## 4 Discussion
After the inoculation of lupine seeds with the endophytes, the count of bacterial cells of the _Pseudomonas_ genus colonising the white lupine roots was greater than the count of _Bacillus_ cells. Additionally, the coinoculation with rhizobia isolated from the Nitrofora preparation and bacteria of the _Pseudomonas_ genus resulted in a larger number of cells colonising the white lupine roots than the coinoculation with the _Bradyrrizobium_ sp. bacteria isolated from the Nitragina preparation. These differences in the degree of root colonisation by the endophytes applied in different variants of the experiment may have been caused by certain allelopathy resulting from the plant-microorganism and microorganism-microorganism interactions. During the development of plants, a certain proportion of the substances they produce are released into the environment in a controlled manner. This is a species-specific 'chemical profile' which includes phenolic compounds--molecules formed as a result of transformations of aromatic amino acids (mainly phenylalanine and, to a lesser extent, tyrosine) or their direct precursors. As results from the data provided in reference publications show, secondary metabolites, especially phenolic compounds and alkaloids, are used by other organisms inhabiting the phytosphere as a chemical signal indicating the presence of an appropriate interaction partner. Flavonoids, which are secreted by the roots of legumes, significantly influence the symbiosis between these plants and rhizobia [40; 41]. These compounds play an important role in the interaction of partners participating in the symbiosis. They mostly affect the expression of Nod genes in symbiotic bacteria. As a result, these bacteria produce the Nod factor, which is a lipochitooligosaccharide responsible for nodulation. Apart from inducing the expression of Nod genes, flavonoids also affect the chemotaxis of microorganisms and thus help to find symbiotic partners. As far as bacteria of the _Bradyrrizobium_ genus are concerned, isoflav (strong activators of Nod genes) do not induce a chemotactic response, whereas weak inducers of Nod genes (hydroxycinamic acids, coniferyl alcohol) are chemoattractts [42]. Besides flavonoids, a wide spectrum of polysaccharides (exopolysaccharide--EPS), which are present on the surface of rhizobia cells and have a species-specific composition, also play an important role in establishing a symbiotic relationship between legumes and symbiotic bacteria [43]. For example, succinoglycans are exopolysaccharide--EPS of particular importance in the formation of symbiotic systems with legumes. They are a necessary factor conditioning the elongation of the infectious strand in _Sinorhizobium melidi_. The increased synthesis of these exopolysaccharides increases the efficiency of nodulation in _Meliotti truncatula_[44]. In 2015, the membrane receptor (EPR3) for bacterial exopolysaccharides was identified in _Lotus japonicus_. Its interaction with EPS depends on their structure. Moreover, researchers also observed that EPR3 synthesis is conditioned by the presence of specific Nod factors. This means that the infection of the host plant by rhizobia can be controlled by two independent sets of receptors receiving both Nod and EPS signals [45; 46]. Phenolic compounds are believed to significantly affect root colonisation not only by rhizobia but also by endophytic bacteria [47]. It is presumed that certain genotypes of these bacteria are highly adapted to colonisation of the rhizosphere of their respective plants and that as in the case of rhizobia, it largely depends on the secretion of bioactive phenolic compounds by the roots [48]. The appearance of these compounds in the environment is recognised and used by bacteria, e.g., from the _Pseudomonas_ and _Azospirillum_ genera, as a chemical signal responsible for the initiation of rhizosphere interactions and indicating the presence of a plant which is an appropriate host for a particular group of microorganisms [48; 49]. According to [PERSON] et al.