The Relative Importance of Shear Forces and Surface Hydrophobicity on Biofilm Formation by Coccoid Cyanobacteria.

Sara I Faria,Rita Teixeira-Santos,Maria J Romeu,Vitor Vasconcelos,Filipe J Mergulhão,João Morais

doi:10.3390/polym12030653

Abstract

Understanding the conditions affecting cyanobacterial biofilm development is crucial to develop new antibiofouling strategies and decrease the economic and environmental impact of biofilms in marine settings. In this study, we investigated the relative importance of shear forces and surface hydrophobicity on biofilm development by two coccoid cyanobacteria with different biofilm formation capacities. The strong biofilm-forming Synechocystis salina was used along with the weaker biofilm-forming Cyanobium sp. Biofilms were developed in defined hydrodynamic conditions using glass (a model hydrophilic surface) and a polymeric epoxy coating (a hydrophobic surface) as substrates. Biofilms developed in both surfaces at lower shear conditions contained a higher number of cells and presented higher values for wet weight, thickness, and chlorophyll a content. The impact of hydrodynamics on biofilm development was generally stronger than the impact of surface hydrophobicity, but a combined effect of these two parameters strongly affected biofilm formation for the weaker biofilm-producing organism. The antibiofilm performance of the polymeric coating was confirmed at the hydrodynamic conditions prevailing in ports. Shear forces were shown to have a profound impact on biofilm development in marine settings regardless of the fouling capacity of the existing flora and the hydrophobicity of the surface.

Highlights

Marine biofouling is an area of intense research due to the considerable economic impacts on marine transport
We investigated the impact of shear forces and surface hydrophobicity on biofilm development by two coccoid cyanobacteria
Our study clearly demonstrated that shear forces and surface properties have a significant impact on biofilm formation by coccoid cyanobacteria, as confirmed the number of biofilm biofilm

Summary

Introduction

Marine biofouling is an area of intense research due to the considerable economic impacts on marine transport. Biofouling on ship hulls increases frictional drag and may result in a fuel consumption increase ranging from 6% to 45%, depending on the size of the vessel [1,2,3,4]. This is associated with increased emissions of greenhouse gases and environmental pollution [3]. Biofouling by macrofouling organisms such as bryozoans, mollusks, polychaeta, tunicates, coelenterates, or fungi occurs after biofilm formation by microfouling organisms such as cyanobacteria and diatoms which are early colonizers [7,8,9,10]. It has been suggested that reducing biofilm formation may be a good strategy to delay macrofouling [11,12,13]

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