Waste plastic and methane emissions are two anthropogenic by-products exacerbating environmental pollution. Methane-oxidizing bacteria (methanotrophs) hold the key to solving these problems simultaneously by utilising otherwise wasted methane gas as carbon source and accumulating the carbon as poly-3-hydroxybutyrate, a biodegradable plastic polymer. Here we present the isolation and characterisation of two novel Methylocystis strains with the ability to produce up to 55.7 ± 1.9% poly-3-hydroxybutyrate of cell dry weight when grown on methane from different waste sources such as landfill and anaerobic digester gas. Methylocystis rosea BRCS1 isolated from a recreational lake and Methylocystis parvus BRCS2 isolated from a bog were whole genome sequenced using PacBio and Illumina genome sequencing technologies. In addition to potassium nitrate, these strains were also shown to grow on ammonium chloride, glutamine and ornithine as nitrogen source. Growth of Methylocystis parvus BRCS2 on Nitrate Mineral Salt (NMS) media with 0.1% methanol vapor as carbon source was demonstrated. The genetic tractability by conjugation was also determined with conjugation efficiencies up to 2.8 × 10^–2 and 1.8 × 10^–2 for Methylocystis rosea BRCS1 and Methylocystis parvus BRCS2 respectively using a plasmid with ColE1 origin of replication. Finally, we show that Methylocystis species can produce considerable amounts of poly-3-hydroxybutyrate on waste methane sources without impaired growth, a proof of concept which opens doors to their use in integrated bio-facilities like landfills and anaerobic digesters.

废塑料和甲烷的排放是两种人为副产物，加剧了环境污染。甲烷氧化细菌（甲烷氧化菌）通过利用原本被浪费的甲烷气体作为碳源并积聚碳作为可生物降解的塑料聚合物3-羟基丁酸酯，而成为解决这些问题的关键。在这里，我们介绍了两种新颖的甲基囊藻菌株的分离和鉴定，当它们来自甲烷等不同废物源（如垃圾填埋场和厌氧消化池气体）上生长时，它们能够产生高达55.7±1.9％的细胞干重的聚3-羟基丁酸酯。Methylocystis糠疹BRCS1从休闲湖泊和隔离Methylocystis哲水蚤使用PacBio和Illumina基因组测序技术对从沼泽中分离的BRCS2进行全基因组测序。除硝酸钾外，这些菌株还显示在氯化铵，谷氨酰胺和鸟氨酸作为氮源上生长。证明了小甲虫BRCS2在含0.1％甲醇蒸气作为碳源的硝酸盐无机盐（NMS）培养基上的生长。遗传易处理性通过缀合也与缀合效率确定到2.8×10 ^-2和1.8×10 ^-2为Methylocystis糠疹BRCS1和Methylocystis帕尔乌斯分别使用具有复制的ColE1起点的质粒BRCS2。最后，我们证明了甲基囊藻 该物种可以在不影响其生长的前提下在废甲烷源上产生大量的聚3-羟基丁酸酯，这一概念证明为它们在诸如垃圾填埋场和厌氧消化池等综合性生物设施中的使用打开了大门。