Definition of Bacillus Thuringiensis

Definition of Bacillus Thuringiensis

Siliang Liu

Professor Erika Paterson


Jan 28th, 2017


Definition of Bacillus Thuringiensis


The purpose of this assignment is to practice defining technical terms to a general audience. In this assignment, I will define a Bacillus Thuringiensisin three forms: 1) a parenthetical definition, 2) a sentence definition and 3) an expanded definition. The goal is to present the explanations in a way that adequately classifies and differentiates the subject that can be understood by a non-technical reader.

Parenthetical definition:

Bacillus Thuringiensis (Bt)is a bacterium that produces proteins, which are toxic to many species of insects (larvae).

Sentence definition:

After dissolving in the high pH insect gut, the Bt toxin turns active and attacks the gut cells by punching holes in it. The Bt then germinates in the gut resulting in a death of the insect in a few days. The Bt is widely used in agriculture, particularly in organic farming and transgenic crops to protect the farming, and the most popular Bt crop is Bt Cotton.

Expanded definition

How does Bt work in an insect gut?
Source: University of California San Diego


1.Bt (including Crystal and spores) being eaten by insects;

2. Different strains of Btare designed to specific type of receptors in insect gut, and each insect species carry specific type of receptors matching certain toxin proteins; once Bt binds to the receptors, insects stop eating crops;

3. The Crystal breaks down gut wall, allowing normal gut bacteria and spores to get into the body;

4. Insects die because of too many germs brought by spores and normal bacteria.

Therefore, farmers are very careful in selecting which strain of Bt to use to target the particular harmful insect as well as to protect the beneficial insect.


Utilizing microorganisms, particularly Bt, as pest control strategies date back to 1901 when a Japanese pathology named ShigetaneIshiwata isolated a bacterium from dead silkworm larvae as the cause of the large silkworm disease, and he later named such bacterium Bacillus sotto. A few years later, a German scientist called Ernst Berliner isolated organism Bacillus thuringiensis, which he named later, from dead Mediterranean flour moth larvae in a German flourmill in 1911. However, it was until 1955 that Thomas Angus, together with Philip Fitz-James and Christopher Hannay discovered that the toxic crystals inside the Btare composed of protein.

The first commercial Bt was produced in France in 1938 to control flour moths. In the United States, Bt-based bio-insecticides were being registered by the US Environmental Protection Agency in 1961. And since 1996, insect-resistant transgenic crops, known as Bt crops, have expanded around the globe and are proving to be quite efficient and helpful in reducing the use of chemical insecticides (Librahim, Griko, Junker and Bulla, 2010).

Potential risks to using Bt

Using genetic engineering to achieve genetic modification and change plant organism may be invasive to the current environment, and using Bt is one of the examples. In addition, insects might be resistant to Bt after a certain period when farmers apply Bt-based insecticides to Bt-crops. Moreover, genetically modified crops could introduce its genes to other native species (has not been proven yet).

Environmental impact

Toxins created by Bt are quickly broken down by exposure to sunlight and acidic soil. Btremains at the top of the soil for several inches but does not dissolve in soil. However, Bt can reproduce in some soils with rich nutrition: though it only lasts for a few days on the ground surface because of sun exposure, Bt beneath the soil surface could exist for months or years; however, Bt does not reproduce in water; research shows that 41% (National Pesticide Information Center) of the Bt toxins in the air remained after 24 hours and the rest are broken down rapidly by sunlight.

Compared with synthetic pesticide, Bt is safer to the environment, as it only kills specific insects and does no harm to beneficial insects, animals, and food. Additionally, it has been proven that transgenic crops can reduce the amount insecticides in runoffs.

Works Cited

[1] Mohamed A Ibrahim,Natalya Griko,Matthew JunkerandLee A Bulla. “Bacillus thuringiensis-A genomics and proteomics perspective”.Bioeng Bugs. 2010 Jan-Feb; 1(1): 31–50.

[2] “Bacillus thuringiensis”.University of California San Diego. Accessed on Jan 28th, 2017.

[3] “Bacillus Thuringiensis – General Fact Sheet”. National Pesticide Information Center. Accessed on Jan 28th, 2017.