- Volume 53, Issue 2, 1968

SUMMARY: Bud formation in Saccharomyces cerevisiae occurs by an extension of the entire parent cell wall, as described previously. The dividing walls between the bud and the parent cell are laid down simultaneously, but the bud septum is completed more rapidly. The dividing walls separate before the bud is mature. Finally, the bud is released by the breakdown of the outer wall. A comparison between bud formation in S. cerevisiae and Rhodotorula glutinis reveals basic differences in the mechanisms which can be related to structures in mycelial fungi.

SUMMARY: Streptococcus lactis organisms grown in a glucose-containing medium pH maintained at pH 6.8 (neutral cocci) contained three- to seven-fold more nisin/unit dry weight than cocci grown in the same medium without pH control (acid cocci, terminal pH 4.2). After chemical fractionation of acid cocci 57% of the nisin was found in the fraction soluble in aqueous ethanol and 36% in a trypsin-insoluble residue. After fractionation of broken cocci (acid and neutral) by differential centrifugation up to 60% of the nisin was found in the 10,000 g sediment (walls). Nisin was also present in the 30,000 g sediment (membranes) and the 100,000 g sediment (ribosomes). The major difference between acid and neutral cocci was in the 100,000 g supernatant fluid (cell sap); cell sap from neutral cocci was 0.28% nisin whereas that from acid cocci was 0.04% nisin. Analysis of the cell wall indicated that it was composed of mucopeptide and polysaccharide. Teichoic acid could not be extracted. The polysaccharide was soluble in hot formamide and accounted for one-third of the dry weight of the wall; it contained rhamnose, galactose, glucose, glucosamine in the molar ratio of 5:1:1:1. Cell walls contributed 31% to the dry weight of acid cocci and 42% to the dry weight of neutral cocci.

SUMMARY: Strains of Dictyostelium discoideum with stable hereditable alterations in growth rate have been isolated on the basis of plaque size following treatment of the myxamoebae with nitrosoguanidine. Myxamoebae of five independently isolated strains which form small plaques were mixed in all possible pairs and allowed to develop. Eight of the ten pairs gave strains with the ability to form large plaques. Several large-plaque strains isolated from such mixtures were found to segregate small-plaque strains during vegetative growth. The results are consistent with the hypothesis that these large-plaque strains result from recombination or complementation in a genome derived at least partially from two parental strains.

SUMMARY: The occurrence of intergeneric transformation between staphylococci as DNA donors and Streptococcus strain challis as recipient was controlled. By various methods 126 DNA preparations were isolated from 21 staphylococcal strains resistant to different antibiotics (18 produced coagulase and DNase; three were white and did not produce coagulase or DNase). Eight of these preparations, originating from four strains of Staphylococcus aureus were active in intergeneric transformation. The streptomycin-resistance marker was transferred, the yield being 0.001-0.017% of that of homospecific reaction. The authors did not succeed in transferring the penicillin-, novobiocin-, erythromycin- and oxytetracyclin-resistance markers. Repeated isolations were required to produce active DNA preparations and none of the various methods yielded active preparations consistently. The staphylococcal streptomycin-resistance marker re-isolated from the transformants of strain challis was transferred to challis with the same or even higher yield than the homospecific marker.

In the staphylococcal strains from which active preparations were obtained, the GC content was 32.7-37.6% and was lower by 4.9-9% from that in strain challis (41.8%).

SUMMARY: Histochemical methods showed that tuber tissue and tissue culture cells of Solanum tuberosum contained phase-dense particles which absorbed neutral red and fluorescent dye, and particles which contained acid phosphatase and a non-specific esterase. It is suggested that these structures may be comparable to the lysosomes of animal tissues and the lysosome-like structures of plant cells which possess similar and additional properties. During infection of Solanum tissues by Phytophthora erythroseptica there was swelling and disruption of these host cell particles, accompanied by the release of acid phosphatase and esterase. Biochemical assay for acid phosphatase confirmed that infection of host cells resulted in the liberation of acid phosphatase from a particulate to the supernatant fluid fraction of cell homogenates.

SUMMARY: Rhizobium japonicum (CC711) was used to infect soybean seeds from which plants were grown. From the root nodules, bacteroid suspensions with initial rates of nitrogen fixation as high as those calculated for bacteroids in intact nodules were prepared. Oxygen, which was required for fixation by intact nodules and bacteroid suspensions, caused the eventual loss of bacteroid nitrogen-fixing ability, accompanied by an increase in O2-uptake. In intact nodules and in bacteroid suspensions, increasing O2 pressures resulted in higher values for K m of nitrogen fixation. V max also increased with increasing pO2 and this was shown to be consistent with the characteristics of nitrogen fixation by anaerobic cell-free extracts of bacteroids which required an energy source (ATP), and a reductant (sodium dithionite).

Higher concentrations of carbon monoxide were required to inhibit nitrogen fixation by intact nodules than by bacteroid suspensions. Carbon monoxide was a competitive inhibitor of nitrogen fixation in bacteroid suspensions and Ki (CO) and Km (N2) values showed that the nitrogenase had about 30 times the apparent affinity for CO that it had for N2.

In cell-free extracts of bacteroids, the nitrogen-fixing activity remained in the supernatant fluid after centrifugation at 100,000 g for 30 min. The extracts were inactivated at 0°. The Km for nitrogen fixation by cell-free extracts was variable, 62-118 (N2 concentration in mm. Hg. pressure), compared with 50-60 for intact nodules and 20 for intact bacteroids when Km for these was measured in the range of pO2 in which it was only slightly affected by O2. The Ki for inhibition of nitrogen fixation by CO in extracts was similar to values obtained with intact bacteroids.

SUMMARY: Several mycoplasmas isolated from pigs and designated b strains were previously found to be different from Mycoplasma hyorhinis and M. granularum, and to comprise four distinct serotypes. In the present study three of these serotypes were identified as M. laidlawii, M. gallinarum and M. iners, respectively. One serotype represented by mycoplasma B3 could not be identified. The isolation of avian serotypes from pigs is discussed in the light of host specificity of mycoplasmas.

SUMMARY: Successful infection of hop tissue culture with Pseudoperonospora humuli was achieved. Infection was obtained from hyphae emerging from surfacesterilized systemically infected stems and petioles. Externally, infection was characterized by sterile aerial hyphae and sporangiophores, and internally by intercellular mycelium and intracellular haustoria. Although a considerable growth of mycelium into the agar medium was observed, it appeared to be dependent on the presence of host tissue. Attempts to establish axenic cultures of P. humuli were unsuccessful.

SUMMARY: The respiratory physiology of Euglena gracilis grown heterotrophically on a defined medium was examined as a function of culture age when growth was supported by glucose, acetate or ethanol as sole carbon source. The endogenous rate of oxygen consumption in general paralleled that of total protein content, usually showing a steady decline through log. and stationary phases of growth. The rate of oxygen consumption stimulated by ethanol or acetate remained fairly constant during log. phase but. decreased sharply in early stationary phase. The specific activities of representative respiratory enzymes remained essentially proportional to one another and to total oxygen consumption, but the activities of malate synthase and the malic enzyme increased greatly in stationary phase glucose-grown organisms. In general, respiratory growth was out of balance with the rate of cell division but in essential balance with the rate of biosynthesis.

SUMMARY: When exponentially growing Bacillus cereus organisms were suspended in buffer or buffered hypertonic sucrose solution and incubated at 37°, a rapid decrease in turbidity of the suspension was observed (autolysis). During autolysis ultraviolet-absorbing substances leaked from the bacteria and over 50% of the total phospholipids was released. Of the amino sugars, main components of the cell walls of this organism, less than 20% was released. Phase-contrast microscopy showed the empty rod-shaped ghosts which increased in number, while the total counts were constant during autolysis.

Mg2+ and Mn2+ inhibited the autolysis; these cations either prevented leakage of ultraviolet absorbing substances or release of phospholipids. Isolated cytoplasmic membranes autolysed when the membranes were incubated at 37° in buffer solution (pH 7.0 to 7.5). It could be assumed, therefore, that the cytoplasmic membranes of Bacillus cereus were lysed faster than the cell walls during autolysis and that the autolysis of the membranes was inhibited by Mg2+ and Mn2+.

SUMMARY: Bacterium ncib 8250 was grown on mandelate, benzyl alcohol, benzoylformate, benzaldehyde or benzoate and also on 2-hydroxy, 4-hydroxy, 3,4-dihydroxy and 4-hydroxy-3-methoxy derivatives of these compounds. Growth rates and yields of organism were measured for many of the substrates. The pathways of oxidation of mandelate and related compounds were investigated by the technique of simultaneous adaptation. Bacterium ncib 8250 did not utilise D-mandelate; L-mandelate was oxidised via benzoylformate, benzaldehyde and benzoate to catechol. Benzyl alcohol was converted to catechol via benzaldehyde and benzoate. The 2-hydroxy-substituted compounds were oxidised to catechol by a parallel pathway. 4-Hydroxy-, 3,4-dihydroxy- and 4-hydroxy-3-methoxy-substituted compounds were all converted to 3,4-dihydroxybenzoate. Catechol and 3,4-dihydroxybenzoate underwent ring cleavage with the ultimate formation of β-oxoadipate.

SUMMARY: The activity of the electron-transport enzymes of baker's yeast or brewer's bottom yeast, grown under anaerobic conditions, was very low. When anaerobic baker's yeast was cultured aerobically to the mid-exponential phase with limited carbon source, the activity of the electron-transport enzymes increased 3- to 10-fold and, correspondingly, the activity in the stationary phase rose 10- to 50-fold. For brewer's bottom yeast the increase of activity induced by oxygen in the aerobic stationary phase was only about 3- to 4-fold and the activity was clearly lower than that of baker's yeast. The activity of the electron-transport enzymes accumulated in the 10,000 g sediment, which under aerobic conditions contained 60-80% of the total activity; the NADPH2 oxidase system formed an exception. The activity of the enzymes of the citric acid cycle also increased under aerobic conditions but only 2- to 10-fold in baker's yeast of the aerobic stationary phase; in brewer's bottom yeast the increase during oxygen adaptation was proportionally greater. The bulk of the enzymes of the citric acid cycle were found in the postmitochondrial supernatant, while the 10,000 g sediment contained 20 to 40% of the total activity.

The 10,000 g sediment of anaerobically grown baker's yeast contained mitochondrial precursors, while the 10,000 g sediment from the aerobic exponential phase contained mitochondria with a more developed structure, showing a respiratory control ratio of 1.4-1.7 with several substrates. The internal structure of the mitochondria was not completely developed until the aerobic stationary phase, where the uptake of oxygen with several substrates also increased many fold.

SUMMARY: An intranuclear spindle of about 40 microtubular fibrils, 200 Å in diameter, convergent to poles close to the inner membrane, with attendant centrioles external to the nuclear envelope, has been identified in sections of synchronously dividing nuclei in vegetative hyphae of Saprolegnia ferax.