## 4 Impact of Plastic Particles on Soil Properties
### Impact of Plastic Particles on the Soil Microbiome and Implication for Soil Metabolism
influence nutrient cycling processes, while plastisphere fungi may play a greater role in organic matter decomposition and nutrient release [77]. This suggests a reason why the degradation of biodegradable polyesters like PHB and PBAT is primarily fungal-driven, whereas conventional MPs like polyethylene (PE) more significantly impact soil bacterial biomass [90]. Therefore, it can be hypothesised that the impact of MPs on fungal communities, especially with bioplastic contamination, could be more pronounced than on bacterial communities. While there is no conclusive evidence that micro-bioplastics (MBPs) disrupt the soil microbiome structure more than conventional MPs, some studies suggest that MBPs could have a stronger impact [101; 103]. For instance, [PERSON] et al. [101] observed that MBPs (PBAT/PLA) might promote beneficial microbial taxa, as opposed to conventional MPs like PE, which could foster more harmful taxa. The question of whether MPs or MBPs have a more severe effect on the soil microbiome remains open to further research. Similarly, some studies [77; 92; 103] point out that MPs impact soil enzyme activity related to nitrogen fixation, potentially decreasing soil nitrogen bioavailability and causing nutrient imbalances. The effect of MBPs on soil metabolism, particularly in relation to nitrogen fixation, appears to be more significant than that of conventional MPs, but more research is needed to draw definite conclusions [77; 92; 103]. The second factor is the impact of MPs on soil mycobiome and microbiome relates to the increase in antibiotic resistance genes (ARGs), metal resistance genes (MRGs), and virulence factors (VFs) in soil. ARGs contribute to the emergence of antibiotic-resistant bacteria, MRGs facilitate the spread of metal-resistant bacteria, and VFs are molecules produced by bacteria, enabling them to cause disease [89]. Previous research indicates [47; 89; 93] that MPs can act as reservoirs for ARGs and MRGs in the soil microbiome, significantly elevating the abundance and co-selection of these genes. MPs combined with organic and metal pollutants, such as tetracycline or copper, can intensify this effect. [PERSON] et al. [89] found that MBPs composed of PBS notably increased ARGs and VFs, whereas conventional MPs had minimal impact. These findings imply that MPs could heighten the risk of spreading multi-resistant bacterial species, including pathogenic variants harmful to soil health. Notably, MBPs might pose a greater risk in this context than conventional MPs. The third factor to consider is the potential of MPs to create natural habitats that foster the proliferation of pathogenic bacteria and fungi in the soil matrix. Various studies [102; 104; 105; 106; 107; 108; 109] have linked the presence or increase of soil pathogens to MP contamination. For example, [PERSON] et al. [107] observed that plastispheres of LDPE and biodegradable much films (starch-based) tend to support higher abundances of certain bacterial phyla (Actinobacteria, Bacteroidetes, and Proteobacteria) and fungal genera (Rhizoctonia and Arthobotrys), which include facultative plant pathogens. Notable pathogenic species associated with MPs in soil are fungi like _Fusarium oxysporum, Corynespora cosiscola_ and _Myrothecium roridum_[102; 110], and the plant pathogenic bacteria are listed as _Actinetobacter jolnnsonii_ and _Escherichia coli_[109]. Moreover, studies have mentioned viruses adhering to various MP types [111]. One study recovered infectious virus particles from biofilms on MPs, noting their enhanced survival compared to those in water [112]. Additionally, irradiation-induced aging of MPs was found to increase the adsorption capacity of viruses on their surfaces [113]. Given current global health threats, the potential role of MPs in transmitting diseases like SARS-CoV-2 through the ecosystem warrants significant research attention. [PERSON] et al. [114] highlighted differences between conventional and biodegradable MPs in their interactions with pathogenic microorganisms.