Table 2.

Overview of in vivo studies of the effects of nano- and microplastic exposure on the gut microbiota (metagenomic analyses). *This has been calculated by the authors based on Bachmanov AA et al. Behav Genet 2002 [73]

Reference	Nano-micro plastics	Dosage	Duration of exposure	Route of exposure	Species	Effects on bacterial diversity	Effects on bacterial phyla composition	Effects on bacterial genera composition
Invertebrates
Zhu et al., Soil Biology and Biochemistry 2018 [97]	Polyvinyl chloride particles 80 to 250 μm	1 μg/kg dry soil	56 days	Soil	Springtail (Folsomia candida)	Alpha diversity ↑ (p < 0.01)	↓ Bacteroidetes ↑ Firmicutes	(Family level: ↑ Bacillaceae)
Ju et al., Environ. Pollut. 2019 [98]	Polyethylene < 500 μm	0.5% dry weight in soil	28 days	Soil	Springtail, (Folsomia candida)	Chao1 diversity index ↓ Phylogenetic diversity whole-tree index↓	No data	↓Wolbachia ↑Bradyrhizobiaceae, Ensifer and Stenotrophomonas
Liu et al., Sci.Total Environ. 2019 [99]	Polystyrene 5 μm	40 mg/L	21 days	Tank water	Crab (Eriocheir sinensis)	Shannon diversity index: ↓	↑ Cyanobacteria, Chloroflexi, Fusobacteria and Proteobacteria ↓ Nitrospirae, Firmicutes, and Bacteroidetes	25 significantly different
Vertebrates
Huang et al., Sc Total Environ. 2020 [80]	Polystyrene; 32–40 μm	100 and 1000 μg/L	28 days	Tank water	Juvenile guppy (Poecilia reticulata)	Shannon diversity index: ↓ Simpson diversity index↑	↑ Proteobacteria ↓ Actinobacteria	↑ Gemmobacter and Rhodobacter
Wan et al., Chemosphere 2019 [100]	Polystyrene 5 and 50 μm	1000 μg/L	7 days	Tank water	Larval zebrafish (Danio rerio)	Chao1 diversity index: ↓ (5 μm)	No significant variation	5 μm: ↓Sphaerotilus, Haliangium and Leptothrix ↑Methyloversatilis, Polynucleobacter, Legionella and Ottowia 50 μm: ↓ Pseudomonas ↑ Flectobacillus and Methylophilus 5 and 50 μm: ↓ Methylobacterium
Gu et al., J. Hazard. Mater. 2020 [82]	Polystyrene 100 nm	5.5 × 10− 12 mg/L	14 days	Tank water	Large yellow Croaker (Larimichthys croceus)	Chao1 diversity index ↓ No variation of Shannon diversity index	↑ Bacteroidetes, Firmicutes ↓ Proteobacteria	↑ Lactobacillus, Parabacteroides, Alistipes
Kang et al. J Hazard. Mater. 2020 [83]	Polystyrene 50 nm (NP) and 45 μm (MP)	2.5 μg/mL	14 days	Artificial sea water	Medaka (Oryzias. melastigma)	Alpha diversity ↑ (MP only)	↓ Bacteroidetes (NP and MP),	NP and MP: ↓ Vicingus, Shewanella ↑ Lewinella, Pseudomonas, Thalassospira, Parahaliea.
Jin et al., Environ. Pollut. 2018 [84]	Polystyrene 0,5 and 50 μm	1000 mg/L	14 days	Tank water	Zebrafish (Danio rerio)	Shannon diversity index: ↑	↑ Firmicutes, ↓ γ-Proteobacteria	29 significantly different
Qiao, Sheng, et al., Sci.Total Environ. 2019 [85]	Polystyrene 5 μm	50–500 μg/L	21 days	Tank water	Zebrafish (Danio rerio)	Shannon diversity index: ↓ 17–29% in the 50 and 500 μg/L MP groups respectively (p < 0.05)	↑ Fusobacteria ↓ Proteobacteria	(Family level: ↑ 12 ↓ 13)
Qiao, Deng, et al., Chemosphere. 2019 [59]	Polystyrene fibre 20-100 μm	10 μg/L	21 days	Tank water	Zebrafish (Danio rerio)	Abundance coverage-based estimator: ↑ 107.5% in the fibre-MP group (p < 0.05) Simpson’s diversity index: ↓ 45.7% in the fibre-MP group (p < 0.05)	↑ Proteobacteria, ↓ Actinobacteria,	↑ Gordonia ↓ Aeromonas, Pseudomonas
Jin et al., Sci.Total Environ. 2019 [60]	Polystyrene 5 μm	1000 μg/L ~  266 μg/kg bw/day*	6 weeks	Drinking water	ICR Mice (Mus musculus)	Phylogenetic diversity whole-tree index ↓	↓ α−Proteobactria γ-Proteobacteria	↓ Parabacteroides, Prevotella, Dehalobacterium, Turicibacter, Bifidobacterium, Phascolarctobacterium, Lachnospira, Haemophilus, Adlercreutzia, Megamonas, Blautia, Dialister and Veillonella ↑ Coprococcus and Anaeroplasma
Lu et al., Sci.Total Environ. 2018 [91]	Polystyrene 0.5 and 50 μm	1000 μg/L ~  266 μg/kg bw/day*	5 weeks	Drinking water	ICR Mice (Mus musculus)	No data	↓ Firmicutes, α-Proteobacteria, Actinobacteria	↓ Oscillospira and Anaerostipes ↑ Parabacteroides, Prevotella, Dehalobacterium, Ruminococcus, Bilophila, Bifidobacterium, Adlercreutzia, Plesiomona, Halomonas and Acinetobacter (after both 0.5 and 50 μm polystyrene MP exposure)
Luo et al., Environ. Sci. Technol 2019 [101]	Pristine polystyrene microspheres 5 μm	1000 μg/L ~  266 μg/kg bw/day*	Gestation and lactation 6 weeks (analysis of dams)	Drinking water	ICR Mice (Mus musculus)	Shannon diversity index: no significant variation	No significant variation of Bacteroidetes, Proteobacteria, Firmicutes ↑ Actinobacteria ↑ Epsilonbacteraeota	14 significantly different
Li et al., Chemosphere. 2020 [93]	Polyethylene 10–150 μm	2–20-200 μg/g feed ~  0.0004, 0.004 and 0.04 μg/kg bw/day*	5 weeks	Feed	C57BL/6 Mice (Mus musculus)	Shannon diversity index: ↑ in the 200 μg/g MP (p < 0.05)	↑ Firmicutes (20–200 μg/g), ↑Melainabacteria (3 dosages) ↓ Bacteroidetes (20–200)	↑ Staphylococcus ↓ Parabacteroides (3 dosages)
Deng et al., Environment International 2020 [94]	Polyethylene 45–53 μm	100 mg/kg/day 5.25 104 particles/day	30 days	Gavage	CD-1 mice (Mus musculus)	Shannon diversity index: no significant variation	↑ Actinobacteria	↑ Lactobacillus ↑ Adlercreutzia ↑ Butyricimonas ↑ Parabacteroides