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The bacterial and archaeal assemblages at two offshore sites located in polar (Greenland Sea; depth: 50 and 2000 m) and Mediterranean (Ionian Sea; depth 50 and 3000 m) waters were studied by PCR amplification and sequencing of the last 450-500 bp of the 16S rRNA gene. A total of 1621 sequences, together with alignable 16S rRNA gene fragments from the Sargasso Sea metagenome database, were analysed to ascertain variations associated with geographical location and depth. The Ionian 50 m sample appeared to be the most diverse and also had remarkable differences in terms of the prokaryotic groups retrieved; surprisingly, however, many similarities were found at the level of large-scale diversity between the Sargasso database fragments and the Greenland 50 m sample. Most sequences with more than 97% sequence similarity, a value often taken as indicative of species delimitation, were only found at a single location/depth; nevertheless, a few examples of cosmopolitan sequences were found in all samples. Depth was also an important factor and, although both deep-water samples had overall similarities, there were important differences that could be due to the warmer waters at depth of the Mediterranean Sea.

Intrinsically disordered regions in eukaryotic proteomes contain key signaling and regulatory modules and mediate interactions with many proteins. Many viral proteomes encode disordered proteins and modulate host factors through the use of short linear motifs (SLiMs) embedded within disordered regions. However, the degree of viral protein disorder across different viruses is not well understood, so we set out to establish the constraints acting on viruses, in terms of their use of disordered protein regions. We surveyed predicted disorder across 2,278 available viral genomes in 41 families, and correlated the extent of disorder with genome size and other factors. Protein disorder varies strikingly between viral families (from 2.9% to 23.1% of residues), and also within families. However, this substantial variation did not follow the established trend among their hosts, with increasing disorder seen across eubacterial, archaebacterial, protists, and multicellular eukaryotes. For example, among large mammalian viruses, poxviruses and herpesviruses showed markedly differing disorder (5.6% and 17.9%, respectively). Viral families with smaller genome sizes have more disorder within each of five main viral types (ssDNA, dsDNA, ssRNA+, dsRNA, retroviruses), except for negative single-stranded RNA viruses, where disorder increased with genome size. However, surveying over all viruses, which compares tiny and enormous viruses over a much bigger range of genome sizes, there is no strong association of genome size with protein disorder. We conclude that there is extensive variation in the disorder content of viral proteomes. While a proportion of this may relate to base composition, to extent of gene overlap, and to genome size within viral types, there remain important additional family and virus-specific effects. Differing disorder strategies are likely to impact on how different viruses modulate host factors, and on how rapidly viruses can evolve novel instances of SLiMs subverting host functions, such as innate and acquired immunity.

Comparative genomics of gene-family size in closely related bacteria The wealth of genomic data in bacteria is helping microbiologists understand the factors involved in gene innovation. Among these, the expansion and reduction of gene families appears to have a fundamental role in this, but the factors influencing gene family size are unclear. AbstractBackground: The wealth of genomic data in bacteria is helping microbiologists understand the factors involved in gene innovation. Among these, the expansion and reduction of gene families appears to have a fundamental role in this, but the factors influencing gene family size are unclear.

Background: The phylogenetic position and evolutionary relationships of Fusobacteria remain uncertain. Especially intriguing is their relatedness to low G+C Gram positive bacteria (Firmicutes) by ribosomal molecular phylogenies, but their possession of a typical gram negative outer membrane. Taking advantage of the recent completion of the Fusobacterium nucleatum genome sequence we have examined the evolutionary relationships of Fusobacterium genes by phylogenetic analysis and comparative genomics tools.