Selection against Spurious Promoter Motifs Correlates with Translational Efficiency across Bacteria

Because binding of RNAP to misplaced sites could compromise the efficiency of transcription, natural selection for the optimization of gene expression should regulate the distribution of DNA motifs capable of RNAP-binding across the genome. Here we analyze the distribution of the −10 promoter motifs that bind the σ70 subunit of RNAP in 42 bacterial genomes. We show that selection on these motifs operates across the genome, maintaining an over-representation of −10 motifs in regulatory sequences while eliminating them from the nonfunctional and, in most cases, from the protein coding regions. In some genomes, however, −10 sites are over-represented in the coding sequences; these sites could induce pauses effecting regulatory roles throughout the length of a transcriptional unit. For nonfunctional sequences, the extent of motif under-representation varies across genomes in a manner that broadly correlates with the number of tRNA genes, a good indicator of translational speed and growth rate. This suggests that minimizing the time invested in gene transcription is an important selective pressure against spurious binding. However, selection against spurious binding is detectable in the reduced genomes of host-restricted bacteria that grow at slow rates, indicating that components of efficiency other than speed may also be important. Minimizing the number of RNAP molecules per cell required for transcription, and the corresponding energetic expense, may be most relevant in slow growers. These results indicate that genome-level properties affecting the efficiency of transcription and translation can respond in an integrated manner to optimize gene expression. The detection of selection against promoter motifs in nonfunctional regions also confirms previous results indicating that no sequence may evolve free of selective constraints, at least in the relatively small and unstructured genomes of bacteria

The role of packaging for consumer products: understanding the move towards ‘plain’ tobacco packaging

The Australian Government intends to introduce plain tobacco packaging in 2012. We consider whether such a move appears justified by examining the wider marketing literature in order to understand the role that packaging has for consumer goods. Packaging is often called the fifth ‘p’ of the marketing mix. It is an effective marketing medium for all consumer products and helps build consumer relationships through possession and usage. Common packaging strategies to promote the product, distinguish products from competitors, communicate brand values and target specific consumer groups include innovative, special edition, value and green packaging. These strategies, combined with the visual and structural aspects of packaging design, such as colour, size and shape, influence consumer perceptions and purchase and usage behaviour. This gives packaging an important role at point-of-purchase and also post-purchase. Packaging also has a close relationship with the product, influencing perceived product attributes, and is a key representative of the brand. We conclude that plain tobacco packaging appears justified, based on the importance of packaging as a promotional tool, and will fundamentally restrict the opportunity for tobacco companies to influence consumers through package design