Non-target effects of bacterial biological control agents on soil Protozoa

Biological control agents (BCAs) have gained increasing interest as an alternative to chemical pesticides in agriculture. Before widespread environmental use, risk assessment of effects on target and non-target organisms are needed. However, the knowledge about the effect of BCAs on non-target soil Protozoa is insufficient to support thorough risk assessment. In this study we report on the effects of Pseudomonas fluorescens DR54 that is a potential BCA active against root pathogenic fungi. We present evidence of negative effects of P. fluorescens DR54 on growth of the amoebae Hartmanella vermiformis and Acanthamoeba sp. cultures and natural assemblages of soil protozoans. The observed effects were larger than those of the P. fluorescens type strain DSM50090 and Enterobacter aerogenes SC and were tentatively attributed to viscosinamide, which is an antimicrobial compound with surfactant properties produced by P. fluorescens DR54.