Publications

4495

Samples from the antrum and fundus of the stomachs of 457 pigs from 22 different herds were screened for the presence of ‘ Candidatus Helicobacter suis’ by pcr , and samples from the antrum and/or fundus of 222 of the stomachs were tested for urease activity. The prevalence of the infection was very low before weaning, increased rapidly after weaning and reached 90 per cent in the adult boars and sows. The agreement between the results obtained with the pcr test and the urease test was very good for some age groups and sampling sites, but poor for other age groups and sampling sites.

Murraya paniculata (orange jasmine) is a popular ornamental rutaceaous plant and is known to be a preferred host for the Asian citrus psyllid, Diaphorina citri (Kuwayana), the primary vector of ‘Candidatus Liberibacter spp.’ that causes citrus Huanglongbing (HLB). HLB is a highly destructive citrus disease worldwide. However, the presence of ‘Ca. Liberibacter spp.’ in M. paniculata remains uncertain (2). Clarification of M. paniculata as a host of ‘Ca. Liberibacter spp.’ has direct impact on HLB control programs. During June of 2006, we identified three M. paniculata trees near a mandarin orchard affected by HLB in Luoding City and two trees from Guangzhou City, Guangdong Province, People's Republic of China. All trees had leaves showing yellowing and mottling symptoms characteristic of HLB. Both symptomatic and asymptomatic leaves were collected. DNA was extracted using the CTAB (cetyltrimethylammoniumbromide) method and assayed by nested-PCR. The general bacterial 16S rDNA primer set fDl/rD1 (3) was used for the first round of amplification. Amplification was conducted as previously described (1), and 2 μl of PCR reaction product were used for a second round of amplification using the same procedure but with 35 PCR cycles with primer set OI1/OI2c (3,4). After agarose gel electrophoresis and staining with ethidium bromide, a 1.1-kb DNA band was unambiguously associated with symptomatic but not asymptomatic leaf samples. Nonnested-PCR using primer set OI1/OI2c alone did not yield a target DNA band or yielded a very weak DNA band. XbaI digestion of the nested-PCR DNA product yielded two fragments, 520 and 640 bp long, characteristic of ‘Ca. L. asiaticus’. PCR amplicons were sequenced and were 1,095 bp long. This sequence shared >98% similarity to sequences of ‘Ca. L. asiaticus’ in the GenBank database. We observed that nested-PCR is necessary for consistent amplification of DNA from ‘Ca. L. asiaticus’ from M. paniculata. We excluded the possible nonspecific amplification associated with nested-PCR by XbaI restriction enzyme digestion and by nucleotide sequence analysis. Our data indicate that M. paniculata is a host of ‘Ca. L. asiaticus’ but the bacterial titer might be low. References: (1) X. Deng et al. Online publication. doi:10.1094/PHP-2007-0419-01-BR. Plant Health Progress, 2007. (2) M. Garnier and J. Bove. Huanglongbing (Greening). Page 46 in: Compendium of Citrus Diseases. 2nd ed. L. W. Timmer et al., eds. The American Phytopathological Society, St. Paul, MN, 2000. (3) S. Jagoueix et al. Int. J. Syst. Bacteriol. 44:379, 1994. (4) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996.

New diseases known locally as ‘hoja de perejil’ of tomato (Lycopersicon esculentum Mill) and ‘brotes grandes’ of potato (Solanum tuberosum L.) were first recognized in surveys of production fields in Bolivia during 2000–2003. Alfalfa (Medicago sativa) witches' broom and little leaf diseases of native weeds Morrenia variegata and mora-mora (Serjania perulacea) were also identified near to production fields. Phytoplasma aetiology was attributed to each of these diseases following detection and initial identification of aster yellows group (16SrI) phytoplasmas in all five diseased plant species. While potato, alfalfa and mora-mora plants contained indistinguishable 16SrI-B strains, ‘hoja de perejil’ (THP) and morrenia little leaf (MVLL)-associated phytoplasma strains shared 97.5 % 16S rRNA gene sequence similarity with ‘Candidatus Phytoplasma asteris’ and related strains and <95 % similarity with all other ‘Candidatus Phytoplasma’ species. Phylogenetic analysis of 16S rRNA gene sequences indicated that the THP and MVLL phytoplasmas represent a novel lineage within the aster yellows (16SrI) group and, on the basis of unique 16S rRNA gene sequences, we propose that THP and MVLL phytoplasmas represent ‘Candidatus Phytoplasma lycopersici’, with THP as the reference strain.

Only five bacterial phyla with members capable of chlorophyll (Chl)–based phototrophy are presently known. Metagenomic data from the phototrophic microbial mats of alkaline siliceous hot springs in Yellowstone National Park revealed the existence of a distinctive bacteriochlorophyll (BChl)–synthesizing, phototrophic bacterium. A highly enriched culture of this bacterium grew photoheterotrophically, synthesized BChls a and c under oxic conditions, and had chlorosomes and type 1 reaction centers. “ Candidatus Chloracidobacterium thermophilum” is a BChl-producing member of the poorly characterized phylum Acidobacteria .

SUMMARY Phytoplasmas are plant‐pathogenic bacteria that are associated with numerous plant diseases. We have previously reported the complete genomic sequence of Candidatus Phytoplasma asteris, OY strain, OY‐M line, which causes mild symptoms. The phytoplasma genome lacks several important metabolic genes, implying that the consumption of metabolites by phytoplasmas in plants may cause disease symptoms. Here we show that the approximately 30‐kb region including the glycolytic genes was tandemly duplicated in the genome of OY‐W phytoplasma, which causes severe symptoms. Almost duplicated genes became pseudogenes by frameshift and stop‐codon mutations, probably because of their functional redundancy. However, five kinds of genes, including two glycolytic genes, remained full‐length ORFs, suggesting that it is advantageous for the phytoplasma to retain these genes in its lifestyle. In particular, 6‐phosphofructokinase is known as a rate‐limiting enzyme of glycolysis, implying that the different number of glycolytic genes between OY‐W and OY‐M may influence their respective glycolysis activities. We previously reported that the phytoplasma population of OY‐W was higher than that of OY‐M in their infected plants. Taking this result into account, the higher consumption of the carbon source may affect the growth rate of phytoplasmas and also may directly or indirectly cause more severe symptoms.