Molecular Genetic Analysis with Microsatellite-like Loci Reveals Specific Dairy-Associated and Environmental Populations of the Yeast Geotrichum candidum

Geotrichum candidum is an environmental yeast, also found as part of the cheese surface microbiota, where it is important in the ripening of many traditional cheeses, such as Camembert. We have previously developed a Multi Locus Sequence Typing (MLST) scheme, which differentiated five clades, of which one contained only environmental isolates, two were composed almost entirely of dairy isolates, and two others contained a mixture of dairy, environmental, and miscellaneous food isolates. In order to provide a simple method to uniquely type G. candidum strains, and in addition to permit investigation of the population structure at a fine level, we describe here a molecular analysis using a set of twelve highly discriminating microsatellite-like markers. The present study consolidates the previously suggested division between dairy and environmental strains, and in addition distinguishes a specifically European group of environmental strains. This analysis permitted the discrimination of 72 genotypes from the collection of 80 isolates, while retaining the underlying meaningful phylogenetic relation between groups of strains.

Isolamento de leveduras patogênicas da microbiota superficial de tamanduás mantidos em cativeiro

A composição da microbiota fúngica do pelame de animais silvestres ainda é pouco conhecida. Estabelecer parâmetros microbiológicos que permitam prever eventos infecciosos oportunistas nesses animais pode ser útil na preservação de espécies amaçadas de extinção. O objetivo dessa investigação foi isolar e identificar leveduras de potencial patogênico do pelame de tamanduás mantidos em cativeiro. Vinte e sete tamanduás, provenientes da Fundação Parque Zoológico de São Paulo (FPZSP) e Parque Municipal Quinzinho de Barros (Zôo-Sorocaba, SP) foram pesquisados. Catorze espécimes serão de tamanduá-bandeira (Mymercophaga tridactyla) e 13 de tamanduá-mirim (Tamandua tetradactyla), dos quais, 63% machos e 37%, fêmeas. A técnica do quadrado do carpete foi empregada na obtenção das amostras de pelame. As leveduras isoladas foram identificadas por meio de suas características morfológicas e por método semi-automatizado ID-32CÒ. Para descrever as variáveis obtidas por meio do instrumento de pesquisa, foram verificadas a frequência de ocorrência e os resultados foram expressos em valores relativos. Foram isoladas, no total, 33 leveduras a partir das amostras de pelame dos 27 tamanduás. As espécies de leveduras isoladas foram: oito Candida guilliermondii (24,2%), três C. famata (9,1%), três C. kefyr (9,1%), duas C. glabrata (6,1%), três Cryptococcus laurentii (9,1%), um C. humicola (3,0%), seis Geotrichum candidum (18,2%), três Malassezia pachydermatis (9.1%), duas Rhodotorula glutinis (6,1%) e dois Trichosporon asahii (6,1%). Pode-se concluir que leveduras reconhecidamente patogênicas podem colonizar a microbiota do tegumento de tamanduás-bandeira e tamanduás-mirim mantidos em cativeiro e representam potencial risco de infecção oportunista para esses animais.

Dendrobaena veneta avoids ethyl pentanoate and ethyl hexanoate, two compounds produced by the soil fungus Geotrichum candidum

Earthworms shape the biological and physicochemical qualities of the soil they choose to reside in, but our understanding of the specific chemicals that attract or repel a particular species of earthworm remains incomplete. Current research indicates that some species feed on and are attracted to fungi, such as Geotrichum candidum. In the present study, as part of our continuing effort to characterize mechanisms of earthworm chemosensation, we tested whether ethyl hexanoate and ethyl pentanoate, two compounds produced by G. candidum, are appetitive to the European nightcrawler (Dendrobaena veneta). In a soil T-maze, both of these compounds significantly repelled individual earthworms in a dosage-dependent manner, this result ran counter to our initial hypothesis. D. veneta also avoided ethyl hexanoate and ethyl pentanoate in an assay we specifically developed to test an earthworms aversion to chemical stimuli in soil. In both of these assays, ethyl hexanoate was aversive at lower concentrations than ethyl pentanoate. These findings further clarify our understanding of the chemical cues that trigger the decision of D. veneta to select a particular soil-environment, and emphasize that different earthworm species may react very differently to commonly encountered chemical stimuli.

Inhibition of Three Citrus Pathogenic Fungi by Peptide PAF56 Involves Cell Membrane Damage

The peptide PAF56 (GHRKKWFW) was reported to be an effective control for the main diseases of citrus fruit during postharvest storage. However, the mechanism of action of PAF56 is still unknown. In this paper, PAF56 might not induce defense resistance of citrus fruit. The SEM results visually indicated that the fungi mycelia became shrunken and distorted after being treated with PAF56. The destructive effects of PAF56 on the mycelial cell membrane of three kinds of pathogenic fungi (Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii) were verified by the K+ leakage and the release of nucleic acid. Furthermore, the interaction between peptide PAF56 and the pathogen spores was investigated, including the changes in cell membrane permeability and dynamic observation of the interaction of fluorescein labeled TMR-PAF56 and Geotrichum candidum spores. The results indicated that the antifungal activity of PAF56 on spores was time-dependent and directly related to the membrane damage. This research provided useful references for further research and practical application of peptides.

Mycobiota Composition of Robiola di Roccaverano Cheese along the Production Chain

Robiola di Roccaverano is a Protected Designation of Origin (PDO) cheese from the Piedmont region of Italy. In this study, the mycobiota occurring during Robiola di Roccaverano production was elucidated. Samples of milk, Natural Milk Cultures (NMC), curd, 5- and 15-days ripened cheese were collected from one dairy plant and the mycobiota was analyzed by the metataxonomic approach. Milk samples showed a high diversity and Cladosporium, Kluyveromyces marxianus, Geotrichum candidum and Debaryomyces hansenii were found with higher relative abundance. This mycobiota remains quite stable in NMC and curd matrices although the relative abundance of K. marxianus and G. candidum yeasts increased significantly and shaped the fungal composition of 5- and 15-day ripened cheese.

Modelling the Effect of Temperature on the Initial Decline during the Lag Phase of Geotrichum candidum

The study of lag phase provides essential knowledge for food quality control. With respect to significance of Geotrichum candidum in the food context, the aim of this study was to quantitatively characterize the relationship between temperature (6–25 °C) and initial decline period during G. candidum lag phase. The decrease in G. candidum cells in the lag phase was primary modelled by Weibull’s model to define the first-decimal reduction time (δ). Subsequently, the lag death rate (LDR) values were recalculated from δ and further modelled by using Arrhenius equations, as well as a square root model, and the models’ suitability was proven by selected statistical indices. The square root model with the estimated parameters b = 0.016 °C−1 h−0.5 and Tmin = −0.72 °C showed better indices relating to goodness of fit based on a low root mean sum of square error (RMSE = 0.028 log CFU mL−1), a higher coefficient of determination (R2 = 0.978), and the lowest value of AIC (AIC = −38.65). The present study provides a solution to the possible application of secondary predictive models to the death rate dependence on temperature during the microbial lag phase. Despite limited practical importance, under specific conditions, it is possible to consider its use, for example, in exposure assessment.

Mycoremediation and toxicity assessment of textile effluent pertaining to its possible correlation with COD

Globally, textile industries are one of the major sectors releasing dye pollutants. This is the first report on the positive correlation between toxicity and chemical oxygen demand (COD) of textile effluent along with the proposed pathway for enzymatic degradation of acid orange 10 using Geotrichum candidum within a very short stretch of time (18 h). Removal efficiency of this mycoremedial approach after 18 h in terms of chemical oxygen demand, biological oxygen demand, total suspended solids, salinity, color and dye concentration in the treated effluent reached to 98.5%, 56.3%,73.2%, 64%, 89% and 87% respectively. Also there was a decrease in pH of the treated effluent. FTIR analysis of the treated effluent confirmed biodegradation. The LCMS analysis showed the degradation of acid orange 10, which was confirmed by the formation of two biodegradation products, 7-oxo-8-iminonapthalene-1,3-disulfonate and nitrosobenzene, which subsequently undergoes stepwise hydrogenation and dehydration to form aniline via phenyl hydroxyl amine as intermediate. The X-ray diffraction studies showed that heavy metal content in the treated effluent has reduced along with decrease in % crystallinity, indicating biodegradation. The connection between toxicity and COD was also inveterated using Pearson’s correlation coefficient. Further the toxicological studies indicated the toxicity of raw textile effluent and relatively lower toxic nature of metabolites generated after biodegradation by G. candidum.