ABSTRACTMethane is becoming a major candidate for a prominent carbon feedstock in the future, and the bioconversion of methane into valuable products has drawn increasing attention. To facilitate the use of methanotrophic organisms as industrial strains and accelerate our ability to metabolically engineer methanotrophs, simple and rapid genetic tools are needed. Electroporation is one such enabling tool, but to date it has not been successful in a group of methanotrophs of interest for the production of chemicals and fuels, the gammaproteobacterial (type I) methanotrophs. In this study, we developed electroporation techniques with a high transformation efficiency for three different type I methanotrophs:Methylomicrobium buryatense5GB1C,Methylomonassp. strain LW13, andMethylobactertundripaludum21/22. We further developed this technique inM. buryatense, a haloalkaliphilic aerobic methanotroph that demonstrates robust growth with a high carbon conversion efficiency and is well suited for industrial use for the bioconversion of methane. On the basis of the high transformation efficiency ofM. buryatense, gene knockouts or integration of a foreign fragment into the chromosome can be easily achieved by direct electroporation of PCR-generated deletion or integration constructs. Moreover, site-specific recombination (FLP-FRT [FLP recombination target] recombination) andsacBcounterselection systems were employed to perform marker-free manipulation, and two new antibiotics, zeocin and hygromycin, were validated to be antibiotic markers in this strain. Together, these tools facilitate the rapid genetic manipulation ofM. buryatenseand other type I methanotrophs, promoting the ability to perform fundamental research and industrial process development with these strains.
Exploration of an Efficient Electroporation System for Heterologous Gene Expression in the Genome of Methanotroph
