# Marine Bacteria Associated with Colonization and Alteration of Plastic Polymers
## 3 Results and Discussion
### In Vitro Colonization and Structural Changes of Polymers through FTIR  
Plastic polymer colonization by bacteria has been reported, through formation of biofilm, at 7 days in coastal marine sediments where microorganism consortia such as several bacteria, diatoms, etc., are also involved [42; 43]. Moreover despite microplastic colonization also depending on chemical parameters such as pH and salinity, the in vitro model system allows circumvention of these variables and studying of polymer colonization by bacteria under controlled conditions. Moreover the in vitro approach would unveil how a particular bacteria species works and what its role is in the alteration of plastic polymers. This would allow addressing whether these bacteria can release plastic-active exoenzymes, with potentially biotechnological benefits, that can successfully alter plastic polymers. In this work, in vitro colonization of polymers by bacteria is assumed through EPS production (Table 2) and bacteria growth over plastic surface for 1 year (Table 3). Moreover in vitro colonization was performed with polypropylene and polystyrene spheres as most plastic fragments, isolated through saline gradient and analyzed with FTIR, were identified as such. This characterization is in accordance with a recent report concerning marine sand of drift line [44]. With the exception of _Myroides gitamensis_, bacteria growth--over whole and mechanically crushed polymer spheres--can be inferred as a significant increment in the weight of polymer spheres was determined compared to those of control spheres (Table 3). Our results indicate that plastic spheres made of PP and PS are susceptible to colonization by bacteria (Table 3). Nonetheless _Bacillus thuringiensis_ and _Proteus pemeri_ showed significative growth in the presence of PP compared to PS spheres (Table 3). Additionally, results also indicate that (i) there are significant differences in the weight of whole polypropylene \begin{table}
\begin{tabular}{c c c} \hline \hline
**Genus Species** & **Phyla** & **EPS (mg L\({}^{-1}\))** \\ \hline _Bacillus thuringiensis_ & & \(4.5\times 10^{-2}\) (*) \\ _Bacillus cereus_ & Firmicutes & \(3.2\times 10^{-2}\) (*) \\ _Bacillus sp._ & & \(1.1\times 10^{-1}\) (*) \\ \hline _Proteus pemeri_ & & \(1.8\times 10^{-3}\) \\ _Alcaligenes faecalis_ & Proteobacteria & \(3.5\times 10^{-2}\) (*) \\ \hline _Myroides gitamensis_ & Bacteroidetes & \(2.9\times 10^{-3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Concentration of exopolysaccharides (EPSs, mg L\({}^{-1}\)) produced by bacteria in in vitro assays (*, \(p<0.05\)). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Polypropylene (PP)**} & \multicolumn{2}{c}{**Polystyrene (PS)**} \\ \cline{2-5}  & **Whole** & **Mechanically Crushed** & **Whole** & **Mechanically Crushed** \\ \hline _Bacillus thuringiensis_ & 157 (*) & 162 (\(\zeta\) *) & 134 (\(\zeta\)) & 137 \\ _Bacillus cereus_ & 130 (\(\zeta\)*) & 114 & 121 (\(\zeta\)) & 122 \\ _Proteus pemeri_ & 137 (\(\zeta\)*) & 153 (\(\zeta\) *) & 125 (\(\zeta\)) & 119 \\ _Bacillus sp._ & 118 (*) & 112 (\(\zeta\)) & 134 (\(\zeta\)) & 141 (\(\zeta\)) \\ _Myroides gitamensis_ & 115 & 104 & 106 & 96 \\ _Alcaligenes faecalis_ & 124 (\(\zeta\)) & 132 (\(\zeta\) *) & 121 (\(\zeta\)*) & 77 \\ \hline \hline \end{tabular} \(\zeta\), significant differences compared to sphere weights in plates without bacteria (control); *, significant differences between respective spheres of PP and PS polymer. **V**, significant differences between whole and mechanically crushed spheres of PP and PS polymer. Significant differences, \(p<0.05\). A value of 100\(\%\) is for whole PP spheres 0.115 \(\pm\) 0.020 \(\mathrm{g}\); for mechanically crushed PP, 0.094 \(\pm\) 0.076 \(\mathrm{g}\); for whole PS spheres 0.133 \(\pm\) 0.004 \(\mathrm{g}\); and for mechanically crushed PS, 0.131 \(\pm\) 0.029 \(\mathrm{g}\).  
\end{table}