Table 1.

Features of the Cas9, Cas12, and Cas13 orthologs that are employed to modify the genomes of superbugs.

Cas Nuclease Orthologs	Origin	Function
SpCas9	Streptococcus pyogenes	Mediated double-stranded DNA break (DSB) creation with blunt end formation.
SpCas9-VQR		It can successfully target and cleave DNA at sites containing up to three mismatches.
dCas9		Control on or off gene expression.
xCas9		It can recognize PAM sequences that are up to five base pairs in length, compared with the three-base-pair PAM sequences required by traditional Cas9.
SPG		It only needs a G nucleotide to make edits.
SPRY		It can take advantage of various protospacer adjacent motif site sequences to modify the genetic material of bacteria.
Cas9n		Nickase activity is used to create a single-stranded break in the target DNA by cutting specific parts of the DNA sequence.
St1Cas9	Streptococcus thermophilus	This allows for better targeting of DNA, reducing unintended effects.
SaCas9	Staphylococcus aureus	Similar to SpCas9, but smaller and easier to deliver via viral or other vector-based systems.
NmCas9	Neisseria meningitidis	It improves specificity and reduces off-target effects.
CjCas9	Campylobacter jejuni	It has lower cleavage activity than spCas9, making it more suitable for applications that require fewer DNA edits.
Cpf1-Cas12a	Prevoltella and Francisella	It has a protospacer adjacent motif (PAM) recognition pattern that allows it to cut DNA at multiple sites in the target sequence.
C2c2-Cas12b	Aquifex aeolicus	Cuts DNA at a specific point and requires a guide RNA to direct it to the appropriate target.
AsCpf1-Cas12c	Acidaminococcus sp.	Smaller editing window, making it ideal for very precise gene-editing applications.
Cas13a	Leptotrichia wadei	RNA editing can be used for gene silencing through RNA interference.