Table 4.

Strains and plasmids used for cloning and overexpression of β-galactosidase encoding genes lacLM from L. helveticus ^a.

Strain or Plasmid	Relevant Characteristics	Reference
Strains
L. helveticus DSM 20075	source of lacLM genes	DSMZ (Braunschweig, Germany)
L. plantarum WCFS1	wild-type, expression host	[39]
L. plantarum TLG02	Δalr, D-alanine auxotroph, expression host	[32]
E. coli NEB5α	cloning host	New England Biolabs (Ipswich, MA)
E. coli MB2159	D-alanine auxotroph, cloning host	[40]
E. coli BL21 Star DE3	expression host	Invitrogen (Carlsbad, CA)
E. coli T7 Express	expression host	Novagen (Darmstadt, Germany)
Plasmids
pET-21d(+)	T7 Promoter, Ampr, C-terminal His-Tag	Novagen (Darmstadt, Germany)
pGRO7	plasmid encoding chaperones GroES and GroEL, Cmr	Takara (Shiga, Japan)
pSIP409	spp-based expression vector, Ermr, gusA controlled by PsppQ	[30]
pSIP609	derivative of pSIP409, erm replaced by alr	[32]
pET21lacLMLh	lacLM from L. helveticus in pET-21d(+)	current study
p409lacLMLh	pSIP409 derivative, containing lacLM from L. helveticus	current study
P609lacLMLh	pSIP609 derivative, containing lacLM from L. helveticus	current study

^a lacLM, β-galactosidase genes; Δalr, D-alanine auxotroph; Amp^r, ampicillin resistance; Erm^r, erythromycin resistance; Cm^r, chloramphenicol resistance; alr, alanine racemase encoding gene; erm, erythromycin resistance gene; spp, sakacin P gene cluster; gusA, β-glucuronidase reporter gene.