Algal biofuels face diverse pathogens

Biologists from the Los Alamos National Laboratory in New Mexico sequenced strains of the Vampirovibrio chlorellavorus bacterium, which can destroy algae cells and render algae ineffective for biofuel production.

Blake Hovde, Los Alamos National Laboratory biologist, said: "DNA sequences show what are likely different species, suggesting a much larger diversity in this family than we originally assumed.

"That means the treatment for one algae pest might not work for another, which can be a big problem for large-scale algae cultivation in the future."

The researchers analysed the genomes to identify those involved in predation, infection and cell death of the algae. They found at least three sets of virulence genes characteristic of bacteria that carry out cell invasion.

V. chlorellavorus attaches to green algae cell walls and destroys its host by pumping in hydrolytic enzymes and degrading the cellular contents, reducing the algae to sludge.

“Once this infection has started, the algae pond can be reduced in as fast as 24 hours,” Hovde told Laboratory News.

“What you get is a bunch of dead algae cells and particles floating around and no more algae can be cultivated in that pond until it has been drained and disinfected. This is very detrimental to any operation trying to develop biomass from algae.”

Infection and loss of productivity can occur when susceptible algal hosts are cultivated in outdoor open pond systems.

As well as large-scale commercial algal production for biofuels, the issue could affect aquaculture feedstocks and algal-based nutraceuticals.

Chlorella algae is a key source of harvestable biomass for biofuels and bioproducts, which provide a more sustainable and environmentally-friendly source of energy than fossil fuels.

The team – whose work was published in Phycological Research – will work with the Joint Genome Institute to characterise six more pest genomes from the same family.