Production of growth-inhibiting factors by Lactobacillus delbrueckii.
OBJECTIVE
The detection of growth-inhibiting factors produced by Lactobacillus delbrueckii.


RESULTS
A bioscreen assay was developed to study the effect of Lact. delbrueckii culture supernatant fluids on the growth of phylogenically or functionally related bacteria in broth cultures. Several growth-inhibiting factors could be distinguished based on differential effects on different test strains, separation by ultrafiltration and sensitivity to heat, proteinase treatment or catalase addition.


CONCLUSIONS
Lactobacillus delbrueckii strain VI1007 was found to produce at least three growth-inhibiting factors, other than lactic acid, when grown under microaerobic conditions in MRS broth. These included H2O2 and a bacteriocin-like, heat- and proteinase-sensitive bactericidal molecule or complex with a molecular weight greater than 50 kDa. A third factor inhibited the growth of Streptococcus thermophilus.


CONCLUSIONS
The assay system used allows the detection of subtle interactions between strains, that are likely to be of ecological importance in mixed cultures but would go unnoticed in classical agar diffusion tests.
van de Guchte
M
M
Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique-CRJ, 78452 Jouy-en-Josas cedex, France. guchte@biotec.jouy.inra.fr
Ehrlich
S D
SD
Maguin
E
E
D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D000898:Antibiosis; D001426:Bacterial Proteins / Q000378:metabolism* / Q000494:pharmacology; D018929:Cell Culture Techniques; D006131:Growth Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007778:Lactobacillus / Q000145:classification / Q000254:growth & development / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D013291:Streptococcus / Q000187:drug effects; D013696:Temperature
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006131:Growth Inhibitors; D006861:Hydrogen Peroxide