TABLE 1.

Type I TA systems identified in bacteria

System	Bacteria	Present on:	Expression	Role	Copy number	Reference(s)
Gram Positive
fst/RNAII	Enterococcus faecalis	pAD1, VRSAp; SaPlbov2 pathogenicity island	Constitutive	PSK	1	5, 7, 81, 82
fst-like/RNAII	E. faecalis, Staphylococcus saprophyticus, Streptococcus mutans, and Lactobacillus casei	Chromosome	Unknown	Carbohydrate metabolism (?)	1	14, 15, 83
sprA1/SprA1ASa	Staphylococcus aureus N315	νΣαβ pathogenicity island	Constitutive	Pathogenicity (?)	1	62, 99
sprG1/SprF1b	S. aureus N315	MGEg ΦSa3 pathogenicity island	Constitutive	Unknown	1	67
txpA/RatA	Bacillus subtilis	Skin element	Constitutive	PSK-like of Skin element, sporulation (?)	Up to 6	63, 97
bsrG/SR4	B. subtilis	SPβ prophage region	ResD O2 limitation response	Unknown	1	64
bsrE/SR5	B. subtilis	Prophage-like region P6	Multistress responsive	Unknown	1	65, 100
bsrH/as-bsrH	B. subtilis	Skin element	ResD O2 limitation response	Unknown	1	19
yonT/SR6	B. subtilis	SPβ prophage region	Multistress responsive	Unknown	1	68
lpt/RNAII	Lactobacillus rhamnosus	Plasmid	Constitutive	PSK (?)	1	84
CDS2517.1/RCd8	Clostridium difficile	Chromosome CRISPR (clustered regularly interspaced short palindromic repeat) 12 region	Coregulated with CRISPR	Unknown	Up to 6	66
Gram Negative
hok/Sok	Escherichia coli	Plasmid R1	Constitutive	PSK	1	8, 10
hok/Sok	Enterobacteriac	Chromosome	Unknown	Persistence	Up to 15	12
hokB/SokB	E. coli K-12	Chromosome	ppGpp induced, Obg (?)	Persistence	1	23
srnB′/SrnC-RNA	E. coli	Plasmid F	Constitutive	PSK	1	11
pndA/PndB-RNA	E. coli	Plasmid R483	Constitutive	PSK	1	11
Ldr/Rdl	E. coli K-12, Salmonella, and Shigella	Chromosome	Unknown	Unknown	Up to 10	17
Ibs/Sib	Enterobacteriad and Helicobacter pylori	Chromosome	Unknown	Unknown	Up to 7	16, 21
shoB/OhsC	E. coli and Shigella	Chromosome	Unknown	Unknown	1	16, 79
zorO/OrzO	E. coli	Chromosome	Unknown	Unknown	2	38, 59
symE/ISymR	E. coli	Chromosome	SOS response (LexA)	RNA recycling upon SOS (?)	1	36
tisb/IstR	Enterobacteriae	Chromosome	SOS response (LexA)	Persistence	1	18, 58
dinQ/AgrAB	E. coli	Chromosome	SOS response (LexA)	Nucleoid compaction	1	20, 60
dinQ-like/AgrAB	Enterobacteriaf	Chromosome	Unknown	Unknown	1	60
ralR/RalA	E. coli	Cryptic prophage Rac	Unknown	Biofilm maintenance (?)	1	35
aapA1/IsoA1	H. pylori	Chromosome	Constitutive	Unknown	Up to 2	31
aapA/IsoA	Helicobacter and Campylobacter	Chromosome and plasmid	Unknown	Unknown	Up to 9	31

^a This system has been predicted to be a homolog of fst/RNAII, initially discovered in E. faecalis (13–15).

^b This system has been predicted to be a homolog of txpA/RatA, initially discovered in B. subtilis (22, 97).

^c Escherichia (4–15), Shigella (7–12), Enterobacter (6), Klebsiella (2), Serratia (5), Vibrio (1), Yersinia (1), Shewanella, Photobacterium, and Photorhabdus (3). Numbers in parentheses indicate copy number.

^d Escherichia (3–7), Shigella (3–6), Citrobacter (1), Salmonella (3), and H. pylori (2, 3). Numbers in parentheses indicate copy number.

^e E. coli, Salmonella (large insertion), Citrobacter, Shigella, Enterobacter, and Klebsiella.

^f E. coli, Salmonella enterica serovar Typhimurium, Citrobacter koseri, Shigella sonnei, Shigella flexneri, Shigella dysenteriae, and Shigella boydii.

^g MGE, mobile genetic element.