Microdialysis Sampling of Quorum Sensing Homoserine Lactones during Biofilm Formation

Abstract

Bacteria communicate chemically through a system called quorum sensing. In this work, microdialysis sampling procedures were optimized to collect quorum sensing molecules produced during in situ biofilm formation directly on the polymeric semipermeable membrane of the microdialysis probe. V. harveyi, a Gram-negative bacterium, was used as the model organism and releases variable chain length acylhomoserine lactones (AHLs) and acyl-oxohomoserine lactones (AOHLs) as signaling molecules during quorum sensing. Eliciting biofilm formation required coating fetal bovine serum onto the poly­(ether sulfone) microdialysis membrane. Dialysates were collected in different experiments either during or after biofilm formation directly on a microdialysis probe. Continuous sampling of C4-AHL, C6-AHL, C8-AHL, C6-OXO-AHL, and C12-OXO-AHL was achieved over a period of up to 4 days. The AHLs and AOHLs in dialysates were concentrated with solid-phase extraction and quantified using LC-MS. Dialysate concentrations obtained for the AOHLs and AHLs ranged between 1 and 100 ppb (ng/mL) and varied between sampling days. This work demonstrates the initial use of microdialysis sampling to collect quorum sensing signaling chemicals during biofilm formation by a Gram-negative bacterial species.

Quorum Quenching in Membrane Bioreactors for Fouling Retardation: Complexity Provides Opportunities

“…For example, the fouling potential of the isolated strain Mesorhizobium ciceri in a full-scale MBR increased 26.8 times when cultivated with Thermomonas fusca (fouling-enhancing bacteria) via the enhanced secretion of C8-HSL compared with cultivation as a single culture. During biofouling development, AHL molecules and QS bacterial communities could exhibit dynamic changes (e.g., dominant AHLs shifting from short-chain to long-chain AHLs), suggesting the succession of QS-regulated communities from colonization to mature biofouling. , …”

“…Thus, there is a pressing need for a comprehensive understanding of QQ impacts on key QS microbial players in MBRs through laboratory culture studies. Of note, the abundant local species diversity within mixed liquor in MBRs could facilitate a multitude of interactions among various microbial strains through both interspecies and intraspecies QS. ,,,, Thus, typically but not inevitably, QS inhibitors targeting only single types of QS signals would be less effective if the intrinsic microbial communities of MBRs are not susceptible. Sequence-based investigation of the intrinsic microbial communities in MBRs is needed before implementing suitable QQ strategies to effectively target keystone QS microbes based on the validated experimental assumptions.…”

“…During biofouling development, AHL molecules and QS bacterial communities could exhibit dynamic changes (e.g., dominant AHLs shifting from shortchain to long-chain AHLs), suggesting the succession of QSregulated communities from colonization to mature biofouling. 60,61 More critically, the precise roles of QS in the biofouling formation are subjected to the spatial and temporal heterogeneity of environmental stresses (i.e., microenvironments) within the biofouling layer in MBRs (Figure 4b), resulting in the localized gradients of QS signals and shaping the distribution of QS mediated behaviors. 36,51,62−66 For example, microbes in the biofouling layer would face oxidative stresses after chemical cleaning methods in MBRs.…”