Publications

4467

Abstract The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an important insect pest of the citrus crop worldwide. It vectors the pathogen ‘Candidatus Liberibacter asiaticus’ (CLas) that causes a serious disease known as citrus greening. Here, we tested the infection frequency of Wolbachia and CLas from 100 D. citri individuals collected from two host plants belonging to families Rutaceae (Citrus reticulata Blanco) and Boraginaceae (Cordia myxa L.) using molecular methods. The following trend of endosymbionts infection in adult D. citri was found; 85.4% (35/41) by Wolbachia, and 19.5% (8/41) by CLas collected from C. reticulata plants and 65.4% (17/26) by Wolbachia, and 15.4% (4/26) by CLas in case of C. myxa plant. However, 61.5% (8/13) nymphs collected from C. reticulata and 20.0% (4/20) collected from C. myxa plants were infected by Wolbachia, while no nymph was infected by CLas collected from either host plants. Findings from this work represent the first report of CLas presence in D. citri feeding on C. myxa plants. By studying the presence of CLas with other endosymbiotic bacteria, future basic and applied research to develop control strategies can be prioritized.

AbstractPhytoplasmas are plant pathogenic bacteria transmitted by insects. As endosymbiotic bacteria that lack a cell wall, their membrane proteins are in direct contact with host cytoplasm. In phytoplasmas the immunodominant membrane proteins (IDPs), are the most abundant proteins of the cell membrane. The antigenic membrane protein (Amp), one of the three types of IDPs, is characterized by a positive selection pressure acting in their extracellular domain. In South America, the ‘CandidatusPhytoplasma meliae’ has been associated to chinaberry yellows disease. In the present work, we describe for the first time the structure, phylogeny and selection pressure of amp gene in sixteen ‘CandidatusPhytoplasma meliae’ isolates. Our results indicate that amp gene sequences preserve the structure, large extracellular domain flanked by to hydrophobic domains in the N- (signal peptide) and C-termini (transmembrane), previously described in its orthologues and high divergence in the amino acids residues from extracellular domain. Moreover, a positive selection pressure was detected predominantly in this region confirming previous reports.

Abstract This report describes a case of canine hemotropic mycoplasmasosis by Candidatus Mycoplasma haematoparvum in a dog. A five-year-old splenectomized dog was referred to the Veterinary Teaching Hospital of the University of Sassari with clinical symptoms and laboratory findings compatible with immune-mediated hemolytic anemia. Epicellular bacteria were detected in the erythrocytes by microscopic examination of blood smears. PCR and sequencing were positive for Candidatus Mycoplasma haematoparvum. Treatment with doxycycline, prednisolone and blood transfusion was administered. Several studies have described the molecular prevalence of M. hemocanis and Candidatus M. haematoparvum, however there are few clinical reports, especially those describing Candidatus M. haematoparvum infection in dogs, for which only two cases have been reported. To the best of our knowledge this is the first case report of a symptomatic infection caused by Candidatus Mycoplasma haematoparvum in Italy. Hemoplasmosis should be considered as a potential cause of hemolytic anemia in dogs. Following treatment with doxycycline and prednisolone, the clinical signs improved without resolution of infection. This condition was the same at the three-year follow-up.

Summary Oxidation of nitrite to nitrate is an important process in the global nitrogen cycle. Recent molecular biology‐based studies have revealed that the widespread nitrite‐oxidizing bacteria (NOB) belonging to the genus ‘ Candidatus Nitrotoga’ may be highly important for the environment. However, the insufficient availability of pure Nitrotoga cultures has limited our understanding of their physiological and genomic characteristics. Here, we isolated the ‘ Ca . Nitrotoga’ sp. strain AM1P, from a previously enriched Nitrotoga culture, using an improved isolation strategy. Although ‘ Ca . Nitrotoga’ have been recognized as cold‐adapted NOB, the strain AM1P had a slightly higher optimum growth temperature at 23°C. Strain AM1P showed a pH optimum of 8.3 and was not inhibited even at high nitrite concentrations (20 mM). We obtained the complete genome of the strain and compared the genome profile to five previously sequenced ‘ Ca . Nitrotoga’ strains. Comparative genomics suggested that lactate dehydrogenase may be only encoded in the strain AM1P and closely related genomes. While the growth yield of AM1P did not change, we observed faster growth in the presence of lactate in comparison to purely chemolithoautotrophic growth. The characterization of the new strain AM1P sheds light on the physiological adaptation of this environmentally important, but understudied genus ‘ Ca . Nitrotoga’.