Properties of exopolymeric substances (EPSs) produced during cyanobacterial growth: potential role in whiting events.

Marlisa Martinho de Brito (1) , Irina Bundeleva (1) , Frédéric Marin (1) , Emmanuelle Vennin (1) , Annick Wilmotte (2) , Laurent Plasseraud (3) , Pieter T. Visscher (1, 4)

1 BGS - Biogéosciences [UMR 6282]
2 InBioS - Integrative Biological Sciences
3 ICMUB - Institut de Chimie Moléculaire de l'Université de Bourgogne [Dijon]
4 Department of Marine Sciences

Extracellular polymeric substances (EPSs) are an important organic carbon reservoir in many pelagic and benthic environments. The production of EPS is intimately associated with the growth of phyto- and picoplankton. EPS plays a critical role in carbonate precipitation through the binding of cations and by acting as a nucleation site for minerals. Large-scale episodes of fine-grained calcium carbonate precipitation in the water column (whiting events) have been linked to cyanobacterial blooms, including of Synechococcus spp. The mechanisms that trigger these precipitation events are still debated. We pose that the cyanobacterial EPS, produced during exponential and stationary growth phases, plays a critical role in the formation of whitings. The aim of this study was to investigate the production of EPS during a 2-month cyanobacterial growth, mimicking a bloom. The production and characteristics of EPS were examined in different growth stages of Synechococcus spp. using various techniques such as Fourier transform infrared (FT-IR) spectroscopy as well as colorimetric and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) assays. We further evaluated the potential role of EPS in carbonate precipitation through in vitro-forced precipitation experiments. EPS produced during the early and late stationary phase contained a larger amount of negatively charged groups than present in EPS produced during the exponential phase. Consequently, a higher Ca2+-binding affinity of the stationary-phase EPS led to the formation of a larger amount of smaller carbonate minerals (< 50 µm) compared to crystals formed in exponential-phase EPS, which were less abundant and larger (> 50 µm). These findings were used to establish a conceptual model for picoplankton-bloom-mediated CaCO3 precipitation that can explain the role of EPS in whitings.

Domaines: Bactériologie

Marlisa Martinho de Brito, Irina Bundeleva, Frédéric Marin, Emmanuelle Vennin, Annick Wilmotte, et al.. Properties of exopolymeric substances (EPSs) produced during cyanobacterial growth: potential role in whiting events.. Biogeosciences, 2023, 20 (15), pp.3165-3183. ⟨10.5194/bg-20-3165-2023⟩. ⟨hal-04185227⟩