Non-growth substrate ethane perturbs core methanotrophy in obligate methanotroph

Obligate methanotrophs grow exclusively on C1 compounds; however, their widespread ecological distribution and ability to produce polyhydroxybutyrate (PHB) under nutrient stress suggest a greater-than-expected degree of metabolic flexibility. However, the metabolic responses of type II obligate methanotrophs to heterogeneous substrate conditions, common in natural and engineered environments, remain poorly understood. Here, we investigated how ethane (C IMPORTANCE: Type II methanotrophs present a dual advantage: mitigating methane emissions and producing bioproducts such as polyhydroxybutyrate (PHB). However, their full potential remains untapped, partly due to a limited understanding of how co-occurring gases influence their metabolism. Methane-rich emissions from both natural and anthropogenic sources are frequently accompanied by secondary gases, such as ethane, which create heterogeneous substrate conditions. This study reveals that ethane, a non-growth co-metabolic substrate, significantly modulates the metabolism of type II obligate methanotrophs, affecting microbial growth, methane oxidation, and PHB synthesis. These results advance our understanding of the metabolic plasticity of these organisms and also reveal new opportunities to leverage secondary substrates for selectively fine-tuning beneficial methanotrophic activities, such as biopolymer production.