Figure 1

Generation and phenotypic analyses of Δami1_Mab. (A) Schematic representation of the genomic region around ami1_Mab (MAB_0318c) in the parental (WT) and Δami1_Mab strains of Mycobacterium abscessus. The size of the PCR amplicons used for genotyping the Δami1_Mab mutants is indicated. (B) PCR profile confirming the proper deletion of ami1_Mab in the mutant strains. The PCR products of 1.6 kb were amplified from Δami1_Mab genomic DNA from rough (R) and smooth (S) variants while a band at 2.4 kb is expected for the parental (WT) strain. (C) In vitro growth curves at 37 °C of the M. abscessus (Mab) WT, Δami1_Mab, and complemented strains, in the R and S variants, respectively. Bacteria were grown in 7H9 broth supplemented with 10% oleic acid-albumin-dextrose-catalase (OADC) and 0.025% tyloxapol. The experiment is one representative of three replicates. (D) Transmission electron microscopy (TEM) of the M. abscessus WT, Δami1_Mab, and complemented strain in the S morphotype. Septa are indicated by black arrows. (E) Cell length measurements from the TEM data. Mean cell length = 1.27 μm for Mab S WT (n = 518); mean cell length = 1.34 μm for Δami1_Mab (n = 557); mean cell length = 1.27 μm from the complemented strain (n = 576), the scale bar represents 500 nm. For statistical analysis, an unpaired t-test with Welch’s correction was performed. p = 0.0035 for WT vs. Δami1_Mab and p = 0.0053 for Δami1_Mab vs. Δami1_Mab complemented (compl.) n.s. stands non statistically significant and ** stands for p < 0.01.