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A novel method of studying the generation of genetic diversity in an undergraduate microbiology laboratory is described. The basis of this approach is the accumulation of mutations that confer a competitive advantage, or growth advantage in stationary phase (GASP) phenotype, to E. coli grown in stationary phase for extended periods of time.

Researchers have commonly treated misrepresentations in survey responses as an impediment to the accurate measurement of a variable or construct of substantive importance. This study builds on that approach and considers whether misreporting bias regarding support for violent extremism—both under- and over-reporting—may then have consequences for how terrorist violence itself unfolds. Using data from nearly 4,000 respondents in thirty-five communes in Burkina Faso, Chad, and Niger collected just prior to a recent wave of terrorist attacks, we find that communes where individuals under-report their true support for violent extremism—as measured with unobtrusive experimental methods—have a greater probability of experiencing subsequent Islamist attacks, controlling for socio-demographic characteristics of the commune, country-level proximity effects, and other time-varying factors. The findings raise important considerations regarding the measurement of extremist support, and they suggest a new tool for identifying communities potentially susceptible to terrorist violence. [ABSTRACT FROM AUTHOR]

Nutritional competence is the ability of bacterial cells to utilize exogenous double-stranded DNA molecules as a nutrient source. We previously identified several genes in Escherichia coli that are important for this process and proposed a model, based on models of natural competence and transformation in bacteria, where it is assumed that single-stranded DNA (ssDNA) is degraded following entry into the cytoplasm. Since E. coli has several exonucleases, we determined whether they play a role in the long-term survival and the catabolism of DNA as a nutrient. We show here that mutants lacking either ExoI, ExoVII, ExoX, or RecJ are viable during all phases of the bacterial life cycle yet cannot compete with wild-type cells during long-term stationary-phase incubation. We also show that nuclease mutants, alone or in combination, are defective in DNA catabolism, with the exception of the Exo[X.sup.-] single mutant. The Exo[X.sup.-] mutant consumes double-stranded DNA better than wild-type cells, possibly implying the presence of two pathways in E. coli for the processing of ssDNA as it enters the cytoplasm.

Natural genetic competence is the ability of cells to take up extracellular DNA and is an important mechanism for horizontal gene transfer. Another potential benefit of natural competence is that exogenous DNA can serve as a nutrient source for starving bacteria because the ability to 'eat' DNA is necessary for competitive survival in environments containing limited nutrients. We show here that eight Escherichia coli genes, identified as homologs of com genes in Haemophilus influenzae and Neisseria gonorrhoeae, are necessary for the use of extracellular DNA as the sole source of carbon and energy. These genes also confer a competitive advantage to E. coli during long-term stationary-phase incubation. We also show that homologs of these genes are found throughout the proteobacteria, suggesting that the use of DNA as a nutrient may be a widespread phenomenon.