Publications

4981

ABSTRACT “ Candidatus Neoehrlichia mikurensis” is a new intracellular pathogen associated with human infection and death. “ Candidatus Neoehrlichia mikurensis” infection in a chronically neutropenic dog from Germany was confirmed by DNA sequencing. The same organism was previously described from ticks and two sick human beings from Germany.

AbstractCandidatus Liberibacter asiaticus (CLas) bacterium has been strongly implicated as the causative agent of huanglongbing (HLB), or citrus greening, which is currently the most devastating citrus disease worldwide. HLB is transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), in a persistent manner. We used quantitative-polymerase chain reaction (PCR) to detect CLas in dissected organs of individual D. citri adults infected with HLB in the laboratory or collected from field-infected citrus trees in South Florida. The proportion of infected (CLas-positive) dissected organs was 47–70% for the salivary glands, 72–80% for the alimentary canal, and 79–97.5% for the rest of the insect body. Statistical analysis indicated that, in both field- and laboratory-infected D. citri, the proportion of infected salivary glands was significantly lower than that of other parts in the insect body. With field-collected psyllids, the relative copy number of CLas genomes, compared with psyllid genomic DNA in each sample, was significantly higher in both the salivary gland and alimentary canal compared with that in the rest of the insect body for both males and females. These results provide the first PCR confirmation of CLas in the alimentary canal and salivary glands of D. citri and strongly suggest that the salivary glands constitute an important transmission barrier to CLas in the psyllid vector. Our results also suggest that CLas may replicate or accumulate in both the alimentary canal and salivary glands of D. citri.

ABSTRACT Many members of the suborder Heteroptera have symbiotic bacteria, which are usually found extracellularly in specific sacs or tubular outgrowths of the midgut or intracellularly in mycetomes. In this study, we describe the second molecular characterization of a symbiotic bacterium in a monophagous, seed-sucking stink bug of the family Lygaeidae (sensu stricto). Chilacis typhae possesses at the end of the first section of the midgut a structure which is composed of circularly arranged, strongly enlarged midgut epithelial cells. It is filled with an intracellular endosymbiont. This “mycetocytic belt” might represent an evolutionarily intermediate stage of the usual symbiotic structures found in stink bugs. Phylogenetic analysis based on the 16S rRNA and the groEL genes showed that the bacterium belongs to the Gammaproteobacteria , and it revealed a phylogenetic relationship with a secondary bacterial endosymbiont of Cimex lectularius and free-living plant pathogens such as Pectobacterium and Dickeya . The distribution and ultrastructure of the rod-shaped Chilacis endosymbiont were studied in adults and nymph stages using fluorescence in situ hybridization (FISH) and electron microscopy. The detection of symbionts at the anterior poles of developing eggs indicates that endosymbionts are transmitted vertically. A new genus and species name, “ Candidatus Rohrkolberia cinguli,” is proposed for this newly characterized clade of symbiotic bacteria.

Five new species of cyanobacteria, Scytonematopsis maxima, Tolypothrix pseudorexia, Hormoscilla irregularis, Phormidium arthurensis, and Godleya alpina, the last belonging to a new genus, are described from cultured material isolated from the alpine zone of Mt Philistine, New Zealand. Tolypothrix pseudorexia resembles Rexia erecta in formation of upright trichomes on agar, but clearly lacks the ability to divide in two planes that is characteristic of the latter species. Godleya displays characteristics of the Scytonemataceae-isopolar hormogone development and binary branching-but groups with a species of Coleodesmium (Microchaetaceae) in analyses of 16S rDNA, despite its morphological differences, thus conflicting with the current classification system. We also show that material referable to the widely reported species Phormidium autumnale is found in the New Zealand alpine zone; molecular data indicate that this is likely the same organism reported recently from the Hutt River, Wellington, New Zealand, a quite different habitat. In this site, a lowland river, the species may form extensive mats. These have not been seen on Mt Philistine.