Microarray-based resequencing of multiple Bacillus anthracis isolates

We used custom-designed resequencing arrays to generate 3.1 Mb of genomic sequence from a panel of 56 Bacillus anthracis strains. Sequence quality was shown to be very high by replication (discrepancy rate of 7.4 × 10(-7)) and by comparison to independently generated shotgun sequence (discrepancy rate < 2.5 × 10(-6)). Population genomics studies of microbial pathogens using rapid resequencing technologies such as resequencing arrays are critical for recognizing newly emerging or genetically engineered strains

The Bacillus anthracis chromosome contains four conserved, excision-proficient, putative prophages

BACKGROUND: Bacillus anthracis is considered to be a recently emerged clone within the Bacillus cereus sensu lato group. The B. anthracis genome sequence contains four putative lambdoid prophages. We undertook this study in order to understand whether the four prophages are unique to B. anthracis and whether they produce active phages. RESULTS: More than 300 geographically and temporally divergent isolates of B. anthracis and its near neighbors were screened by PCR for the presence of specific DNA sequences from each prophage region. Every isolate of B. anthracis screened by PCR was found to produce all four phage-specific amplicons whereas none of the non-B. anthracis isolates, produced more than one phage-specific amplicon. Excision of prophages could be detected by a PCR based assay for attP sites on extra-chromosomal phage circles and for attB sites on phage-excised chromosomes. SYBR-green real-time PCR assays indicated that prophage excision occurs at very low frequencies (2 × 10(-5 )- 8 × 10(-8)/cell). Induction with mitomycin C increased the frequency of excision of one of the prophages by approximately 250 fold. All four prophages appear to be defective since, mitomycin C induced culture did not release any viable phage particle or lyse the cells or reveal any phage particle under electron microscopic examination. CONCLUSION: The retention of all four putative prophage regions across all tested strains of B. anthracis is further evidence of the very recent emergence of this lineage and the prophage regions may be useful for differentiating the B. anthracis chromosome from that of its neighbors. All four prophages can excise at low frequencies, but are apparently defective in phage production

Non-rigid wages and merger profitability reversal under convex costs and centralized unionization

Can a merger from duopoly to monopoly be detrimental for profits? This paper deals with this issue by focusing on the interaction between decreasing returns to labour (which imply firms’ convex costs) and centralized unionization. First, it is highlighted that a wage ‘non-rigidity’ result applies: the post-merger wage is higher than in the pre-merger equilibrium. Second, it is shown that a ‘reversal result’ in relation to merger profitability actually realizes when the union is sufficiently oriented towards wages. Moreover, the higher the reservation wage, the degree of product differentiation, and the union's relative bargaining power, the higher the probability that a merger reduces profits

Merger policy, entry, and entrepreneurship

We assess the impact of merger policy on entry and entrepreneurship. When faced with uncertainty about its prospects, and foreseeing that it may wish to leave the market should profitability prove poor, a rational entrant considers possible exit routes. Horizontal merger reduces competition post-merger which, all else being equal, lowers welfare; but merger also provides a valuable exit route. By facilitating exit and thus raising the value of entry, more lenient merger policy may stimulate entry sufficiently that welfare is increased overall. We calculate the optimal merger policy in the form of a low, but positive, profitability threshold below which merger is permitted despite the adverse impact on post-merger competition. This may be viewed as an extension of the “failing firm defence” to include ailing, low profitability firms as well as imminently failing ones. Merger policy is compared with an entry subsidy, and the implications of strategic firm behaviour for the choice of merger policy are also examined

A study of patent thickets

Report analysing whether entry of UK enterprises into patenting in a technology area is affected by patent thickets in the technology area