Interactions ofCandida albicans with bacteria and salivary molecules in oral biofilms

The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed.     

Antibiotic production by the cyanobacteriumNostoc muscorum

A broad spectrum antimicrobial antibiotic is produced byNostoc muscorum (Lancashire Polytechnic Culture Collection 23) during the post-exponential phase of growth. The antibiotic inhibits the growth of bacteria, notably multiple-resistantStaphylococcus aureus, and a biocide resistantPseudomonas aeruginosa: fungi such as the biodeteriogens,Cladosporium herbarum andHormoconis resinae and yeasts such asCandida albicans andC. pseudotropicalis. The antibiotic has an apparent molecular weight of 2000–3000 Daltons. Production appears to be dependent upon the limitation of one or more nutrients in the medium. author for correspondence     

Toxicity and accumulation of thallium in bacteria and yeast

Thallium sulphate inhibited microbial growth, withBacillus megaterium KM, more sensitive to the metal thanSaccharomyces cerevisiae andEscherichia coli. Inhibition ofB. megaterium KM andS. cerevisiae, but not ofE. coli, was alleviated by increasing the potassium concentration of the medium; inhibition of respiration ofS. cerevisiae, but not ofE. coli, was similarly alleviated. Thallium was rapidly bound, presumably to cell surfaces, byS. cerevisiae andE. coli, and was progressively accumulated by energy-dependent transport systems (probably concerned primarily with potassium uptake) with both organisms. Thallium uptake kinetics suggested more than one transport system operated in yeast, possibly reflecting a multiplicity of potassium transport systems. ApparentK _m andK _i values for competitive inhibition of thallium uptake by potassium indicatedS. cerevisiae to have a higher affinity for thallium uptake than for potassium, whileE. coli had a transport system with a higher affinity for potassium than for thallium. The likely systems for thallium transport are discussed. A mutant ofE. coli with tenfold decreased sensitivity to thallium was isolated and apparently effected surface binding of thallium in amounts equivalent to the wild type organism, but showed no subsequent uptake and accumulation of the metal from buffer, even though it was able to accumulate potassium to normal intracellular concentrations during growth. Abbreviations: Metal are referred to by their recognised atomic symbols (e.g. TI = Thallium; K = potassium; Co = cobalt)     

Antifungal effects of new heterocyclic compounds, 6H-pyrimido[2,1-a]isoindole derivatives

Minimal inhibitory concentrations for 10 new condensed isoindole derivatives were established by the agar diffusion method. Benzo[b]-6H-pyrimido[2,1-a]isoindole-4-one exhibited a broad antifungal effect; the observed MIC (mg/L) were 7 (K. lactis), 8 (C. pseudotropicalis), 17 (W. fluorescens), 22 (E. magnusii), 31 (P. membranaefaciens), 32 (S. alluvius) and 32 (S. cerevisiae). The compound also inhibited the growth ofB. subtilis (MIC 9 mg/L). No effect on the growth ofE. coli was found.     

Antagonistic interactions between fungal pathogens and phylloplane fungi of guava

Dominant phylloplane fungi of guava (Psidium guajava L.) were screened for their antagonistic activities against the two pathogens,Colletotrichum gloeosporioides andPestalotia psidii, bothin vitro andin vivo. Culture filtrates ofAspergillus niger, Fusarium oxysporum andPenicillium citrinum caused more than 50% growth inhibition ofC. gloeosporioides. Filtrates ofCephalosporium roseo-griseum andF. oxysporum were most effective in reducing the growth ofP. psidii. Volatiles produced from the cultures ofA. niger, F. oxysporum, P. citrinum andP. oxalicum inhibited the growth ofC. gloeosporioides, whereas volatiles fromC. roseo-griseum, F. oxysporum andTrichoderma harzianum inhibited the growth ofP. psidii. The inhibitory effect of volatiles decreased with increase in incubation time. In general, the maximum effect of volatiles was noticed after 48 h incubation. Different grades of colony interactions in dual cultures were recognised between the two pathogens and the phylloplane fungi examined. Maximum inhibition ofC. gloeosporioides was caused byAureobasidium pullulans, Cladosporium cladosporioides, epicoccum purpurascens, F. oxysporum andMyrothecium roridum, whereasAspergillus terreus, C. roseo-griseum andP. oxalicum significantly reduced the growth ofP. psidii. Application of a spore suspension of each test fungus inhibited lesion development of guava leaves caused by the test pathogensin vitro. Inhibition was more pronounced when the spore concentration was increased.A. pullulans, C. cladosporioides, E. purpurascens, F. oxysporum, andT. harzianum were found to be strongly antagonistic toC. gloeosporioides. A. niger, A. terreus, C. roseo-grisem andT. harzianum were strongly antagonistic toP. psidii.     

Growth requirements of some fungi causing maduromycosis

Three strains ofMadurella mycetomi, two ofM. grisea, and two ofRhinocladiella mansonii have been studied for possible differences in growth requirements which might be used for distinguishing these species. Under the experimental conditions, an incubation temperature of 37C suitedM. mycetomi about as well as 30C.R. mansonii grew less well at 37C than at 30C, andM. grisea did not grow at the higher temperature. M. grisea andR. mansonii further differed fromM. mycetomi in that they required thiamine for growth. The pH tolerance of all the strains was very wide. Asparagine and potassium nitrate were readily utilized by all the strains, but ammonium salts were not. Urea was poorly used byM. mycetomi; the other species did not use it. A possible relationship ofM. grisea andR. mansonii is discussed.     

Plant growth, phosphorus nutrition, and root morphological responses to arbuscular mycorrhizas, phosphorus fertilization, and intraspecific density

We examined the effects of arbuscular mycorrhizas (AM), phosphorus fertilization, intraspecific density, and their interaction, on the growth, phosphorus uptake, and root morphology of three facultative mycotrophic crops (Capsicum annuum, Zea mays, and Cucurbita pepo). Plants were grown in pots with or without AM at three densities and four phosphorus availabilities for 10 weeks. AM colonization, plant weight, and shoot phosphorus concentration were measured at harvest. Root morphology was assessed for C. annuum and Z. mays. Phosphorus fertilization reduced but did not eliminate AM colonization of all species. AM, phosphorus, and density interacted significantly to modify growth of C. annuum and C. pepo such that increased density and phosphorus diminished beneficial effects of AM. Increased density reduced positive effects of AM on C. annuum and C. pepo shoot phosphorus concentrations. AM altered both Z. mays and C. annuum root morphology in ways that complemented potential phosphorus uptake by mycorrhizas, but increased density and phosphorus diminished these effects. We infer that increased density predominantly influenced plant responses by affecting whether or not carbon (photosynthate) or phosphorus limited plant growth. By exacerbating carbon limitation, high density reduced the benefit/cost ratio of mycorrhizas and minimized their effects.     

Growth characteristics,nutrient allocation and photosynthesis ofCarex species from floating fens

Summary The purpose of this study was to investigate various growth parameters, dry matter and nitrogen, phosphorus and potassium allocation and photosynthesis ofCarex acutiformis, C. rostrata andC. diandra growing in fens with, in this order, decreasing nutrient availability and decreasing aboveground productivity. Plants were grown from cuttings at optimum nutrient conditions in a growth chamber. Growth analysis at sequential harvests revealed that the species had no inherently different relative growth rates which could explain their different productivity, but that their LAR (LWR and SLA) decreased in the orderC. acutiformis, C. rostrata, C. diandra and their NAR increased in this order. All growth parameters decreased during plant growth even under the controlled conditions of the experiment.C. acutiformis allocated relatively much dry matter to the leaves,C. rostrata to the rhizomes andC. diandra to the roots. This may, in part, explain the higher aboveground biomass production ofC. acutiformis in the field. Nitrogen, but not phosphorus and potassium, allocation patterns were different for the three species.C. diandra, the species from the nitrogen-poorest site, had the highest leaf N content of the three species and also a higher chlorophyll content. Related to this, this species had the highest photosynthetic activity of whole plants both when collected from the field and when grown in the growth chamber. The nitrogen productivity was similar for the three species and the photosynthetic nitrogen use efficiency, determined forC. acutiformis andC. diandra, was similar for these two species.C. diandra had the most finely branched root system, i.e., the highest specific root length of the three species and its root surface area to leaf surface area ratio was also the highest. All three species showed higher nitrate reductase activity in the leaves than in the roots when grown on nutrient solution. The growth ofC. diandra at a relatively nutrient-poor site and a rather open low vegetation is assumed to be adapted to its habitat by a relatively high NAR made possible by a high rate of photosynthesis concurrent with a high leaf N content. The growth ofC. acutiformis at a relatively nutrient-rich site and a more dense and higher vegetation is adapted to its habitat by a high LAR.     

Fungal succession and decay of herbicide-treated wheat straw

The effects of alachlor and haloxyfop on wheat straw decay and fungal succession were studied in laboratory trials. Wheat straw segments were immersed in (100 and 1 000 mg/L) herbicides, buried in soil and incubated at 28±1°C for 8 weeks. Both herbicides significantly stimulated the mass loss and N-mineralization of wheat straw. CO₂ evolution was not significantly affected while C-mineralization was inhibited. The pattern of succession of fungi was slightly affected in herbicidetreated wheat straw. However, the frequency of occurrence ofRhizopus stolonifer was lowered throughout all experimental periods. In a pure culture experiment, both alachlor and haloxyfop at 100, 500 and 1 000 mg/L reduced the radial growth ofAlternaria alternata, Aspergillus niger, A. flavus, Penicillium funiculosum, R. stolonifer andTrichoderma harzianum.     

Effect of berberine on growth of the callus cultures of several species

A bacteriostatic concentration of berberine much inhibited growth of the callus cultures ofLithospermum erythrorhizon, Datura inooxia andCarthamus tinctorius, but little inhibited the callus growth ofMacleaya cordata. On the other hand, the high concentration of berberine tended to stimulate the callus growth ofCoptis japonica var.japonica. Among callus cultures of the five species described above, 4-desoxypyridoxine inhibited growth of the callus cultures ofD. innoxia andC. tinctorius. In these two callus cultures, recovery effects of some of the vitamin B₆ group (10 μg/ml) on the inhibition of callus growth by berberine (100 μg/ml) or 4-desoxypyridoxine (50 μg/ml) were observed.     

Effects of tellurite on growth of Saccharomyces cerevisiae

The effects of potassium tellurite on growth and survival of rho⁺ and rho⁰ Saccharomyces cerevisiae strains were investigated. Both rho⁺ and rho⁰ strains grew on a fermentable carbon source with up to 1.2 mM K₂TeO₃, while rho⁺ yeast cells grown on a non-fermentable carbon source were inhibited at tellurite levels as low as 50 μM suggesting that this metalloid specifically inhibited mitochondrial functions. Growth of rho⁺ yeast cells in the presence of increasing amount of tellurite resulted in dose-dependent blackening of the culture, a phenomenon not observed with rho⁰ cultures. Transmission electron microscopy of S. cerevisiae rho⁺ cells grown in the presence of tellurite showed that blackening was likely due to elemental tellurium (Te⁰) that formed large deposits along the cell wall and small precipitates in both the cytoplasm and mitochondria.     

Effect of sorbic acid and potassium sorbate on growth ofBacillus cereus andBacillus subtilis in rice filling of Karelian pasty

Summary The Karelian pasty is a perishable bakery product: the pH of the rice filling is approximately 6.60 and the a_W=0.98. Contamination after baking was shown to be the most important reason for microbial spoilage. The rice fillings of the pasties were artificially contaminated by spores ofBacillus cereus andB. subtilis, and growth at room temperature was followed.B. cereus was totally inhibited by an addition of 0.20% sorbic acid or 0.40% potassium sorbate.B. subtilis was totally inhibited by an addition of 0.10% sorbic acid or 0.26% potassium sorbate. An addition of 0.10% sorbic acid to the filling before baking is recommended. This level of addition does not alter the organoleptic quality of the pasty but is a considerable safety factor for Karelian pasty production.     

Fungal diseases of the respiratory tract

The proportion ofCandida and non-Candida species in the clinical material from patients. with respiratory-tract diseases was determined.C. albicans was isolated in 102 cases. An additional 89 strains of yeasts, isolated in association with respiratory diseases, belonged to 10 non-albicans Candida spp. andCryptococcus spp. The prevailing species, which occurred in 47 cases, wasC. parapsilosis. C. tropicalis, C. glabrata, andC. guilliermondii were isolated in 12, 10, and 9 cases, respectively. Four strains ofC. krusei and three strains ofC. lusitaniae and one strain each ofC. freyschussii, C. robusta, C. zeylanoides, andCryptococcus neoformans were also isolated.     

Reduction of selenium oxyanions by unicellular,polymorphic and filamentous fungi: Cellular location of reduced selenium and implications for tolerance

Summary The ability of several filamentous, polymorphic and unicellular fungi to reduce selenite to elemental selenium on solid medium was examined.Fusarium sp. andTrichoderma reeii were the only filamentous fungi, of those tested, which reduced selenite to elemental selenium on Czapek-Dox agar resulting in a red colouration of colonies. Other organisms (Aspergillus niger, Coriolus versicolor, Mucor SK, andRhizopus arrhizus) were able to reduce selenite only on malt extract agar. Several fungi were able to grow in the presence of sodium selenite but were apparently unable to reduce selenite to elemental selenium, indicating that other mechanisms of selenite tolerance were employed, such as reduced uptake and/or biomethylation to less toxic, volatile derivatives. Sodium selenate was more toxic toFusarium sp. than selenite, and the toxicity of both oxyanions was increased in sulphur-free medium, with this effect being more marked for selenate. Scanning electron microscopy ofAspergillus funiculosus andFusarium sp. incubated with sodium selenite showed the presence of needle-like crystals of elemental selenium on the surfaces of hyphae and conidia, while transmission electron microscopy ofA. funiculosus revealed the deposition of electron-dense granules in vacuoles of selenite-treated fungi. Several yeasts were able to grow on MYGP agar containing sodium selenate or sodium selenite at millimolar concentrations. Sone, notablyRhodotorula rubra andCandida lipolytica, and the polymorphic fungusAureobasidium pullulans were also effective at reducing selenite to elemental selenium, resulting in red-coloured colonies.Schizosaccharomyces pombe was able to grow at selenite concentrations up to 5 mmol L^–1 without any evidence of reduction, again indicating the operation of other tolerance mechanisms.     

Evaluation of Media for Selective Isolation of Yeasts from Oral, Rectal, and Burn Wound Specimens

Six media were evaluated to determine their ability to isolate yeasts and inhibit bacteria. The media included the following: Snyder, Snyder tellurite, Sabouraud tellurite, Littman-gentamicin, molybdate, and Mycosel (BBL). Doses of mixed intestinal gram-negative bacilli and enterococci were most effectively inhibited by Snyder tellurite agar. Klebsiella pneumoniae was the most common bacterial contaminant of the other media. All six media were comparable in isolating yeasts while preventing the growth of the oral bacterial flora. The selection of a basal fungal growth medium for tellurite incorporation to inhibit bacteria but permit growth of yeasts was affected by pH. The bacteriostatic effect of tellurite was decreased with increasing pH of media while fungistatic action was increased. The arbitrary selection of Snyder and Littman agars to isolate yeast from burn wound cultures demonstrated the need to include a selective medium for these specimens. Blood, phenylethyl alcohol blood agar, and Columbia CN blood agar were all inadequate for isolating yeasts from burns. Growth of a variety of filamentous saprophytic and pathogenic dimorphic fungi grew adequately on four of five selective media tested.     

Seasonal variation in allelopathic potential of<Emphasis Type="Italic">Artemisia princeps</Emphasis> var.<Emphasis Type="Italic">orientalis</Emphasis> on plants and microbes

We investigated seasonal variations in allelopathic potential ofArtemisia princeps var.orientalis. Aqueous and meth-anol extracts and volatile substances were prepared in the laboratory from samples collected monthly (April through October). Their impacts were then assessed on the germination and seedling growth ofLactuca sativa andAchyranthes japonica. The allelopathic potential varied with the time of sample collection and the concentration tested. For example, germination ofL. sativa was not inhibited by the aqueous extract but seedling growth (shoots and roots) was, with its seasonal effect being significant. ForA. japonica, seed germination was not inhibited at lower concentrations (except for August samples). However, at higher concentrations and in certain months (especially July), germination was more negatively affected. The degree of seedling growth inhibition also differed by month and by extract concentration, with roots being impacted more than shoots. Volatile substances also had a time-dependent influence on the germination and seedling elongation ofA. japonica. In a separate experiment, the ethyl-acetate and water fractions of a crude methanol extract were prepared monthly fromA. princeps var.orientalis. Here, we examined their antimicrobial activities against three gram-positive bacteria (Bacillus cereus, Bacillus subtilis, andStaphylococcus aureus), two gramnegative bacteria (Escherichia coli andPseudomonas fluorescens), and one lactic acid bacterium,Lactobacillus plantar urn. The ethyl-acetate fraction that was sampled in September was remarkably potent againstB. cereus andB. subtilis, whereas the water fraction collected in August and September showed great antimicrobial activity against the grampositive and -negative bacteria. In contrast,L. plantarum was not inhibited by the water fraction, regardless of the sampling month. Likewise, the ethyl-acetate and water fractions collected in April and October had the lowest levels of antimicrobial activity.     

Cytological aspects of resistance to potassium tellurite conferred on Pseudomonas cells by plasmids

The ultrastructure of strains Pseudomonas putida BS228 and Pseudomonas aeruginosa ML4262 harboring plasmids pBS10, pBS31, and pBS221, which determine resistance to potassium tellurite, was studied. Bacteria were grown in media containing increasing concentrations of potassium tellurite. Crystalline structures containing tellurium appeared in their periplasmic space. The dynamics of crystal growth was studied. Crystals were released into the medium by pinching off of the outer membrane vesicles containing growing crystals. A possible mechanism of this process was described; cytobiochemical peculiarities were discussed.     

Changes in the intracellular concentrations of the adenosine phosphates and nicotinamide adenine dinucleotides ofSaccharomyces cerevisiae during batch fermentation

Significant changes in the intracellular concentrations of adenosine phosphates and nicotinamide adenine dinucleotides were observed during fermentation of grape must by three different strains ofSaccharomyces cerevisiae: S. cerevisiae var.cerevisiae, a typical fermentative yeast strain and two flor-veil-forming strains,S. cerevisiae var.bayanus andS. cerevisiae var.capensis. The intracellular concentration of ATP was always higher inS. cerevisiae var.cerevisiae than in the flor-veil-forming strains. NAD⁺ and NADP⁺ concentrations decreased at faster rates in the flor-veil-forming yeasts than in the other yeast but NADH concentration was the same in all yeasts for the first 10 days of fermentation. NADPH concentration was always lower inS. cerevisiae var.cerevisiae than in the other yeasts and this yeast also showed higher rates of growth and fermentation during the early stages of the fermentation and the presence of non-viable cells at the end of fermentation. In contrast, the flor-veil-forming strains maintained growth and fermentation capabilities for a relatively long time and viable cells were present throughout the entire fermentation process (31 days).The authors are with the Department of Microbiology, Faculty of Sciences, University of Cordoba, Avda. San Alberto Magno s/n, 14004-Córdoba, Spain     

Candidaemia in cancer patients and in children in a neonatal intensive care unit

The species most frequently found in the group of neonates wasC. parapsilosis, its incidence reaching 48%. Other yeasts isolated from blood wereC. albicans (41%),C. tropicalis (7%),C. krusei andC. pseudotropicalis (2% each). Six yeast species (C. albicans 44%,C. parapsilosis 28%,C. tropicalis 11%,C. krusei 8%,C. guilliermondii 6%,C. lusitaniae 3%) were detected in cancer patients. The presence of an intravenous catheter as a possible risk in the development of candidaemia was identified in all neonates and in 69% of cancer patients.C. krusei candidaemia was associated with prophylactic fluconazole therapy.     

Biological control of white rot of onion

Summary Interactions of 123 isolates of fungi, 17 of bacteria and 22 of actinomycetes, respectively, withSclerotium cepivorum were studied in agar culture. They were grouped into 4 different types of reactions. Amongst themTrichoderma viride, Fusarium graminearum, Coniothyrium minitans andGliocladium roseum inhibited the growth ofS. cepivorum and later grew over its colony.T. viride showed a characteristic coiling around the hyphae ofS. cepivorum. T. viride andF. graminearum prevented the development of sclerotia.C. minitans was found to parasitize the sclerotia ofS. cepivorum and produced its pycnidia within them.Aleurisma carnis, Cladosporium elatum, Penicillium expansum, P. nigricans, P. notatum, P. piscarium, P. puberulum, P. rolfsii, P. urticae, P. variabile, Tilachlidium humicola andHelminthosporium sp. inhibited the growth ofS. cepivorum at a distance. Eleven isolates of bacteria and 3 ofStreptomyces sp. showed pronounced antagonistic properties againstS. cepivorum.Experiments were carried out to study the effects on white rot development in soil of organisms selected from agar plate tests. None of the antagonistic micro organisms had any deleterious effects on onion growth. Of the organisms testedP. nigricans gave the best results in controlling white rot infection.This work was carried out at the Department of Botany, The University, Birmingham, England. I wish to thank Prof.C. J. Hickman for his invaluable advice and encouragement.