- Volume 131, Issue 10, 1985

Summary: A proline-producing strain of Serratia marcescens grew more rapidly than the wild-type strain in a medium of high osmolarity due to high concentrations of NaCl, KCl, Na2SO4, (NH4)2 HPO4, sodium glutamate, glucose or sucrose. Growth inhibition by NaCl was partially reversed by proline in the wild-type strain, and by glutamate and proline in the proline-producing strain. Intracellular proline and glutamate concentrations under conditions of high osmolarity were studied. The wild-type strain accumulated endogenously synthesized glutamate, and concentrated proline taken up from the external medium. In contrast, the proline-producing strain accumulated a large amount of endogenously synthesized proline. This increased proline content contributes to the osmotolerance of the proline-producing strain. The growth inhibition by NaCl was also reversed by glycinebetaine in S. marcescens wild-type and proline-producing strains.

Summary: Colony growth kinetics of Streptomyces coelicolor A3(2), the wild-type strain, and J802, a mutant incapable of utilizing agar as the sole carbon and energy source, have been studied on solid medium. General features comparable to colony growth of filamentous fungi were observed in both streptomycete strains. Hyphal frequency at the margins of colonies was assessed as the number of hyphae crossing an are of defined length and increased in an exponential manner with distance from the margin, reaching a maximum at approximately 200 μm. Aerial hyphal initials were formed approximately 350 μm from the margin. Colony radial extension was linear, but in the wild-type strain grown at low medium depths, growth was sometimes multiphasic, with successive phases of linear growth each exhibiting a slower radial growth rate than that of the preceding phase. Hyphal frequency at the colony margin decreased as colony diameter increased, indicating significant changes in environmental conditions in the peripheral growth zone during colony growth. In the primary phase of linear growth, the colony radial growth rate of both strains was independent of medium depth and in the absence of a cellophane membrane was independent of glucose concentration. Colony radial growth rate of strain J802 growing on a cellophane underlay increased with glucose concentration. Hyphal frequency of strain A3(2) increased gradually with medium depth but was independent of glucose concentration. In strain J802, hyphal frequency exhibited a strong dependence on both medium depth and glucose concentration. A threshold glucose concentration for growth was not found and inhibition of strain A3(2) occurred above 1 gl−1. The results agree with many aspects of accepted theories for colony growth of both unicells and filamentous fungi, but suggest production of staling products and/or secondary metabolites to be of equal significance to nutrient limitation in controlling colony development.

Summary: Ca2+ protected yeast ceJls very effectively against the toxic effects of Cd2+; Mg2+had only a slight protecting effect as far as protection against Cd2+-induced release of K+ was concerned. Protection of the yeast cells against Cd2+ toxicity was due to a reduction in Cd2+ uptake in the presence of Ca2+. A single relationship existed between the relative rate of K+ release induced by Cd2+ and the cellular Cd2+concentration. Within the first few minutes of incubating cells with Cd2+. the molar ratio of K+ released and Cd2+ accumulated was 22 and was independent of the amount of CdC12 added. This ratio decreased during incubation of the cells with Cd2+. depending on the external Cd2+concentration.

Summary: A strain of Pseudomonas putida resistant to low concentrations of cadmium (0.25 mm-Cd2+) adapted to growth in the presence of 3 mm-Cd2+ in a chemically defined medium. This increased resistance was rapidly lost if Cd2+ was omitted from the growth medium. P. putida concentrated109Cd2+ actively. Mechanisms appeared to exist for expelling cadmium from cells during the lag and exponential phases and for continued growth in the presence of high intracellular Cd2+ concentrations. Cd2+-resistant cells adapted so as to control both the extent and rate of Cd2+ uptake when compared to control cells.

Summary: X-ray microanalysis of thin cryosections of the cyanobacterium Anabaena cylindrica showed that aluminium was rapidly taken up and accumulated into polyphosphate granules. In addition, aluminium was found in the cell walls but could not be detected in the cytoplasm. The concentration of phosphorus in the medium affected the accumulation pattern; more aluminium was bound in the polyphosphate granules and in the cell walls after growth in phosphorus-rich medium. The accumulation of aluminium in these structures may function as a detoxification mechanism. Treatment with aluminium for 24 h did not cause any significant changes in the elemental composition of polyphosphate granules or cell walls.

Summary: Growth and nitrogenase activity were followed in batch cultures of Anabaena cylindrica PCC 7122 supplemented with a range of protein amino acids and urea at concentrations of 1 and 10 mm. Alanine, arginine, asparagine, aspartate, glutamate, glutamine and serine caused reductions in nitrogenase activity and showed evidence of acting as sources of nitrogen. Suppression of nitrogenase by other amino acids was accompanied by reduced growth. A number of amino acids appeared to be toxic at high concentrations. Cysteine and histidine were toxic at low concentrations.

summary: The haem requirement for growth of the rumen chytridiomycete Neocallimastx Frontalis H8 was satisfied by haem, haemin, haematin, mesoporphyrin IX, coproporphyrins I and III, uroporphyrins I and III, but not deuteroporphyrin IX. Porphyrin degradation products and precursors of porphyrin synthesis did not support growth. Protoporphyrin IX and haemato-porphyrin IX supported growth, indicating that the organism contains ferrochetalase, but was unable to synthesize the porphyrin ring. Haem could be provided by catalase and peroxidase, but not by cytochrome C. Zoosporogenesis was induced in N. Frontalis H8 in rumen fluid principally by haem, haemin and haematin, and to a smaller extent by catalase, peroxidase and protoporphyrin IX. Haem precursors and degradation products were ineffective. Chlorophylls a and b and their ruminai degradation products, plant fraction 1 protein and chelated iron neither stimulated growth nor induced zoosporogenesis. Haem induced partial zoosporogenesis in haem-limited cultures and suspensions of sporangia grown In Vitro.

Summary: Trifluoperazine (TFP), the antipsychotic drug, induces substantial K+ efflux, membrane hyperpolarization and inhibition of H+-ATPase in the yeast Saccharomyces cerevisiae. Investigations on the mechanism of these effects revealed two different processes observed at different incubation conditions. At an acidic pH of 4.5 and an alkalinepH of 7.5, K+ efflux was accompanied by substantial proton influx which led to intracellular acidification and dissipation of ΔΨ formed by cation efflux. The results indicated nonspecific changes in membrane permeability. Similar results were also observed when cells were incubated at pH 5.5–6.0 with higher concentrations of TFP (above 75 μm). On the other hand, low concentrations of TFP (30–50 μm) at pH 5.5–6.0 caused marked membrane hyperpolarization and K+ efflux unaccompanied by the efflux of other cations and by H+ influx. Our experiments indicate that under these conditions K+ efflux was an active process. (1) K+ efflux proceeded only in the presence of a metabolic substrate and was inhibited by metabolic inhibitors. (2) When 0.3–0.9 mm-KCl was present in the medium at pH 6.0, the concentration of K+ within the cells (measured at the end of the incubation with TFP) was much lower than the theoretical concentration of if the distribution of K+ between medium and cell water was at equilibrium (at zero electrochemical gradient). (3) Valinomycin decreased the net K+ efflux and decreased the membrane hyperpolarization induced by TFP, probably by increasing the flux of K+ into the cells along its electrochemical gradient. (4) Conditions which led to active K+ efflux also led to a marked decrease in cellular ATP level. The results indicate that under a specific set of conditions TFP induces translocation of K+ against its electrochemical gradient.

Summary: A mutant of Saccharomyces cerevisiae lacking aconitase did not grow on minimal medium (MM) and had five-to tenfold less NADP+-depcndent glutamate dehydrogenase (GDH) activity than the wild-type, although its glutamine synthetase (GS) activity was still inducible. When this mutant was incubated with glutamate as the sole nitrogen source, the 2-oxoglutarate content rose, and the NADP+-dependent GDH activity increased. Furthermore, carbon-limited cultures showed a direct relation between NADP+-dependent GDH activity and the intracellular 2-oxoglutarate content. We propose that the low NADP+-dependent GDH activity found in the mutant was due to the lack of 2-oxoglutarate or some other intermediate of the tricarboxylic acid cycle.

Summary: Using chemostat cultures of Escherichia coli it was possible to vary respiration rates while maintaining a constant growth rate. This allowed the effect of variations in respiration rates on the accumulation of streptomycin to be studied in cultures at constant growth rates. At a particular dilution rate cultures exhibited higher respiration rates when phosphate limited growth than when carbon limited growth. A ubiquinone-deficient strain had a lower rate of respiration at a particular dilution rate than a related ubiquinone-sufficient strain. In spite of these differences in respiratory activity, the accumulation of streptomycin was identical in carbon-and in phosphate-limited chemostat cultures of ubiquinone-deficient and ubiquinone-sufficient strains. Moreover, accumulation of streptomycin in an anaerobic chemostat culture occurred at the same rate as that in an aerobic chemostat. There was however a lag of 1.5 h before accumulation commenced in the anaerobic culture, a feature that was not apparent in the aerobic culture. These results indicate that the lower rates of respiration in slow-growing bacteria are not responsible for the decreased accumulation of streptomycin in slow-growing compared to fast-growing cultures. Moreover, it seems unlikely that quinones are involved directly (e.g. as carriers) in streptomycin accumulation, since removal of 90% of cellular ubiquinone, or replacement of ubiquinone with a structural analogue, did not affect accumulation as long as mutant and parent cultures grew at the same rate.

Summary: Six azole-derivative antifungal compounds affected several aspects of Candida albicans hyphal development with only a relatively small degree of inhibition of growth rate, measured in terms of ATP concentration, whereas amphotericin B and 5-fluorocytosine affected morphology only when they also substantially inhibited fungal growth rate. At 10−8M, all the azoles tested inhibited branch formation by C. albicans hyphae. At 10−7 M and higher concentrations, clotrimazole and miconazole strongly suppressed emergence of new hyphal outgrowths from parent yeast cells, whereas ICI 153066 and itraconazole had little effect on this phenomenon and ketoconazole and tioconazole had intermediate effects. At the highest concentrations tested (10−5 M) hyphal development was ultimately arrested by the azole compounds and the fungus grew predominantly in the form of budding yeast cells; however, none of the azole antifungals prevented initial emergence of an apparently normal germ tube. The antifungals only exerted their morphological effects when they were present in the culture medium: removal of the compounds after exposure of C. albicans to them led to reversion to normal growth.

Summary: In a chemically defined liquid medium, soybean lecithins (99% pure) were much more effective than, β-sitosterol and cholesterol in stimulating oospore formation by isolate Pct N of Phytophthora cactorum at 20 and 24 °C. Assuming that the 1% impurity is all sterols, such sterol impurity would account for less than 2% of the oospores produced in the presence of lecithins. Lecithins were also stimulatory to sexual reproduction of Phytophthora capsici and Pythium aphanidermatum but notPythium vexans, whereas sterols were stimulatory to sexual reproduction of Pythium aphanidermatum and Pythium vexans but not Phytophthora capsici, Lecithins from soybean were more effective in inducing sexual reproduction by isolate 121F of Phytophthora cactorum than were those from egg yolk. L-α-Phosphatidylethanolamine from soybean was as effective as lecithins in inducing sexual reproduction, whereas L-α-Phosphatidylinositol from soybean and L-α-Phosphatidyl-L-serine from bovine brain were ineffective. Of four synthetic lecithins tested, only dioleoyl-L-α-Phosphatidylcholine was active. The triglycerides and fatty acids tested were inactive. The results suggest that the activity of lecithins is determined by the type and position of fatty acids in the molecular structures.

Summary: The effect of various DNA-damaging agents on a Vibrio species was investigated. The organism was readily mutable by N-methyl-N'-nitro-N-nitrosoguanidine and mitomycin C but not by UV light. No Weigle reactivation of UV-irradiated α3a phage was detected. These results suggest that an error-prone repair mechanism is lacking in this species.

Summary: Trichomes of an Oscillatoria sp. suspended in soft agar in Petri dishes showed active movement away from areas where gaseous exchange had been prevented by placing glass coverslips on the surface. This clearance response occurred only in the light and it was related to gradients of inorganic carbon that formed in the agar layer. In plates incubated in the dark trichomes accumulated in the central areas below glass coverslips but the substance eliciting this response could not be identified. Gradients of diffusible substances were established within lawns of cyanobacteria suspended in soft agar and it was demonstrated that trichomes of Oscillatoria sp. moved towards CO2. HCO3 and O2 in light-dependent chemotactic reactions. No chemotaxis occurred in response to these substances in the dark. The chemotactic responses were detected after 2 h but became increasingly distinct up to 8 h. The chemotactically active concentration of CO2 was greater than the atmospheric concentration since trichomes moved from air towards a source of CO2. Using diffusivity coefficients it was calculated that trichomes of Oscillatoria sp. accumulated at a CO2 partial pressure of 0.02 bar (equivalent to 0.83 mm). With O2 as the chemoattractant the value was 0.35 bar (14.56 mm). These results are discussed with reference to the roles of inorganic carbon and O2 in cyanobacterial metabolism and it is concluded that chemotactic behaviour may be important in movements within the photic zone of sediment environments.

Summary: Prosthecae purified from cells of Asticcacaulis biprosthecum possess active transport systems that transport all 20 amino acids tested. Using ascorbate-reduced phenazine methosulphate in the presence of oxygen, all 20 amino acids are accumulated against a concentration gradient by isolated prosthecae. Results of experiments testing the inhibition of transport of one amino acid by another, and of experiments testing the exchange of exogenous amino acids with those preloaded in prosthecae, along with characteristics of mutants defective in amino acid transport, suggest the presence in prosthecae of three amino acid transport systems. One, the general or G system, transports at least 18 of the 20 amino acids tested. Another system, referred to as the proline or P system, transports seven amino acids (including proline) that are also transported by the G system. The third system transports only glutamate and aspartate, and is referred to as the acidic amino acid transport system or A system.

Summary: Three glucose-phosphorylating enzymes were separated from cell-free extracts of Saccharomyces cerevisiae by hydroxylapatite chromatography. Variations in the amounts of these enzymes in cells growing on glucose and on ethanol showed that hexokinase PI was a constitutive enzyme, whereas synthesis of hexokinase PII and glucokinase were regulated by the carbon source used. Glucokinase proved to be a glucomannokinase with K m values of 0.04 mm for both glucose and mannose. D-Xylose produced an irreversible inactivation of the three glucose-phosphorylating enzymes depending on the presence or absence of ATP. Hexokinase PI inactivation required ATP, while hexokinase PII was inactivated by D-xylose without ATP in the reaction mixture. Glucokinase was protected by ATP from this inactivation. D-Xylose acted as a competitive inhibitor of hexokinase PI and glucokinase and as a non-competitive inhibitor of hexokinase PII.

Summary: Mutants of Escherichia coli K12 unable to grow on phenylacetate have been isolated and mapped. The mutations were located in the relatively ‘silent’ region of the E. coli K12 chromosome at min 30.4 on the genetic map, with the gene order rac pac-1 pac-2 trg.