Experiments in ex-germ-free mice establish a measurable effect of colonization history on gut microbiota assembly, illuminating a potential cause for the high levels of unexplained individuality in host-associated microbial communities.
Replicating experimental evolution from ancestral proteins shows that historical contingency steadily overwhelms chance and necessity as the primary cause of evolutionary variation in molecular sequences on long phylogenetic timescales.
Reward-related cues elicit phasic changes in activity in ventral pallidum neurons, which predict and functionally contribute to the speed of behaviors trained on the basis of act-outcome, but not stimulus-outcome, contingencies.
Experimental mapping of the joint sequence space of an ancient transcription factor (TF) and its DNA binding sites reveals that epistasis across the molecular interface permitted the evolution of a new and specific TF-DNA complex.
Selection imposed by antibiotics may dominate evolutionary forces acting on opportunistic pathogens like Acinetobacter baumannii, yet chance effects and a prior history in biofilm may constrain resistance and impose collateral sensitivities.