## 4 Discussion  
As one of the approaches to the intensification of the growth of phototrophic microorganisms, their co-cultivation with bacteria can be considered. For instance, the co-cultivation was effective in the treatment of wastewater when the following microbial partners were joined in the same biosystem: _Chlorella vulgaris_ and _Bacillus subtilis_[60]; _Pseudomonas_ and _Cyamobacteria_ cells [17]; _Chlorella vulgaris_, _Ettlia_ sp. and _Chlamydomonas reinhardtii_[61]; _Chlorella_ sorokiniana and wastewater bacteria; _AuxenchoIorella protothecoides_ and wastewater bacteria; _C. vulgaris_ and _Pseudomonas putida_; _C. vulgaris_ and _Bacillus licheniformis_; Desmodesus sp. and nitrifying bacteria; _C. sorokiniana_ and denitrifying bacteria; _C. vulgaris_, _Ettlia_ sp., _C. reinhardtii_ and hydrogen consumer denitrifiers; and _Chlorella_, Klebsiella and Acitenobacter cells [39]. Additionally, co-cultivation biosystems are used for commercialization of the microalgae biomass accumulation process [35]. Bacteria synthesizing AHLs are able to regulate the quorum sensing (QS) of microalgae and cyanobacteria. Consortia of bacteria and phototrophic microorganisms are widespread. In nature, they are formed as a result of the symbiotic interaction of microorganisms: microalgae and cyanobacteria cells produce oxygen, which is used by aerobic bacterial cultures that emit carbon dioxide, which phototrophs need. The presence of compounds with a gas transport function in the environment, which appear in the environment as pollutants, in this case can have a positive effect on the structure of mutually beneficial relationships between microorganisms. Studies on this topic are not yet known, but the matter is relevant today. It is possible to obtain new information in this direction by studying synthetic consortia; however, today algal-bacterial synergy is already used in the development of synthetic consortia for the destruction of various xenobiotics [62]. Recently, studies on the influence of the QS mechanism, manifested in the ability of bacterial cells to interact with each other through signaling molecules and to influence algae-bacteria interactions, have been of particular interest [63]. To date, it has been revealed that there are a number of AHL molecules, as well as other lactone-containing QS signaling molecules with different chemical structures and products of their destruction, which can have different effects on microalgae cells [64]. Under certain conditions, the presence of a keto group in the structure of an AHL molecule can lead to its enzyme-free rearrangement and the formation of tetramic acids, which can have a significant aligicidal \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**PFC**} & \multicolumn{4}{c}{**Biomass Ratio “Microalgae:Bacteria”**} \\ \cline{2-7}  & **6:1** & **12:1** & **25:1** & **6:1** & **12:1** & **25:1** \\ \cline{2-7}  & \multicolumn{4}{c}{**Perfluorohexane**} & \multicolumn{4}{c}{**Polyether II**} \\ \hline
0 & 78.1 \(\pm\) 3.7 & 89.1 \(\pm\) 4.1 & 92.7 \(\pm\) 4.3 & 80.4 \(\pm\) 2.5 & 95.1 \(\pm\) 4.1 & 95.7 \(\pm\) 3.3 \\
0.5 & 6.8 \(\pm\) 0.3 & 8.0 \(\pm\) 0.3 & 22.4 \(\pm\) 1.1 & 6.4 \(\pm\) 0.2 & 8.3 \(\pm\) 0.3 & 20.4 \(\pm\) 1.1 \\
1 & 3.0 \(\pm\) 0.1 & 6.0 \(\pm\) 0.2 & 15.0 \(\pm\) 1.7 & 2.0 \(\pm\) 0.1 & 5.0 \(\pm\) 0.1 & 14.0 \(\pm\) 1.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Residual bioluminescence * (%) of photobacteria in media after 24 h of cultivation of a consortium of _P. esterophilus_, _R. ruber_ bacteria and _C. vulgaris_ microalgae in wastewater with 0.15 mM methyl parathion and different PFCs. effect on the growth and photosynthesis of individual microalgae [65]. However, it is known that AHLs secreted by bacteria can bind to microalgae cells and contribute to their self-aggregation and stabilization [66].