The differentiation of cell wall, cytoplasmic membrane and cytoplasm of gram positive bacteria by selective staining

Measurement of the interconnected turgor pressure and envelope elasticity of live bacterial cells

Turgor pressure and envelope elasticity of bacterial cells are two mechanical parameters that play a dominant role in cellular deformation, division, and motility. However, a clear understanding of these two properties is lacking because of their strongly interconnected mechanisms. This study established a nanoindentation method to precisely measure the turgor pressure and envelope elasticity of live bacteria. The indentation force-depth curves of Klebsiella pneumoniae bacteria were recorded with atomic force microscopy. Through combination of dimensional analysis and numerical simulations, an explicit expression was derived to decouple the two properties of individual bacteria from the nanoindentation curves. We show that the Young's modulus of bacterial envelope is sensitive to the external osmotic environment, and the turgor pressure is significantly dependent on the external osmotic stress. This method can not only quantify the turgor pressure and envelope elasticity of bacteria, but also help resolve the mechanical behaviors of bacteria in different environments.

Periplasm, periplasmic spaces, and their relation to bacterial wall structure: novel secretion of selected periplasmic proteins from Pseudomonas aeruginosa

A brief overview of thin sections of cryopreserved walls from select eubacteria will be presented to suggest that all bacteria have functional periplasms, but that these are not necessarily confined to a periplasmic space such as found in typical gram-negative bacteria. Pseudomonas aeruginosa contains many components in its periplasmic space, some of which are required for infection. Throughout its growth cycle, P. aeruginosa blebs-off membrane vesicles that can possess DNA, endotoxin, phospholipase, protease, hemolysin, alkaline phosphatase, and autolysin, each of which must have a molecular phase that resides in the periplasm. These membrane packets make good delivery systems to convey these components to other bacteria and, possibly, tissue. Aminoglycoside antibiotics, such as gentamicin, produce a serious perturbation on the bacterium's surface (separate from the ribosomal effect), which contributes to the killing of the microorganism. Antibiotics such as this increase the size and number of the membrane blebs, which could contribute to septic shock of patients under drug therapy.

Polymorphism in a marine bacterium in relation to population growth

Greenfield, Leonard J. (University of Miami, Miami, Fla.), Janet J. Hines, and Linda L. Boral. Polymorphism in a marine bacterium in relation to population growth. J. Bacteriol. 84:357-363. 1962.-A marine pseudomonad, MB-1, from South Florida waters, exists in three forms: orange (y), lemon-yellow (xy), and white (x), each of which is polymorphic. Replicate growth curves of each form were obtained by culturing at 25 C in 1% peptone-sea water using a controlled inoculum. The controlled inoculum was obtained by growing an isolate on a 1% peptone-sea water agar (1.5%) slant for 24 hr at 25 C, transferring a wire loopful of culture to 50 ml of 1% peptone-sea water in a 125-ml flask, and incubating at 25 C for another 24 hr. The resulting bacterial suspension in 0.5-ml amounts was used to inoculate 50 ml of 1% peptone-sea water broths in which growth was measured. The logarithmic growth phase occurred in x and xy between 12 and 18 hr of incubation; in y, this period was between 18 and 24 hr. The stage of growth could also be characterized by the percentage of cell types present at a given period. In late lag phase, single cells outnumbered binary types by about two to one. During logarithmic growth, the single cells predominated by 2.5 or 2.4 to 1. In the stages following this ratio increased, but all cells showed considerable variation in size. Chains of cells were present in all stages but were reduced in number during the logarithmic phase.

UNSTABLE GENETIC TRANSFORMATION IN BACILLUS SUBTILIS AND THE MODE OF INHERITANCE IN UNSTABLE CLONES

Iyer, V. N. (Canada Department of Agriculture, Ottawa, Ont., Canada). Unstable genetic transformation in Bacillus subtilis and the mode of inheritance in unstable clones. J. Bacteriol. 90:495-503. 1965.-An ultraviolet-induced mutant has been isolated from the double auxotroph of Bacillus subtilis (bearing the linked mutations try(2) and his(2)). This mutant has the property of yielding unstable transformants which, in the case of transformation to prototrophy, can be recognized by reduced colony size on minimal agar. Unstable transformant clones usually become stabilized early during the development of the clone (within 12 generations). Analyses of genotypes emerging from such clones on stabilization indicate that in some of these clones the exogenote is transmitted linearly; its integrity is sufficiently preserved that it can participate in two independent recombination events in two different cells. Genetic markers on the exogenote are expressed in situations where genetic integration has not occurred.

MICROMORPHOLOGY OF DERMATOPHILUS CONGOLENSIS

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.

The bacterial nucleoid revisited

This review compares the results of different methods of investigating the morphology of nucleoids of bacteria grown under conditions favoring short generation times. We consider the evidence from fixed and stained specimens, from phase-contrast and fluorescence microscopy of growing bacteria, and from electron microscopy of whole as well as thinly sectioned ones. It is concluded that the nucleoid of growing cells is in a dynamic state: part of the chromatin is "pulled out" of the bulk of the nucleoid in order to be transcribed. This activity is performed by excrescences which extend far into the cytoplasm so as to reach the maximum of available ribosomes. Different means of fixation provide markedly different views of the texture of the DNA-containing plasm of the bulk of the nucleoid. Conventional chemical fixatives stabilize the cytoplasm of bacteria but not their protein-low chromatin. Uranyl acetate does cross-link the latter well but only if the cytoplasm has first been fixed conventionally. In the interval between the two fixations, the DNA arranges itself in liquid-crystalline form, supposedly because of loss of supercoiling. In stark contrast, cryofixation preserves bacterial chromatin in a finely granular form, believed to reflect its native strongly negatively supercoiled state. In dinoflagellates the DNA of their permanently visible chromosomes (also low in histone-like protein) is natively present as a liquid crystal. The arrangement of chromatin in Epulocystis fishelsoni, one of the largest known prokaryotes, is briefly described.

Prophage induction and filamentation in Bacillus thuringiensis caused by the genotoxic mycotoxin aflatoxin B1

Cultures of the lysogenic strain of Bacillus thuringiensis var. tolworthi were made in the presence of various drugs. The determination of bacterial size and plaque forming units (by using an indicator strain of B. thuringiensis var. galleriae) as well as colony forming units were then performed. Treatment of lysogenic cells by aflatoxin B1: provokes the formation of elongated cells (filamentation); induces a pathway that leads to the induction of prophage. Results of the present study indicated that filament formation and bacteriophage induction are two commonplace effects that occur in virtually every member of this cellular population exposed to low doses of certain drugs such as aflatoxin B1 (10 micrograms/ml); all of which have in common the ability to produce damaging changes in DNA. The following findings support the hypothesis that error-prone repair mechanisms seem to be present in B. thuringiensis as in Escherichia coli.

Isolation of spheroplast membranes and stability of spheroplasts of Bacillus stearothermophilus

Spheroplasts were prepared by lysozyme digestion of the cell wall and ruptured by suspension in 0.15 m NaCl, followed by centrifugation at 30,900 x g for 35 min, and by a final suspension in 0.05 m NaCl for 12 to 16 hr at 5 C. The membrane ghosts were washed four times in tris(hydroxylmethyl)aminomethane (Tris) magnesium buffer and once in distilled water. The intact membranes resembled empty sacs with narrow slits in which the cytoplasm was extruded. A 92% recovery of cell membrane was obtained with all membrane preparations. The spheroplasts do not require a stabilizing medium to keep them from rupturing, and they are stable for 2 to 3 hr when exposed to a temperature of 65 C. The membrane content of the cell increases with age of culture (mid-log, 16.5%; late-log, 17.0%; and stationary, 17.6%) and temperature of growth (55 C, 16.5%; and 65 C, 17.8%), and it is unaffected by composition of the growth medium. The ratio of the protein to lipid content of the membrane increases with the complexity of the medium, age of culture (mid-log, 3.65; late-log, 3.91; and stationary, 4.15), and temperature of growth (55 C, 3.65; and 65 C, 5.22). The ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) content of the membranes was 9.0 to 13.7% and 0.3 to 0.8%, respectively. Reducing sugar (determined as glucose) amounts to 0.9 to 1.0% of the membrane weight and did not significantly vary for the different membrane preparations. Medium composition, age of culture, and temperature of growth have no significant effect on the amount of each amino acid in the membrane. Aspartic acid, glutamic acid, alanine, leucine, and lysine are present in the greatest amount and represent 12.9 to 14.1%, 10.4 to 11.3%, 9.6 to 10.3%, 7.7 to 8.8%, and 7.6 to 8.5% of the membrane peptide, respectively. Prior to the rupture of the spheroplasts, 25.0, 15.7, and 50.0% of the protein, RNA, and DNA, respectively, is lost. In potassium phosphate-magnesium buffer without sucrose, 90% of the protein and RNA and 95% of the DNA is lost from the spheroplasts. In the presence of sucrose, the leakage of RNA and DNA is similar to that observed for spheroplasts suspended in Tris magnesium buffer; however, the leakage of protein is 2.4 times greater.

Observations on the motility and the structure of Vitreoscilla

Two strains of Vitreoscilla were studied. Their trichomes showed gliding motility on surfaces and they were immobile in fluid suspension. Motility is the property of the individual cells which make up the trichome, but floating, living cells rebounded when they touched a surface. A copious slime layer has been demonstrated and its possible roles in gliding motility is discussed. An association of the unique, scalloped, outer layer of the cell walls of these organisms with their curious motility suggested a new hypothesis: a vibratile, actively undulating surface. Specific antiserum caused rapid cessation of gliding motility; pasteurization and fixation prevented the rebound phenomenon. Stained preparations and electron micrographs of thin sections have provided a general description of structure. This shows, at least, that the classification of Vitreoscilla among the bacteria is reasonably founded. Similarities to certain bacteria are seen in the mode of cell division. On the other hand differentiation of central and peripheral cytoplasmic organization is reminiscent of the Myxophyceae, while the diffuse chromatin distribution has precedent in both groups.

Studies on the cytological structure of yeast: electron microscopy of thin sections

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The organelle nature of a particle isolated from Bacillus stearothermophilus

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Demonstration of a cell wall in the large bodies of Proteus vulgaris

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The cytological basis for the role of the primary dye in the gram stain

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Characterization of the protoplasmic constituents of bacillus megaterium

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The action of lysozyme on the cell wall and capsule of Bacillus megatherium

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