A fungal phenoloxidase (tyrosinase) involved in pentachlorophenol degradation

Amylomyces rouxii eliminated 85% of initial pentachlorophenol (PCP) at 12.5 mg l^–1 when grown with 0.1 g tyrosine l^–1, but only 55% without tyrosine. Addition of tyrosine in the culture medium increased the monophenolase activity by 1.8-fold. Tyrosinase is thus indicated to be the phenoloxidase involved in PCP degradation by A. rouxii.     

In vitro inhibition of Candida albicans growth by plant extracts and essential oils

The opportunistic Candida albicans yeast strain ATCC 10261 grows at 37 °C and gives germ tubes after 3 h on corn meal agar and blood plasma. It produces chlamydospores and assimilates sucrose, dextrose, galactose, maltose, trehalose and xylose among the tested carbon sources. Other growth characters were also investigated. The agar diffusion cut plug technique revealed that 200 l of Foeniculum vulgare Miller (fennel), Mentha piperita L. (peppermint) and Citrus limon (lemon) essential oils showed inhibitory actions. Fumigation test of the three essential oils had complete inhibition on the growth. The essential oil of Eucalyptus occidentalis End1 (eucalyptus, eucalypt) had no influence on C. albicans growth by the two tests. Meanwhile, methanol extracts of both leaves and male cones of the conifer Thuja orientalis (eastern thuya) had an inhibitory influence on the growth by two tests (cut plug and filter paper disc assay). In comparative tests the antibiotics mycostatin and dermatin had an inhibitory activity on C. albicans at the concentrations of 50–80 g per hole. Crude methanol extract of leaves of eastern thuya (10–80 g/ml) reduced C. albicans growth and intercellular protein nitrogen on liquid media.     

Water availability affects the growth,accumulation of compatible solutes and the viability of the biocontrol agent Epicoccum nigrum

Growth of the biocontrol fungus Epicoccum nigrum was more sensitive to ionic solute water stress (NaCl) than non-ionic (glycerol) on potato dextrose-based media at –0.5, –3.0 and –5.5 MPa water potentials. Subsequent physiological manipulation of growth of E. nigrum in glycerol-modified media to –3.0 MPa water potential resulted in a significant increase in the accumulation of compatible solutes in both mycelial liquid cultures and spores, but no enhanced accumulation of the desiccation protectant trehalose, when compared to unmodified media (–0.5MPa). The main solute accumulated was glycerol, followed by arabitol. In temporal studies over 20 days maximum accumulation of glycerol occurred in 5-d old cultures with water stressed cultures having 250× greater amounts than those from unmodified medium. The arabitol content was also higher in mycelium and spores produced under water stress. The difference was maximum after 15 days growth. Glucose content decreased over time in mycelial colonies but increased in spores. The germination of conidia from the two treatments was similar, regardless of compatible solute content, even at –9.25 MPa water potential stress. However, germ tube extension was significantly increased at this water potential level. The production of E. nigrum spores at –3.0 MPa water potential resulted in improved survival when stored fresh at 4 and 25 °C. However, freeze-drying severely affected the viability of spores produced on both media (–0.5 or 3.0 MPa). Accumulation of compatible solutes may assist the fungus in better ecological competence and establishment in the phyllosphere, where water availability is often limited.This revised version was published online in October 2005 with corrections to the Cover Date.     

Glucose metabolism in resting cells ofCandida albicans as studied by13C NMR

The metabolism of glucose in resting cells ofCandida albicans was studied by¹³C NMR spectrometry using¹³C-labeled glucose. Under aeration, the formation of ethanol, glycerol, arabitol, mannitol, and trehalose was observed. The addition of inhibitors of the respiratory chain or the omission of aeration resulted in a total loss of formation of those polyols and trehalose, with ethanol being the only detectable product. Thus, respiration seems to favor the production of polyols including glycerol, as well as that of trehalose. With regard to glycerol, this finding is in contrast with the previous observation inSaccharomyces cerevisiae that oxygenation represses its production.     

Cloning and expression of Candida albicans ADE2 and proteinase genes on a replicative plasmid in C. albicans and in Saccharomyces cerevisiae.

Summary A plasmid vector (denoted pRC2312) was constructed, which replicates autonomously in Escherichia coli, Saccharomyces cerevisiae and Candida albicans. It contains LEU2, URA3 and an autonomously replicating sequence (ARS) from C. albicans for selection and replication in yeasts, and bla (ampicillin resistance) and ori for selection and replication in E. coli. S. cerevisiae AH22 (Leu^–) was transformed by pRC2312 to Leu^– at a frequency of 1.41 × 10⁵ colonies per g DNA. Transformation of C. albicans SGY-243 (Ura-) to Ura⁺ with pRC2312 resulted in smaller transformant colonies at a frequency of 5.42 × 10³ per g DNA where the plasmid replicated autonomously in transformed cells, and larger transformant colonies at a frequency of 32 per g DNA, in which plasmid integrated into the genome. Plasmid copy number in yeasts was determined by a DNA hybridization method and was estimated to be 15±3 per haploid genome in S. cerevisiae and 2–3 per genome in C. albicans replicative transformants. Multiple tandem integration occurred in integrative transformants and copy number of the integrated sequence was estimated to be 7–12 per diploid genome. The C. albicans ADE2 gene was ligated into plasmid pRC2312 and the construct transformed Ade^– strains of both C. albicans and S. cerevisiae to Ade⁺. The vector pRC2312 was also used to clone a fragment of C. albicans genomic DNA containing an aspartic proteinase gene. C. albicans transformants harboring this plasmid showed a two-fold increase in aspartic proteinase activity. However S. cerevisiae transformants showed no such increase in proteinase activity, suggesting the gene was not expressed in S. cerevisiae.     

Growth characteristics and oxidative capacity of<Emphasis Type="Italic"> Acetobacter aceti</Emphasis> IFO 3281: implications for <Emphasis Type="SmallCaps">l</Emphasis>-ribulose production

We studied the growth characteristics and oxidative capacities of Acetobacter aceti IFO 3281 in batch and chemostat cultures. In batch culture, glycerol was the best growth substrate and growth on ethanol occurred only after 6 days delay, although ethanol was rapidly oxidized to acetic acid. In continuous culture, both glycerol and ethanol were good growth substrates with similar characteristics. Resting cells in a bioreactor oxidized ribitol to l-ribulose with a maximal specific rate of 1.2 g g^–1 h^–1). The oxidation of ribitol was inhibited by ethanol but not by glycerol. Biomass yield (Y_SX; C-mmol/C-mmol) on ethanol and glycerol was low (0.21 and 0.17, respectively). In the presence of ribitol the yield was somewhat higher (0.25) with ethanol but lower (0.13) with glycerol, with respectively lower and higher CO₂ production. In chemostat cultures the oxidation rate of ribitol was unaffected by ethanol or glycerol. Cell-free extract oxidized ethanol very slowly but not ribitol; the oxidative activity was located in the cell membrane fraction. Enzymatic activities of some key metabolic enzymes were determined from steady-state chemostat with ethanol, glycerol, or ethanol/glycerol mixture as a growth limiting substrate. Based on the measured enzyme activities, metabolic pathways are proposed for ethanol and glycerol metabolism.     

Temnocephalan symbionts of the freshwater crayfish Cherax quadricarinatus from northern Australia

Four species of turbellarian temnocephalan symbionts (Platyhelminthes: Temnocephalida) are reported for the first time from the external surfaces of Cherax quadricarinatus, a freshwater crayfish from northern Australia. Three of these species — Temnocephala rouxii Merton, 1913, Notodactylus handschini (Baer, 1945), and Diceratocephala boschmai Baer, 1953 — are known previously from related crayfish in New Guinea. The newly discovered fourth species, Decadidymus gulosus n. gen., n. sp., has an unusual combination of characters linking it with both the Temnocephalidae and the Scutariellidae. Together the four species possess an array of characters that challenges current concepts of families in the order. D. boschmai has an almost completely ciliated epidermis, a feature otherwise unknown in the order.     

Characterisation of new symbiotic Medicago truncatula (Gaertn.) mutants, and phenotypic or genotypic complementary information on previously described mutants

From a pool of Medicago truncatula mutants—obtained by gamma-irradiation or ethyl methanesulfonate mutagenesis—impaired in symbiosis with the N-fixing bacterium Sinorhizobium meliloti, new mutants are described and genetically analysed, and for already reported mutants, complementary data are given on their phenotypic and genetic analysis. Phenotypic data relate to nodulation and mycorrhizal phenotypes. Among the five new mutants, three were classified as [Nod⁺ Fix^– Myc⁺] and the mutations were ascribed to two loci, Mtsym20 (TRV43, TRV54) and Mtsym21 (TRV49). For the two other new mutants, one was classified as [Nod^–/+ Myc⁺] with a mutation ascribed to gene Mtsym15 (TRV48), and the other as [Nod^– Myc^-/+] with a mutation ascribed to gene Mtsym16 (TRV58). Genetic analysis of three previously described mutants has shown that [Nod^–/+ Myc⁺] TR74 mutant can be ascribed to gene Mtsym14, and that [Nod^–/+ Myc^–/+] TR89 and TRV9 mutants are ascribed to gene Mtsym2 (dmi2). Using a detailed analysis of mycorrhizal phenotype, we have observed a delayed typical arbuscular mycorrhizal formation on some mutants that present thick lens-shaped appressoria. This phenotype was called [Myc^–/+] and mutants TR25, TR26, TR89, TRV9, P1 and Y6 were reclassified as [Myc^–/+]. Mutant P1 was reclassified as [Nod^–/+] because of a late nodulation observed on roots of this mutant.     

Gene expression profiles and intracellular contents of stress protectants in Saccharomyces cerevisiae under ethanol and sorbitol stresses

In response to osmotic stress, proline is accumulated in many bacterial and plant cells. During various stresses, the yeast Saccharomyces cerevisiae induces glycerol or trehalose synthesis, but the fluctuations in gene expression and intracellular levels of proline in yeast are not yet well understood. We previously found that proline protects yeast cells from damage by freezing, oxidative, or ethanol stress. In this study, we examined the relationships between the gene expression profiles and intracellular contents of glycerol, trehalose, and proline under stress conditions. When yeast cells were exposed to 1 M sorbitol stress, the expression of GPD1 encoding glycerol-3-phosphate dehydrogenase is induced, leading to glycerol accumulation. In contrast, in the presence of 9% ethanol, the rapid induction of TPS2 encoding trehalose-6-phosphate phosphatase resulted in trehalose accumulation. We found that intracellular proline levels did not increase immediately after addition of sorbitol or ethanol. However, the expressions of genes involved in proline synthesis and degradation did not change during exposure to these stresses. It appears that the elevated proline levels are due primarily to an increase in proline uptake from a nutrient medium caused by the induction of PUT4. These results suggest that S. cerevisiae cells do not accumulate proline in response to sorbitol or ethanol stress different from other organisms.     

Rapid and extensive vacuolation of the budding yeastsSaccharomyces cerevisiae andCandida albicans by amphotericin B

The effect of amphotericin B (AMPH) on vacuolation in the budding yeastsSaccharomyces cerevisiae andCandida albicans was studied. The minimum inhibitory concentration of AMPH for growth ofS. cerevisiae andC. albicans was 1 µg/ml. In untreated control cultures, mature cells had large central vacuoles in the exponential phase, which hampered the detection of vacuolation effect. Small buds in untreated exponential phase cells, however, only rarely showed vacuoles under the light microscope. Treatment with 0.2 µg/ml of AMPH for 20–30 min induced extensive vacuolation not only in mothers but also buds ofS. cerevisiae. Extensive vacuolation lasted 4 h or more, and growth rate of the cells was much reduced for 8 h or more. Vacuolation itself was not fatal: on removal of the drug most cells gradually recovered from vacuolation and eventually multiplied. A similar effect of AMPH was also observed inC. albicans but at a higher concentration (0.5 µg/ml).     

Ionic regulation of the unicellular green algaDunaliella tertiolecta: Response to hypertonic shock

Summary The evolution of the volume, the Na⁺ and K⁺ contents and the glycerol and ATP contents were investigated after subjectingDunaliella tertiolecta cells to hypertonic shocks. It was found that the variations in the glycerol and the ion contents superimpose as the cell regulates its volume. Hypertonic shock induces a rapid increase (some minutes) in the Na⁺ influx and Na⁺ content followed by a decrease until a new steady value is reached after 30 min of cell transfer. The regulatory mechanism extruding Na⁺ out of the cells was dependent on the presence of K^– or Rb^– ions in the external medium. A transient pumping of K⁺ ions was found after subjecting the cells to a hypertonic shock. This increase in K⁺ content resulted from the transient increase in the K⁺ influxes. The K⁺ pumping mechanism was blocked by the absence of Ca⁺⁺ and Mg⁺⁺ ions in the external medium and was inhibited by DCCD, FCCP and DCMU, whereas ouabain, cyanide and PCMBS were ineffective. The increase in K⁺ content was observed if the hypertonic shock was induced by the addition of NaCl, glycerol or choline chloride. These results are interpreted on the basis of two distinct mechanisms: a Na^–/K^– exchange pump and a Na⁺ independent K⁺ pump. These ionic transfer mechanisms would participate in the osmoregulation ofDunaliella cells and would be of importance, particularly during the onset of the osmotic shock when glycerol synthesis is incomplete.     

Inhibitory effect of dihydroxyacetone onGluconobacter oxydans: Kinetic aspects and expression by mathematical equations

Summary Microbial conversion of glycerol into dihydroxyacetone (DHA) byGluconobacter oxydans was subjected to inhibition by excess substrate. Comparison of cultures containing increasing initial DHA contents (0 to 100 g l^–1) demonstrated that DHA also inhibited this fermentation process. The first effect was on bacterial growth (cellular development stopped when DHA concentration reached 67 gl^–1), and then on oxidation of glycerol (DHA synthesis only occurred when the DHA concentration in the culture medium was lower than 85 g l^–1). Productivity, specific rates and, to a lesser extent, conversion yields decreased as initial concentrations of DHA increased. The changes in the specific parameters according to increasing initial DHA contents were described by general equations. These formulae satisfactorily express the concave aspect of the curves and the reduction in biological activity when the cells were in contact with DHA concentrations of up to 96 g l^–1.Abbreviations X, S, P biomass, substrate, product concentrations - r _x,r _s,r _p rates of growth, consumption and production - ,q _s,q _p specific rates of growth, glycerol consumption and DHA production - Y _x/s, Y_p/s conversion yields of substrate into biomass and product - K _s constant of affinity of cells to the substrate - K _ip product inhibition constant - P _m threshold concentration of DHA in substrate     

Control of arabitol formation in Schizophyllum commune development

Summary Dikaryotic cells of S. commune synthesized polyols throughout the life cycle when grown on glucose, cellobiose, or cellulose. Basidiospores contained arabitol and mannitol which were depleted during germination. The mannitol content of the young germlings rose to normal levels within a day; arabitol accumulation remained depressed for 5 to 7 days and then returned to normal levels characteristic of vegetative cells. Individual homokaryons differed in their production of intracellular polyols, which, unlike germlings, remained constant with cultural age. Homokaryon (str. 699) produced low levels of arabitol but high levels of glycerol while another homokaryon (str. 845) was the reverse. Mixtures of these homokaryons as well as the dikaryon (699×845) produced arabitol and glycerol levels intermediate between the parent homokaryons. High concentrations of glucose did not change the nature of the polyols produced. Arabitol formation could be induced prematurely in germlings or elevated in the dikaryon by growth on acetate or ethanol. Both homokaryons responded to growth on acetate with elevated arabitol production; acetate induction of arabitol formation was repressed in all types of cells if glucose were added simultaneously with acetate. Maltose, cellobiose, and trehalose also stimulated arabitol formation in young germlings, suggesting that glucose repression was the cause of decreased arabitol formation in basidiospore germlings. There was no correlation between the formation of arabitol and the derepression of isocitrate lyase or change in specific activities of alkaline and acid phosphatase in germlings grown on various carbon sources.     

DSP toxin contents inDinophysis fortii and scallops collected at Mutsu Bay,Japan

Cell densities of toxic phytoplankton species responsible for diarrhetic shellfish poisoning (DSP) were monitored at a sampling site in Mutsu Bay, Japan, in 1995.Dinophysis fortii almost completely dominated the toxic phytoplankton community. Okadaic acid (OA) and dinophysistoxin-1 (DTX1) contents in bothD. fortii cells and midgut glands of scallops collected at the same sampling site were determined by HPLC — fluorometry. DTX1 was detected fromD. fortii and scallops. The contents of DTX1 inD. fortii changed markedly during the experimental periods (5–252 pg cell^–1). The highest concentration of DTX1 in the midgut glands of scallops coincided with the period of relatively high cell densities ofD. fortii with the highest content of DTX1 (252 pg cell^–1). The results demonstrate that toxin content in the cells is an important factor affecting the toxicity of shellfish.     

Counterimmunoelectrophoresis and opportunistic fungal infections

Sera from 35 apparently normal humans, 37 compromised human patients, 30 hedgehogs and 30 sheep, were examined for precipitating antibodies to four opportunistic fungi — Absidia corymbifera, Aspergillus fumigatus, Candida albicans and Rhizopus arrhizus — using Counterimmunoelectrophoresis (CIE).Precipitins to A. fumigatus were almost exclusively confined to specimens obtained from the compromised human group (51% of those examined) while Candida precipitating antibodies were detected in the sera of both normal (26%) and compromised (49%) humans and in 10% of the hedgehog specimens. Serum precipitins against the two phycomycetes included in the investigations were rare.Because of the complexity of most fungal antigen extracts, it appears essential that sera be tested against a number of different antigen concentrations if CIE is to be used with confidence in fungal serology.     

Comparative effect of methioninyl adenylate on the growth of Salmonella typhimurium and Pseudomonas aeruginosa

The bacteriostatic effect of methioninyl adenylate (MAMP)—a specific inhibitor of the enzyme methionyl-tRNA synthetase—was investigated on Salmonella typhimurium and Pseudomonas aeruginosa.0.1 mM of this molecule added to the culture, inhibits the growth of S. typhimurium. The inhibition is specifically reversible by 0.1 mM L-methionine. In the same conditions even 1–2 mM MAMP has a very slight effect on the growth rate of P. aeruginosa and only during the first two generations. The same observation was made with the two other members of the fluorescens group P. fluorescens and P. putida.The growth rate of P. testosteroni with 1 mM MAMP in the medium is similar to the growth rate of P. aeruginosa but the other member of the acidovorans group P. acidovorans is much more affected by the same concentration of the inhibitor. — P. multivorans is inhibited by MAMP like P. acidovorans but with a somewhat higher yield at the end of the culture.—MAMP has no effect on P. alcaligenes.The possible reasons for the weak bacteriostatic effect of MAMP on P. aeruginosa were investigated. It was established that the inhibitor enters the cells and is not used as a carbon and energy source. The intracellular methionine concentration in S. typhimurium and in P. aeruginosa is about the same and does not increase when bacteria are cultivated with MAMP. The MTS of the two microorganisms is inhibited by MAMP in vitro to about the same extent. Furthermore the tRNA^met from P. aeruginosa are fully acylated after 3 to 4 generations with this compound. Nevertheless MAMP elicits higher MTS activity in P. aeruginosa and in P. acidovorans after 1 h of incubation. The most striking difference between S. typhimurium and P. aeruginosa is that the intra and extracellular level of 5phosphodiesterase which degrades MAMP is 10–20 fold higher in the second than in the first species.Non Standard Abbreviations MAMP Methioninyl adenylate - MTS methionyl-tRNA synthetase (EC 6.1.1.10) - VTS valyl-tRNA synthetase (EC 6.1.1.0) - Tris trihydroxymethylaminomethane Dedicated to Prof. R. Y. Stanier on the occasion of his 60th birthday     

Activity of North Jordan soil streptomycete isolates against Candida albicans

Eighteen percent of 116 different isolates of Streptomyces recovered from soils of northern Jordan showed activity against Candida albicans. The recovered isolates were distributed into three groups according to the diameter of the inhibition zone on the agar plate: group 1 (5–10 mm, slightly active); group 2 (11–15 mm, moderately active); and group 3 (16–35 mm, highly active). Isolates of group 3 were further grouped into four sub-groups and were culturally and morphologically identified. The u.v. spectra of the fermentation broth for the isolates in sub-group 4 were determined, and showed absorbance peaks ranging between 230 and 300 nm.     

Pollen morphology ofSonchus and related genera,and a general discussion

The pollen morphology of the taxa belonging to the generaAetheorhiza Cass.,Launaea Cass.,Reichardia Roth andSonchus L. in the Iberian Peninsula has been studied with light and electron microscopy. The pollen is 3(-4)-zonocolporate and echinolophate (without polar lacunae, but in general with prelacunae), with equatorial ridges and 15–20 lacunae: 3–4 poral, 6–8 abporal and 6–8 paraporal. Small to medium size, P × E = 19–36 × 23–42 µm; sometimes two different sizes have been found. Exine 3–9 µm thick and ornamentation microreticulate and echinate. The results clearly show the relationships between genera. Moreno-Socías, E., Mejías, J. A., Díez, M. J., 1994: Morfología polínica deLactuceae (Asteraceae) en la Península Ibérica, I.Lactuca y géneros relacionados. — Acta Bot. Malacitana.19: 103–113.     

Formation of Polar Bundles of Pili and the Behavior of Azospirillum brasilenseCells in a Semiliquid Agar

This paper describes the formation of single polar bundles of pili on Azospirillum brasilensecells, the twitching motility of cell aggregates, and a new type of social behavior—the dispersal of bacterial cells in semiliquid agar associated with the formation of granular inclusions (the so-called Gri⁺phenotype)—which is an alternative to swarming (the Swa phenotype). The wild-type A. brasilensecells occurring in a semiliquid agar may show either the Swa⁺Gri^–, or Swa^–Gri^–, or Swa^–Gri⁺phenotype. The formation of single polar flagella (Fla) or polar bundles of pili may reflect two alternative states of A. brasilensecells. The components of the Fla system may be involved in the regulation of the phenotypic variation of azospirilla.     

Carbohydrates in the hypothallus and areolae of the crustose lichen <Emphasis Type="Italic">Rhizocarpon geographicum</Emphasis> (L.) DC.

Carbohydrate concentrations in the marginal hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC. were measured in north Wales, U.K. using gas chromatography. Ribitol, arabitol, and mannitol were the most abundant carbohydrates while α- glucose β-glucose, fructose, sucrose, and trehalose were present in smaller amounts. The concentrations of arabitol, ribitol, mannitol, fructose, and α-glucose were greater in the areolae while the concentration of trehalose was greater in the hypothallus. Concentrations of carbohydrates varied little between sample days. Concentrations of polyols in the hypothallus were not correlated with those in the areolae. These results suggest: 1) the hypothallus has a lower demand for carbohydrates than the areolae or there is limited transport from areolae to hypothallus, 2) increased trehalose in the non-lichenised hypothallus may be an adaptation to withstand stress and desiccation, and 3) polyols are partitioned differently in the hypothallus and areolae.