ABSTRACT
Transformation systems developed for Trichoderma spp. were utilized to improve the biocontrol efficiency of the mycoparasitic fungus Trichoderma harzianum by increasing the copy number of the basic proteinase gene prb1. The transformants were stable and carried from two to ten copies of prb1. High levels of expression of prb1 during fungus-fungus interaction were detected when T. harzianum and Rhizoctonia solani were confronted in vitro. In liquid cultures the proteinase was induced by cell walls of R. solani. Under greenhouse conditions, incorporation of T. harzianum transformants into pathogen-infested soil significantly reduced the disease caused by R. solani in cotton plants.
Subject(s)
Antibiosis/genetics , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Fungal , Pest Control, Biological , Serine Endopeptidases/genetics , Trichoderma/genetics , Blotting, Northern , Blotting, Southern , Chromosome Mapping , DNA, Fungal/genetics , Electrophoresis, Polyacrylamide Gel , Fungal Proteins/analysis , Immunoblotting , Nucleic Acid Hybridization , Plants/microbiology , Plasmids , RNA, Fungal/analysis , RNA, Fungal/genetics , Rhizoctonia/growth & development , Transformation, Genetic , Trichoderma/growth & developmentABSTRACT
Azospirillum brasilense was attracted to capillaries containing either phosphate buffer, distilled water, or saline. The number of bacteria in these capillaries was 3-4×10(4), after 1 h of incubation. In the presence of phosphate buffer + attractants, the number of cells accumulated in the capillary increased only to 5×10(4)-1.1×10(5) cells. It was not possible, therefore, to measure chemotaxis inA. brasilense as distinct from aerotaxis by the capillary method. Chemotaxis was observed in semi-solid agar plates and was determined by a growth band oriented towards the attractant. Positive chemotactic response was obtained with peptone, tryptone, yeast extract, amino acids, organic acids, arabinose and galactose.