# An Exploratory Review of Microplastic Pollution, Associated Microbiomes and Pathogens in Water
## 3 Results and Discussion
### Most Common Microplastic-Associated Taxa and Their Relevance
A notable example is _Corynebacterium_ variable, identified as the dominant taxon on polystyrene MPs in a semi-enclosed harbour in Hong Kong. Although typically associated with soil and water environments, this species can act as an opportunistic pathogen. Itsdominance over MPs suggests that stagnant, low-exchange environments may promote rare and potentially harmful taxa on plastic debris [99; 102]. On the other hand, recent studies confirm that microplastics (MPs) floating in natural waters harbour a variety of antibiotic resistance genes (ARGs), suggesting that MPs may act as fomites not only for pathogenic bacteria but also for genetic elements associated with antimicrobial resistance. The most commonly detected ARGs include:  
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* Sulphonamide resistance genes--especially _su11_ (frequently linked to the integer gene _int11_) and _su12_, both widely observed in MPs biofilms [103]. * Tetracycline resistance genes--various _tet_ genes such as _tetA_ and _tetW_ were repeatedly found [104]. * Macrolide resistance genes--particularly _ermF_, which encodes an rRNA methyltransferase, conferring resistance to macrolides and lincosamides [105]. * Other ARGs--such as chloramphenicol resistance genes (_cat_), aminoglycos resistance genes (_aad_, _aac_), trimethoprim resistance genes (_dfr_), and fluoroquinolone resistance genes (_qnr_). Notably, clinically important \(\beta\)-lactamase genes (_blaCTX-M_, _blaTEM_, _blaSHV_) were detected in _Acinetobacter_, _E. coli_, and other resistant strains isolated from MP surfaces [106]. Due to the differences in MP composition, studies have shown that there are differences in the type of ARGs detected [103; 104]. The most common types of plastics in aquatic environments--PE and PP, as we mentioned before--were also the most frequently colonized by ARG-bearing bacteria [103; 105]. Studies in the Yangtze River estuary revealed that PE and PP fragments with visible biofilms had higher ARG concentrations than the surrounding water or sediments [103; 106]. Other polymer types, including PS, polyethylene terephthalate PET, and polyvinyl chloride PVC, also carried ARGs. Bacteria like _Bacillus_, _Mycobacterium_, and _Pseudomonas_ isolated from these surfaces contained su1, tet, and other ARGs. While surface chemistry may influence colonization, exposure time and environmental availability are likely stronger factors--older, photo-oxidized, or porous plastics become hotspots for ARG accumulation [103]. The occurrence of antibiotic resistance genes (ARGs) on microplastics has been investigated across various regions of the world--from coastal waters and estuaries in Asia, \begin{table}
\begin{tabular}{c c c c c} \hline
**Taxonomy** & **Abundance (\%)** & **Sampling Location** & **Water Type** & **Reference** \\ \hline Proteobacteria-- & \(\sim\)12\% (most & & \\ Pseudomonas & frequent genus) & & & \\ \hline Proteobacteria--Moraellaceae-- & \(\sim\)10\% (enriched & Pearl River Estuary & \\ _Acinetobacter_ & on MPs) & (China) & Fresh (Estuarine) & [72] \\ \hline CampylobacteroDateto-- & \(\sim\)3-4\% (MP & Rhine River & \\ Arcobacteraceae--_Arobacter_ & enrichment) & (Netherlands) & Fresh & [99] \\ \hline Proteobacteria—Alcantivoraceae-- & (present; MP-specific) & Eastern & Marine & [94] \\ _Aleantivorax_ & (present; & Mediterranean Sea & \\ \hline Proteobacteria—Vibrionaceae-- & (present; & \\ _Vibrio_ & dominant order) & NW Mediterranean Sea & Marine & [99] \\ \hline Actinobacteria-- & & & & \\ \hline Corynebbacteriaceae-- & (dominant on PS MPs) & Hong Kong & & \\ _Corynebacterium variable_ & & coastal waters & Marine & [102] \\ \hline \end{tabular}
\end{table} 
Table 7: Dominant bacterial taxa isolated from biofilms on microplastics in freshwater and marine environments (including their average relative abundance, sampling location, and source). to European seas, and inland rivers and lakes throughout the Americas.