Bacillus Thuringiensis Strains Research Articles

A novel anti-dipteran Bacillus thuringiensis strain: Unusual Cry toxin genes in a highly dynamic plasmid environment.

Bacillus thuringiensis emerged as a major bioinsecticide on the global market. It offers a valuable alternative to chemical products classically utilized to control pest insects. Despite the efficiency of several strains and products available on the market, the scientific community is always on the lookout for novel toxins that can replace or supplement the existing products. In this study, H3, a novel B. thuringiensis strain showing mosquitocidal activity, was isolated from Lebanese soil and characterized at an in vivo, genomic and proteomic levels. H3 parasporal crystal is toxic on its own but displays an unusual killing profile with a higher LC50 than the reference B. thuringiensis serovar israelensis crystal proteins. In addition, H3 has a different toxicity order: it is more toxic to Aedes albopictus and Anopheles gambiae than to Culex pipiens Whole genome sequencing and crystal analysis revealed that H3 can produce eleven novel Cry proteins, eight of which are assembled in genes with an orf1-gap-orf2 organization, where orf2 is a potential Cry4-type crystallization domain. Moreover, pH3-180, the toxin-carrying plasmid, holds a wide repertoire of mobile genetic elements that amount to ca 22% of its size., including novel insertion sequences and class II transposable elements Two other large plasmids present in H3 carry genetic determinants for the production of many interesting molecules - such as chitinase, cellulase and bacitracin - that may add up to H3 bioactive properties. This study therefore reports a novel mosquitocidal Bacillus thuringiensis strain with unusual Cry toxin genes in a rich mobile DNA environment.IMPORTANCE Bacillus thuringiensis, a soil entomopathogenic bacteria, is at the base of many sustainable eco-friendly bio-insecticides. Hence stems the need to continually characterize insecticidal toxins. H3 is an anti-dipteran B. thuringiensis strain, isolated from Lebanese soil, whose parasporal crystal contains eleven novel Cry toxins and no Cyt toxins. In addition to its individual activity, H3 showed potential as a co-formulant with classic commercialized B. thuringiensis products, to delay the emergence of resistance and to shorten the time required for killing. On a genomic level, H3 holds three large plasmids, one of which carries the toxin-coding genes, with four occurrences of the distinct orf1-gap-orf2 organization. Moreover, this plasmid is extremely rich in mobile genetic elements, unlike its two co-residents. This highlights the important underlying evolutionary traits between toxin-carrying plasmids and the adaptation of a B. thuringiensis strain to its environment and insect host spectrum.

Biological nitrogen removal capability and pathways analysis of a novel low C/N ratio heterotrophic nitrifying and aerobic denitrifying bacterium (Bacillus thuringiensis strain WXN-23)

A novel heterotrophic nitrification and aerobic denitrification (HNAD) bacteria, identified as Bacillus thuringiensis strain WXN-23, was isolated from husk feed filtrate of a pig farm. It was the first report of Bacillus thuringiensis with the capability for HNAD and could adapt to the condition of low Carbon/Nitrogen (C/N) ratio. Nitrogen could be efficiently removed by the strain WXN-23 in simulated wastewater, be it in single or mixed form nitrogen sources. The nitrogen balance revealed that 63.5% of the initial nitrogen (5.32 mg) was lost in the form of N2. The conditions for maximum total nitrogen (TN) removal efficiency (95.996%) were shaking speed of 126.89 r/min, a carbon C/N ratio of 5.91, the temperature of 32.81 °C, and a pH value of 8.17. The nitrification-denitrification metabolic pathway (NH4+–N→NH2OH→NO2−-N→NO3−-N→NO2−-N→NO→N2O→N2) under aerobic conditions was determined on the basic of characteristic of N removal, N balance analysis, enzyme assay and functional genes amplification results. Strain WXN-23 was effective at wastewater treatment, with TN, NH4+-N, NO3−-N and NO2−-N removal efficiencies of 82.12%, 86.74%, 90.74% and 100%, respectively.

Improving the Bioremediation Technology of Contaminated Environments Using Biosurfactants Produced by Novel Bacillus Isolates

Biosurfactants have many advantages outside chemical one, led for application it through different sectors. So, the present study aimed for improving the bioremediation technology of contaminated environments using biosurfactants produced by novel bacillus isolates. In this regard, novel Egyptian Bacillus thuringiensis and Bacillus toyonensis strains were obtained as most producing isolates of highly active biosurfactants. The optimized conditions for high biosurfactants yield production were established. Also, the stability of the produced biosurfactants at various conditions, pH, temperature and salinity was studied. The biosurfactant has been reported up to 120 ˚C, pH 12 and 10% NaCl. The identified biosurfactants, Decanoic acid and oleamide were applied for wastewater remediation from oil residues and pathogens contamination. The biosurfactant was had high antibacterial activity compared with references antimicrobial drugs, as well as it is enhanced bioremediation technology for petroleum oil residues contaminating sites. Thus, we can say, these biosurfactants could achieve the objectives of sustainable development.

Field Evaluation of Native B. thuringiensis Isolates Against Aphids (Aphis fabae)

Objectives: The purpose of this study was to evaluate the aphicidal activity of native Bacillus thuringiensis (Bt) strains.
 Methods: Soil samples of Provinces 2 and 3 of Nepal were collected randomly for isolation of Bt by acetate selection method. Bt were identified by observing insecticidal crystal proteins (ICPs) by Commassie Brilliant Blue (CBB) staining technique. Aphicidal activity of 12 B. thuringiensis isolates was evaluated by two processes. The preliminary screening was done by spraying the suspension containing the spore and ICPs mixture in Phaseolus species heavily infested with black aphids (Aphis fabae) in fi elds. The second process (selective bioassay) was done by counting the number of aphids (nymphs, instar, winged, wingless) before and after spraying 5ml of suspension containing the spore and ICPs mixture on the leaf or on the beans pods surface infested by Aphids. The mortality percentage of Aphids after treatment was calculated on the 4th day, by counting the live aphids and the result was recorded.
 Results: Preliminary screening for aphicidal activity revealed that 4 isolates ML5(1), CW1(1), SN2(1) and MP2(1) producing spherical crystal protein, showed 100% mortality against nymphs, instar, winged and wingless Aphids. Isolates were effective in controlling the Aphid (Aphis fabae) within 4 days and the part of the plant that was sprayed becomes free of Aphids. Selective bioassay of native isolate MP3(3) was most effective in killing 95.83% of aphids followed by CW2(1), 85.71%, ML5(1), 77.34%, SN3(1), 72.72%, CW1(1), 70.21%.
 Conclusion: This study revealed that indigenous Bacillus thuringiensis of Terai region of Nepal are effective in controlling Aphids.

Novel degradation pathways for Chlorpyrifos and 3, 5, 6-Trichloro-2-pyridinol degradation by bacterial strain Bacillus thuringiensis MB497 isolated from agricultural fields of Mianwali, Pakistan

Over use of organophosphate pesticides including Chlorpyrifos (CPF) has led to contamination of soil and water resources, resulting in serious health problems in humans along with other non-target organisms. The current study was aimed to investigate Chlorpyrifos as well as 3, 5, 6-Trichloro-2-pyridinol (TCP) biodegradation tendency of bacterial strain Bacillus thuringiensis MB497 isolated from wheat/cotton fields of Dera Saleemabad, Mianwali, Pakistan, having a history of heavy Organophosphate pesticides application. HPLC analysis revealed almost 99% degradation of the spiked CPF (200 mg L−1) in M-9 broth, soil slurry and soil microcosm by MB497 after 9 days of incubation. Strain MB497 was also able to degrade and transform TCP (28 mg L−1), up to 90.57% after 72 h of incubation in M-9 broth. A novel compound Di-isopropyl methanephosphonate along with known products of 3, 5, 6-Trichloro-2-pyridinol (TCP), Diethyl thiophospsphate and Phosphorothioic acid were detected as metabolites of CPF by GCMS analysis. Three novel metabolites of TCP (p-Propyl phenol, 2-Ethoxy-4, 4, 5, 5-tetramethyloxazoline and 3-(2, 4, 5-Trichlorophenoxy)-1-propyne) were identified after 72 h. Based on these metabolites, new/amended metabolic pathways for CPF and TCP degradation in these bacteria has been suggested.

Coexistence of cry9 with the vip3A Gene in an Identical Plasmid of Bacillus thuringiensis Indicates Their Synergistic Insecticidal Toxicity.

Bacillus thuringiensis (Bt) strains may express several insecticidal proteins with synergistic features, achieving high insecticidal toxicity and delaying development of resistance in insect pests. Previous work showed that Cry9Aa and Vip3Aa proteins present synergistic activity against Chilo suppressalis. In this study, genome-wide analysis of 489 Bt genomes revealed that cry9A was associated with the vip3A gene in seven Bt strains. Among all Bt genomes analyzed, not a single strain was found to have the cry9A gene alone without the presence of the vip3A gene. The complete genome sequencing of two Bt strains, 4AP1 and 4AO1, revealed that cry9A and vip3A genes were located in the same plasmid in both strains. The genome context analysis suggested a recombination mechanism responsible for the insertion of the cry9A gene into the plasmid containing vip3A. The coexistence of Cry9A with Vip3A proteins in strain 4AP1 was confirmed by liquid chromatography-tandem mass spectrometry and western blot analyses. Furthermore, another Cry9 protein codified by the gene in the identical plasmid also showed synergistic activity with the Vip3A protein. Overall, our results support that cry9 genes coexisted with vip3A and that complete genome sequencing combined with protein expression analysis may be used to identify associations of insecticidal proteins with potential synergistic toxicity.

Argentinean Bacillus thuringiensis strains exhibiting distinct morphology of their parasporal crystals

Argentinean Bacillus thuringiensis strains exhibiting distinct morphology of their parasporal crystals

Long inverted repeats around the chromosome replication terminus in the model strain Bacillus thuringiensis serovar israelensis BGSC 4Q7

Bacillus thuringiensis serovar israelensis is the most widely used natural biopesticide against mosquito larvae worldwide. Its lineage has been actively studied and a plasmid-free strain, B . thuringiensis serovar israelensis BGSC 4Q7 (4Q7), has been produced. Previous sequencing of the genome of this strain has revealed the persistent presence of a 235 kb extrachromosomal element, pBtic235, which has been shown to be an inducible prophage, although three putative chromosomal prophages have been lost. Moreover, a 492 kb region, potentially including the standard replication terminus, has also been deleted in the 4Q7 strain, indicating an absence of essential genes in this area. We reanalysed the genome coverage distribution of reads for the previously sequenced variant strain, and sequenced two independently maintained samples of the 4Q7 strain. A 553 kb area, close to the 492 kb deletion, was found to be duplicated. This duplication presumably restored the equal sizes of the replichores, and a balanced functioning of replication termination. An analysis of genome assembly graphs revealed a transient association of the host chromosome with the pBtic235 element. This association may play a functional role in the replication of the bacterial chromosome, and the termination of this process in particular. The genome-restructuring events detected may modify the genetic status of cytotoxic or haemolytic toxins, potentially influencing strain virulence. Twelve of the single-nucleotide variants identified in 4Q7 were probably due to the procedure used for strain construction or were present in the precursor of this strain. No sequence variants were found in pBtic235, but the distribution of the corresponding 4Q7 reads indicates a significant difference from counterparts in natural B. thuringiensis serovar israelensis strains, suggesting a duplication or over-replication in 4Q7. Thus, the 4Q7 strain is not a pure plasmid-less offshoot, but a highly genetically modified derivative of its natural ancestor. In addition to potentially influencing virulence, genome-restructuring events can modify the replication termination machinery. These findings have potential implications for the conclusions of virulence studies on 4Q7 as a model, but they also raise interesting fundamental questions about the functioning of the Bacillus genome.

Genome sequence of a Vietnamese Bacillus thuringiensis strain TH19 reveals two potential insecticidal crystal proteins against Etiella zinckenella larvae

The soybean pod borer Etiella zinckenella was considered to cause the most severe damage to soybean crop in many Asian countries. However, Bacillus thuringiensis is a spore-forming bacterium which is widely and effectively used for insects and nematodes management strategies as an eco-friendly biopesticide. Therefore, in this study, a whole genome of a promising indigenous Bt strain TH19 was sequenced and two potential insecticidal cry1 genes were revealed. Homology comparisons showed that the amino acid sequences of determined Cry1 proteins were 100% similar to those of the known truncated Cry1Aa4 and full length of Cry1Ia34 proteins in the NCBI database. The recombinant Cry1Aa4 and Cry1Ia34 proteins expressed in Escherichia coli strain BL21 (DE3) were confirmed by Western blot analysis. Insecticidal bioassays with neonatal larvae of E. zinckenella indicated that the toxicities of purified Cry1Aa4 and Cry1Ia34 intensely impacted to E. zinckenella lives, and their combination acted the most efficiently with relative LC50 values of 59.80 ng/cm2, 89.99 ng/cm2 and 38.33 ng/cm2. The histopathological modifications detected in midgut tissue included brush border membrane lysis, vesicles formation, disintegration of the apical membrane, and microvilli breakages. These results demonstrated that Cry1Aa4 and Cry1Ia34 proteins of Bt strain TH19 could account for key factors in biopesticide products against E. zinckenella.

Promising active bioinsecticides produced by Bacillus thuringiensis strain BLB427

Bacillus thuringiensis is gaining worldwide importance in the control of pests in agriculture and public health. Characterization of new isolated strains with original, higher and broader spectrum of activity is an ever developing field. Parasporal inclusions from BLB427, a new B. thuringiensis strain isolated from Tunisian soil, contained 2 major Cry proteins having molecular weights of about 130-135 kDa and 65-70 kDa corresponding to cry1-type and cry2-type genes, respectively. These toxins exhibited high toxicities to Ephestia kuehniella and Spodoptera littoralis larvae, with LC50 values of about 81.91 µg/cm2 (+/- 15.30) and 79.70 µg/cm2 (+/- 36.73), respectively. BLB427 supernatant showed a promising activity against Lepidopteran pests due to the presence of vip3-type gene in this strain. The high toxicity of BLB427 supernatant compared to that of BUPM95, used as control, was due in part to the high copy number of vip3 gene of BLB427 compared to that of vip3Aa16 of BUPM95, as demonstrated by Real-time PCR. This gene was cloned, sequenced and the comparison with the most known vip3 genes in databases, demonstrated that vip3(427) gene and the corresponding protein showed differences that can influence the efficiency of the Vip3(427) toxin against Lepidoptera. After overexpression of Vip3(427) protein in Esherichia coli and its purification using His-Trap column, the toxin showed a promising toxicity against the lepidopteran pest S. littoralis with extremely damages in the larvae midgut traduced by the vacuolization of the apical cells, the damage of microvilli and the disruption of epithelial cells. The results described in the present study proved that B. thuringiensis BLB427 strain could be of a great interest for lepidopteran biocontrol by using its d-endotoxins and/or Vip3 toxins in bioinsecticides formulations.

Promising active bioinsecticides produced by Bacillus thuringiensis strain BLB427

Promising active bioinsecticides produced by Bacillus thuringiensis strain BLB427

Efficacy of entomopathogenic nematode and Bacillus thuringiensis combinations against Holotrichia parallela (Coleoptera: Scarabaeidae) larvae

The larvae of Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae) are notorious soil insect pests that cause severe damage to crop production in China. However, the long-term use of insecticides seriously pollutes the environment and threatens human health. Therefore, an environmentally friendly, alternative control method to insecticides is crucial to effectively control these pests. In this study, we assessed the efficacies of possible combinations of entomopathogenic nematodes (EPNs), the Heterorhabditis beicherriana LF strain and Bacillus thuringiensis (Bt) strain HBF-18 to control H. parallela larvae under laboratory and field conditions. In the laboratory, the newly identified H. beicherriana LF strain showed higher pathogenicity than Heterorhabditis bacteriophora H06, Steinernema carpocapsae ALL and Steinernema carpocapsae SF-SN against H. parallela second instar larvae. The H. beicherriana LF strain exhibited a strong potential to control H. parallela larvae at an optimum temperature of 25 °C and soil moisture of 18%. The H. beicherriana LF strain was compatible with Bt (HBF-18). All EPN-Bt combinations caused significantly higher corrected mortality of H. parallela larvae than nematodes were applied alone after 7 and 11 days; in particular, a stronger synergistic effect was detected when Bt (HBF-18) at LC50 concentrations (0.79 × 107 CFU/g of soil) were combined with EPNs. In the peanut field experiment, synergistic interactions were observed for the combinations of the H. beicherriana LF strain (1 × 103 IJs/plant) and Bt (HBF-18) (1.14 × 1010 CFU/plant) against H. parallela third instar larvae, resulting in a sizable white grub reduction of 83.9 ± 0.82%. Our findings suggested that combining the H. beicherriana LF strain and Bt (HBF-18) is a recommended and practical strategy to manage pests in crop production systems.

Genomics and Proteomics Analyses Revealed Novel Candidate Pesticidal Proteins in a Lepidopteran-Toxic Bacillus thuringiensis Strain.

Discovery and identification of novel insecticidal proteins in Bacillus thuringiensis (Bt) strains are of crucial importance for efficient biological control of pests and better management of insect resistance. In this study, the Bt strain KhF, toxic for Plodia interpunctella and Grapholita molesta larvae, underwent genomics and proteomics analyses to achieve a better understanding of the bases of its pathogenicity. The whole-genome sequencing results revealed that the KhF strain contained nine coding sequences with homologies to Bt insecticidal genes. The lepidopteran toxic mixture of spores and crystals of this Bt strain was subjected to liquid chromatography and tandem mass spectrometry (LC-MS/MS) to assess the protein composition. The results of the proteomic analyses, combined with the toxin gene sequences, revealed that two of the main components of the crystals were two new candidate pesticidal proteins, named KhFA and KhFB. These proteins showed a similarity lower than 36% to the other known Bt toxins. The phylogenetic analysis showed that the KhFA and KhFB grouped with the newly denominated Xpp and Mpp (former ETX/Mtx) pesticidal protein groups, respectively. Altogether, this study has led to the discovery of two novel candidate pesticidal toxins in the lepidopteran toxic KhF strain.

Potential of standard strains of Bacillus thuringiensis against the tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

BackgroundThe tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the key pests of tomato worldwide, causing an estimated crop loss of 80 to 100%. This pest has developed resistance to several pesticides due to overuse, resulting in control failures in the field. The use of biological insecticides as Bacillus thuringiensis that expressed insecticidal proteins can be an alternative tool by insecticides to suppress the pest population.Main bodyLaboratory study investigated the efficacy of standard Bacillus thuringiensis (Bt) strains (4D1, 4D4, 4G1, 4K5 and 4XX4) against T. absoluta. Bioassay was conducted using tomato leaf discs treated with spore crystal lysates prepared from the standard strains, and mortality data was subjected to concentration-mortality probit analysis. The LC50 values for Bt 4D1, Bt 4D4 and Bt 4G1 were 6.10, 6.62 and 8.18 μg/ml for the 2nd instar; 9.90, 10.20 and 11.12 μg/ml for the 3rd instar; and 19.82, 23.16 and 24.54 μg/ml for the 4th instar, respectively, while the Bt 4K5 and Bt 4XX4 were not toxic to T. absoluta.ConclusionThis study suggests that Bt strain 4D1 is effective against different larval instars of the pest and can be used in its management.

Biodegradation of Cellulose by New Recombinants of Rhizobium Harboring Cellulase Genes التخلص الآمن من السلیلوز من خلال تحلیله حیویاً بواسطة إتحادات وراثیة جدیدة من الرایزوبیوم تحمل جینات السلیولیز

Plant biomass is efficiency decomposed by a great number of different microbial enzymes. The enzyme systems in cellulolytic bacteria have been genetically improved via plasmid transfer and genome shortening. In this study six conjugations were done between six parental strains carrying the opposite genetic markers from which 18 transconjugants were evaluated for biodegradation of cellulose. Three strains of Rhizobium leguminosarum bv. trifolii were used as recipients against Bt and Serratia strains expressing cellulose activity as donors. The wild type strains of Bacillus thuringiensis and Rhizobium encoded significant cellulose biodegradation after genome shortening. In addition, all transconjugants resulted from the mating between Bt1 and Rh11 expressed significant cellulase activities after curing. In constrant, all transconjugants results from the mating between Bt2 x Rh6 and Bt2 x Rh11 appeared insignificant differences in cellulase activity before and after curing. Meanwhile, the parental strains Rh6 and Rh11 expressed significant cellulase activity after curing. Furthermore, all transconjugants resulted from the mating between Sm x Rh6 and Sm x Rh15 encoded significant cellulase activity after curing. This work provides efficiently encoded cellulases in genome shortening mutants than in the wild type. The enzymes encoded in this study represented that cellulase expressing genes were located on the bacterial chromosome and plasmids. Though, plant infection of legumes was affected by Rhizobia cellulases which considered as important determinant in nodulation process.

Bacillus thuringiensis strains isolated from Qatari soil, synthesizing δ-endotoxins highly active against the disease vector insect Aedes aegypti Bora Bora

Bacillus thuringiensis (Bt) is a Gram-positive soil bacterium that has been recognized as an effective bioinsecticide active against plant, animal and human pathogenic and disease vector insects. During its sporulation phase, Bt produces crystals consisting of δ-endotoxins, which upon ingestion kill specifically insect larvae. Bt subsp. israelensis (Bti) is very active against dipteran insects. Bti based bioinsecticides are considered as a sustainable solution to control the Dipteran insects responsible of plant, animal and human diseases. In this study, Bti strains isolated from Qatar soil were analyzed for their insecticidal activities against the dipteran insect Aedes aegypti Bora Bora (Culicidae, Diptera) and for their δ-endotoxins yields per cell. Among the local Bti strains, four exceptional strains producing spherical crystals, were found to be more insecticidal than the reference strain Bti H14. When tested for their δ-endotoxin yield, the Bti QBT217 strain, producing typical spherical crystals and having the best insecticidal activity, was recognized as the best candidate strain for potential bioinsecticide production and biological control of dipteran insects, particularly the disease vector insect A. aegypti.

Molecular diversity and hydrolytic enzymes production abilities of soil bacteria.

Soil is an integral part of ecosystem which is niche for varieties of microflora. The present study was investigated to isolate varied strains of bacteria from soil samples of three different geographical regions of Tamil Nadu (India) and evaluate their hydrolytic enzymes (amylase, cellulase, and inulinase) producing potentialities. Among 72 bacterial cultures isolated from Ambattur Industrial Estate, Neyveli Lignite Corporation, and Arignar Anna Zoological Park regions, 41.66, 38.88, and 36.11% of isolates were observed amylase, cellulase, and inulinase producers, respectively. On the other hand, 20.83% of total bacteria isolated from all three regions exhibited concurrent production of amylase, cellulase, and inulinase. Potent isolates depicting maximum enzyme activities were identified as Bacillus anthracis strain ALA1, Bacillus cereus strain ALA3, Glutamicibacter arilaitensis strain ALA4, and Bacillus thuringiensis strain ALA5 based on molecular characterization tools. Further, the thermodynamics parameters, open reading frames (ORFs) regions, and guanine-cytosine (GC) content were determined by distinct bioinformatics tools using 16S rRNA sequences of strains. Minimum free energy values for strain ALA1, strain ALA3, strain ALA4, and strain ALA5 were calculated as −480.73, −478.76, −496.63, and −479.03 kcal/mol, respectively. Mountain plot and entropy predicted the hierarchical representation of RNA secondary structure. The GC content of sequence for strain ALA1, strain ALA3, strain ALA4, and strain ALA5 was calculated as 53.06, 52.94, 56.78, and 53.06%, respectively. Nine ORFs were obtained for strain ALA1, strain ALA3, and strain ALA5 while 10 ORFs were observed for strain ALA4. Additionally, bootstrap tree demonstrated close resemblance of strains with existing bacteria of similar genus. Findings showed higher variability of bacterial diversity as hydrolytic enzymes producers in the investigated geographical regions.

The C. elegans GATA transcription factor elt-2 mediates distinct transcriptional responses and opposite infection outcomes towards different Bacillus thuringiensis strains.

The nematode Caenorhabditis elegans has been extensively used as a model for the study of innate immune responses against bacterial pathogens. While it is well established that the worm mounts distinct transcriptional responses to different bacterial species, it is still unclear in how far it can fine-tune its response to different strains of a single pathogen species, especially if the strains vary in virulence and infection dynamics. To rectify this knowledge gap, we systematically analyzed the C. elegans response to two strains of Bacillus thuringiensis (Bt), MYBt18247 (Bt247) and MYBt18679 (Bt679), which produce different pore forming toxins (PFTs) and vary in infection dynamics. We combined host transcriptomics with cytopathological characterizations and identified both a common and also a differentiated response to the two strains, the latter comprising almost 10% of the infection responsive genes. Functional genetic analyses revealed that the AP-1 component gene jun-1 mediates the common response to both Bt strains. In contrast, the strain-specific response is mediated by the C. elegans GATA transcription factor ELT-2, a homolog of Drosophila SERPENT and vertebrate GATA4-6, and a known master regulator of intestinal responses in the nematode. elt-2 RNAi knockdown decreased resistance to Bt679, but remarkably, increased survival on Bt247. The elt-2 silencing-mediated increase in survival was characterized by reduced intestinal tissue damage despite a high pathogen burden and might thus involve increased tolerance. Additional functional genetic analyses confirmed the involvement of distinct signaling pathways in the C. elegans defense response: the p38-MAPK pathway acts either directly with or in parallel to elt-2 in mediating resistance to Bt679 infection but is not required for protection against Bt247. Our results further suggest that the elt-2 silencing-mediated increase in survival on Bt247 is multifactorial, influenced by the nuclear hormone receptors NHR-99 and NHR-193, and may further involve lipid metabolism and detoxification. Our study highlights that the nematode C. elegans with its comparatively simple immune defense system is capable of generating a differentiated response to distinct strains of the same pathogen species. Importantly, our study provides a molecular insight into the diversity of biological processes that are influenced by a single master regulator and jointly determine host survival after pathogen infection.

Potentials of Indigenous <I>Bacillus thuringiensis</I> Isolates from the soil in controlling <I>Fusarium wilt of Cucumber cause by Fusarium oxysporum f.sp cucumerinum</I>

Cucumber (Cucumis sativus L.) production is generally low in Nigeria due to continuous soil nutrient limitation and diseases. However, the persistence in the use of agrochemicals for cucumber production in Nigeria is associated with high cost and deleterious effects on man, animal and the environment. This study was conducted to investigate the potentials of indigenous Bacillus thuringiensis (Bt), a spore-forming bacterium known for its insecticidal properties in controlling Fusarium wilt of cucumber. Bacillus thuringiensis strains were isolated from soil samples collected from different farm sites in Abeokuta, Nigeria, and identified phenotypically and molecularly. The in-vitro antagonistic activity of B. thuringiensis strains on F. oxysporum f.sp. cucumerinum was evaluated by dual culture method, followed by pot experiment in the screen house. 16S rRNA gene sequencing was performed on the antagonistic B. thuringiensis to confirm Bt species. The results of the in-vitro antagonistic activity revealed that most indigenous B. thuringiensis strains showed significant growth inhibition of Fusarium oxysporium f. sp. cucumerinum. Similarly, application of B. thuringiensis A and C isolates significantly suppressed the incidence of Fusarium wilt of cucumber in the screen house when compared to the control. The 16S rRNA gene sequencing technique identified the isolates A and C as Bacillus thuringiensis strain LTS-209 and Bacillus thuringiensis strain VITSJ-01, respectively. Hence, indigenous B. thuringiensis A and C isolates should be incorporated into cucumber cultivation for controlling Fusarium wilt disease of cucumber.
 Keywords: Cucumber, Bacillus thuringiensis, Fusarium wilt, 16S rRNA gene

Efficacy of integrated microorganisms in controlling root-knot nematode Meloidogyne javanica infecting peanut plants under field conditions

BackgroundPeanut (Arachis hypogaea L.) is considered one of the most important legume and oil crops in Egypt. Root-knot nematodes Meloidogyne spp. is the most damaging nematodes of peanut. Losses can exceed 50% in severely infested soil. Application of nematicides is one of the primary strategies in controlling plant-parasitic nematodes. The nematicides are proven to be hazardous to the environment. A promising alternative is the use of microorganisms antagonistic to plant-parasitic nematodes. Some microorganisms that can grow in the rhizosphere such as Azotobacter and Bacillus bacteria and fungi, e.g., Tricoderma and Paecilomyces represent the front line of defense for roots against nematode attack and ideal for use as biocontrol agents.ObjectivesThe main aim of this study was to evaluate the efficacy of application of yeast fungus Saccharomyces cerevisiae singly or combined with fusant Bas 8; (Bacillus amyloliquefaciens and Lysinibacillus sphaericus Amira strain); Bacillus thuringiensis strain code K, Trichoderma harzianum, or Paecilomyces lilacinus to control the root-knot nematode Meloidogyne javanica infecting peanut plant cv. Giza 6, and to estimate their yield under field conditions.ResultsCompared to the untreated control, all treatments exhibited variable potential inhibitory activities against root-knot nematode M. javanica and enhanced peanut yield production. The most nematode suppressive treatment was the single treatment of Saccharomyces cerevisiae, followed by T. harzianum either singly or combined with the yeast. Moreover, data indicated that application of the combined treatment of yeast plus T. harzianum gave the best results in improving peanut production, plant growth parameters, and seed nutrient contents.ConclusionIt was concluded that integrated application of microorganisms could enhance peanut production and reduce the need for either chemical fertilizers or nematicides.