Ecological advantages of using microbiomethod in an integrated plant protection system

The article presents an analysis of current domestic and world literature data on the use of microbiomethod in plant protection. It has been proven, that biological preparations based on different biotypes of entomopathogenic bacteria Bacillus thuringiensis, due to their high specificity to various insect species and harmlessness to adult bees, warm-blooded and freshwater organisms, remain at the forefront of integrated plant protection systems worldwide. Their amount is up to 95% of all bioinsecticides. Being natural elements of biocenoses, entomopathogenic microorganisms do not harm plants. Moreover, the introduction of a number of bacteria into the soil and on the surface of plants promotes the growth of crops and increase their yield.Given the economic non-competitiveness of bioinsecticides compared to chemical insecticides, their use in Integrated Pest Management (IPM) Systems is appropriate for the control of phytophages against which they are highly effective. The negative result of chemical insecticides is not only the pollution of the environment and products, but also the formation and spread of resistant races and pest populations. The higher cost of microbiomethod is justified by the lack of negative long-term effects of massive use of chemical insecticides.

ORFograph: search for novel insecticidal protein genes in genomic and metagenomic assembly graphs

Background Since the prolonged use of insecticidal proteins has led to toxin resistance, it is important to search for novel insecticidal protein genes (IPGs) that are effective in controlling resistant insect populations. IPGs are usually encoded in the genomes of entomopathogenic bacteria, especially in large plasmids in strains of the ubiquitous soil bacteria, Bacillus thuringiensis (Bt). Since there are often multiple similar IPGs encoded by such plasmids, their assemblies are typically fragmented and many IPGs are scattered through multiple contigs. As a result, existing gene prediction tools (that analyze individual contigs) typically predict partial rather than complete IPGs, making it difficult to conduct downstream IPG engineering efforts in agricultural genomics. Methods Although it is difficult to assemble IPGs in a single contig, the structure of the genome assembly graph often provides clues on how to combine multiple contigs into segments encoding a single IPG. Results We describe ORFograph, a pipeline for predicting IPGs in assembly graphs, benchmark it on (meta)genomic datasets, and discover nearly a hundred novel IPGs. This work shows that graph-aware gene prediction tools enable the discovery of greater diversity of IPGs from (meta)genomes. Conclusions We demonstrated that analysis of the assembly graphs reveals novel candidate IPGs. ORFograph identified both already known genes “hidden” in assembly graphs and potential novel IPGs that evaded existing tools for IPG identification. As ORFograph is fast, one could imagine a pipeline that processes many (meta)genomic assembly graphs to identify even more novel IPGs for phenotypic testing than would previously be inaccessible by traditional gene-finding methods. While here we demonstrated the results of ORFograph only for IPGs, the proposed approach can be generalized to any class of genes.

Aerogels as Pesticides

Aerogels, composed of complex network of interlinked nanostructures, show 50% non-solid volume. Due to their unique properties, they are used as a carrier for active ingredients used to control agricultural pests as well as veterinary medicines. They can also be used as a carrier material for the application of entomopathogenic bacteria and viruses for the biological control of pests. Many aerogel-based formulations of herbicides, insecticides, acaricides, fungicides, bactericides, rodenticides, nematicides, piscicides and molluscicides effectively control the target pests. Practically, aerogels enhance the effectiveness of insecticides by increasing their penetrations. Furthermore, intensive research is required to develop latest aerogel-based pesticides with better utilization under effective integrated pest management programs in agriculture.

Application strategies by selective medium treated with entomopathogenic bacteria Serratia marcescens and Pseudomonas aeruginosa as potential biocontrol against Coptotermes curvignathus

The success of microbial termiticides in controlling termites depends on the ability of microbes to grow in different media and the functionality of the microbes as a resistant barrier or toxic bait. This study was conducted to understand the mortality rate and behaviour changes of the subterranean termite Coptotermes curvignathus Holmgren introduced with different concentrations of Serratia marcescens strain LGMS 1 and Pseudomonas aeruginosa strain LGMS 3 using wood and soil as bacterial transfer medium. In general, higher concentration of bacteria in soil caused a reduction in tunnelling activity and wood consumption and an increase in mortality. However, application on wood revealed a different outcome. Wood treated with S. marcescens of 10 6 CFU ml −1 concentration proved to be more efficient as bait than higher concentration applications as it caused a high mortality rate while still highly palatable for termites. Wood or soil treated with S. marcescens concentration higher than 10 9 CFU ml −1 creates a high toxicity and repellent barrier for termites. Pseudomonas aeruginosa of 10 9 CFU ml −1 concentrations applied on wood served as a slow-acting toxic bait. However, the ability for S. marcescens and P. aeruginosa to survive on wood is low, which made the bait unable to retain a useful level of toxicity for a long period of time and frequent reapplication is needed.

Effects of NF-kB Signaling Inhibitors on Bed Bug Resistance to Orally Provisioned Entomopathogenic Bacteria

Bed bugs are globally important pests and there is an ongoing need for the development and improvement of bed bug control tools. Though promising against other insect pests, the exploration of biological methods for bed bug control is limited. Previously, we identified several species of bacteria that have entomopathogenic effects against bed bugs when ingested. We also described the conservation of several antibacterial responses in bed bugs, including the expression of immune effector genes regulated by NF-kB transcription factors through the Toll and immune deficiency (IMD) signaling pathways. Accordingly, we predicted that chemical inhibition of NF-kB signaling could reduce bed bug resistance to orally provisioned entomopathogenic bacteria, potentially improving their effectiveness as biological control agents. In the present study, we administered four small molecule inhibitors of NF-kB signaling (BMS345541, IKK16, IMD0354, Takinib) to bed bugs by feeding them in a blood meal. We then quantified basal mortality and mortality in response to oral infection with two different entomopathogenic bacteria (Pseudomonas entomophila and Bacillus thuringiensis israelensis). None of the NF-kB signaling inhibitors tested increased mortality above control levels when administered alone, suggesting a lack of direct toxicity. However, one inhibitor (IKK16) significantly enhanced the rate of mortality from oral infection with P. entomophila. Enhanced mortality was independent of direct effects of IKK16 on P. entomophila growth in vitro but was associated with higher bacterial loads in vivo (i.e., reduced resistance). Together, these results provide new insight into the regulation of the bed bug immune system and suggest that administration of entomopathogens in combination with inhibition of immune signaling pathways to reduce infection resistance may be effective for biological control of bed bugs.

Culex quinquefasciatus carrying Wolbachia is less susceptible to entomopathogenic bacteria

In an attempt to evaluate the susceptibility of the mosquito Culex quinquefasciatus to bacterial agents, a population naturally infected with a Wolbachia pipientis wPipSJ native strain was tested against the action of three bacterial mosquitocides, Bacillus thuringiensis subsp. israelensis, Bacillus wiedmannii biovar thuringiensis and Lysinibacillus sphaericus. Tests were carried out on mosquito larvae with and without Wolbachia (controls). Cx. quinquefasciatus naturally infected with the native wPipSJ strain proved to be more resistant to the pathogenic action of the three mosquitocidal bacterial strains. Additionally, wPipSJ was fully characterised using metagenome-assembled genomics, PCR–RFLP (PCR-Restriction Fragment Length Polymorphism) and MLST (MultiLocus Sequence Typing) analyses. This Wolbachia strain wPipSJ belongs to haplotype I, group wPip-III and supergroup B, clustering with other mosquito wPip strains, such as wPip PEL, wPip JHB, wPip Mol, and wAlbB; showing the southernmost distribution in America. The cytoplasmic incompatibility phenotype of this strain was revealed via crosses between wildtype (Wolbachia+) and antibiotic treated mosquito populations. The results of the tests with the bacterial agents suggest that Cx. quinquefasciatus naturally infected with wPipSJ is less susceptible to the pathogenic action of mosquitocidal bacterial strains when compared with the antibiotic-treated mosquito isoline, and is more susceptible to B. thuringiensis subsp. israelensis than to the other two mosquitocidal agents.