A proposed stepwise screening framework for the selection of polycyclic aromatic hydrocarbon (PAH)-degrading white rot fungi.

This study suggests a simple three-step screening protocol for the selection of white rot fungi (WRF) capable of degrading polycyclic aromatic hydrocarbons (PAHs), which combines easily applicable bioassay techniques, and verifies that protocol by evaluating the PAH degradation activity, ligninolytic enzyme secretion, and relevant gene expressions of the selected PAH-degraders. Using 120 fungal strains, a sequence of bioassay techniques was applied: Bavendamm's reaction (Step 1), remazol brilliant blue R (RBBR) decolorization (Step 2); assays for tolerance to four mixed PAHs-phenanthrene, anthracene, fluoranthene, and pyrene (Step 3). This stepwise protocol selected 14 PAH-degrading WRF, including Microporus vernicipes, Peniophora incarnata, Perenniporia subacida, Phanerochaete sordida, Phlebia acerina, and Phlebia radiata. Of these, P. incarnata exhibited the highest PAH degradative activity, ranging from 40 to > 90%, which was related to the time-variable secretions of three extracellular ligninolytic enzymes: laccase, manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP). Laccase and MnP production by P. incarnata tended to be greater in the early stages of PAH degradation, whereas its LiP production became intensified with decreasing laccase and MnP production. Pilc1 and pimp1 genes encoding laccase and MnP were expressed, indicating the occurrence of extracellular enzyme-driven biodegradation of PAH by the fungal strains.

Diversity analysis of Saccharomyces cerevisiae isolated from natural sources by multilocus sequence typing (MLST).

We used multilocus sequence typing (MLST) to analyze the diversity of natural isolates of Saccharomyces cerevisiae, the most important microorganism in alcoholic fermentation. Six loci, ADP1, RPN2, GLN4, ACC1, MET4, and NUP116, in S. cerevisiae genome were selected as MLST markers. To investigate genetic diversity within S. cerevisiae, 42 S. cerevisiae isolated from natural sources in Korea as well as six S. cerevisiae obtained from Genbank and four industrial S. cerevisiae were examined using MLST. Twenty-six polymorphic sites were found in the six loci. Among them, ACC1 had the most genetic variation with eight polymorphic sites. MLST differentiated the 52 strains into three clades. Alcohol fermentation results revealed that S. cerevisiae in Clade III produced less alcohol than those in Clades I and II. These results suggested that MLST is a powerful tool to differentiate S. cerevisiae and can potentially be used to select S. cerevisiae suitable for industrial use.

Two New Species of Cryptococcus sp. and Candida sp. from Wild Flowers in Korea.

Among 80 types of yeast isolated from wild flowers in Daejeon, Korea, two species that have not yet been identified by phylogenetic analysis of the internal transcribed spacer-2 (ITS2) genes and 26S rDNA sequences were identified as Candida sp. 44-C-1 and Cryptococcus sp. 9-D-1. Neither of the newly identified species formed ascospores, while Candida sp. 44-C-1 formed pseudomycelium and Cryptococcus sp. 9-D-1 did not.