Putative Phage Hyperparasite in the Rickettsial Pathogen of Abalone, “Candidatus Xenohaliotis californiensis”

Studies on the ecology of microbial parasites and their hosts are predicated on understanding the assemblage of and relationship among the species present. Changes in organismal morphology and physiology can have profound effects on host–parasite interactions and associated microbial community structure. The marine rickettsial organism, “Candidatus Xenohaliotis californiensis” (WS-RLO), that causes withering syndrome of abalones has had a consistent morphology based on light and electron microscopy. However, a morphological variant of the WS-RLO has recently been observed infecting red abalone from California. We used light and electron microscopy, in situ hybridization and16S rDNA sequence analysis to compare the WS-RLO and the morphologically distinct RLO variant (RLOv). The WS-RLO forms oblong inclusions within the abalone posterior esophagus (PE) and digestive gland (DG) tissues that contain small rod-shaped bacteria; individual bacteria within the light purple inclusions upon hematoxylin and eosin staining cannot be discerned by light microscopy. Like the WS-RLO, the RLOv forms oblong inclusions in the PE and DG but contain large, pleomorphic bacteria that stain dark navy blue with hematoxylin and eosin. Transmission electron microscopy (TEM) examination revealed that the large pleomorphic bacteria within RLOv inclusions were infected with a spherical to icosahedral-shaped putative phage hyperparasite. TEM also revealed the presence of rod-shaped bacteria along the periphery of the RLOv inclusions that were morphologically indistinguishable from the WS-RLO. Binding of the WS-RLO-specific in situ hybridization probe to the RLOv inclusions demonstrated sequence similarity between these RLOs. In addition, sequence analysis revealed 98.9–99.4 % similarity between 16S rDNA sequences of the WS-RLO and RLOv. Collectively, these data suggest that both of these RLOs infecting California abalone are “Candidatus Xenohaliotis californiensis,” and that the novel variant is infected by a putative phage hyperparasite that induced morphological variation of its RLO host.     

The measurement of regional rates of cerebral protein synthesis in vivo

Special issue dedicated to Dr. Louis Sokoloff.     

The Effect of Dietary Energy Restriction on Body Weight Gain and the Development of Noninsulin-Dependent Diabetes Mellitus (NIDDM) in Psammomys obesus

Food intake was restricted to 75% of ad libitum levels in 37 male Psammomys obesus (Israeli Sand Rats) from the ages of 4 (weaning) to 10 weeks. Energy restriction reduced the mean body weight at 10 weeks by 29% compared with 44 ad libitum fed controls. Hyperglycemia was prevented completely in the food-restricted group, and mean blood glucose concentrations were significantly reduced (3.8 ± 0.2 vs. 5.5 ± 0.4 μmol/L; p<0.05) compared with control animals. Plasma insulin concentrations were also decreased significantly compared with ad libitum fed controls (105 ± 13 vs. 241 ± 29 mU/L;p<0.05). Although energy restriction prevented hyperglycemia from developing in 10-week-old P. obesus, 19% of the food restricted animals still developed hyperinsu-linemia. We concluded that hyperphagia between the ages of 4 to 10 weeks may be essential for the development of noninsulin-dependent diabetes mellitus in P. obesus, but that hyperinsulinemia may still occur in the absence of hyperphagia and hyperglycemia, suggesting a significant genetic influence on the development of hyperinsulinemia in this animal model.     

Two novel loci underlie natural differences in Caenorhabditis elegans abamectin responses

Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes.     

Arginine utilization by Mycoplasma fermentans is not regulated by glucose metabolism: A 13C-NMR study

Abstract Electrofusion of protoplasts of two mutant strains of Hansenula polymorpha resulted in high fusion and hybrid yields when the calcium ions present in the conventional fusion medium replaced by zinc ions. The optimal fusion conditions were an alignment field of 0.4 kV cm⁻¹ strength and 2 MHz frequency for 30 s, followed by two consecutive pulses of 12 kV cm⁻¹ strength and 15 μs duration. With 0.05–0.1 mM zinc ions in the fusion medium an average clone number of 10⁴–10⁵ clones per 10⁸ input cells was reached. The presence of about 0.6 mM magnesium ions in the zinc fusion medium was essential.