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Responses of the Microalga Chlorophyta sp. to Bacterial Quorum Sensing Molecules (N‑Acylhomoserine Lactones): Aromatic Protein-Induced Self-Aggregation
journal contribution
posted on 2017-02-24, 00:00 authored by Dandan Zhou, Chaofan Zhang, Liang Fu, Liang Xu, Xiaochun Cui, Qingcheng Li, John C. CrittendenBacteria
and microalgae often coexist during the recycling of microalgal
bioresources in wastewater treatment processes. Although the bacteria
may compete with the microalgae for nutrients, they could also facilitate
microalgal harvesting by forming algal-bacterial aggregates. However,
very little is known about interspecies interactions between bacteria
and microalgae. In this study, we investigated the responses of a
model microalga, Chlorophyta sp., to the typical
quorum sensing (QS) molecules N-acylhomoserine lactones
(AHLs) extracted from activated sludge bacteria. Chlorophyta sp. self-aggregated in 200 μm bioflocs by secreting 460–1000
kDa aromatic proteins upon interacting with AHLs, and the settling
efficiency of Chlorophyta sp. reached as high as
41%. However, Chlorophyta sp. cells were essentially
in a free suspension in the absence of AHLs. Fluorescence intensity
of the aromatic proteins had significant (P <
0.05) relationship with the Chlorophyta sp. settleability,
and showed a positive correlation, indicating that aromatic proteins
helped aggregate microalga. Transcriptome results further revealed
up-regulation of synthesis pathways for aromatic proteins from tyrosine
and phenylalanine that was assisted by anthranilate accumulation.
To the best of our knowledge, this is the first study to confirm that
eukaryotic microorganisms can sense and respond to prokaryotic QS
molecules.