Publications

4774

Abstract BACKGROUND In insects, little is known about the co‐evolution between their primary endosymbionts and hosts at the intraspecific level. This study examined co‐diversification between the notorious agricultural pest Diaphorina citri and its primary endosymbionts (P‐endosymbiont), ‘ Candidatus Carsonella ruddii’ at the population level. RESULTS Maximum likelihood, haplotype network, principal components and Bayesian clustering identified three lineages for D. citri and its P‐endosymbiont: a Western clade containing individuals from Pakistan, Bhutan (Phuentsholing), Vietnam (Son La), USA, Myanmar and China (Ruili, Yunnan); a Central clade, with accessions originating from Southwest China, Bhutan (Tsirang) and Bangladesh; and an Eastern clade containing individuals from Southeast Asia, and East and South China. A more diverse genetic structure was apparent in the host mitochondrial DNA than their P‐endosymbionts; however, the two sets of data were strongly congruent. CONCLUSION This study provides evidence for the co‐diversification of D. citri and its P‐endosymbiont during the migration from South Asia to East and Southeast Asia. We also suggest that the P‐endosymbiont may facilitate investigations into the genealogy and migration history of the host. The biogeography of D. citri and its P‐endosymbiont indicated that D. citri colonized and underwent a secondary dispersal from South Asia to East and Southeast Asia. © 2018 Society of Chemical Industry

Endemic tick-borne relapsing fever (TBRF) has not been documented in Nigeria, yet clinically compatible cases have been described, and soft tick species are endemic in surrounding countries. Consequently, our aim was to investigate if TBRF-associated Borrelia is present in Nigeria.

AbstractHuanglongbing (HLB), also known as citrus greening, is a destructive disease of citrus; it is considered a newly emerging disease which has spread to the Middle East and North Africa (MENA). In Iran, the disease was first found in 2009. In this study, two hypervariable prophage and phage‐related loci, bacteriophage repressor protein C1 (CLIBASIA_ 01645 locus) and prophage terminase gene (CLIBASIA_05610 locus), were used to determine the diversity and characterization of Candidatus Liberibacter asiaticus (CLas) strains associated with HLB samples. Analyses of the CLIBASIA_01645 locus, characteristic of variable tandem repeat numbers (VTRNs), revealed the homogeneity of Iranian CLas isolates: However, this result showed two distinct genotypes (TRN < 10 and TRN > 10) of CLas in Iran. This is the first report documenting the presence of two differentially distributed genotypes of CLas in Iran. Sequence analysis of prophage terminase revealed the presence of two putative prophages (prophage I and prophage II) in the genome of CLas isolates of Iran. Frequency analysis of these two prophages by specific loci revealed the association between prophages populations, the development HLB symptoms and CLas genotypes and their interactions with another obligate symbiontic, HLB phytoplasma.

Abstract Rickettsiales are obligate intracellular bacteria originally found in metazoans, but more recently recognized as widespread endosymbionts of various protists. One genus was detected also in several green algae, but reports on rickettsialean endosymbionts in other algal groups are lacking. Here we show that several distantly related eustigmatophytes (coccoid algae belonging to Ochrophyta, Stramenopiles) are infected by Candidatus Phycorickettsia gen. nov., a new member of the family Rickettsiaceae. The genome sequence of Ca. Phycorickettsia trachydisci sp. nov., an endosymbiont of Trachydiscus minutus CCALA 838, revealed genomic features (size, GC content, number of genes) typical for other Rickettsiales, but some unusual aspects of the gene content were noted. Specifically, Phycorickettsia lacks genes for several components of the respiration chain, haem biosynthesis pathway, or c-di-GMP-based signalling. On the other hand, it uniquely harbours a six-gene operon of enigmatic function that we recently reported from plastid genomes of two distantly related eustigmatophytes and from various non-rickettsialean bacteria. Strikingly, the eustigmatophyte operon is closely related to the one from Phycorickettsia, suggesting a gene transfer event between the endosymbiont and host lineages in early eustigmatophyte evolution. We hypothesize an important role of the operon in the physiology of Phycorickettsia infection and a long-term eustigmatophyte-Phycorickettsia coexistence.

The Asian citrus psyllid (ACP) Diaphorina citri, vector of ‘Candidatus Liberibacter asiaticus’ (CLas), the putative causal agent of citrus Huanglongbing (HLB), is controlled by application of insecticides, which, although effective, has resulted in serious biological imbalances. New management tools are needed, and the technique known as “trap crop” has been attracting attention. A potential plant for use as a trap crop in the management of the ACP is Murraya koenigii (curry leaf). However, for this plant to be used in the field, it needs to be attractive for the vector and must not harbor CLas. To verify the potential of curry leaf as trap crop for the management of HLB, we investigated the ability of D. citri to transmit CLas to M. koenigii, and to other test plants, including M. paniculata (orange jasmine) and cultivar Valencia sweet-orange seedlings. For the tests, the insects were reared on a symptomatic CLas-infected plant and allowed to feed on the three test plant species. The overall maximum transmission rate for the citrus seedlings was 83.3%, and for orange jasmine was 33.3%. Successful transmission of CLas by ACP to the curry-leaf seedlings was not observed, and it was treated as immune to CLas. Supported by the previous results that M. koenigii is attractive for ACP, these results indicate that curry leaf is an excellent candidate for use as a trap crop, to improve the management of the insect vector and consequently of HLB.

Abstract Members of the candidate phylum Acetothermia are globally distributed and detected in various habitats. However, little is known about their physiology and ecological importance. In this study, an operational taxonomic unit belonging to Acetothermia was detected at high abundance in four full-scale anaerobic digesters by 16S rRNA gene amplicon sequencing. The first closed genome from this phylum was obtained by differential coverage binning of metagenomes and scaffolding with long nanopore reads. Genome annotation and metabolic reconstruction suggested an anaerobic chemoheterotrophic lifestyle in which the bacterium obtains energy and carbon via fermentation of peptides, amino acids, and simple sugars to acetate, formate, and hydrogen. The morphology was unusual and composed of a central rod-shaped cell with bipolar prosthecae as revealed by fluorescence in situ hybridization combined with confocal laser scanning microscopy, Raman microspectroscopy, and atomic force microscopy. We hypothesize that these prosthecae allow for increased nutrient uptake by greatly expanding the cell surface area, providing a competitive advantage under nutrient-limited conditions.

Here, we report the draft genome sequence of “ Candidatus Izimaplasma sp.” strain ZiA1 (1.88 Mb and 29.6% G+C content).