Larvicidal activities of indigenousBacillus thuringiensisisolates and nematode symbiotic bacterial toxins against the mosquito vector Culex pipiens(Diptera: Culicidae)

Ahmed, Ashraf M.

doi:10.1603/ice.2016.108782

Cited by 9 publications
(11 citation statements)

References 57 publications
(78 reference statements)

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“…Our data agree with the literature describing the increased efficacy of the use of entomopathogen combinations. Bt plus EPN combination was used against other insect species, such as the Coleoptera Cyclocephala hirta and Cyclocephala pasadenae 49 , the Lepidoptera Spodoptera exigua, Autographa gamma and Plutella xylostella 50 , 51 , and the Diptera Tipula paludosa 52 and Culex pipiens 53 .…”

Section: Discussionmentioning
confidence: 99%

Susceptibility of Drosophila suzukii larvae to the combined administration of the entomopathogens Bacillus thuringiensis and Steinernema carpocapsae
Mastore
¹
,
Quadroni
²
,
Brivio
³

2021
Sci Rep
11
1
12
0
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Non-native pests are often responsible for serious crop damage. Since Drosophila suzukii has invaded North America and Europe, the global production of soft, thin-skinned fruits has suffered severe losses. The control of this dipteran by pesticides, although commonly used, is not recommended because of the negative impact on the environment and human health. A possible alternative is the use of bio-insecticides, including Bacillus thuringiensis and entomopathogenic nematodes, such as Steinernema carpocapsae. These biological control agents have a fair effectiveness when used individually on D. suzukii, but both have limits related to different environmental, methodological, and physiological factors. In this work, we tested various concentrations of B. thuringiensis and S. carpocapsae to evaluate their efficacy on D. suzukii larvae, when administered individually or in combination by using agar traps. In the combined trials, we added the nematodes after 16 h or concurrently to the bacteria, and assessed larvae lethality from 16 to 48 h. The assays demonstrated a higher efficacy of the combined administration, both time-shifted and concurrent; the obtained data also showed a relevant decrease of the time needed to kill the larvae. Particularly, the maximum mortality rate, corresponding to 79% already at 16 h, was observed with the highest concentrations (0.564 µg/mL of B. thuringiensis and 8 × 102 IJs of S. carpocapsae) in the concurrent trials. This study, conducted by laboratory tests under controlled conditions, is a good starting point to develop a further application step through field studies for the control of D. suzukii.

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Section: Discussionmentioning
confidence: 99%

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“…There are multiple studies showing the histopathological effects of Cry toxins in midgut cells observed by light or transmission electron microscopy in different insect orders including lepidopteran [ 47 – 52 ], coleopteran [ 53 ] or dipteran larvae [ 54 – 57 ]. Overall, these reports show that Cry toxins induced severe vacuolization of the cytoplasm of the midgut cells, as well as loss of microvilli structure, cell lysis and columnar cells fragmentation.…”

Section: Discussionmentioning
confidence: 99%

In vivo nanoscale analysis of the dynamic synergistic interaction of Bacillus thuringiensis Cry11Aa and Cyt1Aa toxins in Aedes aegypti
López-Molina
¹
,
Nascimento
²
,
Silva-Filha
³

et al. 2021
PLoS Pathog
13
1
9
0
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The insecticidal Cry11Aa and Cyt1Aa proteins are produced by Bacillus thuringiensis as crystal inclusions. They work synergistically inducing high toxicity against mosquito larvae. It was proposed that these crystal inclusions are rapidly solubilized and activated in the gut lumen, followed by pore formation in midgut cells killing the larvae. In addition, Cyt1Aa functions as a Cry11Aa binding receptor, inducing Cry11Aa oligomerization and membrane insertion. Here, we used fluorescent labeled crystals, protoxins or activated toxins for in vivo localization at nano-scale resolution. We show that after larvae were fed solubilized proteins, these proteins were not accumulated inside the gut and larvae were not killed. In contrast, if larvae were fed soluble non-toxic mutant proteins, these proteins were found inside the gut bound to gut-microvilli. Only feeding with crystal inclusions resulted in high larval mortality, suggesting that they have a role for an optimal intoxication process. At the macroscopic level, Cry11Aa completely degraded the gastric caeca structure and, in the presence of Cyt1Aa, this effect was observed at lower toxin-concentrations and at shorter periods. The labeled Cry11Aa crystal protein, after midgut processing, binds to the gastric caeca and posterior midgut regions, and also to anterior and medium regions where it is internalized in ordered “net like” structures, leading finally to cell break down. During synergism both Cry11Aa and Cyt1Aa toxins showed a dynamic layered array at the surface of apical microvilli, where Cry11Aa is localized in the lower layer closer to the cell cytoplasm, and Cyt1Aa is layered over Cry11Aa. This array depends on the pore formation activity of Cry11Aa, since the non-toxic mutant Cry11Aa-E97A, which is unable to oligomerize, inverted this array. Internalization of Cry11Aa was also observed during synergism. These data indicate that the mechanism of action of Cry11Aa is more complex than previously anticipated, and may involve additional steps besides pore-formation activity.

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“…In spite of the known limitations of these therapeutic strategies, cancer can be cured provided that it is diagnosed at early stages. In the quest for finding an alternative cure for cancer that is more effective and specific, our research group has collected a repository of 68 Bt strains from 300 diverse environmental samples (October 2013–March 2014), isolated out of 16 sites across Saudi Arabia, and their potential larvicidal activity has previously been fully explored [12,27,38]. The present work represents the first report that examines the anticancer activity of nine non-larvicidal and non-hemolytic native Bacillus thuringiensis (Bt) isolates from different regions across Saudi Arabia.…”

Section: Discussionmentioning
confidence: 99%

“…A total of sixty-eight B. thuringiensis (BT) isolates were obtained (October 2013–March 2014) from diverse environmental samples recovered from various locations in Saudi Arabia according to previously published protocols by our group. The full procedures of isolation, culturing and identification of Bt strains are detailed therein [12,27,38].…”

Section: Methodsmentioning
confidence: 99%

Specific Cytotoxic Effects of Parasporal Crystal Proteins Isolated from Native Saudi Arabian Bacillus thuringiensis Strains against Cervical Cancer Cells
Aboul‐Soud
¹
,
Al-Amri
²
,
Kumar
³

et al. 2019
Molecules
23
1
16
0
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Currently, global efforts are being intensified towards the discovery of local Bacillus thuringiensis (Bt) isolates with unique anticancer properties. Parasporins (PS) are a group of Bt non-insecticidal crystal proteins with potential and specific in vitro anticancer activity. However, despite the significant therapeutic potential of PS-producing Bt strains, our current knowledge on the effects of these proteins is limited. Hence, the main objective of this study was to screen Bt-derived parasporal toxins for cytotoxic activities against colon (HT-29) and cervical (HeLa) cancerous cell lines. Nine non-larvicidal and non-hemolytic Bt strains, native to Saudi Arabia, were employed for the isolation of their parasporal toxins. 16S rDNA sequencing revealed a 99.5% similarity with a reference Bt strain. While PCR screening results indicated the absence of selected Cry (Cry4A, Cry4B, Cry10 and Cry11), Cyt (Cyt1 and Cyt2) and PS (PS2, PS3 and PS4) genes, it concluded presence of the PS1 gene. SDS-PAGE analysis revealed that proteolytically-cleavaged PS protein profiles exhibit patterns resembling those observed with PS1Aa1, with major bands at 56 kDa and 17 kDa (Bt7), and 41 kDa and 16 kDa (Bt5). Solubilized and trypsinized PS proteins from all Bt strains exhibited a marked and dose-dependent cytotoxicity against HeLa cancerous cells but not against HT-29 cells. IC50 values ranged from 3.2 (Bt1) to 14.2 (Bt6) with an average of 6.8 µg/mL. The observed cytotoxicity of PS proteins against HeLa cells was specific as it was not evident against normal uterus smooth muscle cells. RT-qPCR analysis revealed the overexpression of caspase 3 and caspase 9 by 3.7, and 4.2 folds, respectively, indicative of the engagement of intrinsic pathway of apoptosis. To the best of our knowledge, this is the first report exploring and exploiting the versatile repertoire of Saudi Arabian environmental niches for the isolation of native and possibly novel Saudi Bt strains with unique and specific anticancer activity. In conclusion, native Saudi Bt-derived PS proteins might have a potential to join the arsenal of natural anticancer drugs.

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Larvicidal activities of indigenousBacillus thuringiensisisolates and nematode symbiotic bacterial toxins against the mosquito vector Culex pipiens(Diptera: Culicidae)

Cited by 9 publications

References 57 publications

Susceptibility of Drosophila suzukii larvae to the combined administration of the entomopathogens Bacillus thuringiensis and Steinernema carpocapsae

Susceptibility of Drosophila suzukii larvae to the combined administration of the entomopathogens Bacillus thuringiensis and Steinernema carpocapsae

In vivo nanoscale analysis of the dynamic synergistic interaction of Bacillus thuringiensis Cry11Aa and Cyt1Aa toxins in Aedes aegypti

Specific Cytotoxic Effects of Parasporal Crystal Proteins Isolated from Native Saudi Arabian Bacillus thuringiensis Strains against Cervical Cancer Cells

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