Candida sergipensis, a new asexual yeast species isolated from frozen pulps of tropical fruits

Sixteen strains of the new yeast species Candida sergipensis have been isolated from frozen pulps of the tropical fruits umbú ( Spondias tuberosa Avr. Cam.) and mangaba ( Hancornia speciosa Gom.). Candida sergipensis was one of the prevalent species in the yeast community of these substrates. The new asexual ascomycetous yeast is phylogenetically related to Candida spandovensis and Candida sorbophila, species belonging to the Wickerhamiella clade, as evidenced by the sequences of the D1/D2 domains of their large subunit ribosomal DNAs. The species C. sergipensis and C. spandovensis can be separated on the basis of growth on 50% glucose agar, xylose and succinate, negative for the first species and positive for the second. The type culture is strain UFMG-R188 (CBS 9567).     

Candida alocasiicola sp. nov., Candida hainanensis sp. nov., Candida heveicola sp. nov. and Candida musiphila sp. nov., novel anamorphic, ascomycetous yeast species isolated from plants

In a taxonomic study on the ascomycetous yeasts isolated from plant materials collected in tropical forests in Yunnan and Hainan Provinces, southern China, four strains isolated from tree sap (YJ2E(T)) and flowers (YF9E(T), YWZH3C(T) and YYF2A(T)) were revealed to represent four undescribed yeast species. Molecular phylogenetic analysis based on the large subunit (26S) rRNA gene D1/D2 domain sequences showed that strain YJ2E(T) was located in a clade together with Candida haemulonii and C. pseudohaemulonii. Strain YF9E(T) was most closely related to C. azyma and strain YWZH3C(T) to C. sorbophila and C. spandovensis. Strain YYF2A(T) was clustered in a clade containing small-spored Metschnikowia species and related anamorphic Candida species. The new strains differed from their closely related described species by more than 10% mismatches in the D1/D2 domain. No sexual states were observed for the four strains on various sporulation media. The new species are therefore assigned to the genus Candida and described as Candida alocasiicola sp. nov. (type strain, YF9E(T) = AS 2.3484(T) = CBS 10702(T)), Candida hainanensis sp. nov. (type strain, YYF2A(T) = AS 2.3478(T) = CBS 10696(T)), Candida heveicola sp. nov. (type strain, YJ2E(T) = AS 2.3483(T) = CBS 10701(T)) and Candida musiphila sp. nov. (type strain, YWZH3C(T) = AS 2.3479(T) = CBS 10697(T)).     

Virulence of Candida parapsilosis, Candida orthopsilosis, and Candida metapsilosis in reconstituted human tissue models

Candida parapsilosis is an increasingly important human pathogen. To study the interactions of C. parapsilosis with human tissues, we evaluated the effects of the CBS 604 type strain and three different clinical isolates on reconstituted human oral epithelial and epidermal tissues. The newly described species Candida orthopsilosis and Candida metapsilosis were also examined in these models. Microscopy of reconstituted tissues infected with yeast cells revealed severe attenuation, morphological changes and cellular damage. C. orthopsilosis caused damage similar to C. parapsilosis isolates, whereas C. metapsilosis was less virulent. To further quantitate tissue damage, we measured lactate dehydrogenase (LDH) in the culture supernatant. The relative LDH measurements correlated with our histopathological observations. We also examined the effect of the lipase inhibitor Ebelactone B and proteinase inhibitor Pepstatin A, to establish the utility of this model for studying factors of C. parapsilosis virulence. Both Ebelactone B and Pepstatin A reduced the destruction of epidermal and epithelial tissues. Our data show that reconstituted human tissues are extremely useful for modeling host interactions with C. parapsilosis and for studying fungal virulence factors.     

<Emphasis Type="Italic">Candida patagonica</Emphasis> sp. nov., a new species of yeast from cellar surfaces

A novel anamorphic yeast species belonging to the genus Candida has been isolated from cellar surfaces in North Patagonia. Morphological and physiological observation and phylogenetic analysis were performed. Pseudomycelium was plentifully produced. No sexual reproduction was observed. From sequence analysis of the 26S rDNA D1/D2 region, Candida bituminiphila and Zygoascus hellenicus were the closest species with 40 and 79 bp substitutions, respectively. C. bituminiphila differed physiologically from the novel species in its ability to assimilate sucrose and erythritol, in not fermenting any sugars, in growing without some vitamin compounds, and in growing at 40°C. All these data support the hypothesis that the new yeast, named Candida patagonica, is a novel species related to C. bituminiphila. The type strain is UNCOMA 159.5 (= CECT 12029 = CBS 10443).     

The potential for harvesting fruits in tropical rainforests: new data from Amazonian Peru

New data shows that edible fruit and nut production in Amazonian forests is substantially lower than most conservationists assume. Direct measures of production in Amazonian Peru show that two terra firma forest types produced significantly less edible fruit than an alluvial soil forest. Swamp forest produced more edible fruit than any other forest type measured. Palms produce 60% of edible fruit productivity, averaged over three forest types, but the most preferred palm fruits are difficult to harvest because they are borne too high for easy access by collectors. Forest fruit collection in Amazonia is less productive in the short-term than all other food-producing activities except for hunting and cattle ranching. Technological, social and political changes are essential so that sustainable but intrinsically low-yielding extractive activities like fruit collecting become more attractive to Amazonians.     

Croton dissectistipulatus, a new species of Euphorbiaceae from Amazonian Brazil

A new species ofCroton,C. dissectistipulatus, is described from Amazonian Brazil. This species is superficially similar toC. timandroides from northeastern and southeastern Brazil, but differs in having petiolate leaves with glandular margins, persistent stipules, conspicuous racemose inflorescences, staminate flowers having externally glabrous sepals and 3 stamens, and pedicellate pistillate flowers. The systematic position ofC. dissectistipulatus relative to the sections ofCroton is discussed.     

Characterization of a new xylitol-producer Candida tropicalis strain

A xylitol-producer yeast isolated from corn silage and designated as ASM III was selected based on its outstanding biotechnological potential. When cultivated in batch culture mode and keeping the dissolved oxygen at 40% saturation, xylitol production was as high as 130 g l(-1) with a yield of 0.93 g xylitol g(-1) xylose consumed. A preliminary identification of the yeast was performed according to conventional fermentation and assimilation physiological tests. These studies were complemented by using molecular approaches based on PCR amplification, restriction-fragment length polymorphism analysis and sequencing of the rDNA segments: intergenic transcribed spacer (ITS) 1-5.8S rDNA-ITS 2, and D1/D2 domain of the 26S rRNA gene. Results from both the conventional protocols and the molecular characterization, and proper comparisons with the reference strains Candida tropicalis ATCC 20311 and NRRL Y-1367, led to the identification of the isolate as a new strain of C. tropicalis.     

Candida arabinofermentans, a new L-arabinose fermenting yeast

Candida arabinofermentans (type strain NRRL YB-2248, CBS 8468), a new yeast that ferments the pentose L-arabinose, is described. The three known strains of this new species were isolated from insect frass of pine and larch trees in the U.S. Phylogenetic analysis of nucleotide sequences from the D1/D2 domain of large subunit (26S) ribosomal DNA places C. arabinofermentans among the methanol-assimilating yeasts and most closely related to Candida ovalis. Strains of the new species produce 0.7-1.9 g/l ethanol from L-arabinose.     

Recombination after protoplast fusion in the yeast Candida tropicalis

Candida tropicalis protoplasts obtained by snail enzyme treatment were induced to fuse by the use of polyethylene-glycol. Heterokaryons formed by two auxotrophic strains were selected by complementation on minimal medium. These heterokaryons were unstable and readily dissociated into their nuclear components. Under appropriate conditions, the parental nuclei of an heterokaryon fused. The homokaryon so obtained was unstable and segregated into various types of auxotrophic and prototrophic recombinants.List of Abbreviations Used MM minimal medium - YEA yeast extract agar (complete medium) - YPGT yeast-peptone-glucosethiol (medium for protoplast preparation) - PTP medium for cell pretreatment (used before the action of snail enzyme) - PEG polyethylene glycol - p-FPA para-fluorophenylalanine - 5-FC 5-fluorocytosine     

A model of xylitol production by the yeast Candida mogii

Production of xylitol from xylose in batch fermentations of Candida mogii ATCC 18364 is discussed in the presence of glucose as the cosubstrate. Various initial ratios of glucose and xylose concentrations are assessed for their impact on yield and rate of production of xylitol. Supplementation with glucose at the beginning of the fermentation increased the specific growth rate, biomass yield and volumetric productivity of xylitol compared with fermentation that used xylose as the sole carbon source. A mathematical model is developed for eventual use in predicting the product formation rate and yield. The model parameters were estimated from experimental observations, using a genetic algorithm. Batch fermentations, which were carried out with xylose alone and a mixture of xylose and glucose, were used to validate the model. The model fitted well with the experimental data of cell growth, substrate consumption and xylitol production.     

Saturnospora ahearnii,a new salt marsh yeast from Louisiana

Saturnospora ahearnii, a new, nonhyphal saturn-spored yeast, is described. The type strain (NRRL Y-7555, CBS 6121) of this species was isolated from the rhizosphere of marsh grass in Louisiana. Comparisons of nuclear DNA complementarity showedS. ahearnii to be closely related toS. saitoi, a species presently known only from Japan.     

Non-albicans Candida species isolated from plastic devices

In this work we point out an occurrence of non-albicans Candida species isolated from catheters, cannulas and drains. We detected eight non-albicans Candida species in 49 examined samples: C. parapsilosis (n = 26), C. tropicalis (n = 12), C. krusei (n = 4), C. claussenii, C. mesenterica (n = 2 for each), C. guilliermondii, C. kefyr and C. lusitaniae (n = 1 for each). Material examined from children hospitalized in intensive care units was the most frequent. Eight samples were from the oncology department, seven from the surgery department, six from the anaesthesiology department, four from the dialysis unit, two from the hematology department, one from the internal medicine department and one from the stomatology department. We examined cannula scraping 26 times (53%), catheter scraping 14 times (28.6%) and drain scraping nine times (18.4%). This revised version was published online in June 2006 with corrections to the Cover Date.     

Cyclic AMP,fructose-2,6-bisphosphate and catabolite inactivation of enzymes in the hydrocarbon-assimilating yeast Candida maltosa

The inactivation of fructose-1,6-bisphosphatase, isocitrate lyase and cytoplasmic malate dehydrogenase in Candida maltosa was found to occur after the addition of glucose to starved cells. The concentration of cyclic AMP and fructose-2,6-bisphosphate increased drastically within 30 s when glucose was added to the intact cells of this yeast. From these results it was concluded that catabolite inactivation, with participation of cyclic AMP and fructose-2,6-bisphosphate, is an important control mechanism of the gluconeogenetic sequence in the n-alkane-assimilating yeast Candida maltosa, as described for Saccharomyces cerevisiae.     

Immune responses to yeast and mycelial forms of Candida albicans in intraperitoneally infected mice

Candida albicans E-139 produced pure mycelial and yeast cultures in a low sulphate medium at different temperatures. The influence of the morphological phase, dose and viability of the fungi on the kinetic of delayed-type hypersensitivity (DTH) and anti-mycelial and anti-yeast antibodies have been studied in mice injected intraperitoneally. The mycelial form elicited higher DTH levels than the yeast phase. This effect seems to be related to its antigenic properties. The effect of dose on the immune response depends on the viability of the fungus. The mycelial cytoplasmic antigens were more effective than the yeast ones in detecting antibodies induced during the experiments, particularly during the later stages of the observation periods, suggesting that such antigens may be useful in the serodiagnosis of Candida infections.     

RTA2, a novel gene involved in azole resistance in Candida albicans

Widespread and repeated use of azoles, particularly fluconazole, has led to the rapid development of azole resistance in Candida albicans. Overexpression of CDR1, CDR2, and CaMDR1 has been reported contributing to azole resistance in C. albicans. In this study, hyper-resistant C. albicans mutant, with the above three genes deleted, was obtained by exposure to fluconazole and fluphenezine for 28 passages. Thirty-five differentially expressed genes were identified in the hyper-resistant mutant by microarray analysis; among the 13 up-regulated genes, we successfully constructed the rta2 and ipf14030 null mutants in C. albicans strain with deletions of CDR1, CDR2 and CaMDR1. Using spot dilution assay, we demonstrated that the disruption of RTA2 increased the susceptibility of C. albicans to azoles while the disruption of IPF14030 did not influence the sensitivity of C. albicans to azoles. Meanwhile, we found that ectopic overexpression of RTA2 in C. albicans strain with deletions of CDR1, CDR2 and CaMDR1 conferred resistance to azoles. RTA2 expression was found elevated in clinical azole-resistant isolates of C. albicans. In conclusion, our findings suggest that RTA2 is involved in the development of azole resistance in C. albicans.     

Degradation and dehalogenation of monochlorophenols by the phenol-assimilating yeast Candida maltosa

The phenol-assimilating yeast Candida maltosa is able to degrade monochlorophenols but cannot grow on these substrates. 3- and 4-chlorophenol were broken down very rapidly by phenol-grown cells under the formation of 4-chlorocatechol, 5-chloropyrogallol and 4-carboxymethylenebut-2-en-4-olide with concomitant release of chloride.2-Chlorophenol was partially converted into cis,cis-2-chloromuconic acid via 3-chlorocatechol which was also obtained from 3-chlorophenol in low amounts. No further metabolites containing chloride were found.The dehalogenation step in the chlorophenol degradation is the cycloisomerization of the cis,cis-chloromuconic acid to 4-carboxymethylenebut-2-en-4-olide in the ortho fission pathway.Dedicated to prof.Dr. E. Bayer, Tübingen, on the occasion of his 65th birthday.