Multilocus sequence analysis of Thermoanaerobacter isolates reveals recombining, but differentiated, populations from geothermal springs of the Uzon Caldera, Kamchatka, Russia

The polyextremophile Natranaerobius thermophilus adopts a dual adaptive strategy to long-term salinity stress, simultaneously accumulating compatible solutes and K. Appl Environ Microbiol 2024;90:e0014524. [PMID: 38578096 PMCID: PMC11107154 DOI: 10.1128/aem.00145-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The bacterium Natranaerobius thermophilus is an extremely halophilic alkalithermophile that can thrive under conditions of high salinity (3.3-3.9 M Na+), alkaline pH (9.5), and elevated temperature (53°C). To understand the molecular mechanisms of salt adaptation in N. thermophilus, it is essential to investigate the protein, mRNA, and key metabolite levels on a molecular basis. Based on proteome profiling of N. thermophilus under 3.1, 3.7, and 4.3 M Na+ conditions compared to 2.5 M Na+ condition, we discovered that a hybrid strategy, combining the "compatible solute" and "salt-in" mechanisms, was utilized for osmotic adjustment dur ing the long-term salinity adaptation of N. thermophilus. The mRNA level of key proteins and the intracellular content of compatible solutes and K+ support this conclusion. Specifically, N. thermophilus employs the glycine betaine ABC transporters (Opu and ProU families), Na+/solute symporters (SSS family), and glutamate and proline synthesis pathways to adapt to high salinity. The intracellular content of compatible solutes, including glycine betaine, glutamate, and proline, increases with rising salinity levels in N. thermophilus. Additionally, the upregulation of Na+/ K+/ H+ transporters facilitates the maintenance of intracellular K+ concentration, ensuring cellular ion homeostasis under varying salinities. Furthermore, N. thermophilus exhibits cytoplasmic acidification in response to high Na+ concentrations. The median isoelectric points of the upregulated proteins decrease with increasing salinity. Amino acid metabolism, carbohydrate and energy metabolism, membrane transport, and bacterial chemotaxis activities contribute to the adaptability of N. thermophilus under high salt stress. This study provides new data that support further elucidating the complex adaptation mechanisms of N. thermophilus under multiple extremes.IMPORTANCEThis study represents the first report of simultaneous utilization of two salt adaptation mechanisms within the Clostridia class in response to long-term salinity stress.

Young «oil site» of the Uzon Caldera as a habitat for unique microbial life

BACKGROUND

The Uzon Caldera is one of the places on our planet with unique geological, ecological, and microbiological characteristics. Uzon oil is the youngest on Earth. Uzon oil has unique composition, with low proportion of heavy fractions and relatively high content of saturated hydrocarbons. Microbial communities of the «oil site» have a diverse composition and live at high temperatures (up to 97 °C), significant oscillations of Eh and pH, and high content of sulfur, sulfides, arsenic, antimony, and mercury in water and rocks.

RESULTS

The study analyzed the composition, structure and unique genetics characteristics of the microbial communities of the oil site, analyzed the metabolic pathways in the communities. Metabolic pathways of hydrocarbon degradation by microorganisms have been found. The study found statistically significant relationships between geochemical parameters, taxonomic composition and the completeness of metabolic pathways. It was demonstrated that geochemical parameters determine the structure and metabolic potential of microbial communities.

CONCLUSIONS

There were statistically significant relationships between geochemical parameters, taxonomic composition, and the completeness of metabolic pathways. It was demonstrated that geochemical parameters define the structure and metabolic potential of microbial communities. Metabolic pathways of hydrocarbon oxidation was found to prevail in the studied communities, which corroborates the hypothesis on abiogenic synthesis of Uzon hydrothermal petroleum.