Insect Physiology Schedule

	Insect Physiology The University of Arizona
	Elizabeth Willott

Insect Physiology - Bacillus thuringiensis

There are several different forms of Bt. This lists only a few

Bt isrealensis and Bt sphaericus (and several others) work well against mosquitoes.
Bt kurstaki works against lepidopterans.
Bt tenebrionis works against coleopterans.

Each involves a toxin or toxins encoded by the bacillus that is active in the gut of the victim.
The toxins are classified:

Cry and Cyt are the first divisions.
Cry stands for crystal; Cyt means cytotoxic.
There are several different Cry and Cyt genes and alleles.

For the key web site maintaining up-to-date information about Bt nomenclature, go to the offsite page:
http://www.biols.susx.ac.uk/home/Neil_Crickmore/Bt/

The key reference, available on-line from the above site, is:
Crickmore, N, Zeigler, DR, Feitelson, J, Schnepf, E, Van Rie, J, Lereclus, D, Baum, J, Dean, DH. 1998. Revision of the nomenclature for the Bacillus thuringiensis pesticidal crystal proteins. Microbiology and Molecular Biology Reviews 62: 807-813.

In this paper, Fig. 1 gives a phylogram of the different Cry and Cyt proteins from different Bacillus thuringiensis strains.
To access the paper, choose "review" in the left column of the page linked to by the address above.

What does Bt bind?
A Biosys search of "Bacillus thuringiensis receptor" on Feb 3, 2003 gave eight hits. On first glance, these seemed contradictory since one paper would claim the Bt receptor is an endoprotease, another that it is cadherin-like. What's the truth? For more information see Bt receptor.

Insect Physiology Home Page