scholarly journals Role of Domain II, Loop 2 Residues of Bacillus thuringiensis CryIAb δ-Endotoxin in Reversible and Irreversible Binding to Manduca sexta and Heliothis virescens

1996 ◽  
Vol 271 (5) ◽  
pp. 2390-2396 ◽  
Author(s):  
Francis Rajamohan ◽  
Jeffrey A. Cotrill ◽  
Fred Gould ◽  
Donald H. Dean
Keyword(s):  
Bacillus Thuringiensis ◽  
Manduca Sexta ◽  
Heliothis Virescens ◽  
Irreversible Binding ◽  
Loop 2

scholarly journals From Commensal to Pathogen: Translocation of Enterococcus faecalis from the Midgut to the Hemocoel of Manduca sexta

mBio ◽  
2011 ◽  
Vol 2 (3) ◽  
Author(s):  
Katie L. Mason ◽  
Taylor A. Stepien ◽  
Jessamina E. Blum ◽  
Jonathan F. Holt ◽  
Normand H. Labbe ◽  
...  
Keyword(s):  
Immune Response ◽  
Gastrointestinal Tract ◽  
Bacillus Thuringiensis ◽  
Mortality Rate ◽  
Enterococcus Faecalis ◽  
Manduca Sexta ◽  
Insecticidal Toxin ◽  
Content Type ◽  
Robust Immune Response

ABSTRACTA dynamic homeostasis is maintained between the host and native bacteria of the gastrointestinal tract in animals, but migration of bacteria from the gut to other organs can lead to disease or death.Enterococcus faecalisis a commensal of the gastrointestinal tract; however,Enterococcusspp. are increasingly frequent causes of nosocomial infections with a high mortality rate. We investigated the commensal-to-pathogen switch undergone byE. faecalisOG1RF in the lepidopteran model hostManduca sextaassociated with its location in the host.E. faecalispersists in the harsh midgut environment ofM. sextalarvae without causing apparent illness, but injection ofE. faecalisdirectly into the larval hemocoel is followed by rapid death. Additionally, oral ingestion ofE. faecalisin the presence ofBacillus thuringiensisinsecticidal toxin, a pore-forming toxin that targets the midgut epithelium, induces an elevated mortality rate. We show that the loss of gut integrity due toB. thuringiensistoxin correlates with the translocation ofE. faecalisfrom the gastrointestinal tract into the hemolymph. Upon gaining access to the hemolymph,E. faecalisinduces an innate immune response, illustrated by hemocyte aggregation, in larvae prior to death. The degree of hemocyte aggregation is dependent upon the route ofE. faecalisentry. Our data demonstrate the efficacy of theM. sextalarval model system in investigatingE. faecalis-induced sepsis and clarifies controversies in the field regarding the events leading to larval death followingB. thuringiensistoxin exposure.IMPORTANCEThis study advances our knowledge ofEnterococcus faecalis-induced sepsis following translocation from the gut and provides a model for mammalian diseases in which the spatial distribution of bacteria determines disease outcomes. We demonstrate thatE. faecalisis a commensal in the gut ofManduca sextaand a pathogen in the hemocoel, resulting in a robust immune response and rapid death, a process we refer to as the “commensal-to-pathogen” switch. While controversy remains regardingBacillus thuringiensistoxin-induced killing, our laboratory previously found that under some conditions, the midgut microbiota is essential forB. thuringiensistoxin killing ofLymantria dispar(N. A. Broderick, K. F. Raffa, and J. Handelsman, Proc. Natl. Acad. Sci. U. S. A. 103:15196–15199, 2006; B. Raymond, et al., Environ. Microbiol. 11:2556–2563, 2009; P. R. Johnston, and N. Crickmore, Appl. Environ. Microbiol. 75:5094–5099, 2009). We and others have demonstrated that the role of the midgut microbiota inB. thuringiensistoxin killing is dependent upon the lepidopteran species and formulation ofB. thuringiensistoxin (N. A. Broderick, K. F. Raffa, and J. Handelsman, Proc. Natl. Acad. Sci. U. S. A. 103:15196–15199, 2006; N. A. Broderick, et al., BMC Biol. 7:11, 2009). This work reconciles much of the apparently contradictory previous data and reveals that theM. sexta-E. faecalissystem provides a model for mammalian sepsis.

scholarly journals Investigating the Properties of Bacillus thuringiensis Cry Proteins with Novel Loop Replacements Created Using Combinatorial Molecular Biology

2008 ◽  
Vol 74 (11) ◽  
pp. 3497-3511 ◽  
Author(s):  
Craig R. Pigott ◽  
Martin S. King ◽  
David J. Ellar
Keyword(s):  
Bacillus Thuringiensis ◽  
Important Determinant ◽  
Large Family ◽  
Cry Proteins ◽  
Diverse Range ◽  
The Family ◽  
Complementarity Determining Regions ◽  
Apical Loop ◽  
Loop 2

ABSTRACTCry proteins are a large family of crystalline toxins produced byBacillus thuringiensis. Individually, the family members are highly specific, but collectively, they target a diverse range of insects and nematodes. Domain II of the toxins is important for target specificity, and three loops at its apex have been studied extensively. There is considerable interest in determining whether modifications in this region may lead to toxins with novel specificity or potency. In this work, we studied the effect of loop substitution on toxin stability and specificity. For this purpose, sequences derived from antibody complementarity-determining regions (CDR) were used to replace native domain II apical loops to create “Crybodies.” Each apical loop was substituted either individually or in combination with a library of third heavy-chain CDR (CDR-H3) sequences to create seven distinct Crybody types. An analysis of variants from each library indicated that the Cry1Aa framework can tolerate considerable sequence diversity at all loop positions but that some sequence combinations negatively affect structural stability and protease sensitivity. CDR-H3 substitution showed that loop position was an important determinant of insect toxicity: loop 2 was essential for activity, whereas the effects of substitutions at loop 1 and loop 3 were sequence dependent. Unexpectedly, differences in toxicity did not correlate with binding to cadherins—a major class of toxin receptors—since all Crybodies retained binding specificity. Collectively, these results serve to better define the role of the domain II apical loops as determinants of specificity and establish guidelines for their modification.

The role of Caenorhabditis elegans insulin‐like signaling in the behavioral avoidance of pathogenic Bacillus thuringiensis

2007 ◽  
Vol 21 (8) ◽  
pp. 1801-1812 ◽  
Author(s):  
Martin Hasshoff ◽  
Claudia Höhnisch ◽  
Daniela Tonn ◽  
Barbara Hasert ◽  
Hinrich Schulenburg
Keyword(s):  
Caenorhabditis Elegans ◽  
Bacillus Thuringiensis ◽  
Behavioral Avoidance

scholarly journals Transcriptional Analysis of the Toxin-Coding Plasmid pBtoxis from Bacillus thuringiensis subsp. israelensis

2006 ◽  
Vol 72 (3) ◽  
pp. 1771-1776 ◽  
Author(s):  
Claudia Stein ◽  
Gareth W. Jones ◽  
Tanya Chalmers ◽  
Colin Berry
Keyword(s):  
Gene Regulation ◽  
Bacillus Thuringiensis ◽  
Transcriptional Regulators ◽  
Transcriptional Analysis ◽  
Host Bacterium ◽  
Large Plasmid ◽  
Coding Sequences ◽  
Physiological Processes ◽  
Insecticidal Toxins

ABSTRACT In Bacillus thuringiensis subsp. israelensis all of the insecticidal toxins are encoded on a single, large plasmid, pBtoxis. Sequencing of this plasmid revealed 125 potential coding sequences, many of which have predicted functions in gene regulation and physiological processes, such as germination. As a first step in understanding the possible role of pBtoxis in its host bacterium, a survey of the transcription of genes with predicted functions was carried out. Whereas many coding sequences, including those previously identified as probable pseudogenes, were not transcribed, mRNA was detected for 29 of the 40 sequences surveyed. Several of these sequences, including eight with similarities to the sequences of known transcriptional regulators, may influence wider gene regulation and thus may alter the phenotype of the host bacterium.

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