5:15 PM - 6:45 PM
[MZZ42-P02] Localization of microorganisms on the surface of ferromanganese crusts from the Takuyo-Daigo Seamount.
Keywords:Ferromanganese crusts, growth structure, DAPI staining, CARD-FISH
Ferromanganese crusts are recognized as one of the next generations metal resources owing to their composition enriched with industrially valuable metals. Although research on their formation processes has been conducted extensively, a comprehensive understanding remains elusive because of their extremely slow growth rate (a few millimeters per million years) and their presence in the deep sea, which is not easily accessible. Growth structures on scales ranging from several tens of micrometers to millimeters, such as columnar, wavy, mottled, and laminar, are generally observed in the ferromanganese crusts and are one of the keys to understanding sedimentary processes. Previous studies have suggested that these structures may be influenced by microorganisms on the surface of ferromanganese crusts (Kato et al., 2018, Kato et al., 2019), but details remain unknown. This study aims to investigate the distribution patterns of microorganisms on ferromanganese crusts and their relationship with the growth structures.
Cryosections were made by using the Kawamoto method (Kawamoto,2003) for four samples collected from the Takuyo-Daigo Seamount at different depths (1432, 2988, and 5373 m) using the remotely operated vehicle Hyper-Dolphin during the KR16-01 cruise. The growth structures were determined by optical microscopic observation, and the major elemental distribution patterns were identified by SEM-EDS analysis. In addition, DAPI staining and the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) methods were applied for the cryosections to confirm microbial cell distribution patterns within each growth structure.
In the samples collected from 1432 m, a mottled structure was developed, while in the samples collected from 2988 and 5373 m, a columnar structure was developed. The brownish areas exhibited a dense accumulation of microbial cells stained by DAPI. The higher abundance of the stained microbial cells was distributed in the samples with columnar structure in contrast to those with mottled structure. The CARD-FISH method also observed similar cell distribution patterns, but the protocol must be improved due to the relatively high background fluorescence. The elemental mapping by SEM-EDS analysis showed that the brownish areas exhibited a lower amount of manganese, the main component of the ferromanganese crusts, compared to other areas. This was consistent with the findings reported by Kato et al.(2018), describing similar characteristics of elemental composition on the crust surface. These results suggest contributing to the formation of columnar structures and local elemental compositional changes by the localization of microorganisms.
[Ref.] Kato et al. (2018) Microbes Environ. 33, 366-377. Kato et al. (2019) PLoS ONE 14(11): e0224888, Kawamoto (2003) Arch. Histol. Cytol. 66, 123–143.
Cryosections were made by using the Kawamoto method (Kawamoto,2003) for four samples collected from the Takuyo-Daigo Seamount at different depths (1432, 2988, and 5373 m) using the remotely operated vehicle Hyper-Dolphin during the KR16-01 cruise. The growth structures were determined by optical microscopic observation, and the major elemental distribution patterns were identified by SEM-EDS analysis. In addition, DAPI staining and the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) methods were applied for the cryosections to confirm microbial cell distribution patterns within each growth structure.
In the samples collected from 1432 m, a mottled structure was developed, while in the samples collected from 2988 and 5373 m, a columnar structure was developed. The brownish areas exhibited a dense accumulation of microbial cells stained by DAPI. The higher abundance of the stained microbial cells was distributed in the samples with columnar structure in contrast to those with mottled structure. The CARD-FISH method also observed similar cell distribution patterns, but the protocol must be improved due to the relatively high background fluorescence. The elemental mapping by SEM-EDS analysis showed that the brownish areas exhibited a lower amount of manganese, the main component of the ferromanganese crusts, compared to other areas. This was consistent with the findings reported by Kato et al.(2018), describing similar characteristics of elemental composition on the crust surface. These results suggest contributing to the formation of columnar structures and local elemental compositional changes by the localization of microorganisms.
[Ref.] Kato et al. (2018) Microbes Environ. 33, 366-377. Kato et al. (2019) PLoS ONE 14(11): e0224888, Kawamoto (2003) Arch. Histol. Cytol. 66, 123–143.