September 22, 2019  |  

The genomes of Crithidia bombi and C. expoeki, common parasites of bumblebees.

Trypanosomatids (Trypanosomatidae, Kinetoplastida) are flagellated protozoa containing many parasites of medical or agricultural importance. Among those, Crithidia bombi and C. expoeki, are common parasites in bumble bees around the world, and phylogenetically close to Leishmania and Leptomonas. They have a simple and direct life cycle with one host, and partially castrate the founding queens greatly reducing their fitness. Here, we report the nuclear genome sequences of one clone of each species, extracted from a field-collected infection. Using a combination of Roche 454 FLX Titanium, Pacific Biosciences PacBio RS, and Illumina GA2 instruments for C. bombi, and PacBio for C. expoeki, we could produce high-quality and well resolved sequences. We find that these genomes are around 32 and 34 MB, with 7,808 and 7,851 annotated genes for C. bombi and C. expoeki, respectively-which is somewhat less than reported from other trypanosomatids, with few introns, and organized in polycistronic units. A large fraction of genes received plausible functional support in comparison primarily with Leishmania and Trypanosoma. Comparing the annotated genes of the two species with those of six other trypanosomatids (C. fasciculata, L. pyrrhocoris, L. seymouri, B. ayalai, L. major, and T. brucei) shows similar gene repertoires and many orthologs. Similar to other trypanosomatids, we also find signs of concerted evolution in genes putatively involved in the interaction with the host, a high degree of synteny between C. bombi and C. expoeki, and considerable overlap with several other species in the set. A total of 86 orthologous gene groups show signatures of positive selection in the branch leading to the two Crithidia under study, mostly of unknown function. As an example, we examined the initiating glycosylation pathway of surface components in C. bombi, finding it deviates from most other eukaryotes and also from other kinetoplastids, which may indicate rapid evolution in the extracellular matrix that is involved in interactions with the host. Bumble bees are important pollinators and Crithidia-infections are suspected to cause substantial selection pressure on their host populations. These newly sequenced genomes provide tools that should help better understand host-parasite interactions in these pollinator pathogens.

September 22, 2019  |  

Bacillus wiedmannii biovar thuringiensis: A specialized mosquitocidal pathogen with plasmids from diverse origins.

Bacillus cereus sensu lato also known as B. cereus group is composed of an ecologically diverse bacterial group with an increasing number of related species, some of which are medically or agriculturally important. Numerous e?orts have been undertaken to allow presumptive di?erentiation of B. cereus group species from one another. FCC41 is a Bacillus sp. strain toxic against mosquito species like Aedes aegypti, Aedes (Ochlerotatus) albifasciatus, Culex pipiens, Culex quinquefasciatus, and Culex apicinus, some of them responsible for the transmission of vector-borne diseases. Here, we report the complete genome sequence of FCC41 strain, which consists of one circular chromosome and eight circular plasmids ranging in size from 8 to 490?kb. This strain harbors six crystal protein genes, including cry24Ca, two cry4-like and two cry52-like, a cry41-like parasporin gene and multiple virulence factors. The phylogenetic analysis of the whole-genome sequence of this strain with molecular approaches places this strain into the Bacillus wiedmannii cluster. However, according with phenotypical characteristics such as the mosquitocidal activity due to the presence of Cry proteins found in the parasporal body and cry genes encoded in plasmids of different sizes, indicate that this strain could be renamed as B. wiedmannii biovar thuringiensis strain FCC41.

July 7, 2019  |  

Complete genome sequence of Melissococcus plutonius DAT561, a strain that shows an unusual growth profile, obtained by PacBio sequencing.

Melissococcus plutonius is the causative agent of European foulbrood, and its isolates were believed to be remarkably genetically homogeneous. However, recent epidemiological and pathogenic studies have shown this pathogen to be more heterogeneous than expected. Herein, we present the whole-genome sequence of M. plutonius DAT561, a representative atypical strain. Copyright © 2018 Okumura et al.

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