Identification and characterisation of short chain rhamnolipid production in a previously uninvestigated, non-pathogenic marine pseudomonad

• Published in: Applied microbiology and biotechnology Vol. 102; no. 19; pp. 8537 - 8549
• Main Authors: Twigg, Matthew S., Tripathi, L., Zompra, A., Salek, K., Irorere, V. U., Gutierrez, T., Spyroulias, G. A., Marchant, R., Banat, I. M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-10-2018; Springer; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Biotechnology; Chains; Congeners; Deoxyribonucleic acid; DNA; Environmental Biotechnology; Enzymes; Fatty acids; Genetic aspects; Genetic engineering; Glycolipids; High-performance liquid chromatography; Homology; Larvae; Life Sciences; Liquid chromatography; Microbial Genetics and Genomics; Microbiology; NMR; Nuclear magnetic resonance; Organic chemicals; Physiological aspects; Phytoplankton; Polycyclic aromatic hydrocarbons; Polymerase chain reaction; Pseudomonas; Relative abundance; Rhamnolipids; rRNA 16S; Stationary phase; Surface tension; Surfactants; Synthesis; Biosurfactant; Non-pathogenic; Rhamnolipid; Marine bacteria; Pseudomonas
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-018-9202-3

This study aimed to identify and characterise biosurfactant compounds produced by bacteria associated with a marine eukaryotic phytoplankton bloom. One strain, designated MCTG214(3b1), was isolated by enrichment with polycyclic aromatic hydrocarbons and based on 16S rDNA, and
gyrB
sequencing was found to belong to the genus
Pseudomonas
, however not related to
P. aeruginosa
. Cell-free supernatant samples of strain MCTG214(3b1) at stationary phase showed significant reductions in surface tension. HPLC-MS and NMR analysis of these samples indicated the presence of five different rhamnolipid (RL) congeners. Di-rhamnolipids accounted for 87% relative abundance and all congeners possessed fatty acid moieties consisting of 8–12 carbons. PCR screening of strain MCTG214(3b1) DNA revealed homologues to the
P. aeruginosa
RL synthesis genes
rhlA
and
rhlB
; however, no
rhlC
homologue was identified. Using the
Galleria mellonella
larvae model, strain MCTG214(3b1) was demonstrated to be far less pathogenic than
P. aeruginosa
. This study identifies for the first time a significantly high level of synthesis of short chain di-rhamnolipids by a non-pathogenic marine
Pseudomonas
species. We postulate that RL synthesis in
Pseudomonas
sp. MCTG214(3b1) is carried out by enzymes expressed from
rhlA
/
B
homologues similar to those of
P. aeruginosa
; however, a lack of
rhlC
potentially indicates the presence of a second novel rhamnosyltransferase responsible for the di-rhamnolipid congeners identified by HPLC-MS.