Bt Research 2015, Vol.6, No.4, 1-12
1
Research Article
Open Access
Thuringiensin: a toxin from
Bacillus thuringiensis
Wiest S.L.F., Pilz Júnior H.L. , Fiuza L.M.
Laboratório de Microbiologia e Toxicologia, Universidade do Vale do Rio dos Sinos – UNISINOS, Av. Unisinos, 950, CEP 93001-970, São Leopoldo, RS,
Brazil
Corresponding author email
Bt Research, 2015, Vol.6, No.4
doi: 10.5376/bt.2015.06.0004
Received: 23 Jun, 2015
Accepted: 28 Jul., 2015
Published: 01 Aug., 2015
Copyright
©
2015
Wiest et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Wiest S.L.F., Pilz Júnior H.L. , and Fiuza L.M., 2015, Thuringiensin: a toxin from
Bacillus thuringiensis
, Bt Research, Vol.6, No.4 1
-
12 (doi:
Abstract
Bacillus thuringiensis
(
Bt
) is an entomopathogenic bacteria widely used in practice for biological control of insect pests,
nematodes and disease vectors.
Your toxicity is related to the ability to produce many virulence factors, including thuringiensins
(β-exotoxins). Most toxins produce by this microorganism are highly specific, therefore the use of it in biological control is
considered environmentally safe and so this bacteria is extensively used in the production of biological insecticides and genetically
modified plants. However, the thuringiensin is considered toxic to almost all life forms, including humans, due to its ability to inhibit
the biosynthesis of RNA polymerase, an enzyme essential to the transfer of genetic information in almost all organisms. This way, the
release of new strains of
Bt
with insecticidal properties for the biological control of pests must pass by verification of the absence of
production of exotoxin, so that non-target organisms are not affected and the use of
Bt
in this field remains safe. Thus, this revision
will discussed the knowledge about features, structure, genetic determinants, biosynthesis, mechanism of action, insecticide spectrum,
security assessment and procedures for identification of thuringiensin in
Bt
strains.
Keywords
Biological control; environmental security; β-exotoxins; thermostable toxin
Background
Bacillus thuringiensis
Berliner (1911) (
Bt
) (Eubacteriales:
Bacillaceae) are a ubiquitous soil bacteria and was
first isolated in 1901, in Japan, by Shigetane Ishiwata,
in sick larvae of
Bombyx mori
(Lepidoptera: Bombycidae)
(silkworm), being initially named sotto disease. Seven
years later, Iwabuchi (1908) called it as
Bacillus sotto
.
In 1911, the same bacteria was found in the province
of Thuringia, Germany, by bacteriologist Ernst
Berliner from infected larvae of
Ephestia kuehniella
(Lepidoptera: Pyralidae) (moth flour-of-Mediterranean)
(Bravo et al., 2012; Ramirez-Lepe and Montserrat
2012). To analyze it, Berliner reported the presence of
parasporal protein crystals (Cry), but did not know
how to describe the role of these proteins in this
microorganism, which remained unknown until 1950
(Federici et al., 2010). Currently, it is known that
Bt
can establish lethal infections in susceptible organisms
to break the midgut cells and replicate itself inside the
hemolymph of living host (Raymond et al., 2010).
Because of their entomopathogenic properties,
Bt
is
widely used in biological control of insect pests practices,
nematodes and vectors of human diseases (Bravo et al.,
2012). The first tests in field using this bacterium were
carried out in 1929, by Husz, in corn fields, for the
control of
Ostrinia nubilalis
larvae (Lepidoptera:
Crambidae) (European corn worm). The positive results
of the experiments caught the attention of agribusiness
industries in this entomopathogenic organism (Kaya
and Vega, 2012). The first commercial formulation of
Bt
,
the insecticide spray Sporeine, was developed in
France in 1938, but had low selectivity and action
limited to few species. The large-scale production was
started only in the 50s, reaching countries such as
Russia, Czechoslovakia, France, Germany and the
United States. However, few strains of
Bt
were used for
the production of spray insecticides to date, representing
about 2% of the marketable insecticides (Pardo-López
et al., 2013).
On the other hand, with the development of molecular
techniques and biotechnological advances, it has
become possible the genetic manipulation of plants,
through the insertion of small sequences of genes
from
B. thuringiensis
expressing toxic proteins of the
