Identification rank and representation of truncated 16S rRNA from Nss. spL115 with 16S sequence truncated from the 5'-end. 16S rRNA of Nitrosospira sp. Strain L115 was truncated from its 5' end 10 nt a time for 89 times. Identification of each truncated 16S rRNA was simulated, with RES = 5, WIN = 3, and isotopic masses in RNase T1 catalog. The solid line is the identification rank, with the primary y-axis on the left. Rank 0 means one of the three Nitrosospira (Nss. multi5, Nss. spT7, and Nss. spD11) in the catalog is ranked as the highest-fractional representation bacterium in the sample. Rank -1 means one of the three Nitrosospira in the catalog is ranked as the second most represented bacterium in the sample, and so on. The dashed line is the fractional representation of the highest ranked Nitrosospira in the catalog, with the secondary y-axis on the right.