Sporulation progress

The sporulation process in Bacillus subtilis has been studied principally with KMnO₄ fixation, but also, for the purpose of comparison, with OsO₄ and mixtures of both fixatives. At a very early stage, the pre-spore is seen to consist of what seems to be the nuclear material and granular substance, surrounded by a layer of dense material destined to become the innermost layer of the spore coat. At a subsequent stage, a light interspace is observed that is destined to become the spore cortex. The mature spore shows a very complex structure. The spore coat is composed of three layers, the middle layer of which consisted of 5 to 8 lamellae of thin membranes and interspaces, both about 20 to 25 A thick. Between the inner layer of the spore coat and the spore cortex, a thin membrane with an affinity to the cortex can be observed. The spore coat is enclosed within two envelopes, one loosely surrounding the core, and the other adhering to it. The process of spore maturation has been studied in detail. Certain peculiar cellular structures have been observed that seemed to represent features of abnormal sporulation processes.

Fixation

The fine structure of Bacillus subtilis has been studied by observing sections fixed in KMnO₄, OsO₄, or a combination of both. The majority of examinations were made in samples fixed in 2.0 per cent KMnO₄ in tap water. Samples were embedded in butyl methacrylate for sectioning. In general, KMnO₄ fixation appeared to provide much better definition of the boundaries of various structures than did OsO₄. With either type of fixation, however, the surface structure of the cell appeared to consist of two components: cell wall and cytoplasmic membrane. Each of these, in turn, was observed to have a double aspect. The cell wall appeared to be composed of an outer part, broad and light, and an inner part, thin and dense. The cytoplasmic membrane appeared (at times, under KMnO₄ fixation) as two thin lines. In cells fixed first with OsO₄ solution, and then refixed with a mixture of KMnO₄ and OsO₄ solutions, the features revealed were more or less a mixture of those revealed by each fixation alone. A homogeneous, smooth structure, lacking a vacuole-like space, was identified as the nuclear structure in a form relatively free of artifacts. Two unidentified structures were observed in the cytoplasm when B. subtilis was fixed with KMnO₄. One a tortuous, fine filamentous element associated with a narrow light space, was often found near the ends of cells, or attached to one end of the pre-spore. The other showed a special inner structure somewhat similar to cristae mitochondriales.

Location and composition of spore mucopeptide in Bacillus species

Spore integuments of Bacillus coagulans were prepared containing nearly all the hexosamine and α, ε-diaminopimelic acid (DAP) present in intact spores. Subsequent autolytic action resulted in the destruction and removal of the residual cortical structure and "cortical membrane" leaving the appearance of the inner and outer spore coats unchanged in electron micrographs. Concurrently, all the hexosamine and DAP in the preparation was released mainly as non-diffusible mucopeptide containing alanine, glutamic acid, DAP, and all the glucosamine and muramic acid. Some diffusible peptides containing alanine, glutamic acid, and DAP were also present but there was little protein or carbohydrate. Lysozyme digestion of integument preparations from heated spores of Bacillus 636, B. subtilis, B. coagulans, and B. stearothermophilus specifically removed the residual cortex and cortical membrane with the release of the mucopeptide. In B. cereus T, only the residual cortex and part of the mucopeptide were solubilized by lysozyme. The effect of several reagents and enzymes upon the appearance and removal of hexosamine from B. coagul ans spore integuments is reported. The results show that spore mucopeptide is mainly located in the residual cortex and cortical membrane and suggest that these structures consist essentially of mucopeptide. The implications of these results in relation to the "contractile cortex" theory of heat resistance in spores are discussed.

Isolation and preliminary characterization of bacteriophages for Bacillus subtilis

Romig, W. R. (University of California, Los Angeles), and A. M. Brodetsky. Isolation and preliminary characterization of bacteriophages for Bacillus subtilis. J. Bacteriol. 82:135-141. 1961.-A simplified procedure for direct isolation of phages for Bacillus subtilis from soil was developed. Phage enrichment was accomplished by growing streptomycin-resistant B. subtilis in medium previously inoculated with the soil sample. Contaminating soil bacteria were eliminated by adding bactericidal quantities of streptomycin and the phages were isolated by conventional agar layer techniques. By this method 1 or more subtilis phages were isolated from 15 of 18 soil samples tested. Several of these phages were unusually sensitive to chloroform and all of them were relatively unstable when stored at refrigerator temperatures. Of 6 phages retained for study, 1 was temperate for B. subtilis, but attempts to obtain stably lysogenic bacteria following infection with this phage were unsuccessful. All 6 phages had identical host ranges and were able to lyse all strains of B. subtilis tested, as well as several related species of Bacillus.

The composition and structure of bacterial spores

The composition of the insoluble "integuments" and soluble "contents" fractions of spores of four Bacillus species of widely differing heat resistance were compared. Electron microscopy of thin sections was also used to determine and compare the morphological structures in the integument preparations. The soluble fractions of the thermophiles, B. coagulans and B. stearothermophilus, had a higher content of hexose and dipicolinic acid. The hexose content of both fractions of the four species was related to heat resistance. Integument fractions consisted chiefly of protein together with variable amounts of the mucopeptide constituents, alpha, epsilon-diaminopimelic acid (DAP) and hexosamine. In the thermophiles the DAP and hexosamine were found chiefly in the insoluble integuments fractions, while in B. cereus and B. subtilis most of this material was soluble. Integument preparations, containing mainly protein with little mucopeptide, consisted chiefly of outer and inner spore coats, while preparations having more mucopeptide contained also residual cortical material and a cortical membrane (possibly the germ cell wall). The results suggest that spore integuments consist of mainly proteinaceous outer and inner coats together with variable amounts of residual cortex and cortical membrane which contain the mucopeptide material.

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.

THE CONTROL OF SULPHATE REDUCTION IN BACTERIA

1. An enzyme from Escherichia coli 9723 that reduces adenosine 3'-phosphate 5'-sulphatophosphate to inorganic sulphite is described. Extracts of E. coli K(12) and Bacillus subtilis 1379 contain a similar enzyme. 2. This reductase and sulphite reductase (EC 1.8.1.2) of E. coli 9723, E. coli K(12) and of B. subtilis are repressed by growth in the presence of l-cystine. Cysteine synthase (EC 4.2.1.22) is unaffected. 3. Growth of E. coli 9723 on inorganic sulphite represses the sulphate-activating enzymes (EC 2.7.7.4 and 2.7.1.25) almost completely but has little effect on sulphite reductase. Growth on 0.042-0.056mm-l-cystine gives a similar result. 4. Such differential repression by cyst(e)ine prevents E. coli, when growing on sulphite, from synthesizing unnecessary enzymes.

IN VIVO COMPLEMENTATION STUDIES

Nishihara, Mutsuko (University of California, Los Angeles), and W. R. Romig. Temperature-sensitive mutants of Bacillus subtilis bacteriophage SP3. II. In vivo complementation studies. J. Bacteriol. 88:1230-1239. 1964.-A plate-spotting procedure was used in initial attempts to group the temperature-sensitive Bacillus subtilis phage SP3 mutants by complementation. The results obtained did not show any clear patterns of reactions among the mutants. Crosses were, therefore, repeated in broth at a temperature of 49 C, which greatly reduced the extent of replication of each mutant type alone. The data on mixed infections indicated that there was a minimum of six complementation groups. Of the 12 isolates, 7 did not seem to complement with each other; the rest complemented with each other and with the seven noncomplementing mutants. There was a positive correlation between the complementation reaction of a pair and the recovery of wild-phenotype phages from a 49 C broth lysate. The relative proportion of phages capable of forming wild-phenotype plaques on plates incubated at 46 C to the total number of plaque-forming units was higher in a lysate of a mixed infection with two mutants than in lysates of each mutant alone. Moreover, this frequency was higher for a mixed lysate made at 49 C than for a lysate of the same two mutants made at 37 C. These observations suggested that genetic recombination might occur at 49 C, and that the increased recovery of wild-phenotype phages in lysates made at this temperature might be due to a selective advantage for these phages. Recombination experiments at 37 C with some complementing pairs gave frequencies of 2.0 to 4.8%. The ratio of wild-phenotype revertants to total phages in the stock lysates used for these crosses at 37 C was less than 10(-6). The noncomplementing mutants were not conclusively shown to be nonidentical.

ELECTRON MICROSCOPE STUDY OF THE RELATIONSHIP BETWEEN MESOSOME LOSS AND THE STABLE L STATE (OR PROTOPLAST STATE) IN BACILLUS SUBTILIS

Ryter, Antoinette (Institut Pasteur, Paris, France), and Otto E. Landman. An electron microscope study of the relationship between mesosome loss and the stable L-state (or protoplast state) in Bacillus subtilis. J. Bacteriol. 88:457-467. 1964.-In a prior publication, it was postulated that inability of protoplasts to restart cell-wall synthesis and cell division and the inability of stable mass-conversion L forms to return to the bacillary state were both equivalent and both due to the interruption of a membrane-associated reaction sequence. It was further postulated that this reaction sequence might reside in the mesosome. In the present publication, it is shown by means of electron microscopy of thin sections that protoplasts and L forms do not contain mesosomes. The sequence of events leading to loss of the mesosomes during protoplasting is as follows. Soon after lysozyme addition, the mesosomes are extruded from the cell interior into the space between cell wall and cytoplasmic membrane. Mesosome fragments in the form of small vesicles gather at the poles of the cells and are released, along with intact protoplasts, when the wall fragments. (Sudden shift of bacilli to hypertonic environment also causes extrusion and fragmentation of mesosomes, but this damage is later repaired.) In intact bacilli, mesosomes are in contact with both the peripheral membrane and nuclear material. Upon extrusion of the mesosomes, a direct attachment between nuclear material and cytoplasmic membrane is observed. Deoxyribonucleic acid (DNA)-membrane attachment may play a role in the control of DNA replication. Bacillus subtilis L-colonies consist of irregularly shaped bodies of varying sizes, bounded only by a membrane. Many of the smaller bodies do not contain nuclear material, and many of the large ones appear inviable. Division is accomplished by a disorganized-appearing constriction process. There are no septa.

X-RAY DIFFRACTION STUDY OF A DNA WHICH CONTAINS URACIL

Three-dimensional structure of DNA from PBS2 bacteriophage, which contains uracil in place of the more usual thymine, is the same as that of "normal" DNA. The difference in secondary structure between DNA and RNA thus appears to be due to the 2'-hydroxyl group alone.

MECHANISM OF RESISTANCE TO ACTINOMYCIN IN BACILLUS SUBTILIS

Polsinelli, M. (University of Pavia, Pavia, Italy), O. Ciferri, G. Cassani, and A. Albertini. Mechanism of resistance to actinomycin in Bacillus subtilis. J. Bacteriol. 88:1567-1572. 1964.-Strains of Bacillus subtilis were rendered resistant to actinomycin D by serial transfer in increasing concentrations of the drug. Resistance to the antibiotic appeared to be due to an altered cell-wall permeability, because the resistant strains did not take up actinomycin. No evidence was found for the presence of an enzyme(s) degrading actinomycin. Deoxyribonucleic acid (DNA) extracted from the actinomycin-resistant strains was found to bind actinomycin to the same extent as the DNA extracted from susceptible strains. The genetic nature of the resistance to actinomycin was demonstrated by means of transformation. Resistant strains appeared to have almost completely lost their transformability, as well as the tendency to autolyze.

INHIBITION OF BACTERIAL GROWTH BY DRUGS OF THE MORPHINE SERIES

The growth of Escherichia coli is reversibly inhibited by drugs of the morphine series. The order of inhibitory effectiveness for the drugs tested was levallorphan > levorphanol > dextrorphan > nalorphine > morphine. The synthetic analgesic, levorphanol, was studied in greater detail. Its effectiveness was found to be strongly dependent on the pH of the medium. Raising the pH of the medium provides a higher concentration of the neutral free base which is thought to diffuse across cell membranes more readily. However, considerations other than the rate of entry of drug into the cells must be of importance since an already established growth inhibition is promptly reversed upon lowering the pH of the medium. Two mutants of Escherichia coli with altered sensitivity to levorphanol were isolated.

ISOLATION OF OBLIGATELY ANAEROBIC PSYCHROPHILIC BACTERIA

Sinclair, N. A. (Washington State University, Pullman), and J. L. Stokes. Isolation of obligately anaerobic psychrophilic bacteria. J. Bacteriol. 87:562-565. 1964.-A total of 11 strains of strictly anaerobic psychrophilic bacteria have been isolated from soil, mud, and sewage. The organisms grow well at 0 C in liquid and on solid media, and grow only in the complete absence of oxygen. On the basis of shape, sporulation, flagellation, and strictly anaerobic growth, all of the organisms were classified as strains of Clostridium. Some of the biochemical properties of the strains and the effect of temperature on growth are described.

ACETOLACTATE METABOLISM AND THE PRESENCE OF A DIHYDROXY ACID DEHYDRATASE IN MICRO-ORGANISMS

1. The growth characteristics of nine micro-organisms on complex broth and defined media, usually with a single nitrogen source (other than vitamins), were examined as a necessary step before growth of cells for enzyme assays. Six of these bacteria gave a positive colour test with a creatine-potassium hydroxide reagent, indicating the presence of acetoin, which other investigators have shown is formed via the intermediate, alpha-acetolactate. 2. Cell-free extracts of exponential-phase cells of Bacillus subtilis, Staphylococcus aureus, Proteus morganii, Acetobacter rancens (two strains), A. kuetzingianus, A. acetosus, Acetomonas (Acetobacter) melanogenus and Acetomonas (Acetobacter) suboxydans (A.T.C.C. no. 621) were found to contain the enzyme, dihydroxy acid dehydratase (2,3-dihydroxy acid hydro-lyase). 3. The specific activity of the dehydratase from organisms grown on valine- and isoleucine-deficient media was greater than those grown on a complex broth or media containing complete amino acid mixtures. The omission of valine plus isoleucine from a medium containing 19 amino acids caused an increase in the dehydratase specific activity of Staphylococcus aureus and Proteus morganii. 4. The rate of keto acid formation from alphabeta-dihydroxyisovalerate by extracts of six of the above-named organisms was faster than, but somewhat proportional to, the similar rate from alphabeta-dihydroxy-beta-methyl-n-valerate as substrate. 5. These findings may be related to acetolactate synthesis, acetoin formation and valine-isoleucine biosynthesis in the above-mentioned micro-organisms.

UPTAKE AND INCORPORATION OF THYMINE, THYMIDINE, URACIL, URIDINE, AND 5-FLUOROURACIL INTO THE NUCLEIC ACIDS OF BACILLUS SUBTILIS

Bodmer, Walter F. (Stanford University School of Medicine, Palo Alto, Calif.), and Susan Grether. Uptake and incorporation of thymine, thymidine, uracil, uridine, and 5-fluorouracil into the nucleic acids of Bacillus subtilis. J. Bacteriol. 89:1011-1014. 1965.-From 55 to 95% of uracil, uridine, or 5-fluorouracil (FU) added to the culture medium is incorporated into the acid-insoluble fraction of cells of Bacillus subtilis strains SB 19 (prototroph) and SB 503 (FU-resistant). Thymine is poorly incorporated (less than 1%); thus, the incorporation of thymidine is limited (less than 12%) by the rapid degradation of the nucleoside to thymine, probably by the enzyme thymidine phosphorylase. Uracil, uridine, and FU were not incorporated into the deoxyribonucleic acid (DNA) of either strain, whereas all the incorporated thymidine was found in the DNA.

TRANSFORMATION OF BACILLUS SUBTILIS TO MOTILITY AND PROTOTROPHY: MICROMANIPULATIVE ISOLATION OF BACTERIA OF TRANSFORMED PHENOTYPE

Stocker, B. A. D. (Stanford Medical Center, Palo Alto, Calif.). Transformation of Bacillus subtilis to motility and prototrophy: micromanipulative isolation of bacteria of transformed phenotype. J. Bacteriol. 86:797-804. 1963.-A nonmotile (nonflagellated, fla(-)) try(-) strain of Bacillus subtilis was transformed to fla(+) and to try(+) by wild - type deoxyribonucleic acid (DNA) at comparable rates. Bacteria of fla(+) phenotype were recognized by their motility approximately 3 hr after uptake of DNA, and bacteria of try(+) phenotype at about the same time by their elongation into filaments in a medium lacking tryptophan. Of phenotypically transformed bacteria of each sort isolated by micromanipulation, the majority produced only transformed progeny, a mixture of transformed and untransformed, or a mixture of two kinds of transformant. Some produced only untransformed progeny, or progeny transformed only at a locus linked to that concerned in their phenotypic transformation. In a few clones, some partial heterozygotes were present even ten generations after DNA uptake. In nonmotile clones derived from motile isolates, the unilinear transmission of motility to one to four descendants was detected; it is attributed to persistence of a corresponding number of units of some product of an unincorporated fla(+) gene, probably flagella or cell walls each carrying several flagella. No pedigrees indicating unilinear transmission of an unincorporated fla(+) gene were observed.

GLOBIGII

Survival of Bacillus subtilis var. globigii in a simulated Martian environment was demonstrated. Previous contact with the simulated Martian soil or atmosphere reduced germination or outgrowth of unheated spores, or both. Inoculation into simulated Martian soil and then flushing with a simulated Martian atmosphere were lethal to both vegetative cells and spores. After one diurnal temperature cycle (26 to -60 C), the majority of of cells present were spores. No further effect of the diurnal cycle on survival was noted in any of the experimental samples.