Alpha and beta diversity
Alpha diversity was assessed based on species richness in addition to
species evenness and richness, to determine the baseline differential
characteristics of the EV microbiome in the control and asthma EBC
samples (Figure 1A ). The asthma group showed significantly
higher alpha diversity (p <0.05) for all four
measurements. The observed OTUs and Chao1 estimates showed greater
species richness in the asthma EBC samples: Chao1 showed a more moderate
increase compared to the observed OTU values. Similarly, the Shannon and
Simpson diversity indices both demonstrated higher alpha diversity
measures in the asthma group than those in the healthy control group,
with the most dramatic increase seen in the Shannon diversity index.
PCoA (based on Bray-Curtis distance of all control and asthmatic patient
samples) yielded a primary principal coordinate (PCo1) of 20.13%, while
the secondary principal coordinate (PCo2) yielded a value of 8.1%
(Figure 1B ). Generally, EBC samples belonging to the healthy
control group were clustered below 0.0 along the PCo1 axis and were
evenly distributed along the PCo2 axis. Although there were several
asthma patient samples in the same cluster of the control group, several
asthmatic samples were tightly clustered around the 0.3 value on the
PCo1 axis and 0.0 on the PCo2 axis, with only a few control samples
included in the cluster. Diversity assessment for the eosinophilic and
non-eosinophilic asthmatic patients’ EBC samples yielded no significant
differences in any of the four alpha diversity metrics or the PCoA plot
for beta diversity (p >0.05) (Figure S1 ).