## 3 Results
### Effect of Joint Presence of PFCs and OPCs on Consortia of Bacterial and Microalgae Cells  
As already noted, PFCs and OPCs are present in urban wastewater, as well as in the wastewaters of enterprises using them [23; 24; 25]. Among other things, these substances are also contained in dust, which can enter water bodies together with precipitation. Microalgae, especially of the genus _Chlorella_, are actively used for wastewater treatment, including as parts of consortia. Wastewater is also offered as a medium for the accumulation of phototrophic biomass, where other microorganisms can be cultivated in parallel. It is known that \(N\)-acyl homoserine lactones (AHL) produced by Gram-negative bacterial cells stimulate the growth of microalgae, in particular those of the genus _Chlorella_[57; 58]. On the one hand, this information sets a new direction in the search for ways to increase the productivity of the processes of directed accumulation of phototrophic biomass. On the other hand, it causes concern from the point of view of uncontrolled development of bacterial-algal consortia in environmental objects. In this regard, it is necessary to investigate the process of accumulation of biomass of microalgae of the genus _Chlorella_ in association with bacterial cells when using wastewater containing PFCs and OPCs simultaneously as a nutrient medium. Such a study simulates a situation that may take place in real ecosystems, as xenobiotics can enter water bodies, which helps accelerate the accumulation of phototrophic biomass. The presence of other microorganisms can lead to even more intensive cell growth. To study changes in the rate of accumulation of _Chlorella_ microalgae biomass in the presence of bacteria capable of producing AHLs, three synthetic consortia were formed. At the same time, they were obtained by joint immobilization of microalgae biomass and a bacterial consortium at different ratios (Table 2). A previously developed immobilized artificial consortium was based on microorganisms belonging to Gram-positive (_R. ruber_) and Gram-negative (_P. esterophilus_) bacterial cell types and was capable of jointly performing rapid and efficient degradation of OPCs [42]. Such a combination of components, in our opinion, should ensure the presence of bacterial AHLs in close proximity to _C. vulgaris_ cells, as well as facilitate gas exchange (O\({}_{2}\) and CO\({}_{2}\)) between microorganisms. Among other things, such an immobilized consortium is a kind of nature-like model, as bacterial cells and phototrophic microorganisms coexist in water bodies of the environment, forming self-immobilizing biosystems (biofilms, floccules, mats), as well as being based on natural solid organic-mineral particles present in ecosystems. The study of changes in the rate of accumulation of microalgae biomass in the presence of bacteria was carried out in wastewater with the simultaneous presence of a PFC (perfluorohexane or polyether II) at different initial concentrations and an OPC (methyl parathion). It was found that in all the studied variations (Table 2), after 20 h, the degree of degradation of methyl parathion in the medium was 100%. Previously, for a bacterial consortium based on _P. esterophilus_ V-1436D and _R. ruber_ AC-1513D cells with a mass ratio of 2:1 [42], a similar result with the same concentration of methyl parathion was achieved in 24 h [42]. In this work, the joint immobilization of bacterial cells and microalgae cells probably provided constant oxygen access to bacteria and the removal of carbon dioxide from them by microalgae cells, which provided intensification of the degradation process of methyl parathion. From the data obtained (Table 2), it followed that the ratio of the biomasses of different microorganisms in the composition of the pellet affects the level of concentration of intracellular ATP of immobilized and suspended cells.