Published in Scientific Bulletin. Series F. Biotechnologies, Vol. XXI
Written by Mariana-Grațiela SOARE (VLADU), Caterina TOMULESCU, Liliana-Claudia BLASS, Narcisa BĂBEANU

The microbial antagonists represent natural means to combat the phytopathogens in order to obtain healthy crops. The abiotic factors such as temperature, pH, NaCl concentration in the growth medium and medium composition have decisive influence on the existence and development of microorganisms. Here are presented the results of the influence of these factors on development of Pseudomonas sp. and Bacillus sp. strains. Two of these strains, B1 and Bm, identified as Pseudomonas putida respectively Bacillus mycoides were recently isolated and showed remarkable activity in in vitro biocontrol of the phytopathogens Erwnia carotovora and Xanthomonas campestris. During experiments were tested, in the same conditions, two other strains Bacillus subtilis ICCF 84 and Pseudomonas putida ICCF 391 from CultureCollection of Industrial Importance Microorganisms (CMII). To study the influence of abiotic factors were chosen five values of temperature, five for the pH and five values for concentration of NaCl from medium. The best results regarding microbial growth were obtained for temperature values of 28 and 32°C, NaCl concentration in the culture medium between 0.5-4% and the pH between 5 and 8. Regarding the composition of the culture medium, of the four types of media, the best for the antagonists growth and development proved to be the medium M44 containing yeast extract, peptone and glycerol.

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