Effect of the N-hexanoyl-L-homoserine Lactone on the Carbon Fixation Capacity of the Algae–Bacteria System

Abstract

Algae–bacteria systems are used widely in wastewater treatment. N-hexanoyl-L-homoserine lactone (AHL) plays an important role in algal-bacteria communication. However, little study has been conducted on the ability of AHLs to regulate algal metabolism and the carbon fixation ability, especially in algae–bacteria system. In this study, we used the Microcystis aeruginosa + Staphylococcus ureilyticus strain as a algae–bacteria system. The results showed that 10 ng/L C6-HSL effectively increased the chlorophyll-a (Chl-a) concentration and carbon fixation enzyme activities in the algae–bacteria group and algae group, in which Chl-a, carbonic anhydrase activity, and Rubisco enzyme increased by 40% and 21%, 56.4% and 137.65%, and 66.6% and 10.2%, respectively, in the algae–bacteria group and algae group, respectively. The carbon dioxide concentration mechanism (CCM) model showed that C6-HSL increased the carbon fixation rate of the algae–bacteria group by increasing the CO2 transport rate in the water and the intracellular CO2 concentration. Furthermore, the addition of C6-HSL promoted the synthesis and secretion of the organic matter of algae, which provided biogenic substances for bacteria in the system. This influenced the metabolic pathways and products of bacteria and finally fed back to the algae. This study provided a strategy to enhance the carbon fixation rate of algae–bacteria consortium based on quorum sensing.

Cyanobacterial Blooms Formation by Enhanced Ecological Adaptability and Competitive Advantage of <em>Microcystis</em>— Non-Negligible Role of Quorum-Sensing

“…The premise of exploring exogenous AHLs function is that these AHLs produced by other organisms can affect Microcystis. Yan et al found that the addition of 3-OH-C4-HSL extracted from bacterial sludge could promote microalgal growth, alike to the function of endogenous AHLs [41], whereas Xue et al found that exogenous AHLs addition decreased Microcystis growth rate [62]. Based on numerous studies, exogenous AHLs affect Microcystis in several aspects alike to endogenous AHLs.…”

“…This suggested that even the same exogenous AHLs analogs may pose opposite effects on EPSs and MCs secretion [28]. In aspect of nutrition/energy metabolism activities, a part of exogenous AHLs can change relative genes expression and enzymes activities to regulate metabolic processes such as carbon/nitrogen metabolism in Microcystis [28,62,63]. C6-HSL can increase carbon sequestration efficiency to promote Microcystis growth [62].…”

“…In aspect of nutrition/energy metabolism activities, a part of exogenous AHLs can change relative genes expression and enzymes activities to regulate metabolic processes such as carbon/nitrogen metabolism in Microcystis [28,62,63]. C6-HSL can increase carbon sequestration efficiency to promote Microcystis growth [62]. Under joint action of above three aspects, Microcystis cells growth and aggregation for colonies formation also changed.…”

“…Based on this, researchers could control MCBs by introducing QQ signals-secreting microorganisms. To achieve QQ, many studies also applied exogenous AHLs and/or AHLs structural analogs as QS inhibitors against Microcystis cell proliferation [62]. For instances, Microcystis aeruginosa and Synechocystis sp.…”

Carbonic anhydrase versatility: from pH regulation to CO2 sensing and metabolism

“…In insects, this chemosensing process is involved in prey-seeking behavior (Cummins et al, 2014), whereas in vertebrates, it is involved in taste perception (Chandrashekar et al, 2009), lung function (Kunert et al, 2022), and the control of immunity (Strowitzki et al, 2022). In algae, aquatic plants, diatoms, and cyanobacteria, CO 2 /bicarbonate sensing is highly relevant in order to supply sufficient CO 2 for photosynthesis, and hence, sophisticated carbon-concentrating mechanisms have independently evolved in many such organisms (Momayyezi et al, 2020;Santhanagopalan et al, 2021;Zhang et al, 2022;Liao et al, 2023;Shimakawa et al, 2023).…”