Table 4 A brief summary of known/putative functions of the TCSs identified in S. mutans UA159

TCS-1

HK-VicK

RR-VicR

SMU.1516

SMU.1517

Biofilm development, competence development, oxidative stress tolerance, acid tolerance, autolysin production, glucan metabolism, fructan metabolism.

[7, 8, 10, 24, 40, 42, 43]

TCS-2

HK-CiaH

RR-CiaR

SMU.1128

SMU.1129

Sucrose-dependent biofilm formation, competence development, multiple stress response, bacteriocin production

[12, 44, 45]

TCS-3

HK-CovS

RR-CovR

SMU.1145

SMU.1146

Acid tolerance, hydrogen peroxide resistance, murine macrophage killing.

[12, 46]

TCS-4

HK-KinF

RR-LlrF

SMU.928

SMU.927

Acid tolerance, pp(G)pp metabolism, control of alarmone synthesis.

[47, 48]

TCS-5

HK- ScnK

RR- ScnR

SMU.1814

SMU.1815

Bacteriocin production*.

[49]*

TCS-6

HK- SpaK

RR- SpaR

SMU.660

SMU.659

Bacteriocin production*, self-protection against anti-microbial peptides*.

[50–52]*

TCS-7

HK- PhoR

RR-YcbL

SMU.1037

SMU.1038

Unknown.

TCS-8

HK-KinG

RR-LlrG

SMU.1009

SMU.1008

Bacteriocin resistance, substrate transport in cell envelope stress.

[53, 54]

TCS-9

HK-LevS

RR-LevR

SMU.1965

SMU.1964

Biofilm formation, acid tolerance, fructan metabolism.

[55, 56]

TCS-10

HK-LytS

RR-LytT

SMU.577

SMU.576

Biofilm formation, oxidative stress tolerance, autolysis, fructan metabolism, cell wall metabolism*.

[57]*, [48, 58]

TCS-11

HK-LiaS

RR-LiaR

SMU.486

SMU.487

Biofilm formation, acid tolerance, cell envelope stress response, bacteriocin production, bacteriocin resistance, sucrose-dependent adherence.

[37, 59–62]

TCS-12

HK-HK11

RR-RR11

SMU.1548

SMU.1547

Unknown.

TCS-13

HK-ComD

RR-ComE

SMU.1916

SMU.1917

Biofilm formation, quorum sensing, competence development, bacteriocin production.

[9, 44, 63–65]

TCS-14

HK

RR

SMU.45

SMU.46

Unknown.

Orhpan RR1

RR-GcrR

SMU.1924

Sucrose-dependent adherence, glucan metabolism, pH homeostasis, competence development.

[66–72]