Background: The structure and dynamics of breast tissue microbiomes can have far-reaching influences on women’s health, particularly on breast tumor development. However, there is currently little understanding on the ecological processes that shape the structure and dynamics of breast tissue microbiomes.
Methods: Here we fill the gap by applying three metacommunity models for investigating the community assembly and diversity maintenance, including Sloan near neutral model, Harris et al. multisite neutral and Tang & Zhou niche-neutral hybrid models to reanalyze the 16s-rRNA sequencing datasets of 23 healthy, 12 benign tumor, and 33 malignant tumor tissue samples. To remedy the practical difficulty in collecting tissue microbiome samples, we adopted a sophisticated random re-sampling (up to 1000 times) scheme in applying the three metacommunity models for analyzing the patterns in the breast tissue microbiomes.
Results: First, we found that, at the community/metacommunity levels, the mechanisms of microbiome assembly and diversity maintenance of breast tissue microbiomes were predominantly driven by stochastic drifts of bacteria demography (division, death and dispersal of bacterial cells), whereas the deterministic selection forces such as tumor progression were insignificant. However, at species level, on average, approximately 10% and 5% species were above (positively-selected) and below (negatively-selected) neutral, respectively. Furthermore, malignant tumor may raise the positively selected species up to 17%. Second, malignant tumor appears to inhibit microbial dispersal as evidenced by lowered migration rates, compared with the migration in normal and benign tumor tissues.
Conclusions: The mechanisms of microbiome assembly and diversity maintenance of breast tissue microbiomes were predominantly driven by stochastic drifts, and malignant tumor may inhibit microbial dispersal. These theoretic findings can be inspirational for further investigating the relationships between tissue microbiomes and breast tumor progression/development.