Isolation and characterization of indigenous quorum quenching bacteria from activated sludge

Abstract:

[Background] In recent years, the application of quorum quenching (QQ) technology in the prevention and control of membrane biofouling has received extensive attention. However, limited QQ bacteria have been successfully isolated and identified. More efficient signal molecule degrading bacteria awaits identification and further investigation. [Objective] Isolate more efficient QQ bacteria from native real membrane bioreactor (MBR) activated sludge and extending QQ bacteria resources. [Methods] Agrobacterium tumefaciens A136 was used as the reporter strain, to test isolated strain's C8-HSL (N-octanoyl-DL-homoserine lactone) degradation. Reporter Chromobacterium violaceum VIR24 was used to quantify signal molecules degradation of QQ bacteria. 16S rRNA gene sequencing was used to identify isolated bacteria, phylogenetic trees taxonomic of the isolates were then constructed. Scanning electron microscopy (SEM) was used to determine the morphology of bacteria. Coculture of QQ strain and typical biofilm forming bacteria was conducted to analyze biofilm inhibition ability of isolates. QQ beads was prepared using polyvinyl alcohol and sodium alginate. [Results] Six QQ strains were successfully isolated and identified, among which a Gram negative rod strain Delftia sp. JL5 showed the highest efficiency in C8-HSL degradation. Besides, our results showed that JL5 significantly inhibited biofilm formation of both Pseudomonas aeruginosa PAO1 and Pantoea ananatis SK-1, which are two typical N-acyl-homoserine lactones (AHL) dependent biofilm forming bacteria. Furthermore, JL5 remained high AHL degrading activity after being entrapped in QQ beads. Its AHL degrading efficiency was higher than the widely reported Rhodococcus sp. BH4. [Conclusion] We successfully isolated QQ bacteria. The isolates showed high C6/C8-HSL degrading ability. The bacteria inhibited biofilm formation efficiently. This research set solid foundation for further application of QQ bacteria in biofouling control.