Abstract
Marine bacteria contribute significantly towards the fouling consortium, both directly (modern foul release coatings fail to prevent “slime” attachment) and indirectly (biofilms often excrete chemical cues that attract macrofouling settlement). This study assessed the natural product anti-biofilm performance of an extract of the seaweed, Chondrus crispus, and two isolated compounds from terrestrial sources, (+)-usnic acid and juglone, against two marine biofilm forming bacteria, Cobetia marina and Marinobacter hydrocarbonoclasticus. Bioassays were developed using quantitative imaging and fluorescent labelling to test the natural products over a range of concentrations against initial bacterial attachment. All natural products affected bacterial attachment; however, juglone demonstrated the best anti-biofilm performance against both bacterial species at a concentration range between 5–20 ppm. In addition, for the first time, a dose-dependent inhibition (hormetic) response was observed for natural products against marine biofilm forming bacteria.
Highlights
The underwater hull of a ship is exposed to the corrosive seawater environment, and to the constant accumulation of biofouling
Overall, when comparing equivalent peptone concentrations for the two different sea waters (ASW vs. natural sea water (NSW)), no significant differences in planktonic growth rate were found
We concluded that using artificial sea water (ASW) as an alternative to NSW
Summary
The underwater hull of a ship is exposed to the corrosive seawater environment, and to the constant accumulation of biofouling. Biofouling, or marine growth, includes any attaching organisms, such as biofilms (mainly bacteria and diatoms), tubeworms, mussels, barnacles and algae. Overall, biofouling is a major concern for submersed manmade structures, while, especially, vessel performance can be severely affected in terms of speed, hydrodynamic efficiency, fuel consumption and weight. Marine biofilms, which are mainly comprised of bacteria and diatoms embedded in an extracellular matrix [1], constitute a major component of the overall biofouling and may lead to a 14%. In September, 2008, further applications of TBT coatings were prohibited, in a treaty ratified by the International Maritime Organisation (IMO), due to its toxic effects in the wider marine environment, causing shell deformations in oysters, sex changes (imposex) in whelks and immune response, neurotoxic and genetic effects in other marine species [4]
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