TABLE 4.

Antimicrobial activities of S. thermophilus LMD-9 and derivatives against a defined set of indicator strains

Indicator strain	Inhibitory zone produced by the induced producer strainsa
	LMD-9 (D U E F) +	Δ2 (D) +	Δ3 (E F) +	Δ4 (U E F) +	Δ5 (D U) +	Δ6 (D E F) +	Δ7 (D U E F) −	Δ8 (D U E F) −
S. thermophilus LMG18311	6.5 ± 0.5	6.5 ± 0.5	3.5 ± 0.5c	3.6 ± 0.4c	6.7 ± 0.4	6.5 ± 0.5	6.5 ± 0.5	6.5 ± 0.5
E. faecalis JH2-2	3.5 ± 0.4	3.4 ± 0.3	NDb	ND	3.4 ± 0.4	3.5 ± 0.4	1.8 ± 0.2c	1.9 ± 0.2c
E. faecalis JH2-SS	3.5 ± 0.5	2.0 ± 0.1c	ND	ND	2.0 ± 0.1c	3.5 ± 0.5	1.9 ± 0.2c	1.8 ± 0.2c
L. lactis subsp. cremoris MG1363	3.0 ± 0.2	2.0 ± 0.1c	ND	ND	2.0 ± 0.1c	2.0 ± 0.1c	1.9 ± 0.2c	1.9 ± 0.2c
B. coagulans NCIMB8523	3.0 ± 0.1	3.0 ± 0.2	ND	ND	3.0 ± 0.1	3.1 ± 0.2	2.0 ± 0.2c	2.0 ± 0.1c
L. monocytogenes IHE-92	3.3 ± 0.4	3.3 ± 0.3	ND	ND	3.4 ± 0.4	3.3 ± 0.4	2.4 ± 0.3c	2.2 ± 0.2c

^aAntimicrobial activity was assayed using the overlay protocol, in the presence of 400 ng/ml D9C-30. The numbers represent the radii of the inhibitory zones around the producer colonies measured around at least 60 colonies (20 colonies from three independent experiments). The results are given as mean values ± standard deviations. The letters in parentheses indicate the content in bac_St genes of the producer strain: D, blpD_St; U, blpU_St; E, blpE_St; F, blpF_St. The presence (+) or absence (−) of blpG_St, encoding the putative disulfide oxidase, is also indicated.

^bND, not detected.

^cHighly significant difference in the size of the inhibitory zone produced by the LMD-9 derivative compared to the wild-type LMD-9 strain (Student's t test with a P value of <0.01) (Table 3).