Fig 1.
Schematic representation of a phototrophic microbial mat.
Photosynthetic cyanobacteria fix CO2 and excrete organic matter that can be utilized by heterotrophs. Filamentous anoxygenic phototrophs oxidize sulfide to produce elemental sulfur that can be utilized by other bacteria involved in the sulfur cycle.
Fig 2.
Microbial mat cultivation with specific light wavelengths.
(a) Average temperature and pH during mat cultivation. (b) Images of microbial mats cultivated at different wavelengths and controls.
Fig 3.
Differences in relative abundance of community members in microbial mats and hot spring water.
The relative abundance of community members was examined in microbial mats before (indicated as "IM") and after irradiation in triplicates with light at 625, 730, or 890 nm for 20 days. Samples cultivated in the dark and with combined light served as controls. Hot spring water around the devices was also sampled on days, 0, 7, 14, and 20 (indicated as "HSW" with w0, w1, w2, and w3, respectively). Averaged abundance in triplicates of ≥1% in at least one experimental condition, the three phototrophs, and Sulfurihydrogenibium sp. (OTU3) dominant in hot spring water are shown.
Fig 4.
Phylogenetic tree based on abundant sequences in initial/experimental mats and increased/decreased sequences associated with specific light wavelengths for the phylum Chloroflexi, Firmicutes, and Dictyoglomi.
The tree shows sequences obtained from the Nakabusa microbial mats in previous studies (bold) and this study (bold, red).
Fig 5.
Phylogenetic tree based on abundant sequences in initial/experimental mats and increased/decreased sequences associated with specific light wavelengths for the phylum Chlorobi, Hydrogenedentes and Planctomycetes.
The tree shows sequences obtained from the Nakabusa microbial mats in previous studies (bold) and this study (bold, red).
Fig 6.
Phylogenetic tree based on abundant sequences in initial/experimental mats and increased/decreased sequences associated with specific light wavelengths for the phylum Proteobacteria, Thermotogae and EM3.
The tree shows sequences obtained from the Nakabusa microbial mats in previous studies (bold) and this study (bold, red).
Fig 7.
Phylogenetic tree based on abundant sequences in initial/experimental mats and increased/decreased sequences associated with specific light wavelengths for various other phyla.
The tree shows sequences obtained from the Nakabusa microbial mats in previous studies (bold) and this study (bold, red).
Table 1.
Abundant members with relative abundance ≥1% in the experimental mats, targeted cyanobacteria, and dominant bacterium in hot spring water.
Nearest neighbors of the sequence list based on BLAST search from all NCBI database sequences and type material.
Table 2.
Standard deviations and coefficient of variations between triplicates for Fig 3 listing abundant members in microbial mats.
Table 3.
Biodiversity in the different samples including experimental mats, initial mat, and hot spring water.
Fig 8.
Semi-logarithmic histograms of fold changes in bacterial abundance at the indicated wavelengths.
Fold changes of relative OTU abundance under the different light conditions as compared to controls grown in the dark are shown with blue, orange, and green bars for devices 1, 2, and 3, respectively. The base of the logarithm for the fold change was 51/12.