Investigation of the role of cell hydrophobicity and EPS production in the aggregation of the marine diatom Cylindrotheca closterium under hypo- saline conditions

Demir-Yilmaz, Irem; Novosel, Nives; Levak Zorinc, Maja; Mišić Radić, Tea; Souad Ftouhi, Malak; Guiraud, Pascal; Ivošević DeNardis, Nadica; Formosa-Dague, Cecile (2023) Investigation of the role of cell hydrophobicity and EPS production in the aggregation of the marine diatom Cylindrotheca closterium under hypo- saline conditions. Marine environmental research, 188 . ISSN 0141-1136

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Abstract

Aggregation of diatoms is of global importance to understand settling of particulate organic carbon in aquatic systems. In this study, we investigate the aggregation of the marine diatom Cylindrotheca closterium during the exponential growth phase under hypo-saline conditions. The results of the flocculation/flotation experiments show that the aggregation of the diatom depends on the salinity. In favorable growth conditions for marine diatoms (salinity of 35), the highest aggregation is achieved. To explain these observations, we used a surface approach combining atomic force microscopy (AFM) and electrochemical methods to characterize both the cell surface properties and the structure of the extracellular polymeric substances (EPS) cell produce, and to quantify the amount of surface-active organic matter released. At a salinity of 35, the results showed that diatoms are soft, hydrophobic and release only small amounts of EPS organized into individual short fibrils. In contrast, diatoms adapt to a salinity of 5 by becoming much stiffer and more hydrophilic, producing larger amounts of EPS that structurally form an EPS network. Both adaptation responses of diatoms, the hydrophobic properties of diatoms and the release of EPS, appear to play an important role in diatom aggregation and explain the behavior observed at different salinities. This biophysical study provides important evidence allowing to get a deep insight into diatom interactions at the nanoscale, which may contribute to a better understanding of large- scale aggregation phenomena in aquatic systems.

Item Type:	Article
Uncontrolled Keywords:	aggregation ; atomic force microscopy ; cell hydrophobicity ; Cylindrotheca closterium ; extracellular polymeric substances ; hypo-saline stress
Subjects:	NATURAL SCIENCES > Interdisciplinary Natural Sciences NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
Divisions:	Division for Marine and Enviromental Research
Projects:	Project title Project leader Project code Project type Od površinskih svojstava stanica alga do pokazatelja stresa u vodenim ekosustavima-CELLSTRESS Nadica Ivošević DeNardis IP-2018-01-5840 HRZZ JCJC project FLOTALG (ANR-18-CE43- 0001-01) Cecile Formosa DaguE UNSPECIFIED Agence Nationale de la Recherche
Depositing User:	Nadica Ivošević DeNardis
Date Deposited:	26 Jun 2023 13:11
URI:	http://fulir.irb.hr/id/eprint/7975
DOI:	10.1016/j.marenvres.2023.106020

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