Structural Organization of DNA in Chlorella Viruses

Chlorella viruses have icosahedral capsids with an internal membrane enclosing their large dsDNA genomes and associated proteins. Their genomes are packaged in the particles with a predicted DNA density of ca. 0.2 bp nm−3. Occasionally infection of an algal cell by an individual particle fails and the viral DNA is dynamically ejected from the capsid. This shows that the release of the DNA generates a force, which can aid in the transfer of the genome into the host in a successful infection. Imaging of ejected viral DNA indicates that it is intimately associated with proteins in a periodic fashion. The bulk of the protein particles detected by atomic force microscopy have a size of ∼60 kDa and two proteins (A278L and A282L) of about this size are among 6 basic putative DNA binding proteins found in a proteomic analysis of DNA binding proteins packaged in the virion. A combination of fluorescence images of ejected DNA and a bioinformatics analysis of the DNA reveal periodic patterns in the viral DNA. The periodic distribution of GC rich regions in the genome provides potential binding sites for basic proteins. This DNA/protein aggregation could be responsible for the periodic concentration of fluorescently labeled DNA observed in ejected viral DNA. Collectively the data indicate that the large chlorella viruses have a DNA packaging strategy that differs from bacteriophages; it involves proteins and share similarities to that of chromatin structure in eukaryotes

Sarcoidosis and mechanisms of unexpected death

Sarcoidosis is a multisystem disease of uncertain etiology characterized by multifocal areas of discrete and confluent granulomatous inflammation that may rarely be responsible for sudden and unexpected death. Two cases are reported to demonstrate disparate pathological features in fatal cases, one involving cardiac sarcoidosis, and the other neurosarcoidosis with hypothalamic infiltration. Sarcoidosis in individuals dying suddenly may be completely unrelated to the death, contributory or causal. Cardiovascular causes of sudden death in sarcoidosis include arrhythmias associated with cardiomyopathy and ischemia, ventricular rupture, and cor pulmonale due to pulmonary hypertension; respiratory causes include hemorrhage and upper airway obstruction; central nervous system causes include arrhythmias from infiltration of autonomic centers, epilepsy, and obstructive hydrocephalus from brainstem involvement; and gastrointestinal deaths may be due to hemorrhage from esophageal varices associated with portal hypertension. The diagnosis relies on the demonstration of typical noncaseating granulomas and the exclusion of other infective and environmental diseases with similar histopathological findings.Roger W. Byard, Nicholas Manton and Michael Tsoko

Life-Style and Genome Structure of Marine <i>Pseudoalteromonas</i> Siphovirus B8b Isolated from the Northwestern Mediterranean Sea

<div><p>Marine viruses (phages) alter bacterial diversity and evolution with impacts on marine biogeochemical cycles, and yet few well-developed model systems limit opportunities for hypothesis testing. Here we isolate phage B8b from the Mediterranean Sea using <i>Pseudoalteromonas</i> sp. QC-44 as a host and characterize it using myriad techniques. Morphologically, phage B8b was classified as a member of the <i>Siphoviridae</i> family. One-step growth analyses showed that this siphovirus had a latent period of 70 min and released 172 new viral particles per cell. Host range analysis against 89 bacterial host strains revealed that phage B8b infected 3 <i>Pseudoalteromonas</i> strains (52 tested, >99.9% 16S rRNA gene nucleotide identity) and 1 non-<i>Pseudoaltermonas</i> strain belonging to <i>Alteromonas</i> sp. (37 strains from 6 genera tested), which helps bound the phylogenetic distance possible in a phage-mediated horizontal gene transfer event. The <i>Pseudoalteromonas</i> phage B8b genome size was 42.7 kb, with clear structural and replication modules where the former were delineated leveraging identification of 16 structural genes by virion structural proteomics, only 4 of which had any similarity to known structural proteins. In nature, this phage was common in coastal marine environments in both photic and aphotic layers (found in 26.5% of available viral metagenomes), but not abundant in any sample (average per sample abundance was 0.65% of the reads). Together these data improve our understanding of siphoviruses in nature, and provide foundational information for a new ‘rare virosphere’ phage–host model system.</p></div