Publications

4891

Summary Many hemipterans are associated with symbiotic bacteria, which are usually found intracellularly in specific bacteriomes. In this study, we provide the first molecular identification of the bacteriome‐associated, obligate endosymbiont in a G ondwanan relict insect taxon, the moss bugs ( H emiptera: C oleorrhyncha: P eloridiidae), which represents one of the oldest lineages within the H emiptera. Endosymbiotic associations of fifteen species of the family were analysed, covering representatives from S outh A merica, A ustralia/ T asmania and N ew Z ealand. Phylogenetic analysis based on four kilobases of 16 S –23 S r RNA gene fragments showed that the obligate endosymbiont of P eloridiidae constitute a so far unknown group of G ammaproteobacteria which is named here ‘ Candidatus Evansia muelleri’. They are related to the sternorrhynchous endosymbionts C andidatus   P ortiera and C andidatus   C arsonella. Comparison of the primary‐endosymbiont and host ( COI  + 28 S rRNA ) trees showed overall congruence indicating co‐speciation the hosts and their symbionts. The distribution of the endosymbiont within the insect body and its transmission was studied using FISH . The endosymbionts were detected endocellularly in a pair of bacteriomes as well as in the ‘symbiont ball’ of the posterior pole of each developing oocyte. Furthermore, ultrastructural analysis of the M alpighian tubules revealed that most host nuclei are infected by an endosymbiotic, intranuclear bacterium that was determined as an A lphaproteobacterium of the genus R ickettsia .

Summary Knowledge of intraspecific variation in symbioses may aid in understanding the ecology of widespread insects in different parts of their range. We investigated bacterial symbionts of A delges tsugae , a pest of hemlocks in eastern N orth A merica introduced from A sia. Amplification, cloning, and sequencing of bacterial 16 S rDNA , in situ hybridizations, and electron microscopy revealed that A . tsugae harbours up to five bacterial phylotypes, according to population. Three G ammaproteobacteria species are maternally transmitted. The first, designated ‘ C a . P seudomonas adelgestsugas’ resides in the haemocoel, and was detected in all populations except T aiwan. The second phylotype, ‘ C a . S erratia symbiotica’, resides in bacteriocytes of populations on T suga sieboldii in J apan and in E . N orth A merica. The third phylotype, designated ‘ C a . A nnandia adelgestsuga’, clustered within a lineage of several insect endosymbionts that included B uchnera aphidicola . It was detected in bacteriocytes in all populations, and in salivary glands of first instars. Two B etaproteobacteria phylotypes were detected in some J apanese T . sieboldii and eastern N orth A merica populations, and were observed only in salivary glands with no evidence of maternal transmission. Our results support the ideas that symbiont gain and loss has been volatile in adelgids, and that symbionts may help to trace the source of invasive species.

ABSTRACT The draft genome sequence of a single orange Beggiatoa (“ Candidatus Maribeggiatoa”) filament collected from a microbial mat at a hydrothermal site in Guaymas Basin (Gulf of California, Mexico) shows evidence of extensive genetic exchange with cyanobacteria, in particular for sensory and signal transduction genes. A putative homing endonuclease gene and group I intron within the 23S rRNA gene; several group II catalytic introns; GyrB and DnaE inteins, also encoding homing endonucleases; multiple copies of sequences similar to the fdxN excision elements XisH and XisI (required for heterocyst differentiation in some cyanobacteria); and multiple sequences related to an open reading frame (ORF) (00024_0693) of unknown function all have close non- Beggiatoaceae matches with cyanobacterial sequences. Sequences similar to the uncharacterized ORF and Xis elements are found in other Beggiatoaceae genomes, a variety of cyanobacteria, and a few phylogenetically dispersed pleiomorphic or filamentous bacteria. We speculate that elements shared among filamentous bacterial species may have been exchanged in microbial mats and that some of them may be involved in cell differentiation.

ABSTRACT We report here the draft genome sequence of “ Candidatus Liberibacter americanus” strain PW_SP. The 1,176,071-bp genome, with 31.6% G+C content, comprises 948 open reading frames, 38 tRNAs, and three complete rRNAs.

Summary A novel moderately thermophilic, facultatively anaerobic chemoorganotrophic bacterium strain P3M ‐2 T was isolated from a microbial mat developing on the wooden surface of a chute under the flow of hot water (46° C ) coming out of a 2775‐m‐deep oil exploration well ( T omsk region, R ussia). Strain P3M ‐2 T is a moderate thermophile and facultative anaerobe growing on mono‐, di‐ or polysaccharides by aerobic respiration, fermentation or by reducing diverse electron acceptors [nitrite, F e( III ), As ( V )]. Its closest cultivated relative (90.8% rRNA gene sequence identity) is I gnavibacterium album , the only chemoorganotrophic member of the phylum C hlorobi . New genus and species M elioribacter roseus are proposed for isolate P3M ‐2 T . Together with I . album , the new organism represents the class I gnavibacteria assigned to the phylum Chlorobi . The revealed group includes a variety of uncultured environmental clones, the 16S rRNA gene sequences of some of which have been previously attributed to the candidate division ZB1 . Phylogenetic analysis of M . roseus and I . album based on their 23S rRNA and RecA sequences confirmed that these two organisms could represent an even deeper, phylum‐level lineage. Hence, we propose a new phylum Ignavibacteriae within the Bacteroidetes – C hlorobi group with a sole class I gnavibacteria , two families I gnavibacteriaceae and M elioribacteraceae and two species I . album and M . roseus . This proposal correlates with chemotaxonomic data and phenotypic differences of both organisms from other cultured representatives of C hlorobi . The most essential differences, supported by the analyses of complete genomes of both organisms, are motility, facultatively anaerobic and obligately organotrophic mode of life, the absence of chlorosomes and the apparent inability to grow phototrophically.