Slime wars: bacteria harnessed to fight biofouling

Warfare between bacteria could provide an environmentally friendly solution to biofouling, according to Dhana Rao and her colleagues at the University of NSW.

It’s a new approach from a team which until now has been looking at how seaweeds combat fouling-the unsightly build-up of seaweed and marine animals on boat hulls which reduces ship speeds, increases fuel and maintenance and costs marine industries billions of dollars a year.

“We have shown that bacteria which live on seaweeds produce toxins to thwart potential rivals and dislodge competitors. Unwittingly this germ warfare also promises to bring about a solution to biofouling,” says Rao.

The paints currently used to control fouling contain toxic compounds which persist in the environment. One of them, tri-butyl tin, is so damaging that it is being phased out in 2008 by international agreement.

All surfaces immersed in seawater eventually become encrusted with an accumulated layer of organisms.

Biofouling begins innocuously enough with a layer of bacterial slime or biofilm. But this allows other organisms to gain a foothold, and soon leads to a teeming, thriving, biofouling community that is difficult to remove.

Rao studied the biofilms growing on a green seaweed which somehow remains free of fouling. Her work focused on two bacteria growing within the slime, Pseudoaltermonas tunicata and Roseobacter gallaeciensis.

The research team found the bacteria produced toxins that gave them a competitive edge against other rival surface-dwelling bacteria.

The study was the first to demonstrate that inhibitory compounds produced by marine bacteria can provide a competitive advantage during biofilm formation.

“When larvae or algal spores are exposed to biofilms, they land on the surface, check it out and go through a settlement process,” Rao says.

The UNSW group found that the two bacteria inhibited the settlement of larger fouling organisms at remarkably low levels. An understanding of how they do this could lead to a solution to biofouling, she said.

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