The great potential of entomopathogenic bacteria Xenorhabdus and Photorhabdus for mosquito control: a review

Abstract

The control of insects of medical importance, such as Aedes aegypti and Aedes albopictus are still the only effective way to prevent the transmission of diseases, such as dengue, chikungunya and Zika. Their control is performed mainly using chemical products; however, they often have low specificity to non-target organisms, including humans. Also, studies have reported resistance to the most commonly used insecticides, such as the organophosphate and pyrethroids. Biological control is an ecological and sustainable method since it has a slow rate of insect resistance development. Bacterial species of the genera Xenorhabdus and Photorhabdus have been the target of several research groups worldwide, aiming at their use in agricultural, pharmaceutical and industrial products. This review highlights articles referring to the use of Xenorhabdus and Photorhabdus for insects and especially for mosquito control proposing future ways for their biotechnological applicability. Approximately 24 species of Xenorhabdus and five species of Photorhabdus have been described to have insecticidal properties. These studies have shown genes that are capable of encoding low molecular weight proteins, secondary toxin complexes and metabolites with insecticide activities, as well as antibiotic, fungicidal and antiparasitic molecules. In addition, several species of Xenorhabdus and Photorhabdus showed insecticidal properties against mosquitoes. Therefore, these biological agents can be used in new control methods, and must be, urgently considered in short term, in studies and applications, especially in mosquito control.

Drosophila suzukii Susceptibility to the Oral Administration of Bacillus thuringiensis, Xenorhabdus nematophila and Its Secondary Metabolites

“…As suggested by various authors, Xn also interferes with the immune system by means of its secondary metabolites and surface compounds [ 16 , 17 , 34 , 35 , 36 ]. Xn inhibits the synthesis of eicosanoids affecting cell-mediated processes [ 15 , 37 ], and, besides this, like Bt, Xn can damage the host intestine [ 38 , 39 , 40 ]. In the late phase, the symbiotic bacterium proliferates in the hemolymph and is responsible for the lethality induced by these nematocomplexes thanks to its toxic secondary metabolites [ 11 , 41 ].…”

“…We therefore isolated and analyzed secretions obtained from the pathogen culture broth. The electrophoretic pattern shows the presence of a protein pool with a molecular weight range between 10 and 45 kDa, in which compounds specifically affecting the intestinal epithelium were identified [ 40 , 54 ]. However, secretions obtained from Xn, administered at a concentration of 10 µg/mL, caused a SWD mortality rate that did not exceed 33% after 48 h. This relatively low efficacy could be due to the oral administration, and thus to the amount of food containing the secretions, which the larvae ingest.…”

Photorhabdus spp.: An Overview of the Beneficial Aspects of Mutualistic Bacteria of Insecticidal Nematodes

“…In the agricultural sector, the current production practices are not sufficient to control insect pests and pathogens safely and with 100% efficacy. Growing dissatisfaction with the chemicals that are used for plant pest control has increased, due to their negative impacts on human health and non-target organisms, contamination, toxicity to the environment, and resistance development [ 1 , 2 , 3 ]. Thus, it has become imperative to decrease the use of these unsafe pesticides and replace them with benign ecologically sound products for crop pest control, in the context of sustainable agriculture.…”

“…These bacteria can reduce the chemical inputs used for plant protection, and stabilize ecological changes [ 4 ]. Conceivably, entomopathogenic bacterial species of the genus Photorhabdus (Enterobacteriales: Morganellaceae) may be a favorable alternative for expanding the biocontrol of many plant pests and pathogens, via their secretion of various arrays comprising effective bioactive metabolites [ 2 , 5 , 6 , 7 , 8 , 9 ]. This concept is based on a huge number of Photorhabdus genes that encode for producing relevant compounds, e.g., enzymes, toxins, antibiotics, and bacteriocins.…”

Chemical ecology of an apex predator life cycle

“…Upon infection, the bacteria are released into the insect blood cavity and together the nematode and bacterium kill and consume the insect for their own reproduction before developing into the bacteria-colonized infective stage again to repeat the cycle {Richards, 2009; Stock, 2019}. EPNBs have been applied as insecticide alternatives to promote agricultural productivity and to help prevent transmission of insect diseases like dengue and West Nile virus {Lacey, 2012; Javal, 2019; da Silva, 2020}.…”