TABLE 1.
Known Amd resistance-encoding genes and the functions of their productsa
| Gene(s) (alias[es]) | [ppGpp] dependence | Reference(s) | Function |
|---|---|---|---|
| mrdA (pbpA) | Unknown | 10, 11, 19 | Cell division and elongation |
| mrdB (rodA) | Unknown | 10, 20 | |
| mreB (envB) | Unknown | 18 | |
| mreC | Unknown | 18 | |
| ftsQ | No | 21, 22 | |
| ftsA | No | 21, 22 | |
| ftsZ | No | 21, 22 | |
| rpoB | Yes | 35 | RNA synthesis |
| cysB | Partly | 31, 32 | Cysteine biosynthesis |
| cysE | Partly | 31, 32 | |
| argS (lov) | Yes | 23 | tRNA synthetases |
| alaS | Yes | 23 | |
| slt | No | 32 | Transglycosylation |
| lon | Unknown | 29 | Rcs regulatory system |
| rcsB | Unknown | 29, 30 | |
| rcsC | Unknown | 29, 30 | |
| yrfF (mucM, igaA) | Unknown | 29 | |
| cyaA | Unknown | 26, 27 | Global regulation |
| crp | Unknown | 26, 27 | |
| spoTb | Yes | 28 | ppGpp degradation and synthesis |
| rfa, rfb, rfcb | 28 | Lipopolysaccharide | |
| galEb | Yes | 28 | |
| aroK | Yes | 34 | Shikimate kinase |
a
Elevated cellular levels of ppGpp (known as the stringent response) give increased Amd resistance. Some of the known resistance-encoding genes have been shown to confer resistance or not to confer resistance, depending on the cell's capacity to produce ppGpp.