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The primary sigma factor of Staphylococcus aureus, [[sigma].sup.SA], regulates the transcription of many genes, including several essential genes, in this bacterium via specific recognition of exponential growth phase promoters. In this study, we report the existence of a novel staphylococcal phage G1-derived growth inhibitory polypeptide, referred to as G1ORF67, that interacts with [[sigma].sup.SA] both in vivo and in vitro and regulates its activity. Delineation of the minimal domain of [[sigma].sup.SA] that is required for its interaction with G1ORF67 as amino acids 294 to 360 near the carboxy terminus suggests that the G1 phage-encoded anti-[sigma] factor may occlude the -35 element recognition domain of [[sigma].sup.SA]. AS would be predicted by this hypothesis, the G1ORF67 polypeptide abolished both RNA polymerase core-dependent binding of [[sigma].sup.SA] to DNA and [[sigma].sup.SA]-dependent transcription in vitro. While G1ORF67 profoundly inhibits transcription when expressed in S. aureus cells in mode of action studies, our finding that G1ORF67 was unable to inhibit transcription when expressed in Escherichia coli concurs with its inability to inhibit transcription by the E. coli holoenzyme in vitro. These features demonstrate the selectivity of G1ORF67 for S. aureus RNA polymerase. We predict that G1ORF67 is one of the central polypeptides in the phage G1 strategy to appropriate host RNA polymerase and redirect it to phage reproduction.

A genomic analysis of 18 P. aeruginosa phages, including nine newly sequenced DNA genomes, indicates a tremendous reservoir of proteome diversity, with 55% of open reading frames (ORFs) being novel. Comparative sequence analysis and ORF map organization revealed that most of the phages analyzed displayed little relationship to each other.

Researchers describe the isolation of the gutS gene in E. coli. This gene is induced by selenium and telluride, which are both toxic to living cells in high concentrations.

Sequencing and cloning of an arsenic inducible operon present in the chromosome of Escherichia coli using a lacZ transcriptional gene fusion library shows that this operon is analogous in terms of protein sequence and genetic organization to the plasma induced ars determinant. This ars operon is functionally significant in the detoxification of metalloid in Escherichia coli and its expression can be induced by exposure to sodium arsenite at 5 micro grams/liter. The experimental set up of the cloning and sequencing of an arsenic inducible operon is discussed.

Ner repressors of D108 and Mu transposable phages have identical, alpha-helical secondary structures. The Ner repressors are essential for the regulation of the early transposase operon expression and for progress in the phage growth along a lytic pathway. The nonhelical structures of the D108 Ner and Mu Ner are beta-stranded. The Ner operators exhibit Raman marker band in the Raman spectra, which enables the determination of the structure of the Ner repressors.

Abstract Background Bacteriophage classification is mainly based on morphological traits and genome characteristics combined with host information and in some cases on phage growth lifestyle. A lack of molecular tools can impede more precise studies on phylogenetic relationships or even a taxonomic classification. The use of methods to analyze genome sequences without the requirement for homology has allowed advances in classification. Results Here, we proposed to use genome sequence signature to characterize bacteriophages and to compare them to their host genome signature in order to obtain host-phage relationships and information on their lifestyle. We analyze the host-phage relationships in the four most representative groups of Caudoviridae, the dsDNA group of phages. We demonstrate that the use of phage genomic signature and its comparison with that of the host allows a grouping of phages and is also able to predict the host-phage relationships (lytic vs. temperate). Conclusions We can thus condense, in relatively simple figures, this phage information dispersed over many publications.