Interaction with Soil Bacteria Affects the Growth and Amino Acid Content of Piriformospora indica

Exploration of the effect of soil bacteria on growth and metabolism of beneficial root endophytic fungi is relevant to promote favorable associations between microorganisms of the plant rhizosphere. Hence, the interaction between the plant-growth-promoting fungus Piriformospora indica and different soil bacteria was investigated. The parameters studied were fungal growth and its amino acid composition during the interaction. Fungus and bacteria were confronted in dual cultures in Petri dishes, either through agar or separated by a Perspex wall that only allowed the bacterial volatiles to be effective. Fungal growth was stimulated by Azotobacter chroococcum, whereas Streptomyces anulatus AcH 1003 inhibited it and Streptomyces sp. Nov AcH 505 had no effect. To analyze amino acid concentration data, targeted metabolomics was implemented under supervised analysis according to fungal-bacteria interaction and time. Orthogonal partial least squares-discriminant analysis (OPLS-DA) model clearly discriminated P. indica-A. chroococcum and P. indica-S. anulatus interactions, according to the respective score plot in comparison to the control. The most observable responses were in the glutamine and alanine size groups: While Streptomyces AcH 1003 increased the amount of glutamine, A. chroococcum decreased it. The fungal growth and the increase of alanine content might be associated with the assimilation of nitrogen in the presence of glucose as a carbon source. The N-fixing bacterium A. chroococcum should stimulate fungal amino acid metabolism via glutamine synthetase-glutamate synthase (GS-GOGAT). The data pointed to a stimulated glycolytic activity in the fungus observed by the accumulation of alanine, possibly via alanine aminotransferase. The responses toward the growth-inhibiting Streptomyces AcH 1003 suggest an (oxidative) stress response of the fungus.

[Toxicological evaluation of biopreparations on the basis of nitrogen-fixing bacteria]

A comparative analysis of results of toxicological research of microbiological preparations on the basis of different species of nitrogen-fixing microorganisms of Azotobacter, Agrobacterium, Azospirillum general and pathogenic properties of strains-producers has been carried out. A possibility to improve methodical principles of toxicological estimation and hygienic regulation of associative nitrogen-fixing microorganisms-producers and preparations on their basis in the industrial objects and environment is substantiated. The paper is presented in Ukrainian.

Azotobacter keratitis

Ten cases of Azotobacter keratitis were identified at the Baylor College of Medicine and Cullen Eye Institute, Houston, from 1972 to 1980. Azotobacter are large, pleomorphic, aerobic, Gram-negative rods of the family Azotobacteraceae. The genus comprises four species (A beijerinckii, A chroococcum, A paspali, and A vinelandii) that are found in soil and water throughout the world. To our knowledge, Azotobactger species have not previously been recognized as causing human, animal, or plant disease. On the basis of the similarity of the organisms, other cases of Azotobacter keratitis may have been identified erroneously as Moraxella species.