From Exception to Rule: Widespread Production of Methylated Rhamnolipids in the Burkholderia cepacia Complex
- 1INRS-Armand-Frappier sante biotechnologie
Abstract
Although Burkholderia cenocepacia exhibits biosurfactant-dependent phenotypes and possesses an rhl operon, the chemical identity of its surface-active product has long remained unresolved. The rhl operon of B. cenocepacia harbors an additional gene, rhlM, predicted to encode a methyltransferase, and recently linked to methylated rhamnolipid synthesis in a few Burkholderiaceae. Here, we hypothesized that this biosurfactant remained cryptic due to low expression under standard laboratory conditions. Using a chromosomal Prhl-luxCDABE fusion reporter, we screened diverse nutritional conditions and identified a defined medium containing galactose and urea that strongly induced rhl transcription. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses of B. cenocepacia K56-2 extracts identified the biosurfactants as methylated dirhamnolipid congeners, predominantly L-rhamnosyl-L-rhamnosyl-3-hydroxytetradecanoyl-3-hydroxytetradecanoate methyl ester (RR-C14-C14Me). Extending our analysis across the Burkholderia cepacia complex (Bcc) revealed that methylated rhamnolipid production is widespread and restricted to rhl-positive species. Comparative genomic and protein structural analyses further demonstrated high conservation of both the rhlM-containing operon architecture and the RhlM protein across the Bcc. Together, our findings identify the long-standing cryptic biosurfactant of B. cenocepacia as methylated rhamnolipids and establish rhamnolipid methylation as a conserved hallmark across the Bcc, shifting the paradigm of rhamnolipid structural diversity from an isolated exception to a widespread rule.
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BibTeX
@misc{roy2026from,
title = {{From Exception to Rule: Widespread Production of Methylated Rhamnolipids in the Burkholderia cepacia Complex}},
author = {M. Dagenais Roy and M.-C. Groleau and X. Perron and E. Deziel},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.01.756062},
url = {https://www.biorxiv.org/content/10.64898/2026.10.01.756062v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - From Exception to Rule: Widespread Production of Methylated Rhamnolipids in the Burkholderia cepacia Complex
AU - M. Dagenais Roy
AU - M.-C. Groleau
AU - X. Perron
AU - E. Deziel
PY - 2026
DA - 2026/10/01
PB - bioRxiv
DO - 10.64898/2026.10.01.756062
UR - https://www.biorxiv.org/content/10.64898/2026.10.01.756062v1
AB - Although Burkholderia cenocepacia exhibits biosurfactant-dependent phenotypes and possesses an rhl operon, the chemical identity of its surface-active product has long remained unresolved. The rhl operon of B. cenocepacia harbors an additional gene, rhlM, predicted to encode a methyltransferase, and recently linked to methylated rhamnolipid synthesis in a few Burkholderiaceae. Here, we hypothesized that this biosurfactant remained cryptic due to low expression under standard laboratory conditions. Using a chromosomal Prhl-luxCDABE fusion reporter, we screened diverse nutritional conditions and identified a defined medium containing galactose and urea that strongly induced rhl transcription. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses of B. cenocepacia K56-2 extracts identified the biosurfactants as methylated dirhamnolipid congeners, predominantly L-rhamnosyl-L-rhamnosyl-3-hydroxytetradecanoyl-3-hydroxytetradecanoate methyl ester (RR-C14-C14Me). Extending our analysis across the Burkholderia cepacia complex (Bcc) revealed that methylated rhamnolipid production is widespread and restricted to rhl-positive species. Comparative genomic and protein structural analyses further demonstrated high conservation of both the rhlM-containing operon architecture and the RhlM protein across the Bcc. Together, our findings identify the long-standing cryptic biosurfactant of B. cenocepacia as methylated rhamnolipids and establish rhamnolipid methylation as a conserved hallmark across the Bcc, shifting the paradigm of rhamnolipid structural diversity from an isolated exception to a widespread rule.
ER -