Publications

4852

Bacteria called ‘Fritschea’ are endosymbionts of the plant-feeding whitefly Bemisia tabaci and scale insect Eriococcus spurius. In the gut of B. tabaci, these bacteria live within bacteriocyte cells that are transmitted directly from the parent to oocytes. Whiteflies cause serious economic damage to many agricultural crops; B. tabaci fecundity and host range are less than those of Bemisia argentifolii, possibly due to the presence of this endosymbiont. The B. tabaci endosymbiont has been characterized using electron microscopy and DNA analysis but has not been isolated or propagated outside of insects. The present study compared sequences for 11 endosymbiont genes to genomic data for chlamydial families Parachlamydiaceae, Chlamydiaceae and Simkaniaceae and to 16S rRNA gene signature sequences from 330 chlamydiae. We concluded that it was appropriate to propose ‘Candidatus Fritschea bemisiae’ strain Falk and ‘Candidatus Fritschea eriococci’ strain Elm as members of the family Simkaniaceae in the Chlamydiales.

ABSTRACT Ecological studies on three bacterial lineages symbiotic in aphids have shown that they impose a variety of effects on their hosts, including resistance to parasitoids and tolerance to heat stress. Phylogenetic analyses of partial sequences of gyrB and recA are consistent with previous analyses limited to 16S rRNA gene sequences and yield improved confidence of the evolutionary relationships of these symbionts. All three symbionts are in the Enterobacteriaceae . One of the symbionts, here given the provisional designation “ Candidatus Serratia symbiotica,” is a Serratia species that has acquired a symbiotic lifestyle. The other two symbionts, here designated “ Candidatus Hamiltonella defensa” and “ Candidatus Regiella insecticola,” are sister groups to one another and together show a relationship to species of Photorhabdus .

Abstract Objective—To determine whether Ctenocephalides felis can transmit Mycoplasma haemofelis (Mhf) and Candidatus Mycoplasma haemominutum (Mhm) through hematophagous activity between cats. Animals—11 cats. Procedure—2 cats were carriers of either Mhf or Mhm. Nine cats had negative results via polymerase chain reaction (PCR) assay for Mhf and Mhm DNA; 3 of those cats were infected from the chronic carriers via IV inoculation of blood. At the time of maximum organism count for each of the Mycoplasma spp, 1 chamber containing 100 C felis was bandaged to the amplifier cats. Five days later, fleas, feces, larvae, or eggs from each chamber were analyzed for Mycoplasma spp DNA. Viable fleas from the chambers were allocated into new chambers (3 Mhm and 6 Mhf) and attached to naïve cats for 5 days. Cats were monitored daily for clinical signs and weekly via CBC and PCR assay for infection with Mhf or Mhm for a minimum of 8 weeks. Results—Uptake of Mhf and Mhm DNA into fleas, feces, and, potentially, eggs and larvae was detected. Of the naïve cats fed on by Mhf-infected fleas, 1 cat transiently yielded positive PCR assay results for Mhf on 1 sampling date without clinical or hematologic changes consistent with Mhf infection. Conclusions and Clinical Relevance—Results suggest that hematophagous transfer of Mhm and Mhf into fleas occurred and that C felis is a possible vector for Mhf via hematophagous activity. (Am J Vet Res 2005;66:1008–1012)

TXW-1, aBorreliastrain isolated in March 1998 from an adult maleDermacentor variabilistick feeding on a coyote from Webb county, Texas, USA, was characterized by using randomly amplified polymorphic DNA (RAPD) analysis, RFLP and sequence analysis offlaBandrrs(16S rRNA gene), DNA–DNA hybridization analysis, SDS-PAGE and Western blotting with mAbs. It shows different banding patterns in RFLP analysis offlaBand forms distinct branches in phylogenetic analysis derived fromflaBandrrsgenes. It differs from other borreliae based on the banding patterns obtained by RAPD analysis. This strain contains a small, 38-kDa endoflagellar protein. DNA–DNA hybridization experiments revealed that the levels of DNA reassociation between TXW-1 and previously described relapsing fever borreliae were 38·64 % (Borrelia turicatae), 38·40 % (Borrelia parkeri), 7·39 % (Borrelia hermsii) and 18·30 % (Borrelia coriaceae). However, the level of DNA relatedness betweenB. parkeriandB. turicataewas 78·78 %. Sequence analyses offlaBandrrsgenes indicate that the similarities of nucleotide sequences among TXW-1 andB. turicataeorB. parkeriare less than that betweenB. turicataeandB. parkeri, and that the genetic distances among TXW-1 andB. turicataeorB. parkeriare greater than that betweenB. turicataeandB. parkeri. TXW-1 lacks anospCgene. Electron microscope observations showed that this spirochaete had different morphological structures compared to previously described relapsing fever borreliae. All the results obtained from the above-mentioned analyses indicate that TXW-1 is different from other describedBorreliaspecies and that it represents a novel species ofBorrelia. We have been unable to revive frozen cultures and so can not meet the requirements of the Bacteriological Code to deposit viable type material at two different culture collections. Therefore we use theCandidatusdesignation; based on these results, the species ‘CandidatusBorrelia texasensis' is proposed.

This study examined whether genes that are less conserved than the 16S rRNA gene can distinguish Candidatus Phytoplasma australiense strains that are identical based on their 16S rRNA genes, with a view to providing insight into their origins and distribution, and any patterns of association with particular plant hosts. Sequence analysis of the tuf gene and rp operon showed that Ca . P. australiense strains could be differentiated into four subgroups, named 16SrXII‐B ( tuf ‐Australia I; rp ‐A), 16SrXII‐B ( tuf ‐New Zealand I; rp ‐B), 16SrXII‐B ( tuf ‐New Zealand II) and 16SrXII‐B ( rp ‐C). Strawberry lethal yellows 1, strawberry green petal, Australian grapevine yellows, pumpkin yellow leaf curl and cottonbush witches’ broom phytoplasmas were designated members of the 16SrXII‐B ( tuf ‐Australia I; rp ‐A) subgroup. The strawberry lethal yellows 2 and cottonbush reduced yellow leaves phytoplasmas were assigned to the 16SrXII ( tuf ‐New Zealand II; rp ‐B) subgroup. No relationship was observed between these phytoplasma subgroups and collection date, location or host plant. However, the study revealed evolutionary divergence in the 16SrXII group.

Pinus silvestris and Pinus halepensis trees grown in Germany and Spain, respectively, showing abnormal shoot branching, dwarfed needles and other symptoms were examined for the presence of plant-pathogenic mollicutes (phytoplasmas). While phytoplasmas could not be detected unambiguously with microscopical methods, PCR amplification using universal phytoplasma primers yielded positive results. Samples collected from symptomatic and non-symptomatic plant parts of both symptomatic Pinus silvestris and Pinus halepensis trees tested positive. Also, surrounding non-symptomatic trees proved to be phytoplasma-infected. Comparisons revealed that the 16S rRNA gene sequences of the phytoplasmas identified in Pinus silvestris and Pinus halepensis were nearly identical. However, the pine phytoplasma is only distantly related to other phytoplasmas. The closest relatives are members of the palm lethal yellowing and rice yellow dwarf groups and ‘Candidatus Phytoplasma castaneae’, which share between 94·5 and 96·6 % 16S rRNA gene sequence similarity. From these data it can be concluded that the phytoplasmas identified in the two Pinus species represent a coherent but discrete taxon; it is proposed that this taxon be distinguished at putative species level under the name ‘Candidatus Phytoplasma pini’.