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. 2021 Nov 1;12:6270. doi: 10.1038/s41467-021-26545-9

Fig. 1. Heme cluster 2 enables Acinetobacter baumannii to utilize hemoproteins for growth.

Fig. 1

a Two putative heme acquisition gene clusters in A. baumannii. Annotations of the proteins encoded by these genes are listed above the arrows. Both heme clusters contain a unique TonB-dependent outer membrane receptor (HemTR and HphR). Heme cluster 2 contains a Slam called HsmA adjacent to a predicted substrate of unknown function (HphA). b–e To tease apart the roles of the putative clusters in heme-dependent growth, WT, single and double transposon mutant A. baumannii (AB5075) strains were iron starved on LB agar supplemented with 200 µM dipyridyl. Cells were inoculated into RPMI supplemented with the following heme sources: 1 µM hemoglobin (b and c), 75 nM hemoglobin (d), and 2 µM hemin with 4 µM human serum albumin (HSA) (e). Hemoglobin concentrations expressed in terms of heme equivalents. Growth at 37 °C was monitored with optical density (OD) at 600 nM. Values plotted represent the mean ± standard error of the mean from three independent experiments.