# C3 Compound Metabolism in the Thermoacidophilic Methanotroph Methylacidiphilum fumariolicum SolV

## TL;DR

A heat-loving methane-consuming microbe can grow on alcohol and ketone compounds, expanding its metabolic versatility in geothermal environments.

## Contribution

The discovery that Methylacidiphilum fumariolicum SolV can grow on C3 compounds like 2-propanol and acetone, independent of CO2 and lanthanides.

## Key findings

- Strain SolV grows on 2-propanol and acetone with growth rates of 0.054 h⁻¹ and 0.042 h⁻¹, respectively.
- Transcriptomic analysis revealed upregulation of a gene cluster including a novel acetone monooxygenase (PMO3) during growth on C3 substrates.

## Abstract

Terrestrial and oceanic geothermal areas emit substantial amounts of hydrocarbons in the form of methane and the short‐chain alkanes ethane and propane. Under hydrothermal conditions, these alkanes can also be oxidised to their respective alcohols and ketones, with a preference for the 2‐position. The thermoacidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV, isolated from the Solfatara volcano, was previously shown to oxidise methane as well as the short‐chain hydrocarbons propane and ethane. Here, we show the growth of strain SolV on the C3 compounds 2‐propanol and acetone with growth rates of 0.054 h−1 and 0.042 h−1, respectively. In contrast to methanotrophic growth (rate 0.07 h−1), growth was not dependent on CO2 or lanthanides. Respiration experiments on steady‐state continuous cultures showed an apparent affinity of 0.4 μM acetone and 5.4 μM 2‐propanol. Transcriptomic analysis of these cultures showed that a gene cluster including a novel acetone monooxygenase (PMO3), previously identified in the closely related species Methylacidiphilum caldifontis, was highly upregulated under growth on C3 substrates. These results support the versatile metabolism of verrucomicrobial methanotrophs. The conversion of other compounds besides methane can be important in view of the ecological relevance of methanotrophs.

Terrestrial and oceanic geothermal areas emit substantial amounts of small hydrocarbons. The thermoacidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV, isolated from the Solfatara volcano, was shown to grow on 2‐propanol and acetone using steady‐state continuous cultures.