Alternative methods of mosquito control are needed to tackle the rising burden of mosquito-borne diseases while minimizing the use of synthetic insecticides, which are threatened by the rapid increase in insecticide resistance in mosquito populations. Fungal biopesticides show great promise as potential alternatives because of their ecofriendly nature and ability to infect mosquitoes on contact. Here we describe the temporospatial interactions between the mosquito Aedes aegypti and several entomopathogenic fungi. Fungal infection assays followed by the molecular assessment of infection-responsive genes revealed an intricate interaction between the mosquito immune system and entomopathogenic fungi. We observed contrasting tissue and time-specific differences in the activation of immune signaling pathways and antimicrobial peptide expression. In addition, these antifungal responses appear to vary according to the fungal entomopathogen used in the infection. Enzyme activity-based assays coupled with gene expression analysis of prophenoloxidase genes revealed a reduction in phenoloxidase (PO) activity in mosquitoes infected with the most virulent fungal strains at 3 and 6d post-fungal infection. Moreover, fungal infection led to an increase in midgut microbiota that appear to be attributed in part to reduced midgut reactive oxygen species (ROS) activity. This indicates that the fungal infection has far reaching effects on other microbes naturally associated with mosquitoes. This study also revealed that despite fungal recognition and immune elicitation by the mosquito, it is unable to successfully eliminate the entomopathogenic fungal infection. Our study provides new insights into this intricate multipartite interaction and contributes to a better understanding of mosquito antifungal immunity.
Mate finding in most moth species involves long-distance signaling via female-emitted sex pheromones. There is a great diversity of pheromone structures used throughout the Lepidoptera, even among closely related species. The conundrum is how signal divergence has occurred. With strong normalizing selection pressure on blend composition and response preferences, it is improbable that shifts to pheromones of diverse structures occur through adaptive changes in small steps. Here, we present data supporting the hypothesis that a major shift in the pheromone of an Ostrinia species occurred by activation of a nonfunctional desaturase gene transcript present in the pheromone gland. We also demonstrate the existence of rare males that respond to the new pheromone blend. Their presence would allow for asymmetric tracking of male response to the new blend and, thus, evolution of an Ostrinia species with structurally different sex pheromone components.
Strains of aerobic, Gram-positive, rod-shaped, round-spore-forming bacteria were isolated from different geographical locations and a subsequent polyphasic study was undertaken to clarify the taxonomic position of the round-spore-forming isolates strain KSC-SF6gT, strain M32 and strain NBRC 12622. 16S rRNA gene sequence similarities demonstrated that these strains were most closely affiliated with Bacillus pycnus NRRL NRS-1691T (98 %), with species of Kurthia (96 %) and Viridibacillus (94–96 %) as the next nearest relatives. However, while DNA–DNA hybridization studies showed approx. 70 % reassociation among strains KSC-SF6gT, M32 and NBRC 12622, DNA–DNA hybridization values between these strains and B. pycnus NRRL NRS-1691T never exceeded 13 %. Differences in the molecular structure of the cell-wall peptidoglycan could not differentiate these strains sufficiently from other closely related genera (Viridibacillus and Kurthia). However, Lys–Asp was present in strains KSC-SF6gT, M32 and NBRC 12622, whereas l-Lys–d-Glu was reported in B. pycnus NRRL NRS-1691T. The menaquinone MK-7 was dominant in strains KSC-SF6gT, M32 and NBRC 12622 and members of the genus Kurthia, whereas MK-8 was abundant in Viridibacillus species. Strains KSC-SF6gT, M32 and NBRC 12622 exhibited fatty acid profiles consisting of major amounts of anteiso-C15 : 0 (∼50 %) and iso-C15 : 0 (∼25 %) and moderate amounts of anteiso-C17 : 0 (∼7 %), which discriminated them from closely related B. pycnus NRRL NRS-1691T and species of Viridibacillus (iso-C15 : 0; 46–74 %). The authors propose that strains KSC-SF6gT, M32 and NBRC 12622 and B. pycnus NRRL NRS-1691T be reclassified into a separate genus based on clear-cut differences in discriminative taxonomic markers and the distant placement of B. pycnus and the novel strains described herein from other species of this clade according to current 16S rRNA gene sequence-based relatedness (∼4 % difference in sequence). We propose the placement of these isolates into the novel genus Rummeliibacillus gen. nov. For the new taxon comprising strains KSC-SF6gT, M32 and NBRC 12622, we propose the name Rummeliibacillus stabekisii gen. nov., sp. nov. (the type species of Rummeliibacillus), represented by the type strain KSC-SF6gT (=NRRL B-51320T =NBRC 104870T). In addition, Bacillus pycnus, which bears traits distinct from other round-spore-forming species [i.e. absence of growth at high NaCl (7 %), positive reaction for gelatin liquefaction], is reclassified as Rummeliibacillus pycnus comb. nov. (type strain JCM 11075T =NRRL NRS-1691T) based on phylogenetic affiliations and phenotypic characterization.
Microbiology Society journals contain high-quality research papers and topical review articles. We are a not-for-profit publisher and we support and invest in the microbiology community, to the benefit of everyone. This supports our principal goal to develop, expand and strengthen the networks available to our members so that they can generate new knowledge about microbes and ensure that it is shared with other communities.
A great diversity of pheromone structures are used by moth species (Insecta: Lepidoptera) for long-distance mating signals. The signal/response channel seems to be narrow for each species, and a major conundrum is how signal divergence has occurred in the face of strong selection pressures against small changes in the signal. Observations of various closely related and morphologically similar species that use pheromone components biosynthesized by different enzymes and biosynthetic routes underscore the question as to how major jumps in the biosynthetic routes could have evolved with a mate recognition system that is based on responses to a specific blend of chemicals. Research on the desaturases used in the pheromone biosynthetic pathway for various moth species has revealed that one way to make a major shift in the pheromone blend is by activation of a different desaturase from mRNA that already exists in the pheromone gland. Data will be presented to support the hypothesis that this process was used in the evolution of the Asian corn borer, Ostrinia furnacalis species. In that context, moth sex-pheromone desaturase genes seem to be evolving under a birth-and-death process. According to this model of multigene family evolution, some genes are maintained in the genome for long periods of time, whereas others become deleted or lose their functionality, and new genes are created through gene duplication. This mode of evolution seems to play a role in moth speciation, as exemplified by the case of the Asian corn borer and European corn borer, Ostrinia nubilalis species.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)