Sunday, November 22, 2009


Biological control of harmful vectors in foods is a dream many scientists have, as it does not leave any harmful residues of chemicals used commonly to sanitize the products. Most famous example is the potential showed by Bacillus thuringensis in controlling pests in food grains. Discovery in 1917 of bacteriophage, viruses that stay within the bacteria,and kill others that cause diseases in humans is another example. Consumption of pre-biotics is also intended to increase the population of "friendly' bacteria in the GI tract providing protection against smaller population of infectious bacteria. How ever the revolutionary findings that good bacteria always exist along with bad ones and they can be used for getting rid of the latter under favorable conditions, may have potential in improving the present agricultural practices by incorporating such a biological "warfare" component to prevent contamination at field level. .

Thanks to some smart work carried out by a group of scientists in the US on controlling Salmonella contamination of tomatoes which created a furore in that country recently, a new avenue seems to be opening for using friendly bacteria to destroy Salmonella. Though the finding is mainly in tomatoes, the concept should work for many fruits and vegetables which carry contamination from the field all the way to the kitchen, posing risks to the unsuspecting consumer. Through laborious field work these scientists were able to isolate some bacterial species from the tomato farms which were found to be effective in killing harmful pathogens like Salmonella, Listeria, E.coli O15:H7, though Vibrio was found to be resistant. Similar work in baby carrot field yielded some bacteria with similar properties. If similar work is taken up seriously many "helpful" bacteria can be unearthed with potential to counteract food contamination due to many pathogenic organisms.

The trail blazers in biological control were the plant protection scientists who could develop many biopesticides for reducing use of chemical pesticides in agriculture. Biopestide preparations are to day are available based on Agrobacterium, Bacillus, Psuedomonas, Streptomyces, fungi such as Ampelomyces, Candida, Coneothyrium and Trichoderma. The pioneering work by Japanese in developing the bacterial preservative, Nisin and Diplococci from Lactic streptococci and similar products like acidophilin, lactoacidin, lactolin etc from Lactobacillus species have already established the potential in using bacteria and other microorganism to fight against food borne pathogens.

The bacterial "warfare" strategy for Salmonella deploys live bacteria instead of any extracted or purified fractions with antibacterial activity and unlike bio-pesticides they target pathogenic bacteria, instead of the pests and insects. How such isolated good organisms can be deployed remains to be seen. It could be a treatment of the produce with a suspension of the good bacteria to make the hostile ones ineffective or application of the suspension in the field itself as pre-harvest operation. Probably some more work is needed to fine tune the technology. It cannot be considered a fool proof process as those pathogens gaining entry into the produce through cracks and crevices are immune to the action of the 'basher' bacteria. None the less it is a welcome break through that has potential for adoption by the fruits and vegetables growing community in future.


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