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Protozoa Help Fight Mosquitoes
January 21, 2011 21:38

A common means of fighting mosquitoes nowadays is using toxic bacterial proteins. However, these biological substances do not live long after being introduced in the environment; moreover, mosquitoes tend to become resistant to them quite quickly. Russian geneticists and medics united their efforts in solving this problem and suggested encapsulating toxic proteins of Brevibacillus laterosporus in protozoa before treating mosquitoes.

It is easier to fight mosquitoes, while they are still at larval stage and didn’t leave their home water body yet. Treating technique is quite simple – crystal toxic proteins of Bacillus thuringiensis and Bacillus sphaericus are put in water. These crystals are insoluble in water, however, when mosquito larvae eat them, these crystals are digested, become active and disturb digestive system of insects. Well, there is a problem that protein crystals quickly settle down to the bottom and mix with sediment particles. Mosquito larvae do not eat these proteins in this case. Researchers suggest prolonging lifetime of toxic bacterial protein crystals by encapsulating them into something buoyant – in a protozoan cell, for instance. This cell will keep a toxin active until a mosquito larva eats it.

Another problem exists – mosquitoes tend to form resistance to bacterial toxins. Various pests eventually become resistant to nearly all existing pesticides, which human beings develop and introduce. Therefore, is high time to start using new substances with pesticide properties. Researchers suggested using crystal toxic proteins of another bacterium, Brevibacillus laterosporus, which are toxic for larvae for various insects, including mosquitoes.



The highest amount of crystal is synthesized by Brevibacillus laterosporus during spore formation stage of development. Researchers have grown sufficient biomass of these bacteria, performed cell degradation, and isolated fractions of spores, crystals and a mixture of spores and crystals. These fractions were added in different concentrations to a suspension of protozoa – infusorians Tetrahymena pyriformis or amoebae Entamoeba moshkovskii. After grazing on toxins for two hours, protozoa were transferred into vials, containing larvae of Anopheles stephensi, a malaria mosquito.

Spores and proteins of Brevibacillus laterosporus are harmless for protozoa. Spores are also harmless for mosquito larvae, however, crystals by themselves or in mixture with spores, cause death of insects. After being ate by protozoa, crystals and spores become 2-3 time more toxic for mosquitoes, and pure toxin increases its toxicity by the order of magnitude. Moreover, time, required for half of larvae population to die, reduces 2.5-3 times.

Encapsulated crystal proteins of Brevibacillus laterosporus appeared to be an effective insecticide in laboratory conditions, researchers report in the Biotechnology scientific magazine. Possible explanation is that amoebae and infusorians accumulate significant amount of spores and toxic protein, thus concentrating the toxin.



Source: Science & Technologies

Kizilova Anna

Tags: Russian Scientists     

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