I can see CRISPR now, even when phage are gone: a view on alternative CRISPR-Cas functions from the prokaryotic envelope
Purpose of review: CRISPR-Cas systems are prokaryotic immune systems against invading nucleic acids that adapt as new environmental threats arise. There are emerging examples of CRISPR-Cas functions in bacterial physiology beyond their role in adaptive immunity. This highlights the poorly understood, but potentially common, moonlighting functions of these abundant systems. We propose that these noncanonical CRISPR-Cas activities have evolved to respond to stresses at the cell envelope. Recent findings: Here, we discuss recent literature describing the impact of the extracellular environment on the regulation of CRISPR-Cas systems, and the influence of CRISPR-Cas activity on bacterial physiology. These described noncanonical CRISPR-Cas functions allow the bacterial cell to respond to the extracellular environment, primarily through changes in envelope physiology. Summary: This review discusses the expanding noncanonical functions of CRISPR-Cas systems, including their roles in virulence, focusing mainly on their relationship to the cell envelope. We first examine the effects of the extracellular environment on regulation of CRISPR-Cas components, and then discuss the impact of CRISPR-Cas systems on bacterial physiology, concentrating on their roles in influencing interactions with the environment including host organisms.
© 2015 Wolters Kluwer Health, Inc. Owing to the rapidly expanding field, we have undoubtedly omitted some relevant studies. We apologize in advance to those authors whose work we did not cite. Conflicts of interest: D.S. W. is supported by NIH grant R01-AI110701 and a Burroughs Wellcome Fund Investigator in the Pathogenesis of Infectious Disease award. T.R.S. and D.S. W. have filed provisional patents based on CRISPR-Cas technological applications. H.K.R. has no conflict of interest.
Accepted Version - nihms678847.pdf