# Biological Control of Phototrophic Biofilms in a Show Cave: The Case of Nerja Cave
## 4 Discussion
There is no information about a possible lytic activity on cyanobacteria or an explanation for their abundance. Regarding eukaryotes, sample 1 showed abundance of uncultured _Amoebozoa_ groups, such as the lobose amoebas of the order _Dactylopodida_ that ingest cyanobacteria, algae, bacteria, yeasts and particulate matter, as well as _Echinamoebabida_, and other group without assignment. Protozoa are traditionally considered the main predators of bacteria, as this is a lifestyle common to this group. Predatory protozoa exist in both aquatic and terrestrial environments and represent a major component in nutrient remineralization or'microbial loop.' [PERSON] and [PERSON] [25] reported a list of protozoa (including _Amoebozoa_) that predated on a wide variety of cyanobacterial species (_Anabaena_, _Nostoc_, _Microcystis_, _Oscillatoria_, _Gloeocapsa_, _Phormidium_, _Lyngbyba_, _Synechococcus_, etc.). The genus _Gregarina_ of the SAR supergroup was abundant in sampling site 1. According to [PERSON] et al. [26] there are more than 300 species of _Gregarina_ that mainly infect coleoptera and orthoptera, but also colembola, diptera, lepidoptera, hypenoptera, etc. The presence of parasitic gregarins, in sample 1, must be related to the population of insects in the cave, since they have a great abundance of parasitic species. [PERSON] et al. [27] identified in various samples of Nerja Cave sequences of the species _Gregarina blattarum_. _Gregarina blattarum_ has been found in different species of cockroaches: _Blattta orientalis_, _Periplaneta americana_, _Periplaneta discoidales_, _Blattella germanica_, _Parcoblatta pennsylvanica_ and _Blaberus cranifer_ and is the most widely studied species of _Gregarina_[28]. A review of the literature reveals a series of predatory bacteria on cyanobacteria and algae, mainly the genera _Lysobacter_, _Bacillus_, _Cytoplasa_, _Myxobacteria_, _Herpetosibron_, _Enifer_, _Vampirooccus_, _Vampiroviibrio_, _Cupiravidus_, _Pseudomonas_, _Steutrophomonas_, _Acinetobacter_ and _Delftia_[22; 29; 30; 31]. From all these genera, in sample 2 were present _Lysobacter_, _Bacillus_ and uncultured members of the order _Cytophagales_, not being able to rule out the possible existence of other bacteria with similar capacities from the extensive list of uncultured members. From the NGS analysis, the possible predatory activity and implication of _Lysobacter_ in sample 2 was evident. [PERSON] [32] found that the densities of cyanobacterial and lytic bacteria populations correlated well and that bacteria attacked cyanobacteria in two ways, by excreting exoenzymes or by fixing them to the cell. [PERSON] et al. [33] studied the _Lysobacter_ genome confirming the ability to produce proteolytic enzymes. In addition, the genome revealed the presence of a high number of genes encoded for proteases, endopeptidases and metalloendopeptidases. The genus _Bacillus_ was also abundant in sample 2 and could reinforce the predatory activity on this sample. Considering the analysis of eukaryotes, the uncultured members of _Schizophreniaalida_ (_Amoebozoa_) stand out in sample 2. This group of protosteloid amoebas is predator of bacteria and fungi in terrestrial ecosystems, where they have a global distribution [34]. The genus _Acanthamoeba_ (_Amoebozoa_) was present in sample 2B. Cyanobacteria are an adequate food source for amoebas, ciliates and flagellates, among the first is notable the genus _Acanthamoeba_ and the species _A. castellanii_[35; 36]. _Acanthamoeba castellanii_ were found in some other caves [37; 38]. [PERSON] et al. [35] evaluated the capacity of five amoebas, among them _A. castellanii_, on the cyanobacteria _Synechococcus elongatus_, _Leptolyngbya_ sp. and _Anabaena_ sp., demonstrating a predatory activity. [PERSON] et al. [36] showed that _A. castellanii_ consumed unicellular and filamentous cyanobacteria. Predation was initiated by complete engulfment of the unicellular cyanobacterium and, in the case of the filamentous, by rupture of the filaments, followed by digestion in the vacuoles.