Publications

4926

ABSTRACT Here we report a novel clade of secondary endosymbionts associated with insects and other arthropods. Seed bugs of the genus Nysius (Hemiptera: Lygaeidae) harbor the primary gammaproteobacterial symbiont Schneideria nysicola within a pair of bacteriomes in the abdomen. Our survey of Nysius species for their facultative bacterial associates consistently yielded a novel type of alphaproteobacterial 16S rRNA gene sequence in addition to those of Wolbachia . Diagnostic PCR survey of 343 individuals representing 24 populations of four Nysius species revealed overall detection rates of the alphaproteobacteria at 77.6% in Nysius plebeius , 87.7% in Nysius sp. 1, 81.0% in Nysius sp. 2, and 100% in Nysius expressus . Further survey of diverse stinkbugs representing 24 families, 191 species, and 582 individuals detected the alphaproteobacteria from an additional 12 species representing six families. Molecular phylogenetic analysis showed that the alphaproteobacteria from the stinkbugs form a distinct and coherent monophyletic group in the order Rickettsiales together with several uncharacterized endosymbionts from fleas and ticks. The alphaproteobacterial symbiont clade was allied to bacterial clades such as the endosymbionts of acanthamoebae, the endosymbionts of cnidarians, and Midichloria spp., the mitochondrion-associated endosymbionts of ticks. In situ hybridization and electron microscopy identified small filamentous bacterial cells in various tissues of N. plebeius , including the bacteriome and ovary. The concentrated localization of the symbiont cells at the anterior pole of oocytes indicated its vertical transmission route through host insect generations. The designation “ Candidatus Lariskella arthropodarum” is proposed for the endosymbiont clade.

AbstractIn 2010, cabbages (Brassica oleracea L.) showing symptoms of proliferated axillary buds, crinkled leaves and plant stunting with shortened internodes typical to phytoplasma infection were found in a breeding facility in Beijing, China. Three symptomatic plants and one symptomless plant were collected, and total DNA was extracted from the midrib tissue and the flowers. With phytoplasma universal primers R16F2n/R16R2, a special fragment of 1247 bp (16S rDNA) was obtained from all three symptomatic cabbage plants, but not from the one symptomless cabbage plant. The 16S rDNA sequence showed 99% similarity with the homologous genes of the aster yellows group phytoplasma (16SrI group), and the phytoplasma was designed as CWBp‐BJ. Phylogenetic and computer‐simulated restriction fragment length polymorphism (RFLP) analysis of the 16S rDNA gene revealed that CWBp‐BJ belongs to subgroup 16SrI‐B. This is the first report of a phytoplasma associated with cabbage witches’‐broom in China.

The taxonomic positions of three thermophilic actinomycetes isolated from arid soil samples were established by using a polyphasic approach. The organisms had chemical and morphological features that were consistent with their classification in the genus Amycolatopsis . 16S rRNA gene sequence data supported the classification of the isolates in the genus Amycolatopsis and showed that they formed distinct branches in the Amycolatopsis methanolica subclade. DNA–DNA relatedness studies between the isolates and their phylogenetic neighbours showed that they belonged to distinct genomic species. The three isolates were readily distinguished from one another and from the type strains of species classified in the A. methanolica subclade based on a combination of phenotypic properties and by genomic fingerprinting. Consequently, it is proposed that the three isolates be classified in the genus Amycolatopsis as representatives of Amycolatopsis granulosa sp. nov. (type strain GY307T = NCIMB 14709T = NRRL B-24844T), Amycolatopsis ruanii sp. nov. (type strain NMG112T = NCIMB 14711T = NRRL B-24848T) and Amycolatopsis thermalba sp. nov. (type strain SF45T = NCIMB 14705T = NRRL B-24845T).

Summary The name Arthromitus has been applied collectively to conspicuous filamentous bacteria found in the hindguts of termites and other arthropods. First observed by Joseph Leidy in 1849, the identity of these filaments has remained contentious. While Margulis and colleagues declared them to be a life stage of Bacillus cereus , others have assumed them to belong to the same lineage as the segmented filamentous bacteria (SFB) from vertebrate guts, a group that has garnered much attention due to their unique ability to specifically modulate their host's immune response. Both SFB and Arthromitus filaments from arthropod guts were grouped under provisional name ‘ Candidatus Arthromitus’ by Snel and colleagues as they share a striking similarity in terms of their morphology and close contact to the host gut wall. While SFB form a distinct lineage within the family Clostridiaceae , the identity of the filaments from arthropod guts remains elusive. Using whole‐genome amplification of single filaments capillary picked from termite guts and fluorescence in situ hybridization of 16S rRNA with group‐specific oligonucleotide probes, we show that they represent a monophyletic lineage within the family Lachnospiraceae distinct from that of SFB. Therefore, ‘ Candidatus Arthromitus’ can no longer be used for both groups. Given the historic precedence, we propose to reserve this name for the filaments that were originally described by Leidy. For the SFB from vertebrate guts, we propose the provisional name ‘ Candidatus Savagella’ in honour of the American gut microbiologist Dwayne C. Savage, who was the first to describe that important bacterial group.