Fig. 4

The majority of the ~500 OTUs were dominated by four phyla: Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were the dominant phyla in the lung microbial communities. Identities were established using sequence homology with 16SrRNA gene sequences. Different proportions of phyla can be seen at different developmental stages of the lung. More than 85% of the reads belonged to these four phyla (two-tailed z test; p < 0.01). PBS alone was used as a control which shows less abundance among the four dominant phyla