Water and Sediments of an Acidic Hot Spring—Distinct Differentiation with Regard to the Microbial Community Composition and Functions

Abstract

Over the last half-century, microbial communities of the Kamchatka hot springs have been largely studied using molecular, radioisotopic, and cultural approaches. Generally, these results were obtained for mixed samples of water with sediments, for only hydrothermal water, or for only sediment samples. Simultaneous comparative analysis of the microbial communities of water and sediments was performed for only one Kamchatka hot spring with circumneutral pH. Here, the microbial communities of both sediments and water (separately) of hot spring #4229 (the Uzon Caldera, Kamchatka) with a temperature of 50–56 °C and pH of 3.2 were analyzed by 16S rRNA gene V4 fragment amplicon sequencing. It was revealed that the microbial community of sediments was represented by uncultured phylogenetically deep-branching lineages of archaea, such as ARK-15 within Thermoplasmatota and ‘Ca. Marsarchaeales’ from the Thermoproteota phyla. Metagenome analysis showed that these archaea most probably carried out the degradation of organic matter. The microbial community of the hot water is represented by thermoacidophilic, (micro)aerobic, chemolithoautotrophic, hydrogen- and sulfur-oxidizing bacteria of the genera Hydrogenobaculum (phylum Aquificota) and Acidithiobacillus (phylum Pseudomonadota). Radioisotopic tracing and DNA-stable-isotope probing techniques proved their role as primary producers in the hot spring. The experiment revealed significant differences in the composition and functions of the microbial communities of sediments and water through the example of a typical acidic hot spring in Kamchatka.

Acidithiobacillia class members originating at sites within the Pacific Ring of Fire and other tectonically active locations and description of the novel genus ‘Igneacidithiobacillus’

“…The pH was regulated by adding limestone slurry of 500 g L −1 calcium carbonate in the pulp. The presence of limestone in the environment of clade 1B strains seems to be a key factor for their growth, establishment, or prevalence ( Figure 3B ; Supplementary Table S2 ), serving either as carbon dioxide source upon limestone dissolution in acid liquors ( Esparza et al, 2019 ; Maltseva et al, 2023 ) or as a pH buffer (e.g., Sasowsky et al, 1995 ). Although cultured representatives of the 1B clade (DBS-4, YP-5, 175Fe35, FY-2, TST3, ZJJN-1, ZJJN-2, and ZJJN-3) have not been tested for the effect of calcium carbonate on their growth and/or oxidation performance, they have all been reported to grow in a medium composed of organics (0.01% yeast extract or peptone; Ni et al, 2008 ; Feng et al, 2012 ; Li et al, 2018 ).…”

“…The pH was regulated by adding limestone slurry of 500 g L −1 calcium carbonate in the pulp. The presence of limestone in the environment of clade 1B strains seems to be a key factor for their growth, establishment, or prevalence (Figure 3B; Supplementary Table S2), serving either as carbon dioxide source upon limestone dissolution in acid liquors (Esparza et al, 2019;Maltseva et al, 2023) or as a pH buffer (e.g., Sasowsky et al, 1995).…”