# Microbial Life on the Surface of Microlgistics in Natural Waters
## 3 Microplastics as Substrate for the Microbial Colonization in Marine and Freshwater Environments
Study of bacterial community composition of biofilms developed in seawater on the low- and high-density polyethylene, and polypropylene showed that differences in biofilm composition were stronger after one week of incubation and were not so dramatically at the latest stages of the biofilm formation when representatives of families such as _Flavobacteriaceae_, _Rhodobacteraceae_, _Planctomyectaceae_ and _Phylobacteriaceae_ were abundant on all surfaces [69]. Study of microbial community composition on fragments of polyethylene terephthalate bottles in the North Sea (UK) provided with denaturing gradient gel electrophoresis and sequencing analysis showed that it comprised of bacteria belonging to Bacteroides, Proteobacteria and Cyanobacteria [70]. Analysis of microbial communities from biofilms on microplastics (polyethylene, polypropylene, and polystyrene), floating in a bay of the island of Elba in the Mediterranean Sea showed that plastisphere of all MP particles consisted of representatives from the orders _Flavobacteriales_, _Rhodobacterales_, _Cytophages_, _Rickettisiales_, _Alteromonasales_, _Citinophages_, and _Oceanospirillales_[71]. So, according to data summarized in Table 1, all dominated bacteria in microbial communities in biofilms covered microplastic particles belong to Gram-negative bacteria (Table 1). There are only several studies devoted to the compositions of biofilms of microplastic found in freshwater systems [72]. Meanwhile, it was shown that microplastics in rivers provide attractive niches for microorganisms which can be transported by rivers \begin{table}
\begin{tabular}{c c c c c} \hline
**Microorganisms** & **Characteristics** & **Type of Plastic, Location** & **Time of Biofilm Development** & **References** \\ \hline \multirow{3}{*}{_Gammaproteobacteria_} & Gram-negative & & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \cline{2-4}  & & Gram-negative & & \\ \hline \end{tabular}
\end{table} 
Table 1: Dominated microorganisms in biofilms on microplastics found in salinity waters. to marine environments and serve a vector of bacterial assemblages [73]. According to results of [PERSON] with coauthors [74] bacterial communities colonizing different substrates (5 \(\times\) 5 cm pieces of ceramic tile, glass, aluminum, polyethylene terephthalate, leaf litter, and cardboard) incubated in the river, pond and artificial recirculating laboratory stream were well differentiated from each other, and there were significant differences in the microbial composition of biofilms depending on sites, but there were no differences in the microbial composition of biofilm developed on plastic in comparison with other solid substrates. Dominant bacterial phyla for all biofilms were the same, namely, _Proteobacteria_, _Bacteroidetes_, _Firmicutes_ and _Verrucomicobia_. However, river biofilms had higher relative abundances of the phylum Acidobacteria and the genera _Nitrospira_ and lower relative abundances of _Proteobacteria_; meanwhile the biofilms formed in ponds had significantly higher relative abundances of the phyla _Proteobacteria_, _Firmicutes_ and _Chlorofexi_. Higher relative abundance of the families _Burkholderiaceae_, _Nitrospiraaceae_ and _Nitrosomonodaceae_ and lower abundance of the family _Erythbroacteraceae_ was observed in the river biofilms.