Scientists from Danisco have identified peculiar regions of a starter culture's genome that allow the bacteria to be resistant to infections by bacteriophages (bacterial viruses).
Danisco has stated it will exploit these breakthrough findings to develop food cultures with enhanced resistance to infections by bacteriophages, and further strengthen the company's position as a biotech world leader. "These results represent a long searched and entirely natural solution to bacteriophage for all culture-using industries where phage attacks are causing downgraded product batches and significantly reduced yield," said Patrick Boyaval, innovation director in Danisco's Dangé-Saint-Romain laboratories in France. Bacteriophages, the most abundant biological entity on the plant, are viruses that target bacteria, rather than human, plant or animal cells. For every bacterium, there is a phage that likes to latch on to them, take over their life processes and multiply. The baby phages then burst out to attack other nearby targets, thus killing the host cell. And for companies like Danisco that produce domesticated bacteria for industrial applications such as yoghurt and cheese production, bacteriophages represent a challenge to maintaining the quality of their starter cultures. The strength of Danisco Cultures was reflected recently in the company's financial report for the first nine months of 2006/7, in which the division helped drive organic growth for both Bioingredients and its overarching Ingredients sector. Bioingredients, which comprises cultures and Danisco's Genencor enzymes business, saw sales of DKK1.282 bn (c €172m) during the nine-month period - 39 per cent of revenue for Ingredients as a whole. The new research, published today in Science, could have implications for this division by eventually leading to cultures with improved resistance to phages, which would have a knock-on effect for the finished product quality. Danisco researchers, led by Philippe Horvath, focused on sequences in the bacteria genome called Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR). Computer models indicated that the bacterium's resistance to the phages was related to CRISPR1 spacer content. They then tested this using Streptococcus thermophilus DGCC7710, a species used extensively as a starter culture for yoghurt and cheese production. By manipulating the strain's DNA using molecular biology tools, and adding new spacers, the researchers found that the new bacteria were resistant to the bacteriophages. "Remarkably, the resulting strain [with added spacers] gained resistance to phage, which suggested that these two spacers have the ability to provide phage resistance de novo," they wrote in today's issue of Science. While the company stated that it would exploit these breakthrough findings to develop bacteriophage-resistant cultures, Horvath is quoted by Reuters as saying that the company has no intentions of developing such cultures out of respect for concerns over GMOs in food. "We'll let nature do the work for us by simply challenging the bacterium with the phage," he said. The research was carried out by Danisco scientists from R&D sites in France and the USA, in collaboration with Sylvain Moineau's research group from Université Laval, in Canada. Source: Science 23 March 2007, Volume 315, Pages 1709-1712
"CRISPR Provides Acquired Resistance Against Viruses in Prokaryotes"
Authors: R. Barrangou, C. Fremaux, H. Deveau, M. Richards, P. Boyaval, S. Moineau, D.A. Romero, and P. Horvath