Differential expression of Arabidopsis sulfurtransferases under various growth conditions.

Sulfurtransferases (Str) comprise a group of enzymes widely distributed in archaea, eubacteria, and eukaryota which catalyse the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors. Neither the in vivo sulfur donors nor the acceptors of Str could be clearly identified in any of the organisms investigated so far. In Arabidopsis thaliana 20 Str proteins have been identified and grouped according to sequence homology. To investigate their respective in vivo function, Arabidopsis plants were grown in sterile hydroponic cultures at different sulfate (50, 500, and 1500 microM) and phosphate (0.1 and 1mM) concentrations, and in medium supplemented with 1mM thiosulfate. Northern blot analysis revealed the differential expression of the Str investigated. Thiosulfate Str activity was significantly increased at low sulfate concentrations in the medium. The Str mRNA levels were highly dependent on the developmental stage of the Arabidopsis plants. The expression of most Str analysed increased with progressing plant age in parallel with increasing 3-mercaptopyruvate and thiosulfate Str activities. The Str investigated were differentially expressed in a light/dark cycle whereas Str enzyme activities were not affected by the light conditions. The results indicate that each Str is regulated in a different way and plays an individual specific role in the plant metabolism.     

L-asparaginase activity of Mycobacterium phlei under various growth conditions.

Seven Mycobacterium strains were grown statically on salts-glycerol-asparagine (Sauton) or on salts-glucose-glutamate (Sym) media. At desired time of incubation, the bacteria were washed with water, disintegrated with powdered corundum and in resulting cell-free extracts L-asparaginase activity was determined by the Conway method. The majority of experiments were performed on M. phlei which exhibited considerable rise in L-asparaginase activity with increasing age of the culture. This change did not occur on Sym medium because of Zn2+, which proved to abolish the effect of the enzyme induction in vivo but did not inhibit the activity in vitro. Addition of rifampicin to Sauton culture media resulted in a low enzyme level. Exogenous asparagine and glycerol were not indispensable for the enzyme synthesis and could be replaced by glutamate and glucose, respectively.     

Stability of antibiotics under growth conditions for thermophilic anaerobes.

It was shown that the inhibitory effect of kanamycin and streptomycin in a growing culture of Clostridium thermohydrosulfuricum JW 102 is of limited duration. To screen a large number of antibiotics, their stability during incubation under the growth conditions of thermophilic clostridia was determined at 72 and 50 degrees C by using a 0.2% yeast extract-amended prereduced mineral medium with a pH of 7.3 or 5.0. Half-lives were determined in a modified MIC test with Escherichia coli, Staphylococcus aureus, and Bacillus megaterium as indicator strains. All compounds tested were similar at the two temperatures or more stable at 50 than at 72 degrees C. The half-life (t1/2) at pH 7.3 and 72 degrees C ranged from 3.3 h (k = 7.26 day-1, where k [degradation constant] = 1/t1/2) for ampicillin to no detectable loss of activity for kanamycin, neomycin, and other antibiotics. Apparently some compounds (e.g., lasalocid and neomycin) became more potent during incubation (k greater than 0). A change to pH 5.0 caused some compounds to become more labile (e.g., kanamycin) and others (e.g., streptomycin) to become more stable than at pH 7.3.     

In vitro storage ofXanthosoma spp. under minimal growth conditions

Xanthosoma germplasm requires regular subeulturing if stored in vitro under optimal culture conditions. An experiment was carried out to investigate whetherXanthosoma can be stored continuously under minimal growth conditions. Growth was reduced by incubation at low temperatures (9°C, 13°C and 17°C) and by adding mannitol (3.0% w/v) to the medium. Three investigatedXanthosoma species,Xanthosoma brasiliense, Xanthosoma robustum andXanthosoma sagittifolium could be stored in the dark for at least two years at 13°C. Addition of mannitol to the medium resulted in higher survival rates after three years of continuous storage. The storage period could be extended to at least 48 months forX. robustum andX. sagittifolium by annual subculture and regrowth under optimal culture conditions.     

Mycelial growth of the snow mold fungus, Sclerotinia borealis, improved at low water potentials: an adaption to frozen environment

The snow mold fungus, Sclerotinia borealis, shows optimal growth at 4°C on potato dextrose agar (PDA) and can grow even at subzero temperature. Its mycelial growth was improved on frozen PDA at −1°C and on PDA containing potassium chloride (KCl) (water potential, −4.27 to −0.85 MPa) or d(−) sorbitol (−3.48 to −0.92 MPa). Its optimal growth temperature shifted from 4 to 10°C on PDA amended with KCl or sorbitol, indicating that inherent optimal growth occurs at high temperatures. These results suggest that S. borealis uses concentrated nutrients in the frozen environment and that such physiologic characteristics are critical for the fungus to prevail at subzero temperatures.     

Survival of directionally solidified B-lymphoblasts under various crystal growth conditions.

Reduction of temperature during freezing brings about two complex and interrelated phenomena: (1) crystal nucleation and subsequent growth processes and (2) change in biophysical properties of a biological system. The purpose of this investigation is to relate the morphology of the solid phase with the survival of a cell. To this end, B-lymphoblasts were exposed to directional solidification in phosphate-buffered saline + 0.05 M dimethyl sulfoxide. Directional solidification is a freezing technique which allows the morphology of the interface to be varied without varying the chemical history that a cell would experience during a constant cooling rate protocol. Results indicated that, for the range of experimental conditions tested, a maximum survival of approximately 78% could be achieved using a temperature gradient of 25(10)3 K/m and an interface velocity of 23(10)-6 m/s (cooling rate: 35 K/min). Survival dropped off sharply for freezing at faster cooling rates with little or no variation in survival for different crystal growth conditions. Survival at slower cooling rates decreased with decreasing cooling rate. It was observed, however, that the presence of secondary branches in the ice phase correlated with lower survival for a given cooling rate. These results indicated that not only is the redistribution of solute during freezing a potential source of damage during freezing but ice/cell interactions are also. Thus, the cooling rate alone may not be adequate to describe the freezing process.     

Mycelial growth and exo-biopolymer production by submerged culture of various edible mushrooms under different media

AIMS: The effect of synthetic media on the submerged mycelial growth and exo-biopolymer production in various edible mushrooms was investigated in shake flask culture. METHODS AND RESULTS: Among 19 mushrooms examined, the relatively high yield in mycelial biomass and exo-biopolymer production was achieved in potato malt peptone (PMP) medium. In particular, Ganoderma lucidum NO. 1 and Phellinus linteus KCTC 6190 showed favourable growth in PMP medium with exo-biopolymer concentration of 1170 and 1520 mg l(-1), respectively. CONCLUSIONS: Enhanced exo-biopolymer production was achieved from Ganoderma lucidum NO. 1 and Phellinus linteus KCTC 6190 in a 5L batch fermentor, indicating approximately 5000 and 2410 mg l(-1), respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: The exo-biopolymer production and mycelial growth from various mushrooms were found to be strongly controlled by different complex media.     

Macromolecule synthesis in Escherichia coli BB under various growth conditions.

The kinetic behavior of the macromolecule synthesis of Escherichia coli during balanced growth in various media at different temperatures as investigated. The results indicate that macromolecule contents per cell can be expressed as exponential functions of the specific growth rate at a given temperature. It was shown that the content per cell at the zero growth rate was constant in each macromolecule component, irrespective of the growth temperature. The rate of ribonucleic acid (RNA) synthesis per unit weight of deoxyribonucleic acid and that of protein synthesis per unit weight of RNA were taken as efficiencies of RNA and protein synthesis, respectively; both of them were found to be dependent on the growth rate and temperature. The efficiency of RNA synthesis was found to be very high at a high growth rate, whereas that of protein synthesis was found to decrease above certain growth rate. At the same growth rate, an increase in the growth temperature resulted in a decrease in the efficiency of RNA synthesis but an increase in that of protein synthesis.     

Experimental apparatus for selection of adherent microorganisms under stringent growth conditions.

A bioreactor apparatus is described for studying bacterial attachment. A cyclic, on-off, flow regime was imposed within the apparatus. Model calculations illustrate the utility of this flow pattern in the selection and maintenance of slow-growing, adherent organisms. The apparatus is believed to have general utility in testing bacterial attachment influenced by many types of experimental or environmental constraints, including variations in fluid dynamics, presence of toxic substances (metals or organics), nature of the substratum surface, concentrations of limiting nutrients, and competition between bacterial strains. As an example application, the apparatus was employed to test 14 bacterial strains for surface attachment in a nutrient-limited growth medium. The medium was developed, using the chemical equilibrium program MINEQL, for planned studies of biofilms in a solution with a chemically defined composition that permits calculation of trace metal speciation. The apparatus was used to select organisms with growth and attachment characteristics that could not be evaluated by conventional batch, or chemostat, culture conditions. When supplied with acetate, pyruvate, or succinate as a carbon and energy source, the gram-negative strains Pseudomonas cepacia 17616 and Zoogloea sp. WGO4 showed superior attachment characteristics to glass surfaces in the chemically defined medium but only moderate fluid-phase growth. The gram-positive Arthrobacter sp. strain 9G4D and gram-negative species P. pickettii and Zoogloea sp. WNJ8, when supplied with pyruvate as a carbon and energy source, were capable of superior growth in the fluid phase but formed only a low to moderate biofilm surface coverage.     

Variability of Bacillus thuringiensis under various growth conditions

When a lysogenic culture of Bacillus thuringiensis subsp. galleriae 69-6 was grown under the batch conditions, 93-99% of cells in the population produced R-form colonies and ca. 1% yielded S-form colonies. The amount of spore-forming cells was 99% in R-variants and 8% in S-variants. The quantity of S-variants rose abruptly to 99% when the culture was grown under the chemostat conditions. The number of S-variants increased with the rate and the duration of growth. The process was influenced by growth-limiting factors. Temperate phage variants capable of host culture lysis on solid media (i.e. h-mutants) were not found under the conditions of batch cultivation. However, such phage particles (h-mutants) appeared under the conditions of chemostat. The titre of these phage particles reached 10(8), 10(7) and 10(4) particles per 1 ml at limitation with yeast extract, glucose and phosphorus, respectively. Under the conditions of chemostat, the particles behaved as temperate ones and their growth was not found. Irrespective of the limitation, the phage titre did not correlate with the ratio of R and S-forms in the population. When the growth was limited with phosphorus, the quantity of S-forms increased abruptly while the spontaneous induction of the phage was inhibited. The quantity of cells capable of spore formation decreased in the cultures isolated from the chemostat and grown on MPA: 69-80% of the cells in R-forms and merely 8% in S-forms.     

Dynamics of Deinococcus radiodurans under controlled growth conditions

Deinococcus radiodurans is a potent radiation resistant bacterium with immense potential in nuclear waste treatment. In this investigation, the translational and rotational dynamics of dilute suspensions of D. radiodurans cultured under controlled growth conditions was studied by the polarized and depolarized dynamic light-scattering (DLS) techniques. Additionally, confocal laser scanning microscopy was used for characterizing the cultured samples and also for identification of D. radiodurans dimer, tetramer, and multimer morphologies. The data obtained showed translational diffusion coefficients (DT) of 1.2 x 10(-9), 1.97 x 10(-9), and 2.12 x 10(-9) cm2 /s, corresponding to an average size of 3.61, 2.22, and 2.06 microm, respectively, for live multimer, tetramer, and dimer forms of D. radiodurans. Depolarized DLS experiments showed very slow rotational diffusion coefficients (DR) of 0.182/s for dimer and 0.098/s for tetramer morphologies. No measurable rotational diffusion was observed for multimer form. Polarized DLS measurements on live D. radiodurans confirmed that the bacterium is nonmotile in nature. The dynamics of the dead dimer and tetramer D. radiodurans were also studied using polarized and depolarized DLS experiments and compared with the dynamics of live species. The dead cells were slightly smaller in size when compared to the live cells. However, no additional information could be obtained for dead cells from the polarized and depolarized dynamic light-scattering studies.