# Microbial Life on the Surface of Microlgistics in Natural Waters
## 2 Bacterial Neuston as a Source of Microorganisms for Interaction with Microplastics
No significant difference between the bacterial compositions of bacterioneuston and underlying waters cell was found in Mediterranean coastal stations with Proteobacteria as dominated phylum [49] and in communities of neuston in seven sites located across the northern Yellow Sea and Bohai Sea in China [50]. However, there are also a lot of studies that indicate the difference in bacterial compositions of neuston and the subsurface water [51]. Bacterial strains isolated from the surface biofilm were represented in the genera _Bacterium_, _Chromobacterium_, _Pseudomonas_, _Flavobacterium_, _Caulobacter_, _Cryombacterium_ and the _Enterobacteriaceae_ family [41,51,52]. Analysis of bacterial neuston compositions in six lakes showed that despite differences in environmental conditions, the fraction of bacteria was very similar and the class of Gram-negative bacteria _Betrarobeducteria_, the phylum _Proteobacteria_, was predominant, followed with the phylum of mostly Gram-positive bacteria _Actinobacteria_[35]. Significantly higher numbers of Gram-negative heterotrophic bacteria in the neuston than in the underlying water layers were found in freshwater lakes [53]. Bacterial composition of bacterial neuston in high mountain lake in the Pyrenees consisted of _Betrarobeducteria_ and _Actinobacteria_ (>75% of the community composition), _Gammaproteobacteriaia_ (between 8% and 12%), _Alphaproteobacteria_ (between 1% and 5%), and _Firmicutes_ (1%) [54]. So, generally it seems that the bacterial community of bacterioneuston is similar in most cases to bacteria occurred in the water column, however, due to different factors such as physico-chemical, specific environmental and meteorological conditions the development of bacterial population of neuston could result in change of its structure. There are many cases when the biological hazards and water quality of natural aquatic systems is determined by the biodiversity of the bacterioneuston. At the water--air interface along with bacterioneuston there is pathobacterioneuston and, moreover, the concentration of pathogenic bacteria in the surface film may exceed 10-1000 times their content in the underlying layers of water. A significant number of pathogenic strains were isolated from the surface film of seawater including _Aeromonas hydrophilla_, _Escherichia coli_, _Pseudomonas aeruginosa_, _Salmonella_ spp., _Staphylococcus aureus_, _Streptococcus faecalis_, _Klebsiella pneumoniae_, _Alcaligenes_ spp., _Microoccus_ spp., and viruses [36,55-57]. Apparently, bacterial neuston plays a special role in the interaction of microplastics and microorganisms. Among microplastics floating in the ocean, the largest amounts belong to polyethylene, 54.5%, and polypropylene, 16.5% from the total quantity of MPs debris. They have lower density than water, have hydrophobic surfaces, and are present on the surface of water bodies [58]. Microbial cells of bacterioneuston, including pathogenic ones which are concentrated at the air-water interface, could attach to microplastic particles followed by biofilm formation.