If the bacteria are in a competitive environment, they will quickly lose resistance because DNA replication and protein production takes energy and time. So they will replicate slightly slower than bacteria without the added metabolic load.
If the resistance gene is on a plasmid it will likely lose it and selection will likely pick the bacteria without the added metabolic load of keeping a useless plasmid around. In this case it will take just as long to develop resistance as the first time (until it captures DNA with the antibiotic resistance on it).
If it has integrated into the chromosomal DNA, it will likely randomly mutate a few nucleotides to limit the amount of energy spent producing the protein. But the extra DNA will likely not cause enough of a difference in metabolic load to make them uncompetitive. This will allow them to regenerate the antibiotic resistance much faster than they did initially because they only have to randomly mutate a few nucleotides to get back their resistance
goatbears t1_j0kijcz wrote
Reply to Can antibiotic-resistant bacteria strains lose their resistance over generations, if they stop being exposed to the antibiotic? by enjrolas
If the bacteria are in a competitive environment, they will quickly lose resistance because DNA replication and protein production takes energy and time. So they will replicate slightly slower than bacteria without the added metabolic load.
If the resistance gene is on a plasmid it will likely lose it and selection will likely pick the bacteria without the added metabolic load of keeping a useless plasmid around. In this case it will take just as long to develop resistance as the first time (until it captures DNA with the antibiotic resistance on it).
If it has integrated into the chromosomal DNA, it will likely randomly mutate a few nucleotides to limit the amount of energy spent producing the protein. But the extra DNA will likely not cause enough of a difference in metabolic load to make them uncompetitive. This will allow them to regenerate the antibiotic resistance much faster than they did initially because they only have to randomly mutate a few nucleotides to get back their resistance