Composition of lipids produced by some strains ofCandida species. Production of single-cell oil in a chemostat culture

Fatty acid composition of the lipids produced by four strains ofCandida species was studied. Oleic acid was the principal fatty acid. Cellular lipids ofCandida sp. andC. pulcherima were rich in palmitic acid. Lipids fromC. lipolytica contained a significant amount of palmitoleic acid, whereasC. farinosa produced oil rich in stearis and α-linolenic acid. Analysis of cellular lipids ofCandida sp. andC. pulcherima during growth on a nitrogen-limited medium showed that oils accumulated in the exponential growth phase were more unsaturated than those accumulated in the decelerating and stationary phases. In a chemostat culture,Candida sp. accumulated about 40% of lipid. The specific rate of lipid formation, at a dilution rate ofD=0.09/h, was 35 mg of lipid per g of biomass per h and the yield of lipid on glucose was 11.4%.     

酵母菌促进铅和镉胁迫下麻疯树生长的研究

为了筛选对铅和镉具有抗性和吸附性的酵母菌,构建麻疯树根系-酵母菌联合修复体系,促进高浓度铅和镉胁迫下麻疯树的生长。该研究分别从麻疯树的根段、珙桐的茎段、珙桐的根段分离到3株具有铅、镉抗性的酵母菌,分别命名为Jc、Di1、Di2,测定了三者对铅、镉的抗性和吸附性,并将筛选出的2株能吸附铅、镉的酵母菌菌株接种到麻疯树幼苗,研究接种两种酵母菌的麻疯树植株对铅、镉胁迫的响应。结果表明:经形态学和生理生化特征观察,Jc初步鉴定红酵母属(Rhodotorula sp.),Di1为假丝酵母属(Candida sp.),Di2为德巴利酵母属(Debaryomyces sp.)。三种酵母菌对铅、镉都有一定的抗性,其抗性能力的大小为JcDi2Di1。Di1和Jc对铅和镉都具有一定的吸附性将其用于接种麻疯树幼苗。与不接种酵母菌(CK)的麻疯树植株相比,接种Di1和Jc的麻疯树植株在根、茎、叶、全株干重方面显著增加,叶绿素、全株氮、全株磷浓度显著增加,SOD、POD、CAT的活性提高,丙二醛(MDA)浓度显著下降。从综合接种效应来看,Jc、Di1作为铅、镉的钝化剂,是铅、镉胁迫下促进麻疯树生长的备选菌株,这对于提高麻疯树对铅、镉污染土壤修复效率具有重要的意义。     

Effects of Cultural Conditions on Mononucleotide Phosphorylating Activity of Yeast Cells

It was found that the AMP phosphorylating activity of Candida sp. N–25–2 (a hydrocarbon assimilating yeast) was affected extremely by the liquid volume of cultural medium and the concentration of inorganic salts in medium. The yeast cells having no fermentative activity showed a strong activity of AMP phosphorylation when they were cultured under relative anaerobic conditions. It was observed that the glucose consumption of yeast cells was promoted by the addition of Mg²⁺ ion and AMP into the reaction system, and that the AMP phosphorylation was promoted in the presence of F-1,6-DP or phosphaenolpyruvate.

The cells of Candida sp. N–25–2 grown on glucose medium had a remarkable fermentative activity, while the cells grown on acetate or ethanol medium had a weak activity. On the other hand, it was found that the cells grown at strong aeration on glucose medium were able to produce remarkably the phosphorylated substances from mononucleotides, when F-1,6-DP was added as a phosphate donor. Similar phenomenon was observed in case of the cells grown on the carbon sources such as acetate, ethanol and hydrocarbon.     

Aggregate formation in a freshwater bacterial strain induced by growth state and conspecific chemical cues

We investigated the induction of aggregate formation in the freshwater bacterium Sphingobium sp. strain Z007 by growth state and protistan grazing. Dialysis bag batch culture experiments were conducted in which these bacteria were grown spatially separated from bacteria or from co‐cultures of bacteria and predators. In pure cultures of Sphingobium sp. strain Z007, the concentrations of single cells and aggregates inside and outside the dialysis membranes developed in a similar manner over 3 days of incubation, and the proportions of aggregates were highest during the exponential growth phase. Cell production of Sphingobium sp. strain Z007 was enhanced in the presence of another isolate, Limnohabitans planktonicus, from an abundant freshwater lineage (R‐BT065) outside the bags, and even more so if that strain was additionally grazed upon by the bacterivorous flagellate Poterioochromonas sp. However, the ratios of single cells to aggregates of Sphingobium sp. strain Z007 were not affected in either case. By contrast, the feeding of flagellates on Sphingobium sp. strain Z007 outside the dialysis bags led to significantly higher proportions of aggregates inside the bags. This was not paralleled by an increase in growth rates, and all cultures were in a comparable growth state at the end of the experiment. We conclude that two mechanisms, growth state and the possible release of infochemicals by the predator, may induce aggregate formation of Sphingobium sp. strain Z007. Moreover, these infochemicals only appeared to be generated by predation on cells from the same species.     

Modulation of tolerance to Cr(VI) and Cr(VI) reduction by sulfate ion in a <Emphasis Type="Italic">Candida</Emphasis> yeast strain isolated from tannery wastewater

The main aim of this study was to investigate the influence of the sulfate ion on the tolerance to Cr(VI) and the Cr(VI) reduction in a yeast strain isolated from tannery wastewater and identified as Candida sp. FGSFEP by the D1/D2 domain sequence of the 26S rRNA gene. The Candida sp. FGSFEP strain was grown in culture media with sulfate concentrations ranging from 0 to 23.92 mM, in absence and presence of Cr(VI) [1.7 and 3.3 mM]. In absence of Cr(VI), the yeast specific growth rate was practically the same in every sulfate concentration tested, which suggests that sulfate had no stimulating or inhibiting effect on the yeast cell growth. In contrast, at the two initial Cr(VI) concentrations assayed, the specific growth rate of Candida sp. FGSFEP rose when sulfate concentration increased. Likewise, the greater efficiencies and volumetric rates of Cr(VI) reduction exhibited by Candida sp. FGSFEP were obtained at high sulfate concentrations. Yeast was capable of reducing 100% of 1.7 mM Cr(VI) and 84% of 3.3 mM Cr(VI), with rates of 0.98 and 0.44 mg Cr(VI)/L h, with 10 and 23.92 mM sulfate concentrations, respectively. These results indicate that sulfate plays an important role in the tolerance to Cr(VI) and Cr(VI) reduction in Candida sp. FGSFEP. These findings may have significant implications in the biological treatment of Cr(VI)-laden wastewaters.     

Studies on the Low Temperature Fermentation

A marine yeast, strain MM313 was isolated from a marine sediment sample at depth of 1120 m. The organism was identified as a Candida sp. MM313. The yeast was able to utilize n-paraffin, n-C₁₀ to n-C₂₀. Regardless of its origin, the organism grew in a medium prepared with fresh water. However, the cell yield increased with increasing concentration of each salt in sea water in the medium and reached a maximum value at the concentration of 75%. The cultivation temperature for the maximum rate of growth and that for the maximum level of growth were 28° and 10°C, respectively. Several cultural conditions were investigated. The cell yields to n-paraffins were about 85% at 15°C after 4 days and 56% at 28°C after 3 days under optimal conditions.     

Candida-induced Oral Epithelial Cell Responses

Objective: Oropharyngeal candidiasis (OPC), caused by Candida albicans, is the most common oral infection in HIV⁺ persons. Oral epithelial cells are considered important for innate host defense against OPC with production of cytokines in response to C. albicans and the ability to inhibit Candida growth in vitro. The purpose of this study was to determine if Candida similarly induces cytokines by oral epithelial cells from HIV⁺ persons, including those with OPC, as well as to determine if cytokines can influence the oral epithelial cell anti-Candida activity. Methods: Supernatants from oral epithelial cells from HIV⁺ persons with and without OPC cultured with Candida were evaluated for cytokines by ELISA, or cytokines were added to the standard growth inhibition assay using epithelial cells from HIV⁻ persons. Results: Results showed low Candida-induced epithelial cell cytokine production from HIV⁺ persons, but with some elevated proinflammatory cytokines (TNF-α, IL-6) in those with OPC compared to those without OPC. The addition of specific proinflammatory or Th cytokines had no effect on oral epithelial cell anti-Candida activity in healthy HIV⁻ persons. Conclusion: These results suggest that oral epithelial cells from HIV⁺ persons can contribute at some level to the oral cytokine milieu in response to Candida during OPC, but that cytokines do not appear to influence oral epithelial cell anti-Candida activity.     

THE EFFECT OF PHOSPHATE STATUS ON THE KINETICS OF CYANOPHAGE INFECTION IN THE OCEANIC CYANOBACTERIUM SYNECHOCOCCUS SP. WH78031

Phycoerythrin-containing Synechococcus species are considered to be major primary producers in nutrient-limited gyres of subtropical and tropical oceanic provinces, and the cyanophages that infect them are thought to influence marine biogeochemical cycles. This study begins an examination of the effects of nutrient limitation on the dynamics of cyanophage/Synechococcus interactions in oligotrophic environments by analyzing the infection kinetics of cyanophage strain S-PM2 (Cyanomyoviridae isolated from coastal water off Plymouth, UK) propagated on Synechococcus sp. WH7803 grown in either phosphate-deplete or phosphate-replete conditions. When the growth of Synechococcus sp. WH7803 in phosphate-deplete medium was followed after infection with cyanophage, an 18-h delay in cell lysis was observed when compared to a phosphate-replete control. Synechococcus sp. WH7803 cultures grown at two different rates (in the same nutritional conditions) both lysed 24 h postinfection, ruling out growth rate itself as a factor in the delay of cell lysis. One-step growth kinetics of S-PM2 propagated on host Synechococcus sp. WH7803, grown in phosphate-deplete and-replete media, revealed an apparent 80% decrease in burst size in phosphate-deplete growth conditions, but phage adsorption kinetics ofS-PM2 under these conditions showed no differences. These results suggested that the cyanophages established lysogeny in response to phosphate-deplete growth of host cells. This suggestion was supported by comparison of the proportion of infected cells that lysed under phosphate-replete and-deplete conditions, which revealed that only 9.3% of phosphate-deplete infected cells lysed in contrast to 100% of infected phosphate-replete cells. Further studies with two independent cyanophage strains also revealed that only approximately 10% of infected phosphate-deplete host cells released progeny cyanophages. These data strongly support the concept that the phosphate status of the Synechococcus cell will have a profound effect on the eventual outcome of phage-host interactions and will therefore exert a similarly extensive effect on the dynamics of carbon flow in the marine environment.     

Yeast cultivation in lettuce brine

The use of lettuce brine, a by-product of the vegetable fermentation industry, as a medium for yeast cultivation was investigated. Six strains of yeast, Saccharomyces sp., Pichia sp., Rhodotorula sp., Candida sp., Kluyveromyces sp. and Trichospora sp. grew well in diluted lettuce brine under aerobic conditions. The acid brine becomes neutral after yeast cultivation. The yeast strains reached the maximum growth after the first day of cultivation. Trichosporon sp. was found to grow best in the brine with the maximum specific growth rate at 0.09 h⁻¹ and growth yield of 67%. This revised version was published online in November 2006 with corrections to the Cover Date.     

Establishment of callus and cell suspension cultures from Gypsophila paniculata leaf segments and study of the attachment of host cells by Erwinia herbicola pv. gypsophilae

Callus and cell suspension cultures were initiated from leaf segments of G. paniculata. Fresh and dry weights measurements of callus showed that callus growth was optimal on MS medium supplemented with 1.0 mg l^–1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.2 mg l^–1 benzyladenin (BA). Calli cultured on this medium, showed a two-fold increase in fresh weight by the fourth week of incubation. The initiated hard green callus was repeatedly subcultured on MS medium containing increasing concentrations of 2,4-D in order to increase its friability. The friable callus was then used for establishment of a cell suspension culture. Maximum growth of the suspension culture was on medium supplemented with 1.0 mg l^–1 2,4-D and 0.2 mg l^–1 BA.The suspension culture was used for studying plant host attachment in both electron and light microscopy. Upon infection with E. herbicola, plant cells showed aggregate formation within 24 h of infection. In the presence of the pathogenic Ehg,the number of aggregates formed was 342 aggregates ml^–1, in the presence of the non-pathogenic Ehg154 aggregates ml^–1 and in the control 115 aggregates ml^–1. These results show that the pathogenic strain causes formation of cell aggregates 5.8 times greater than the non-pathogenic one. Based on these results, it can be hypothesized that bacterial cells of the pathogenic strains bind to the plant cells and may form a bridge for attachment of plant cells to one another. Observations by electron microscope show that bacterial cells do attach to plant cells and that this attachment might be via formation of a bridge between the bacteria and the plant cell.     

Behavior of cell aggregate of Carthamus tinctorius L. cultured cells and correlation with red pigment formation

The formation processes of Carthamus tinctorius cell aggregates in a growth medium and the correlation of red pigment formation with cell aggregate sizes were investigated. About 80% of cell aggregates in the growth medium were > 1.00 mm in size. The growth rate of large cell aggregates was more rapid than that of small cell aggregates. Most cell aggregates > 0.50 mm in size became larger or smaller than their original sizes during the culture. A high level of red pigment formation was observed when cell aggregates obtained by the preculture using cell aggregates < 1.00 mm in size were cultured in the production medium.     

Lytic Enzymes for Gram-negative Bacteria Produced by Bacillus subtilis YT-25

The available energy, gross protein value, phosphorus availability and palatability of 16 samples of single cell protein were evaluated in 20 bioassays using total 2,136 depleted chicks.

Four protein samples were products from Aspergillus tamarii grown on waste water of a fish processing factory, three were from Aspergillus oryzae grown on either acetic acid medium or cooked soybean waste, three were from Candida sp. grown on citrus molasses extracted from peel wastes of citrus processing plants, four were from Candida utitis grown on wood molasses produced from various wood wastes, and two were from Pseudomonas sp. and Alteromonas thlasomethanolica grown on methanol.

Five of 16 samples had excellent nutritive value, comparable to single cell proteins available commercially in Europe. All samples were palatable to the chicks, and no sign of acute toxicity was observed.     

Considerations on the use of commercially available yeast biomass for the treatment of metal-containing effluents

Summary Three strains ofSaccharomyces cerevisiae and one strain of aCandida sp. obtained from different industrial sources were screened for uptake of silver and copper. Considerable differences in metal uptake capacities were found between the different strains ofS. cerevisiae and betweenS. cerevisiae and theCandida sp. used. Copper uptake capacities ranged from 0.05 mmol g^–1 dry wt to 0.184 mmol g^–1 dry wt while values of 0.034 mmol Ag g^–1 dry wt and 0.193 mmol Ag g^–1 dry wt biomass were observed. Use of ion-selective electrodes (ISEs) enabled the detection of copper complexing agents (possibly proteins and carbohydrates) released by yeasts into the surrounding medium. In contrast, these compounds had no silver complexation abilities. Langmuir and Scatchard transformations of metal adsorption isotherms suggested differences in the mechanisms involved in metal uptake by the various yeasts. The differences between strains ofS. cerevisiae were due possibly to differences in cell wal composition. Different methods of preparation of biomass (fresh, air, oven and freeze-dried) had little effect on metal uptake in comparison with fresh biomass. Storage of fresh waste biomass at 4°C for 20 days had no effect on metal biosorption capacities. It was also observed that individual batches of waste biomass produced from different fermentation runs had consistent metal uptake capacities. The implications of the above results on the use of waste yeast biomass for treatment of metal-containing effluents are discussed.     

Susceptibilities of Yeasts to Yeast Cell Wall Lytic Enzyme of Arthrobacter luteus

The susceptibilities of various strains of yeast to a yeast cell wall lytic enzyme produced by Arthrobacter lutens were examined. Twenty six strains of yeasts, mainly in the genera Saccharomyces and Candida were tested. They were tested after growth attained to the logarithmic or to the resting stage in different media (malt extract medium or n-paraffin medium) and various culture conditions (shaking or stationary liquid cultures or agar slopes).

The effects of various treatments, such as heating, or treatment with 2-mercaptoethanol or sodium dodecylsulfate on their susceptibility were also examined.

These various conditions and treatments greatly influenced the susceptibilities of the yeast cells, suggesting that they affected the composition and/or structure of the yeast cell walls.     

Comparison of the morphologies of a flotable and non-flotable strain of Saccharomyces cerevisiae

In previous paper, Saccharomyces cerevisiae LBG H620 and DAM 2155 were compared regarding their ability to float. LBG H620 did not float at all; cells' surface properties indicated that the yeast LBG H620 has a high surface hydrophilicity and a high electrokinetic potential; yeast DSM 2155 possesses high hydrophobicity and a low electrokinetic potential [Tybussek et al. (1994) J Appl Microbiol Biotechnol 41:13–22]. In the present paper, the morphologies of these two yeast strains are compared. Strain LBG H620 formed only single or dudding cells, strain DSM 2155 formed cell aggregates, their size depending on the cultivation condiotions: in the presence of adequate substrate concentration cell aggregates were formed, and during substrate limitation single cell dominated. During rerspiratory growth rather small spherical aggregates and during respiratory/fermentative growth long-strain aggregates were observed *** DIRECT SUPPORT *** AG903053 00004     

Detection of Candida sp. mannan antigen by indirect ELISA-inhibition

Summary We have obtained mannans from four Candida species: C. albicans A, C. albicans B and C. tropicalis; antimannan sera against C. albicans A, C. albicans B and C. tropicalis were obtained by immunizing rabbits sub-cutaneously with the respective yeast extract. The efficacy of these sera in reacting with mannans obtained from three Candida sp. has been proven by indirect ELISA-inhibition.Any of three immune sera can be used to detect mannan antigen from the three Candida sp. tested. This confirms the existence of crossed reactivity and the possibility of detecting mannan antigen in serum from patients infected by different Candida sp., although we had only one immune serum and one Candida mannan.     

In vitro inhibitory activity of EDTA against planktonic and adherent cells ofCandida sp.

Candida sp. can cause infections of indwelling medical devices associated with biofilm formation, which are difficult to treat due to insensitivity of adherent microorganisms to host defence mechanisms and standard antimicrobial therapy. The aim of this paper was to determine the effect of EDTA (disodium salt) on the adhesion ofCandida sp. to some catheters and also on biofilm formation by the yeasts and its eradication in relation to cytotoxicity of this chelating agent to the cell cultures. The adhesion process and biofilm formation, and also EDTA cytotoxicity to green monkey kidney (GMK) cell culture were determined using MTT tetrazolium salt [3-(4,5-dimethylthiazol-2-yl) ?2,5-diphenyltetrazolium bromide)] reduction assay. EDTA inhibited the growth of free-floating forms ofCandida sp. strains with minimal inhibitory concentration (MIC) from 0.06 to 0.25 mM; the minimal fungicidal concentration (MFC) values ranged from 64 to 128 mM. The prevention ofCandida sp. adhesion on the catheters used or eradication of the adherent cells was achieved at 0.5 to 4.0 mM EDTA. Also biofilm formation was prevented by 0.5 to 4.0 mM EDTA. Much higher concentration of EDTA (32 to 128 mM) was needed to eradicate the mature biofilm. EDTA at concentration up to 1 mM was not toxic for GMK cells. At higher concentration, toxicity of EDTA to GMK cells was correlated with the concentration of this agent and the time of exposure. Summing up, EDTA may be regarded as a useful agent rather in prophylaxis of candidal infections of medical devices.     

Biodegradation of polyethylene glycol by symbiotic mixed culture (obligate mutualism)

Neither Flavobacterium sp. nor Pseudomonas sp. grew on a polyethylene glycol (PEG) 6000 medium containing the culture filtrate of their mixed culture on PEG 6000. The two bacteria did not grow with a dialysis culture on a PEG 6000 medium. Flavobacterium sp. grew well on a dialysis culture containing a tetraethylene glycol medium supplemented with a small amount of PEG 6000 as an inducer, while poor growth of Pseudomonas sp. was observed. Three enzymes involved in the metabolism of PEG, PEG dehydrogenase, PEG-aldehyde dehydrogenase and PEG-carboxylate dehydrogenase (ether-cleaving) were present in the cells of Flavobacterium sp. The first two enzymes were not found in the cells of Pseudomonas sp. PEG 6000 was degraded neither by intact cells of Flavobacterium sp. nor by those of Pseudomonas sp., but it was degraded by their mixture. Glyoxylate, a metabolite liberated by the ether-cleaving enzyme, inhibited the growth of the mixed culture. The ether-cleaving enzyme was remarkably inhibited by glyoxylate. Glyoxylate was metabolized faster by Pseudomonas sp. than by Flavobacterium sp., and seemed to be a key material for the symbiosis.     

Comparison of fermentation properties and specific enzyme activities of free and calcium-alginate-entrapped Saccharomyces cerevisiae

Summary Physiological properties have been determined for calcium-alginate-entrapped Saccharomyces cerevisiae in comparison to cells in suspension under identical culture conditions. Cells grown in the form of microcolonies in the alginate beads showed faster glucose uptake and ethanol productivity with simultaneously decreased product and cell yields. Increased specific hexokinase and phosphofructokinase activities could be determined in these cells. Immobilized single cells showed only slightly enhanced glucose turnover and no higher specific hexokinase activity. The significant alterations in physiology are apparently connected with growth of the cells in aggregates. Offprint requests to: H.-J. Rehm