BackgroundThe
human respiratory tract harbours diverse microbial communities crucial
for health, but their dynamics during environmental perturbations like
smoking remain poorly understood. While smoking is a major risk factor
for various diseases, its compartment-specific effects on the
respiratory microbiome and potential recovery following cessation have
not been fully elucidated. Here, we present a longitudinal, multi-site
study of respiratory microbiome dynamics in smokers undergoing
cessation, benchmarked against healthy never-smokers.MethodsUsing
standardized sampling of the anterior nares, oropharynx, and
bronchoalveolar lavage (BAL), combined with 16S rRNA gene amplicon
sequencing and rigorous contamination controls, we characterized
community composition, diversity, inter-individual variability, and
microbial interactions across airway compartments.ResultsSmokers
exhibited pronounced microbiome alterations: nasal richness increased,
while lung richness and core taxa were decreased. Smoking-induced
changes were compartment-specific and most pronounced in nose and lung.
The degree of individual-specific differences in community structure was
elevated in smokers and correlated with smoking history. Short-term
cessation (6 weeks) led to minor shifts in genus abundance but increased
similarity between oropharyngeal and lung communities, whereas
long-term cessation (1 year) resulted in partial restoration,
particularly in lung and nasal microbiomes. Some genera, including Haemophilus and Prevotella_7,
showed persistent alterations, suggesting lasting smoking effects.
Network analyses revealed that smoking disrupted microbial co-occurrence
and reduced community connectivity, whereas cessation partially
restored interaction networks, with central taxa remaining altered and
dynamics differing between oropharynx and lung, reflecting different
underlying ecological assembly processes. Recovery trajectories were
highly individualized, with lung microbiomes influenced by deterministic
processes and upper airway microbiomes shaped by stochastic factors,
explaining site-specific responses and the persistence of personalized
microbial signatures.ConclusionThese
results provide the first time-resolved, multi-compartment
characterization of respiratory microbiome recovery after smoking
cessation, revealing that smoking leaves lasting, site-specific imprints
on airway microbial communities and interactions. Our findings
underscore the need for individual and compartment-specific approaches
when designing microbiome-based interventions to support respiratory
health.