Elucidating an Oxidative Stress Response of Type I Methanotroph through an Integrated Systems Approach

Abstract

With the effects of climate instability becoming more and more noticeable, there has been an ever-present need for new ideas for mitigating greenhouse gas emissions. The utilization of methanotrophs has become an apparent choice to help decrease methane emissions because they can uniquely use methane as a carbon source. This work will describe how these microorganisms can efficiently metabolize one of the strongest chemical bonds through a unique enzyme known as methane monooxygenase. It is known that even if a material or, in this case, an organism, can metabolize methane, it still cannot compete with industrial processes already in place in terms of being economically feasible. Literature has now shown a push for these methanotrophs to decrease methane emissions and create a valuable product as a result. It is essential to gain a better understanding of metabolism to exploit it for a higher product yield. This work will mention a robust bacteria - Methylomicrobium buryatense 5GB1 - that has a high growth rate (0.224 h-1) and has shown high uptake rates of methane (6.1 mmol h-1) [1]. Also, a similar species, Methylotuvimicrobium alcaliphilum 20Z, is described as a potential substitute for 5GB1 since they show identical behavior under oxygen-limited conditions and are of the same genus [2]. These Type I methanotrophs are also appealing due to their alkaliphilic nature and preference for medium with large amounts of salt, making contamination more difficult. This work will utilize these unique microbes to investigate a novel oxidative stress phenotype. It will aim to demonstrate the optimal manner in which to obtain this phenotype and how the manipulation of previous conditions can affect future phenotypes. This work will explain methanotrophs' benefits in reducing methane emissions, but it will also describe a novel method to produce organic compounds. Specifically, the organic compound most produced is formate. With the conditions in these experiments, the formate excretion was increased by an order of magnitude from reported values. To better under the metabolic mechanisms in place, transcriptomic data was analyzed. This data depicted a downregulated methane oxidation pathway, except for formate dehydrogenase. Other up-regulated enzymes, such as methyltransferases and superoxide dismutase, indicate that the cell is responding to the oxidative stress conditions. These experiments focus on gaining an understanding of the metabolism of methanotrophs as well as determining their behavior under oxidative stress.