Bacteria could zap zebra mussels

By Matthew Renta

SOUTH LAKE TAHOE — The recent discovery of a bacteria that can kill zebra and quagga mussels has raised hopes for private and public organizations fighting to control the environmentally hazardous species.

New York State Museum researchers Daniel Molloy and Denise Mayer discovered a bacteria strain — Pseudomonas fluorescens — that can kill zebra and quagga mussels without killing other native species in the ecosystem.

“The ‘eureka moment’ did not come, interestingly enough, when we discovered the bacteria could kill zebra and quagga mussels, but came when we discovered the lack of sensitivity among non-target species,” Mayer said in a phone interview.

Scientists have found plenty of agents capable of killing the mussels, but in most instances they’ve also killed everything else in an ecosystem, Mayer said.

P. fluorescens infiltrates and destroys the mussels’ digestive system. Mayer and Molloy exposed fish, native mussels, waterfowl and other species to the bacteria and found they were unaffected.

“Our tests show the bacteria kills 100 percent of the target specimens when exposed,” Mayer said.

Dead cells of the strain are equally lethal as live cells, proving the mussels died from a natural toxin found in the strain’s cells — not from a bacterial infection, Mayer and Molloy also discovered.

“This is very significant because it means future commercial formulations will contain dead cells, further reducing environmental concerns,” Mayer said.

Commercial formulations

Marrone Bio Innovations, based in Davis, is in the process of getting federal approval of the first commercial formula using the bacteria discovered by Mayer and Molloy.

Zequanox — the name of the product that combines P. fluorescens with other naturally occurring ingredients such as sugar — could be approved in the first quarter of 2011, with sales commencing later in the year, said CEO and founder of the company Pam Marrone.

“We’ve been working on Zequanox for the past five years,” Marrone said. “We’ve had to find a way to grow it large-scale, commercial size, so customers could use it.”

Marrone tested the formula with Power Generation, a Canadian power supply company, and the U.S. Bureau of Reclamation. The tests determined Zequanox can kill mussel populations attached to pipes and other industrial material.

Marrone has begun testing to learn whether the product could be used in open-water scenarios. In a quarry infested with zebra mussels, Zequanox showed “some effect,” Marrone said.

Marrone would also need to identify an application device that could deliver Zequanox to infestation sites in open water.

“There is some precedence for that type of device, as people have used similar devices to treat water for algae or bacteria,” she said.

A different company would most likely be tasked with formulating such, Marrone said.

Local implications

Quagga and zebra mussels have not entered Lake Tahoe. In the past three years the Tahoe Regional Planning Agency implemented a lakewide boat inspection program in an effort to prevent aquatic invasive species from entering into the waters of Lake Tahoe.

The recent discovery of P. fluorescens is “encouraging,” said Ted Thayer, manager of the agency’s Aquatic Invasive Species Program.

“It’s exciting to have the tools available should the lake have an introduction (of non-native mussels),” he said.

However, Thayer pointed out the inspection program is designed to prevent a variety of species from entering the lake, including noxious weeds and other invertebrates.

Furthermore, Zequanox has yet to be successfully applied to open-water situations, Thayer said.

“It would be great if they can perfect it to the point where it could be used in a place like Lake Tahoe, but right now, there is no change to our inspection program,” he said.