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Abstract Objective This work was performed in support of a separate study investigating the activity of pesticidal proteins produced by Bacillus thuringiensis against the Asian citrus psyllid, Diaphorina citri. The fourteen Bacillus isolates chosen were selected from a large, geographically diverse collection that was characterized only by biochemical phenotype and morphology of the parasporal crystal, hence, for each isolate it was desired to determine the specific pesticidal proteins produced, assign each to a Bacillus cereus multilocus sequence type (ST), and predict their placement within the classical Bt serotyping system. In addition, phylogenetic distances between the isolates and Bacillus thuringiensis serovar type strains were determined by calculating digital DNA-DNA hybridization (dDDH) values among the isolates. Results Based on the assembled sequence data, the isolates were found to be likely representatives of the Bt serovars kurstaki (ST 8), pakistani (ST 550), toumanoffi (ST 240), israelensis (ST 16), thuringiensis (ST 10), entomocidus (ST 239), and finitimus (ST 171). In cases where multiple isolates occurred within a predicted serovar, pesticidal protein profiles were found to be identical, despite the geographic diversity of the isolates. As expected, the dDDH values calculated for pairwise comparisons of the isolates and their apparent corresponding Bt serovar type strains were quite high (> 98%), however dDDH comparisons of the isolates with other serovar type strains were often surprisingly low (

Objective: This work was performed in support of a separate study investigating the activity of pesticidal proteins produced by Bacillus thuringiensis against the Asian citrus psyllid, Diaphorina citri. The fourteen Bacillus isolates chosen were selected from a large, geographically diverse collection that was characterized only by biochemical phenotype and morphology of the parasporal crystal, hence, for each isolate it was desired to determine the specific pesticidal proteins produced, assign each to a Bacillus cereus multilocus sequence type (ST), and predict their placement within the classical Bt serotyping system. In addition, phylogenetic distances between the isolates and Bacillus thuringiensis serovar type strains were determined by calculating digital DNA-DNA hybridization (dDDH) values among the isolates. Results: Based on the assembled sequence data, the isolates were found to be likely representatives of the Bt serovars kurstaki (ST 8), pakistani (ST 550), toumanoffi (ST 240), israelensis (ST 16), thuringiensis (ST 10), entomocidus (ST 239), and finitimus (ST 171). In cases where multiple isolates occurred within a predicted serovar, pesticidal protein profiles were found to be identical, despite the geographic diversity of the isolates. As expected, the dDDH values calculated for pairwise comparisons of the isolates and their apparent corresponding Bt serovar type strains were quite high (> 98%), however dDDH comparisons of the isolates with other serovar type strains were often surprisingly low (< 70%) and suggest unrecognized taxa within Bt and the Bacillus cereus sensu lato. [ABSTRACT FROM AUTHOR]

The microbial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) (Bacillales: Bacillaceae) are well known for their efficacy and safety in mosquito control. In order to assess their potential value in future mosquito control strategies in western Kenya, the current study tested the susceptibility of five populations of Anopheles gambiae complex mosquitoes (Diptera: Culicidae), collected from five diverse ecological sites in this area, to Bti and Bs under laboratory conditions. In each population, bioassays were conducted with eight concentrations of larvicide (Bti/Bs) in four replicates and were repeated on three separate days. Larval mortality was recorded at 24 h or 48 h after the application of larvicide and subjected to probit analysis. A total of 2400 An. gambiae complex larvae from each population were tested for their susceptibility to Bti and Bs. The mean (± standard error of the mean, SEM) lethal concentration values of Bti required to achieve 50% and 95% larval mortality (LC50 and LC95 ) across the five populations were 0.062  (± 0.005) mg/L and 0.797 (± 0.087) mg/L, respectively. Corresponding mean  (± SEM) values for Bs were 0.058 (± 0.005) mg/L and 0.451 (± 0.053) mg/L, respectively. Statistical analysis indicated that the five populations of An. gambiae complex mosquitoes tested were fully susceptible to Bti and Bs, and there was no significant variation in susceptibility among the tested populations.

In this paper, we report a morphological study of the crystals and spores of different shapes synthesized by seven different strains of Bacillus thuringiensis. Crystals and spores were separated after 48 h of culture on T3 agar medium and imaged under a scanning electron microscope (SEM). Sizes of the crystals and spores were determined using Image J software. The results showed that crystal and spore sizes were normally distributed. In addition, the volumes and aspect ratios of the crystals and spores were calculated. The statistical analysis of the data showed the variability of the size distribution and morphological data of the crystals produced by the analyzed strains. Furthermore, variations in spore size and shape within the same serovar were observed, indicating that, perhaps, there are still some unexplored differences between strains of this serovar, making them less identical than what was believed so far. [ABSTRACT FROM AUTHOR]

The review presents materials on microbiocontrol of vector mosquitoes using entomopathogenic bacteria Bacillus thuringiensis ssp. israelensis (Bti). Control of invasive ectoparasites is a major health issue, as mosquito species are capable of transmitting diseases, including extremely dangerous human and animal infections (malaria, tularemia, yellow fever, hemorrhagic fevers, dengue fever, taiga (or tickborne) encephalitis, filariasis, Ku fever, cattle anaplasmosis and many other infections and invasions). Bti is considered worldwide as a promising microbial agent that combines targeted efficacy in protective measures and environmental safety. The study of the effect of Bti δ-endotoxins on the intestinal epithelium of Aedes genus mosquitoes, search and characterization of specific receptors are extremely important for understanding the mechanism of action and activity of entomocidal proteins, the basis of the pathogenic effect of polytypic B. thuringiensis. Synergism, a combination of selective larvicidal action of natural Bti strains in combination with strategies of resistance emergence preventing demonstrate a wide range of possibilities of their use and unique evolutionary features of this endospore-forming bacterium as a modern larvicidal agent against Aedes aegypti population. [ABSTRACT FROM AUTHOR]

In this paper, we report a morphological study of the crystals and spores of different shapes synthesized by seven different strains of Bacillus thuringiensis. Crystals and spores were separated after 48 h of culture on T3 agar medium and imaged under a scanning electron microscope (SEM). Sizes of the crystals and spores were determined using Image J software. The results showed that crystal and spore sizes were normally distributed. In addition, the volumes and aspect ratios of the crystals and spores were calculated. The statistical analysis of the data showed the variability of the size distribution and morphological data of the crystals produced by the analyzed strains. Furthermore, variations in spore size and shape within the same serovar were observed, indicating that, perhaps, there are still some unexplored differences between strains of this serovar, making them less identical than what was believed so far.

Xenorhabdus and Photorhabdus spp. (Enterobacteriaceae) can synthesize and release secondary metabolites that play crucial roles in their pathogenicity by suppressing the immunity of target insects. The insect immunity contributes to defense against the pathogenicity of Bacillus thuringiensis (Bt). This study tested a hypothesis that bacterial immunosuppresants could enhance the susceptibility of mosquitoes (Aedes albopictus and Culex pipiens pallens) to Bt. Three symbiotic bacteria [X. nematophila (Xn), X. hominickii (Xh), and P. temperata temperata (Ptt)] were cultured in nutrient broth to allow them to produce secondary metabolites. Bacillus thuringiensis israelensis (BtI) was highly toxic to both culicid mosquitoes with median lethal concentration (LC50, spores/ml) of 2.9 × 105 and 2.2 × 105 at 16 h after treatment, respectively. Addition of each bacteria-cultured broth enhanced BtI toxicity to these mosquito larvae. The LC50 values of BtI to Ae. albopictus larvae were reduced to 1.5 × 105 in Xn mixture, 1.7 × 105 in Xh mixture, and 1.9 × 105 in Ptt mixture. The LC50 values of BtI t o Cx. pipiens pallens larvae were also reduced to 1.2 × 105 in Xn mixture, 1.3 × 105 in Xh mixture, and1.5 × 105 in Ptt mixture. Adding benzylideneacetone or oxindole produced f r om Xn and Ptt also enhanced BtI toxicities to these mosquito larvae. Based on these results, we developed a new mosquitocidal Bt formulation called "Dip- Kill" consisting of 80% Xn-cultured broth, 10% BtI (1010 spores/ml), and 10% preservative. Dip-Kill at 1,000 ppm was superior to a commercial BtI product at its recommended dose. [ABSTRACT FROM AUTHOR]

Mosquitoes are both vectors of disease and a hindrance to outdoor activities. Since its discovery in 1976, the larvicide Bacillus thuringiensis var. israelensis (Bti) has proven its effectiveness in controlling mosquito populations, with negligible environmental impact. We performed an integrated, 5-year study on the potential ecological direct and indirect effects of mosquito control agent Bacillus thuringiensis var. israelensis (Bti applied as VectoBac1 WG) on phytoplankton communities in the Camargue temporary wetlands of the French Mediterranean coast. Mosquito larvae are considered major algae predators, so a distinct reduction in mosquito larva density (>80%) in natural wetlands due to Bti-treatment could be expected to indirectly affect these phytoplankton communities. Physical parameters and phytoplankton were sampled in the water of three temporary oligohaline pools between 2006 and 2011 in the following order: T0=1 day before treatment (control) - T2=2 days after treatment - T5=5 days after treatment - T11=11 days after treatment. No negative effects on phytoplankton densities and diversity could be attributed to Bti-treatment: no plytoplankton proliferation was observed in these treated pools. However, changes in the density of phytoplankton taxonomical groups were observed: the Diatoms group was reduced and replaced by other algal groups typical of temporary wetlands and able to tolerate drought. These results suggest that the phytoplankton community's evolution in total density, density of phytoplankton taxonomical groups and community structure is largely driven by natural environmental factors and by the ecological complexity of these temporary wetlands. [ABSTRACT FROM AUTHOR]

Two commercial preparations of Bacillus thuringiensis var. israelensis VectoBac WDG and Mousticide WP were evaluated and compared for larval control of Anopheles stephensi a malaria vector in Pakistan under laboratory and semi field conditions. An. stephensi larvae were susceptible to VectoBac WDG and Mousticide WP but susceptibility was higher for VectoBac WDG. In semi field experiment, VectoBac WDG @ 0.4 mg/L (1X LC100) and1.6 mg/L (4X LC100) remained more effective against An. stephensi L3 larvae up to day 7 whereas larval mortality dropped below 50% at day 14 of post VectoBac WDG application. Mousticide WP @ 1.22 mg/L (1X LC100) produced 79.33% mean mortality of An. stephensi L3 at 1 day post treatment. The larval mortality dropped to 30% at day 14 of post treatment with Mousticide WP. No significant difference was seen in larval mortality between two dose rates of VectoBac WDG and Mousticide WP. © 2014 Friends Science Publishers [ABSTRACT FROM AUTHOR]

A qualitative and quantitative population survey of immature and adult Chironomidae was conducted for 1 year in a country club wetlands in northeast Florida, USA. Glyptotendipes paripes and Goeldichironomus carus were the 2 predominant chironomid species in the wetlands. Adults of these 2 species emerged at nuisance levels from Apr through Jun, and in Aug and Sep. Polypedilum , Cryptochironomus , Tanytarsini, and Tanypodinae collected in low numbers during the survey were not identified to species. In laboratory bioassays, LC 90 values of technical grade temephos against G. paripes and G. carus were 0.01 and 0.009 ppm, respectively. For s-methoprene the LC 90 values were 0.082 and 0.055 ppm, and for Bacillus thuringiensis serovariety israelensis ( Bti ) 1.056 and 0.467 ppm, respectively. In experimental field plots in the wetlands, 5% AI Skeeter Abate® (temephos) pellets at 0.1 kg AI/ha reduced midge larvae by 52-86% and at 0.2 kg/ha by 74-92% during 4 weeks posttreatment. Sand formulated technical powder of Bti at 1,000,000 and 2,000,000 ITU (International Toxic Units) Bti /m 2 reduced midge larvae by 47-52% and 82-88%, respectively, during 6 to 20 days posttreatment. STRIKE® pellets (4.25% AI s -methoprene) at 0.14 kg AI/ha suppressed a maximum of 80% total chironomid adult emergence at 7 days posttreatment; this IGR at 0.28 kg AI/ha reduced adult emergence up to 92% during 15 days posttreatment. Temephos and Bti were more cost-effective and provided midge control for relatively longer period than s -methoprene in the field evaluations. [ABSTRACT FROM AUTHOR]

Abstract: The toxicity of Bacillus thuringiensis subsp. israelensis to dipteran larvae (mosquitoes and black flies) depends on the presence of the pBtoxis plasmid. In this paper, two antibiotic resistance tagged pBtoxis were transferred by conjugation to other Bacillus cereus group strains. Among 15 potential recipients, only a lepidopteran active B. thuringiensis subspecies kurstaki and a B. cereus strain received the plasmid pBtoxis with a low transfer rate of about 10−8 transconjugants/recipient. The resulting B. thuringiensis subspecies kurstaki transconjugant was active to both lepidopteran and dipteran targets and the B. cereus transconjugant was active against dipteran insects. Phase contrast microscopy showed that the B. cereus transconjugants could produce only round crystalline inclusion bodies while B. thuringiensis subspecies kurstaki transconjugant could produce both round and bipyramidal crystals during sporulation. SDS–PAGE revealed that all the major mosquitocidal proteins from pBtoxis could express in the two transconjugants, including Cry4Aa, Cry4Ba, Cry10Aa, Cry11Aa and Cyt1Aa. However, none of the experiment showed any indications of mobilising abilities of pBtoxis. The limited number of strains, which could receive and maintain pBtoxis using a conjugational helper plasmid, indicates a very narrow host range of the B. thuringiensis subsp. israelensis pBtoxis plasmid. [Copyright &y& Elsevier]

The susceptibility of Anopheles sinensis to Bacillus thuringiensis subsp. israelensis ( Bti ) was evaluated through exposure to varying concentrations of Bti . Mosquitoes were collected from five field populations of southern and central China (Zhongshan, Hengxian, Wuchang, Xinzhou, and Ruichang) and compared with a standard laboratory strain. The LC 50 values were 146.4, 50.4, 57.9, 50.0, 41.6 and 24.6 ng/mL, respectively. Differences in susceptibility to Bti ranging from 1.7 to 5.9-fold compared with the laboratory strain. The Zhongshan strain had the greatest resistance. At low doses, Bti displayed residual effects. Peak mortality occurred from the first to the fourth day. Exposure to low doses increased the duration of larval development and decreased the duration of pupal development, indicating that low doses of Bti have a sublethal effect on their hosts. [ABSTRACT FROM AUTHOR]