In addition to the differentially abundant taxa, a total of 14,444 different KOs were characterized, of which 624 were statistically significant across groups. Pathways from the significant KOs were obtained, resulting in 269 KEGG pathways (Table ) of which 207 were statistically significant. Figure illustrates the distribution of some of those pathways across groups, whereby the top thirty statistically significant pathways are represented in Figure . Notably, "microbial metabolism in diverse environment", "carbon metabolism" and "glyoxylate and dicarboxylate metabolism" pathways were increased compared to the control and iPD groups, compared to the PD-/LRRK2+ and PD+/LRRK2+ groups (Figure ). Furthermore, arginine, proline, phenylalanine, and butanoate metabolism exhibited the same trend, i.e., significatively decreased in PD-/LRRK2+ compared to the control and iPD groups (Figure ). In contrast, an increase in ribosomal genes was observed in PD-/LRRK2+ and PD+/LRRK2+ groups, suggesting that dust-borne bacteria might be compensating the lower metabolism (Figure ). Finally, both beta-lactam and vancomycin resistance appear to be elevated in PD-/LRRK2+ and PD+/LRRK2+ (Figure ). Overall, the pathways results (Figure )