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. 2024 Mar 14;13(3):257. doi: 10.3390/antibiotics13030257

Figure 2.

Figure 2

A schematic bacterial cell pertaining to Acinetobacter baumannii. The situation and structures of important virulence factors include the capsule, outer membrane proteins (Omps), lipopolysaccharide (LPS), Csu pilus, type IV pilus, efflux pumps and secretion systems (SSs). As shown, the secretion systems exert molecules (proteins) into the extracellular zone. Two types of T5bSS and T5cSS have been detected in A. baumannii. Although there are five sub-groups of T5SS (e.g., T5aSS, T5bSS, T5cSS, T5dSS and T5eSS) in Gram-negative bacteria, only two sub-groups of T5bSS and T5cSS are detected among the A. baumannii strains. Among these two secretion systems, T5cSS is the main secretion system that can be identified in A. baumannii populations. The efflux pumps—excluding ABC and RND families—take protons from the bacterial periplasm space into the cytoplasm and simultaneously excrete antibiotics from the bacterial cytoplasm into the periplasm space. The ABC family consumes ATP to excrete the antibiotic molecules from the bacterial periplasm space into the extracellular space. It acts as uniport efflux pump. On the other hand, the RND family takes the protons from the periplasm space into the cytoplasmic space and simultaneously excretes the antibiotic molecules from the periplasm space into the extracellular space [68,80,86].