This week’s articles describe a second messenger that coordinates CRISPR-Cas immunity in bacteria and show how metabolism mediates protective crosstalk between the gut and resident microbes.
MICROBIOLOGY
Bacterial defense amplification
Kazlauskiene et al. found that cyclic oligoadenylates produced by the CRISPR effector complex subunit Cas10 activate the nuclease Csm6 to defend against viral infection (see also Amitai and Sorek).
HOST-MICROBE INTERACTIONS
Healthy guts exclude oxygen
Byndloss et al. showed how the bacterial metabolite butyrate instructs a metabolic pathway in colonocytes that protects the host against the expansion of pathogenic bacteria (see also Cani).
