19 research outputs found
Physiological adaptations of yeasts living in cold environments and their potential applications
Artículo de publicación ISIYeasts, widely distributed across the Earth, have successfully colonized cold environments despite their adverse conditions for life. Lower eukaryotes play important ecological roles, contributing to nutrient recycling and organic matter mineralization. Yeasts have developed physiological adaptations to optimize their metabolism in low-temperature environments, which affect the rates of biochemical reactions and membrane fluidity. Decreased saturation of fatty acids helps maintain membrane fluidity at low temperatures and the production of compounds that inhibit ice crystallization, such as antifreeze proteins, helps microorganisms survive at temperatures around the freezing point of water. Furthermore, the production of hydrolytic extracellular enzymes active at low temperatures allows consumption of available carbon sources. Beyond their ecological importance, interest in psychrophilic yeasts has increased because of their biotechnological potential and industrial uses. Long-chain polyunsaturated fatty acids have beneficial effects on human health, and antifreeze proteins are attractive for food industries to maintain texture in food preserved at low temperatures. Furthermore, extracellular cold-active enzymes display unusual substrate specificities with higher catalytic efficiency at low temperatures than their mesophilic counterparts, making them attractive for industrial processes requiring high enzymatic activity at low temperatures. In this minireview, we describe the physiological adaptations of several psychrophilic yeasts and their possible biotechnological applications.Fondecyt 1130333
Instituto Antartico Chileno (INACH, Chile)
RT_07-1
Identification and analysis of metabolite production with biotechnological potential in Xanthophyllomyces dendrorhous isolates
Artículo de publicación ISIAbstract Antarctic microorganisms have developed different
strategies to live in their environments, including
modifications to their membrane components to regulate
fluidity and the production of photoprotective metabolites
such as carotenoids. Three yeast colonies (ANCH01,
ANCH06 and ANCH08) were isolated from soil samples
collected at King George Island, which according to their
rDNA sequence analyses, were determined to be Xanthophyllomyces
dendrorhous. This yeast is of biotechnological
interest, because it can synthesize astaxanthin as its main
carotenoid, which is a powerful antioxidant pigment used
in aquaculture. Then, the aim of this work was to characterize
the ANCH isolates at their molecular and phenotypic
level. The isolates did not display any differences in their
rDNA and COX1 gene nucleotide sequences. However,
ANCH01 produces approximately sixfold more astaxanthin
than other wild type strains. Moreover, even though
ANCH06 and ANCH08 produce astaxanthin, their main
carotenoid was b-carotene. In contrast to other X. dendrorhous
strains, the ANCH isolates did not produce mycosporines.
Finally, the ANCH isolates had a higher
proportion of polyunsaturated fatty acids than other wild
type strains. In conclusion, the reported X. dendrorhous
isolates are phenotypically different from other wild type
strains, including characteristics that could make them
more resistant and better able to inhabit their original
habitat, which may also have biotechnological potential.CONICY
The expression of genes involved in microcin maturation regulates the production of active microcin E492
The production of active microcin E492, a channel-forming bacteriocin, was studied in exponential and stationary phase. The structural gene for this bacteriocin (mceA) is transcribed in exponential as well as in stationary phase, but the active form is produced only during the exponential phase of growth. An inactive form of microcin E492 was purified from the stationary phase. The production of the inactive form correlated with the lack of transcription in the stationary phase of two genes (mceIJ) involved in microcin E492 maturation, consequently behaving as the inactive form purified from mutants in these genes. The inactive form of microcin purified from the stationary phase as well as the inactive form purified from mutants in the maturation genes (mceC, I, J) were unable to compete with the active form when tested using a viability test on sensitive cells. This result strongly suggests that the inactive form of microcin caused by the lack of expression of the maturation genes i
Amplicon-metagenomic analysis of fungi from antarctic terrestrial habitats
© 2017 Baeza, Barahona, Alcaíno and Cifuentes. In cold environments such as polar regions, microorganisms play important ecological roles, and most of our knowledge about them comes from studies of cultivable microorganisms. Metagenomic technologies are powerful tools that can give a more comprehensive assessment of microbial communities, and the amplification of rDNA followed by next-generation sequencing has given good results in studies aimed particularly at environmental microorganisms. Culture-independent studies of microbiota in terrestrial habitats of Antarctica, which is considered the driest, coldest climate on Earth, are increasing and indicate that micro-diversity is much higher than previously thought. In this work, the microbial diversity of terrestrial habitats including eight islands of the South Shetland Archipelago, two islands on the Antarctic Peninsula and Union Glacier, was studied by amplicon-metagenome analysis. Molecular analysis of the studied localities cluste
Purification and characterization of a novel cold adapted fungal glucoamylase
Background: Amylases are used in various industrial processes and a key requirement for the efficiency of these
processes is the use of enzymes with high catalytic activity at ambient temperature. Unfortunately, most amylases isolated
from bacteria and filamentous fungi have optimal activity above 45 °C and low pH. For example, the most commonly
used industrial glucoamylases, a type of amylase that degrades starch to glucose, are produced by Aspergillus
strains displaying optimal activities at 45–60 °C. Thus, isolating new amylases with optimal activity at ambient temperature
is essential for improving industrial processes. In this report, a glucoamylase secreted by the cold-adapted
yeast Tetracladium sp. was isolated and biochemically characterized.
Results: The effects of physicochemical parameters on enzyme activity were analyzed, and pH and temperature
were found to be key factors modulating the glucoamylase activity. The optimal conditions for enzyme activity were
30 °C and pH 6.0, and the Km and kcat using soluble starch as substrate were 4.5 g/L and 45 min−1, respectively. Possible
amylase or glucoamylase encoding genes were identified, and their transcript levels using glucose or soluble
starch as the sole carbon source were analyzed. Transcription levels were highest in medium supplemented with
soluble starch for the potential glucoamylase encoding gene. Comparison of the structural model of the identified
Tetracladium sp. glucoamylase with the solved structure of the Hypocrea jecorina glucoamylase revealed unique structural
features that may explain the thermal lability of the glucoamylase from Tetracladium sp
Modeling the interfacial interactions between CrtS and CrtR from xanthophyllomyces dendrorhous, a P450 system involved in astaxanthin production
Xanthophyllomyces dendrorhous is a natural source of astaxanthin, a carotenoid widely used in the food industry. In this yeast, astaxanthin is synthesized from β-carotene by a cytochrome P450, CrtS, which depends on CrtR, the four-domain cytochrome P450 reductase (CPR). Although Saccharomyces cerevisiae has an endogenous CPR (ScCPR), expression of CrtS does not result in astaxanthin production unless it is coexpressed with CrtR. Assuming that CrtS could interact with the FMN-binding domain of either CrtR or ScCPR (XdFMNbd and ScFMNbd, respectively), the aim of this work was to identify possible interaction differences between these alternative complexes by protein modeling and short molecular dynamics simulations. Considering the recently proposed membrane orientation of a mammalian P450, our CrtS-CrtR model predicts that both N-terminal ends stand adjacent to the membrane plane, allowing their anchoring. Compared with the possible interface between CrtS and both FMNbd, the Xanthophyl
Identification and characterization of yeasts isolated from sedimentary rocks of Union Glacier at the Antarctica
© 2016, Springer Japan. The study of the yeasts that inhabit cold environments, such as Antarctica, is an active field of investigation oriented toward understanding their ecological roles in these ecosystems. In a great part, the interest in cold-adapted yeasts is due to several industrial and biotechnological applications that have been described for them. The aim of this work was to isolate and identify yeasts from sedimentary rock samples collected at the Union Glacier, Antarctica. Furthermore, the yeasts were physiologically characterized, including the production of metabolites of biotechnological interest. The yeasts isolated that were identified at the molecular level belonged to genera Collophora (1 isolate), Cryptococcus (2 isolates), Sporidiobolus (4 isolates), Sporobolomyces (1 isolate) and Torrubiella (2 isolates). The majority of yeasts were basidiomycetous and psychrotolerant. By cross-test assays for anti-yeast activity, it was determined that Collophora sp., Sporidiob
Antarctic yeasts: analysis of their freeze-thaw tolerance and production of antifreeze proteins, fatty acids and ergosterol
Background: Microorganisms have evolved a number of mechanisms to thrive in cold environments, including the production of antifreeze proteins, high levels of polyunsaturated fatty acids, and ergosterol. In this work, several yeast species isolated from Antarctica were analyzed with respect to their freeze-thaw tolerance and production of the three abovementioned compounds, which may also have economic importance. Results: The freeze-thaw tolerance of yeasts was widely variable among species, and a clear correlation with the production of any of the abovementioned compounds was not observed. Antifreeze proteins that were partially purified from Goffeauzyma gastrica maintained their antifreeze activities after several freeze-thaw cycles. A relatively high volumetric production of ergosterol was observed in the yeasts Vishniacozyma victoriae, G. gastrica and Leucosporidium creatinivorum, i.e., 19, 19 and 16 mg l(-1), respectively. In addition, a high percentage of linoleic acid with respect to total fatty acids was observed in V. victoriae (10%), Wickerhamomyces anomalus (12%) and G. gastrica (13%), and a high percentage of alpha linoleic acid was observed in L. creatinivorum (3.3%). Conclusions: Given these results, the abovementioned yeasts are good candidates to be evaluated for use in the production of antifreeze proteins, fatty acids, and ergosterol at the industrial scale.Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT), Fondecyt grant no. 1130333
Screening and characterization of amylase and cellulase activities in psychrotolerant yeasts
Artículo de publicación ISIBackground: Amylases and cellulases have great potential for application in industries such as food, detergent, laundry, textile, baking and biofuels. A common requirement in these fields is to reduce the temperatures of the processes, leading to a continuous search for microorganisms that secrete cold-active amylases and cellulases. Psychrotolerant yeasts are good candidates because they inhabit cold-environments. In this work, we analyzed the ability of yeasts isolated from the Antarctic region to grow on starch or carboxymethylcellulose, and their potential extracellular amylases and cellulases.
Result: All tested yeasts were able to grow with soluble starch or carboxymethylcellulose as the sole carbon source; however, not all of them produced ethanol by fermentation of these carbon sources. For the majority of the yeast species, the extracellular amylase or cellulase activity was higher when cultured in medium supplemented with glucose rather than with soluble starch or carboxymethylcellulose. Additionally, higher amylase activities were observed when tested at pH 5.4 and 6.2, and at 30-37 degrees C, except for Rhodotorula glacialis that showed elevated activity at 10-22 degrees C. In general, cellulase activity was high until pH 6.2 and between 22-37 degrees C, while the sample from Mrakia blollopis showed high activity at 4-22 degrees C. Peptide mass fingerprinting analysis of a potential amylase from Tetracladium sp. of about 70 kDa, showed several peptides with positive matches with glucoamylases from other fungi.
Conclusions: Almost all yeast species showed extracellular amylase or cellulase activity, and an inducing effect by the respective substrate was observed in a minor number of yeasts. These enzymatic activities were higher at 30 degrees C in most yeast, with highest amylase and cellulase activity in Tetracladium sp. and M. gelida, respectively. However, Rh. glacialis and M. blollopis displayed high amylase or cellulase activity, respectively, under 22 degrees C. In this sense, these yeasts are interesting candidates for industrial processes that require lower temperatures.FONDECYT
113033
Amyloid formation modulates the biological activity of a bacterial protein
The aggregation of proteins into amyloid fibrils is the hallmark feature of a group of late-onset degenerative diseases including Alzheimer, Parkinson, and prion diseases. We report here that microcin E492, a peptide naturally produced by Klebsiella pneumoniae that kills bacteria by forming pores in the cytoplasmic membrane, assembles in vitro into amyloid-like fibrils. The fibrils have the same structural, morphological, tinctorial, and biochemical properties as the aggregates observed in the disease conditions. In addition, we found that amyloid formation also occurs in vivo where it is associated with a loss of toxicity of the protein. The finding that microcin E492 naturally exists both as functional toxic pores and as harmless fibrils suggests that protein aggregation into amyloid fibrils is an evolutionarily conserved property of proteins that can be successfully employed by bacteria to fulfill specific physiological needs