Methylotrophic bacteria use reduced carbon compounds with no carbon-carbon bonds such as methanol or methane gas as their only source of energy and carbon. Understanding how these tiny organisms interact at the molecular level may help us decipher and optimize their important role in carbon cycling. A large number of bacteria use quorum sensing (QS) systems as their method of communication. Through QS, bacteria are able to modify their gene expression depending on the cell density of their species. In one well-studied form of QS, Gram-negative bacteria use acyl-homoserine lactones (acyl-HSLs) as chemical signals. However, common general methods for identifying acyl-HSLs involve tandem mass spectrometry or general reporter assays, both of which may fail to detect some signals depending on their chemical structure. All known acyl-HSLs incorporate methionine via S-adenosyl methionine, which can be used to detect these signals via feeding of isotopically labeled methionine. We have taken advantage of this to develop an inverse-labeling strategy for identifying quorum sensing signals, in which we feed methylotrophic bacteria a 13C-labeled carbon source and 12C methionine, and subsequently look for corresponding mass shifts via LC-MS. We have optimized this method and applied it to several diverse methylotrophs with known signals to demonstrate its generality. We believe this approach will be useful for identifying new methylotroph QS signals in the future.

Identification of methylotroph quorum sensing signals using an inverse stable isotopic labeling approach

ACS Spring Meeting 2021

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