Involvement of membrane vesicles in long-chain-AHL delivery in Paracoccus species

Bacteria are known to communicate with each other through signalling molecules that regulate gene expression within the population. However, the way in which hydrophobic signals are released and transmitted among bacterial population is not well understood. Recent studies show that membrane vesicles (MVs) are involved in delivering hydrophobic signals, such as in N-hexadecanoyl-l-homoserine lactone (C16-HSL) signalling in Paracoccus denitrificans Pd1222. In this study, we identified the AHLs produced in Paracoccus aminophilus JCM7686, Paracoccus aminovorans NBRC16711, Paracoccus thiocyanatus JCM20756, Paracoccus versutus JCM20754 and Paracoccus yeei ATCC BAA-599, and show that the main AHL produced in all the strains is C16-HSL. Our results show that these Paracoccus species also release MVs that carry C16-HSL, but at different proportions. Most of the strains carry C16-HSL in MVs, while in P. aminophilus JCM7686, very little C16-HSL was detected in MVs, but was found in other fractions of the supernatant. Given the utilization of a common signal, we showed that these Paracoccus species can share signals with P. denitrificans Pd1222, and examined the role of MVs in signalling. Our study provides new insights into the way in which bacteria communicate using hydrophobic signals.