Polish Journal of Environmental Studies Vol. 11, No. 5 (2002), 501-507 Epiphytic Bacteria Inhabiting the Yellow Waterlily (Nuphar luteum L.) W. Donderski, A. Kalwasińska Department of Water Microbiology and Biotechnology, Nicolas Copernicus University, Gagarina 9, 87-100 Toruń, Poland Received: 5 March, 2002 Accepted: 17April, 2002 Abstract Studies on the development dynamics and the physiological properties of heterotrophic bacteria growing on the surface of the yellow waterlily {Nuphar luteum L.) during the plants' development cycle were carried out. It was stated that the number of the epiphytic bacteria is different in the examined sections of the plant. The number is higher on bottom parts of petioles and rhizomes but lower on the surface of leaf blades and petioles beneath the leaf blade. The number of the epiphytic bacteria oscillated between 0.54 x 10 6 and 37.85 x 10 6 cells per lg of wet weight of the plant. The gram negative rods dominated among the epiphytic bacteria, the majority of which was slowly growing strains. Among the epiphytic bacteria the most numerous strains were those hydrolyzing fat, starch, and protein; the least numerous were the chitinolytic bacteria. Keywords: epiphytic bacteria, heterotrophic bacteria, generic composition, physiological properties, macrophytes Introduction It is estimated that the number of epiphytic bacteria on the surface of algae is between 10 3 and 10 6 cells/cm 2 [1]. Their number on the surface of tissue plants oscil- lates between 10 5 and 10 6 cells/cm 2 [2, 3, 4, 5]. Epiphytic bacteria colonizing a plant are food for nu- merous protozoans, snails, mayfly larvae and Chironomidae larvae [6]. For many detritus eaters they are a source of biogenes such as nitrogen, carbon, phos- phorus, and sulphur [4]. According to Baker [6], secre- tions of epiphytic bacteria are crucial nutrition for fresh- water snails. Epiphytic microflora also produce growth factors which can be used by macrophytes [6]. The re- search conducted by Strzelczyk and Mielczarek [7] shows that the metabolic activity of the epiphytic bacteria is higher than that of planktonic and benthic bacterias, and depends on a colonized plant and metabolized substaces. Correspondence to: Prof. W. Donderski The objective of this research is identification of the heterotrophic epiphytic bacteria inhabiting the yellow waterlily, determining their number, development dy- namics, morphology and some physiological properties. Materials and Methods Study Area The object of microbiological research were epiphytic bacteria colonizing the yellow waterlily (Nuphar luteum L.), growing in the littoral zone of Moty Bay, located in the southern part of Jeziorak Lake. This lake belongs to the Hawian Lake District and the Drweca - Vistula catchment area. This is an eutrophic water basin of the channel type, meridionally oriented, which was created during the last glaciation. The lake surface is 32.3 km 2 ,