Isolation and screen of quorum quenching bacteria in situ

Abstract:

[Background] N-acylhomoserine lactones (AHLs) are used as the main quorum-sensing signaling molecules in many Gram-negative bacteria. [Objective] To screen and identify new quorum quenching (QQ) bacteria from soil organisms. [Methods] We used “washer method” to grow organisms by cultivation in situ. QQ bacteria were screened through “agar slice”, “reporter plate” and the assay of β-galactosidase activity. The phylogenetic status was determined based on 16S rRNA gene homology analysis. [Results] Here, 502 organisms were obtained from the soil samples in situ and screened for AHL-degrading bacteria using A. tumefaciens NTL4 (pZLR4) as a reporter strain. Eleven isolates degraded AHLs within 24 h. Based on their 16S rRNA gene sequences similarities, five isolates (3-49, 3-58, 61, 66, 120) and four isolates (3-59, 151, 3-41, 2-34) were assigned to the genera Pseudomonas and Acinetobacter. Strain 2-63 and 129 were identified as Proteus sp. and Rheinheimera sp., respectively. Most of these strains degraded strongly 3OC12-HSL and were active against 3OC6-HSL and 3OC8-HSL. [Conclusion] This study showed that Proteus sp. and Rheinheimera sp. may degrade AHLs, which might provide new biocontrol resources to control of the quorum sensing-dependent bacterial diseases.