fig4

Figure 4. Range of mechanisms of how the MGE-encoded beneficial functions might help their host bacteria to cross the colonization bottleneck. These functions include (A) aiding host metabolism and growth by encoding genes such as AMGs and CAZymes; (B) antagonizing competitor bacteria by encoding type VI secretion systems and bacteriocins; (C) resisting antibiosis competition by encoding ARGs, such as reuterin resistance genes^[69]; and (D) defending the host from parasitic MGEs through Inc types, superinfection exclusion, and plasmid and phage defense systems. MGE: Mobile genetic element; AMGs: auxiliary metabolic genes; CAZymes: carbohydrate-active enzymes; ARGs: antibiotic resistance genes.