Ambigols from the Cyanobacterium Fischerella ambigua increase Prodigiosin Production in Serratia sp.

Screening a library of 573 cyanobacteria extracts for inhibition of the quorum sensing regulated prodigiosin production of Serratia marcescens, an extract of the cyanobacterium Fischerella ambigua (Näg.) Gomont 108b was found to drastically increase the prodigiosin production. Bioactivity-guided isolation of the active compounds resulted in the two new natural products ambigol D and E along with the known ambigols A and C. Ambigol C treatment increased prodiginine production of Serratia sp. ATCC 39006 (S39006) by a factor of 10, while ambigols A and D were found to have antibiotic activity against this strain. RNA-Seq of S39006 treated with ambigol C and subsequent differential gene expression and functional enrichment analyses indicated a significant downregulation of genes associated with the translation machinery and fatty acid biosynthesis in Serratia, as well as increased expression of genes related to the uptake of l-proline. These results suggest that the ambigols increase the prodiginine production in S39006 not by activating the SmaIR quorum sensing system, but possibly by increasing the precursor supply of l-proline and malonyl-CoA. Overall design: Six samples were analyzed in this study. Two different treatments were utilized with three biological replicates of each. The two treatments included growth of Serratia sp. ATCC 39006 with 15.6 µM ambigol C and with DMSO (solvent control).