Transcriptomic profiling of Methylococcus capsulatus (Bath) during growth with two different methane monooxygenases

Area of Science:

• Microbiology
• Biochemistry
• Genomics

Background:

• Methylococcus capsulatus (Bath) utilizes membrane-bound (pMMO) and soluble (sMMO) methane monooxygenases for methane oxidation.
• Copper availability in the growth medium dictates the expression of pMMO versus sMMO.
• The genetic mechanisms governing this switch and the full scope of genes involved remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms and gene expression changes associated with the switch between pMMO and sMMO production in M. capsulatus.
• To identify copper-responsive gene clusters and their roles in methane oxidation.
• To investigate alterations in the respiratory chain and the prevalence of c-type cytochromes during different MMO expression states.

Main Methods:

• Transcriptome analysis using microarrays to compare gene expression in pMMO- and sMMO-producing cells.
• Mass spectrometry to identify expressed c-type cytochromes.
• Analysis of gene expression patterns in response to varying copper concentrations.

Main Results:

• 137 differentially expressed genes were identified, with 87 up-regulated during sMMO production.
• Three copper-responsive gene clusters were discovered, including one associated with sMMO.
• Significant changes in the respiratory chain were observed, with quinones identified as key electron donors for pMMO.
• 35 c-type cytochromes were detected, 21 of which are copper-responsive, and some are located on the cell surface.

Conclusions:

• The switch between pMMO and sMMO involves extensive transcriptional reprogramming affecting energy metabolism and transport.
• Copper availability significantly influences gene expression, including specific gene clusters and numerous c-type cytochromes.
• The presence of cell-surface c-type cytochromes suggests potential extracellular electron transfer mechanisms in M. capsulatus.