TITLE:
Functional Characterization of CRISPR-Cas System in the Ethanologenic Bacterium Zymomonas mobilis ZM4
AUTHORS:
Ge Dong, Mingxiong He, Hong Feng
KEYWORDS:
Zymomonas mobilis, CRISPR-Cas, Transcription, Immune, Interference
JOURNAL NAME:
Advances in Microbiology,
Vol.6 No.3,
March
15,
2016
ABSTRACT: CRISPR-Cas (clustered regularly interspaced short palindromic repeats—CRISPR
associated proteins) is a RNA-guided defense immune system that prevents some
genetic elements such as plasmids and virus from getting into the bacterial
cells. Zymomonas mobilis is an
ethanologenic bacterium, which encodes a subtype I-F CRISPR-Cas system containing
three CRISPR loci and a far distant cas gene cluster. Reverse transcription (RT)-PCR analysis revealed that the CRISPR
loci were transcribed on both strands. The Cas proteins were suggested to be
expressed based on the previous transcriptomic analysis. Challenging with the
invader plasmids containing the artificial protospacer with the protospacer
adjacent motif (PAM) of NGG or GG exhibited immune interference activity. However,
PAM motif of GG seems more effective than NGG in interference activity. Further,
the artificial CRISPR arrays with the spacer sequences targeting to the
specific genome sites could also lead to strong immune activity, resulting in
almost no transformant grown on the agar plates. It was suggested that bacteria
like Z. mobilis ZM4 are lack of the
rejoining function to heal the double breakage of genomic DNA made by the
CRISPR system. Conclusively, the Type I-F CRISPR-Cas system in Z. mobilis ZM4 is active to functionally
defense the invading DNA elements.