosomal nucleus.
vesicular
ndcleus;
below,
vegetative