Autism spectrum disorder (ASD) seriously affects children’s health, while the gut microbiome has been widely hypothesized to be involved in the regulation of ASD behavior. This study investigated and compared the number, diversity, and population structure of gut microbiota between healthy and ASD children and their susceptibility to zinc oxide nanoparticles (ZnONPs) based on the measurement of live cell number, living/dead bacterial staining test, flow cytometry observation and bacterial community analysis using 16S rRNA gene amplicon sequencing. The result of this present study revealed that ASD children not only significantly reduced the live cell number and the community diversity of gut bacteria, but also changed the gut bacterial community composition compared to the healthy children. In addition, this result revealed that ZnONPs significantly reduced the number of live bacterial cells in the gut of healthy children, but not in that of ASD children. In contrast, ZnONPs generally increased the gut bacterial community diversity in both ASD and healthy children, while a greater increase was found in ASD children than that of healthy children. Furthermore, this study successfully isolated and identified some representative nanoparticle-resistant bacteria based on the color, shape, and edge of colony as well as the 16S rDNA sequence analysis. The community of nanoparticle-resistant bacteria differed in between healthy and ASD children. Indeed, the representative strains 6-1, 6-2, 6-3 and 6-4 from healthy children were identified as Bacillus anthracis, Escherichia coli, Bacillus cereus and Escherichia coli with sequence similarity of 97.86%, 99.86%, 99.03% and 99.65%, respectively, while the representative strains 8-1, 8-2 and 8-3 from ASD children were identified as Bacillus cereus, with sequence similarities of 99.58%, 99.72% and 99.72%, respectively. Overall, this study demonstrated that ZnONPs caused a change in number, diversity, and species composition of gut bacteria, but differed in healthy and ASD children.

Autism spectrum disorder (ASD) seriously affects children’s health. In our previous study, we isolated and identified a bacterium (Lactobacillus plantarum strain 6-1) that is resistant to propionic acid (PA), which has been reported to play a significant role in the formation of ASD. In order to elucidate the mechanism of the resistance to PA, this study investigated the change in the metabolic and proteomic profile of L. plantarum strain 6-1 in the presence and absence of PA. The results show that 967 and 1078 proteins were specifically identified in the absence and the presence of PA, respectively, while 616 proteins were found under both conditions. Gene ontology enrichment analysis of 130 differentially expressed proteins accumulated in the presence and absence of PA indicated that most of the proteins belong to biological processes, cellular components, and molecular functions. Pathway enrichment analysis showed a great reduction in the metabolic pathway-related proteins when this resistant bacterium was exposed to PA compared to the control. Furthermore, there was an obvious difference in protein–protein interaction networks in the presence and the absence of propionic acid. In addition, there was a change in the metabolic profile of L. plantarum strain 6-1 when this bacterium was exposed to PA compared to the control, while six peaks at 696.46, 1543.022, 1905.241, 2004.277, 2037.374, and 2069.348 m/z disappeared. Overall, the results could help us to understand the mechanism of the resistance of gut bacteria to PA, which will provide a new insight for us to use PA-resistant bacteria to prevent the development of ASD in children.