Introduction: Did Adaptive and Directed Mutation Evolve to Accelerate Stress-Induced Evolutionary Change?: Saier, M.H., Jr.; What Limits the Efficiency of Double-Strand Break-Dependent Stress-Induced Mutation in Escherichia coli?: Shee, C.; Ponder, R.; Gibson, J.L.; Rosenberg, S.M.; Fitness Effects of Mutations in Bacteria: Gordo, I.; Perfeito, L.; Sousa, A.; Stress-Induced Modulators of Repeat Instability and Genome Evolution: Fonville, N.C.; Ward, R.M.; Mittelman, D.; Transcriptional De-Repression and Mfd Are Mutagenic in Stressed Bacillus subtilis Cells: Martin, H.A.; Pedraza-Reyes, M.; Yasbin, R.E.; Robleto, E.A.; Transposon-Mediated Adaptive and Directed Mutations and Their Potential Evolutionary Benefits: Zhang, Z.; Saier, M.H., Jr.; Specific and Nonspecific Host Adaptation during Arboviral Experimental Evolution: Novella, I.S.; Presloid, J.B.; Smith, S.D.; Wilke, C.O.; Author Index; Subject Index.