Yuriko Nagano

Aquimarina macrocephali sp. nov., isolated from sediment adjacent to sperm whale carcasses.

A Gram-negative, rod-shaped, non-spore-forming, strictly aerobic strain with gliding motility, designated JAMB N27(T), was isolated from sediment adjacent to sperm whale carcasses off Kagoshima, Japan, at a depth of 219 m. Strain JAMB N27(T) contained MK-6 as the major isoprenoid quinone and iso-C₁₅:₀, iso-C₁₅:₁, C₁₆:₁ and iso-C₁₇:₁ as the predominant fatty acids. Casein, chitin, gelatin and starch were degraded. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain JAMB N27(T) represented a separate lineage within the genus Aquimarina. The DNA G+C content of strain JAMB N27(T) was 33.1 mol%. DNA-DNA relatedness values between strain JAMB N27(T) and type strains of species of the genus Aquimarina were significantly lower than the cut-off value accepted for the definition of a novel species. Therefore, strain JAMB N27(T) represents a novel species, for which the name Aquimarina macrocephali sp. nov. is proposed. The type strain is JAMB N27(T) (=JCM 15542(T)=NCIMB 14508(T)).

Cultured and Uncultured Fungal Diversity in Deep-Sea Environments

The importance of fungi found in deep-sea extreme environments is becoming increasingly recognized. In this chapter, current scientific findings on the fungal diversity in several deep-sea environments by conventional culture and culture-independent methods are reviewed and discussed, primarily focused on culture-independent approaches. Fungal species detected by conventional culture methods mostly belonged to Ascomycota and Basidiomycota phyla. Culture-independent approaches have revealed the presence of highly novel fungal phylotypes, including new taxonomic groups placed in deep branches within the phylum Chytridiomycota and unknown ancient fungal groups. Future attempts to culture these unknown fungal groups may provide key insights into the early evolution of fungi and their ecological and physiological significance in deep-sea environments.

Cladomarine, a new anti-saprolegniasis compound isolated from the deep-sea fungus, Penicillium coralligerum YK-247

Cladomarine, a new anti-saprolegniasis compound isolated from the deep-sea fungus, Penicillium coralligerum YK-247

Cold-Adapted Yeasts in Deep-Sea Environments

Deep sea, the world’s largest cold environment, is an environment of extreme conditions, such as high hydrostatic pressure and low nutrient availability, and has an average water temperature between −1 and 4 °C in most areas of deep sea. Living organisms in deep sea are considered to be adapted to cold environments. Yeast diversity commonly found in deep sea is represented by Rhodosporidium spp., Rhodotorula spp., Candida spp., Cryptococcus spp., Pichia spp., Sporobolomyces spp., and Trichosporon spp. This representation of yeasts is similar to yeasts found in other cold environments. Only psychrotolerant yeasts have been reported from deep-sea environments to date. However, the majority of yeasts isolated from deep-sea environments show better growth in deep-sea simulated conditions, such as 3 °C/40 MPa, than yeasts isolated from terrestrial environments. In comparison with prokaryotic microorganisms, yeasts in deep-sea environments are relatively underexplored, with few studies carried out on their physiology. Although the true yeast diversity and their ecology in deep-sea environments remains unclear, the intention of this chapter is to discuss current knowledge on deep-sea yeast diversity and their physiological characteristics and adaptation mechanisms to cold and high pressure in the model yeast Saccharomyces cerevisiae.

Involvement of flocculin in negative potential-applied ITO electrode adhesion of yeast cells.

The purpose of this study was to develop novel methods for attachment and cultivation of specifically positioned single yeast cells on a microelectrode surface with the application of a weak electrical potential. Saccharomyces cerevisiae diploid strains attached to an indium tin oxide/glass (ITO) electrode to which a negative potential between −0.2 and −0.4 V vs. Ag/AgCl was applied, while they did not adhere to a gallium-doped zinc oxide/glass electrode surface. The yeast cells attached to the negative potential-applied ITO electrodes showed normal cell proliferation. We found that the flocculin FLO10 gene-disrupted diploid BY4743 mutant strain (flo10Δ /flo10Δ) almost completely lost the ability to adhere to the negative potential-applied ITO electrode. Our results indicate that the mechanisms of diploid BY4743 S. cerevisiae adhesion involve interaction between the negative potential-applied ITO electrode and the Flo10 protein on the cell wall surface. A combination of micropatterning techniques of living single yeast cell on the ITO electrode and omics technologies holds potential of novel, highly parallelized, microchip-based single-cell analysis that will contribute to new screening concepts and applications.

Quellenin, a new anti- Saprolegnia compound isolated from the deep-sea fungus, Aspergillus sp. YK-76

Saprolegnia parasitica, belonging to oomycetes, is one of virulent pathogen of fishes such as salmon and trout, and causes tremendous damage and losses in commercial aquacultures by saprolegniasis. Previously, malachite green, an effective medicine, had been used to control saprolegniasis. However, this drug has been banned around the world due to its mutagenicity. Therefore, novel anti-saprolegniasis compounds are urgently needed. As a new frontier to discover bioactive compounds, we focused on the deep-sea fungi for the isolation of anti-saprolegniasis compounds. In this paper, on the course of anti-saprolegniasis agents from 546 cultured broths of 91 deep-sea fungal strains, we report a new compound, named quellenin (1) together with three known compounds, diorcinol (2), violaceol-I (3) and violaceol-II (4), from deep-sea fungus Aspergillus sp. YK-76. This strain was isolated from an Osedax sp. annelid, commonly called bone-eating worm, collected at the São Paulo Ridge in off Brazil. Compounds 2, 3 and 4 showed anti-S. parasitica activity. Our results suggest that diorcinol and violaceol analogs and could be good lead candidates for the development of novel agents to prevent saprolegniasis.

New metabolites, sarcopodinols A and B, isolated from deep-sea derived fungal strain Sarcopodium sp. FKJ-0025

ABSTRACT Fungal strain FKJ-0025 was isolated from deep-sea sediment collected at the Wakamiko Caldera in Kagoshima Bay (water depth: 200 m). The fungal strain FKJ-0025 was identified as the genus Sarcopodium based on its morphology and internal transcribed spacer (ITS) sequence. Two new compounds, designated sarcopodinols A (1) and B (2), were isolated together with the known compound SF-227 (3).