Influence of rhizobacterial culture media on plant growth and on inhibition of fungal pathogens

The type of culture media significantly influenced the growth-promoting or growth-inhibiting effect of seven Pseudomonas spp. isolates on cucumber, as did the type of bacterial isolate. All the bacterial isolates also inhibited fungal growth, in vitro and the degree of inhibition depended on the growth medium of the two cultures. The degree of inhibition was affected by the growth-rate of the fungal pathogen. Proteolytic activity was detected in the supernatants of the cultures of six out of seven bacterial isolates and was media-dependent. High proteolytic activity was measured in supernatants of bacteria grown in two organic-based media, Tryptic Soy Broth and SNB nutrient broth, and/or in a Mineral medium. In contrast, proteolytic activity was almost undetectable after growth in King's B medium. Proteolytic activity was significantly increased when the concentration of proteose peptone in King's B medium was reduced by 50 and 75 percent.