Zbl. Bakt. II. Abt., Bd. 133, S. 426-435 (1978) [From Istituto di Microbiologia agraria e tecnica dell'Universita di Pisa - Centro di Studio per Ill, Microbiologia del Suolo, C.N.R., 56100 Pisa, Italia] Interrelationships between Soil Microorganisms and Polystyrene A. SERITTI, U. CITERNESI, A. A. LEPlDI, M. P. NUTI, G. BERNACCHI, and G. PICC! With 22 Figures Summary Transmission and scanning electron microscopy along with a.utoradiographic procedures were used for evaluating the interrelationship between soil microorganisms and polystyrene. Two hypo- theses, allowing to explain the properties of polystyrene as a soil conditioner, were investigated: the first is concerned with a possible action of soil microorganisms on the compound; the second, reciprocally, with the polystyrene interference on microorganisms. Radioactivity translocation of 14C-Ecolyte-polystyrene along fungal hyphae and asexual fructification of strains, isolated from soil, as well as cytological modification at the cell wall level of the same microfungi, cultivated in the presence of polystyrene have been a.scertained. Zusammenfassung Zur Kennzeichnung der Wechselbeziehungen zwischen Bodenmikroorganismen und Polystyrol wurden elektronenmikroskopische und autoradiographische Methoden benutzt. Zwei Hypothesen wurden verfolgt, urn die Eigenschaften von Polystyrol als Bodenverbesserungsmittel zu erklaren: die erste befaf3t sich mit der moglichen Einwirkung der Mikroben auf den Kunststoff, die zWClte mit dem Effekt von Polystyrol auf die Mikroflora. Es wurde bewiesen, daf3 14C-Ecolyte-Polystyrol durch das Myzel von Fadenpilzen verlagert wurde, andererseits lief3en sich die Veranderungen in der asexuellen Fruktifizierung und in dem Aufbau der Zellwande der mikroskopischen Pilze nach- weisen. In a previous paper concerning the soil-conditioning properties of several synthetic polymers, an increase of the polystyrene-conditioning power in different soils within the first two months after the soil treatment was noticed, in connection with undama- ged conditions of soil microflor2. (SEQUI et al. 1972). On the contrary, no increase of soil structure indexes was detectable when soils were maintained under sterile condi- tions. These data suggested that some kind of interrelationships took place between polymer and soil microflora. An increase of soil structure could arise, for instance, either by an influence of soil on the polystyrene properties, concerned with the interrelation- ships between the polymer and soil constituents, or otherwise by a modification, very likely a damage, of the microbial structures in connexion with the polystyrene presence. As a matter of fact, the influence of microorganisms on polystyrene could easily be realized if the polymer undergoes a microbial attack, although, according to literature data (TsuRu 1971 and POTTS et al. 1972), it is apparently not the case.