**4. Conclusion and outlook**

In this chapter, the most powerful CLSM method for investigation of cyanobacteria—the fluorescence microscopic spectroscopy—was presented. This method allows to study living cyanobacterial cells via noninvasive and nondestructive technique and obtained in-vivo information about weak variations in single-cell functioning. It should be noted that CLSM provides some other interesting techniques, which can give deep insight into physiological processes that rules cyanobacterial life, such as FRAP [68–69, 105, 106] and hyperspectral microscopy [44]. FRAP is used to measure the mobility of phycobilisomes in intact cyanobacterial cells and hyperspectral microscopy helps to determine pigment localization and distribution in living cyanobacterial cells. Moreover, several time-dependent techniques for investigation of the dynamic properties of photosynthetic apparatus of cyanobacteria, such as PAM, can be implemented at a single-cell level by means of CLSM.

A limited number of examples, presented here, of possible fluorescence microscopic spectroscopy implementation (e.g., the investigation of biological diversity and monitoring of physiological state of cyanobacterial cultures) can significantly rise an effectiveness of the routine procedures in environmental monitoring and industrial culture production. Confocal microscopic spectroscopy gives a unique opportunity to introduce automation into these processes.

On the other hand, the indirect application of the presented results of the single-cell spectroscopic investigations can give a new information to improve remote sensing control. Spectral information recorded by satellite-carried sensors is already used for mapping of algae distribution, and due to the high frequency of data collection provides a database for estimation of phytoplankton dynamics over large areas [107]. Presented investigation gives an opportunity to control also cyanobacterial communities. The elaborated technique can be supported with algorithm that includes a new mathematical fitting strategy which automatically can cope with the environmentally caused variations of the cyanobacterial fluorescence spectra. Moreover, an additional fluorescence information on the physiological state of cyanobacterial cultures provides a new information for predictive modeling and aquatic management, alternatively to the delayed fluorescence described in [108].

The formalization of the genera identification and cultural physiological state analysis give an opportunity to develop a compact on-a-chip nanoelectronic device for preliminary on-line investigation of the field samples in situ and in vivo and for controlling of the laboratory cultures during industrial incubation.

Obviously, the proposed methods require further development, including evaluation of more species representing more phytoplankton classes, and including non-taxonomic features, such as photoadaptation. Although the quantitative measurements were not performed in this study, they could be possible while all stages will be standardized. However, this work already demonstrates a high potential of fluorescence microscopic spectroscopy. We suggest that CLSM methods have potential application for several of the approaches noted earlier and also other studies regarding photosynthetic apparatus of cyanobacteria. We hope that the unique cell-biology of cyanobacteria will encourage further investigations because of their growing importance in rural biotechnology and commercial production.
