The scientific community working in the field of insect pathology is experiencing an increasing academic and industrial interest in the discovery and development of new bioinsecticides as environmentally friendly pest control tools to be integrated, in combination or rotation, with chemicals in pest management programs. In this scientific context, market data report a significant growth of the biopesticide segment. Acquisition of new technologies by multinational Ag-tech companies is the center of the present industrial environment. This trend is in line with the requirements of new regulations on Integrated Pest Management. After a few decades of research on microbial pest management dominated by Bacillus thuringiensis (Bt), novel bacterial species with innovative modes of action are being discovered and developed into new products. Significant cases include the entomopathogenic nematode symbionts Photorhabdus spp. and Xenorhabdus spp., Serratia species, Yersinia entomophaga, Pseudomonas entomophila, and the recently discovered Betaproteobacteria species Burkholderia spp. and Chromobacterium spp. Lastly, Actinobacteria species like Streptomyces spp. and Saccharopolyspora spp. have gained high commercial interest for the production of a variety of metabolites acting as potent insecticides. With the aim to give a timely picture of the cutting-edge advancements in this renewed research field, different representative cases are reported and discussed.

Brevibacillus laterosporus, a bacterium characterized by the production of a unique canoe-shaped lamellar body attached to one side of the spore, is a natural inhabitant of water, soil and insects. Its biopesticidal potential has been reported against insects in different orders including Coleoptera, Lepidoptera, Diptera and against nematodes and mollusks. In addition to its pathogenicity against invertebrates, different B. laterosporus strains show a broad-spectrum antimicrobial activity including activity against phytopathogenic bacteria and fungi. A wide variety of molecules, including proteins and antibiotics, have been associated with the observed pathogenicity and mode of action. Before being considered as a biological control agent against plant pathogens, the antifungal and antibacterial properties of certain B. laterosporus strains have found medical interest, associated with the production of antibiotics with therapeutic effects. The recent whole genome sequencing of this species revealed its potential to produce polyketides, nonribosomal peptides, and toxins. Another field of growing interest is the use of this bacterium for bioremediation of contaminated sites by exploiting its biodegradation properties. The aim of the present review is to gather and discuss all recent findings on this emerging entomopathogen, giving a wider picture of its complex and broad-spectrum biocontrol activity.

Microbial biopesticides include several microorganisms like bacteria, fungi, baculoviruses, and nematode-associated bacteria acting against invertebrate pests in agro-ecosystems. The biopesticide sector is experiencing a significant growth and many discoveries are being developed into new biopesticidal products that are fueling a growing global market offer. Following a few decades of successful use of the entomopathogenic bacterium Bacillus thuringiensis and a few other microbial species, recent academic and industrial efforts have led to the discovery of new microbial species and strains, and of their specific toxins and virulence factors. Many of these have, therefore, been developed into commercial products. Bacterial entomopathogens include several Bacillaceae, Serratia, Pseudomonas, Yersinia, Burkholderia, Chromobacterium, Streptomyces, and Saccharopolyspora species, while fungi comprise different strains of Beauveria bassiana, B. brongniartii, Metarhizium anisopliae, Verticillium, Lecanicillium, Hirsutella, Paecilomyces, and Isaria species. Baculoviruses are species-specific and refer to niche products active against chewing insects, especially Lepidopteran caterpillars. Entomopathogenic nematodes (EPNs) mainly include species in the genera Heterorhabditis and Steinernema associated with mutualistic symbiotic bacteria belonging to the genera Photorhabdus and Xenorhabdus. An updated representation of the current knowledge on microbial biopesticides and of the availability of active substances that can be used in integrated pest management programs in agro-ecosystems is reported here.

BackgroundBluetongue (BT) epidemics have affected the Mediterranean island of Sardinia since 2000. While Culicoides imicola represents the main bluetongue virus (BTV) vector, other European Culicoides biting midges, possibly implicated in virus transmission, have been detected here. Understanding their distribution, seasonal abundance, and infection rates is necessary to predict disease incidence and spread across coastal and inland areas, and to define their role in virus overwintering.MethodsBiting midge abundance was determined by light traps on selected farms representing diverse climatic conditions of Sardinia. Livestock-associated Culicoides species were morphologically and molecularly identified. Infection rates in prevailing midge species captured in 2013 during a BTV-1 outbreak were determined using RT-qPCR based virus detection in insect body pools, supplemented by specific body region analyses. The seasonal infection prevalence in Culicoides samples collected in 2001 in a BTV-2 affected farm was also determined.ResultsThe Newsteadi complex (C. newsteadi species A and species B) prevailed among all biting midge species (47.7 %), followed by C. imicola (27.8 %) and the Obsoletus complex (C. obsoletus and C. scoticus) (17.6 %). Whilst Culicoides imicola was more abundant along the coast, the Newsteadi complex was frequently collected at higher altitude and the Obsoletus complex was notably associated to cattle farms. Culicoides pulicaris and C. punctatus abundance was found to be marginal in all farms. BTV was detected in parous female samples of all these species, and the full dissemination of the virus within the body of C. imicola, C. obsoletus, C. scoticus, and Newsteadi complex species was confirmed by analyses of thorax and head, containing salivary glands. Higher infection rates were associated with C. scoticus, C. newsteadi species A and species B, compared to C. imicola. The virus was detected in C. newsteadi species A and C. obsoletus in winter and spring, whereas it was mainly found in summer and autumn in C. imicola.ConclusionsIn Sardinia, bluetongue virus is transmitted by multiple Culicoides vectors, including C. imicola and the Newsteadi complex being the most important. The Newsteadi complex and other midge species can play an important role in internal areas and are likely to be directly involved in virus overwintering.

Mining activities represent a major source of environment contamination. The aim of this study was to evaluate the use of bees and ants as bioindicators to detect the heavy metal impact in post-mining areas. A biomonitoring programme involving a combination of honeybee hive matrices analysis and ant biodiversity survey was conducted over a 3-year period. The experimental design involved three monitoring stations where repeated sampling activities focused on chemical detection of cadmium (Cd), chrome (Cr) and lead (Pb) from different matrices, both from hosted beehives (foraging bees, honey and pollen) and from the surrounding environment (stream water and soil). At the same time, ant biodiversity (number and abundance of species) was determined through a monitoring programme based on the use of pitfall traps placed in different habitats inside each mining site. The heavy metal content detected in stream water from the control station was always below the analytical limit of quantification. In the case of soil, the content of Cd and Pb from the control was lower than that of mining sites. The mean heavy metal concentrations in beehive matrices from mining sites were mainly higher than the control, and as a result of regression and discriminant analysis, forager bee sampling was an efficient environmental pollution bioindicator. Ant collection and identification highlighted a wide species variety with differences among habitats mostly associated with vegetation features. A lower variability was observed in the polluted landfill characterised by lack of vegetation. Combined biomonitoring with forager bees and ants represents a reliable tool for heavy metal environmental impact studies.

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Outer spore envelope proteins of pathogenic bacteria often present specific virulence factors and tools to evade the defence system of their hosts. Brevibacillus laterosporus, a pathogen of invertebrates and an antimicrobial-producing species, is characterised by a unique spore coat and canoe-shaped parasporal body (SC-CSPB) complex surrounding the core spore. In the present study, we identified and characterised major proteins of the SC-CSPB complex of B. laterosporus, and we investigated their entomopathogenic role. Employing a proteomic approach and a B. laterosporus-house fly study model, we found four highly conserved proteins (ExsC, CHRD, CpbA and CpbB) that function as insect virulence factors. CpbA was associated with a significantly higher mortality of flies and greater relative gene expression levels during sporulation, compared to the other SC-CSPB proteins. Taken together, we suggest that spore surface proteins are a part of a complex set of toxins and virulence factors that B. laterosporus employs in its pathogenicity against flies.

The interest in using plant-growth-promoting bacteria (PGPB) as biopesticides is significantly growing as a result of the discovery of new properties of certain beneficial microbes in protecting agricultural crops. While several rhizobial species have been widely exploited for their ability to optimize plant use of environmental resources, now the focus is shifted to species that are additionally capable of improving plant health and conferring resistance to abiotic stress and deleterious biotic agents. In some cases, PGPB species may directly act against plant pathogens and parasites through a variety of mechanisms, including competition, protective biofilm formation, and the release of bioactive compounds. The use of this type of bacteria is in line with the principles of ecosustainability and integrated pest management, including the reduction of employing chemical pesticides. Several strains of Bacillus, Paenibacillus, Brevibacillus, Pseudomonas, Serratia, Burkholderia, and Streptomyces species have been the subject of specific studies in this direction and are under evaluation for further development for their use in biological control. Accordingly, specific case studies are presented and discussed.