In order to distinguish bacteria with and without plasmids, and thereby with and without antibiotic resistance, the researchers modified the bacteria genetically. The red cells carry plasmids, while green cells have lost the plasmid. The bacteria were studied under different conditions. In this case the bacteria are cultivated in small, round alginate beads.
illustration from scientific article in NPJ Biofilms and Microbiomes.
Creationist mode: 
It's beginning to look like Creationism's divine malevolence is winning its antibiotic arms race with medical science.
Danish scientists working at the University of Copenhagen have discovered that it has even thought of a way to overcome one of the treatments used against antibiotic resistant bacteria - discontinuing their use for a period to allow the non-resistant forms to reassert their dominance in the bacterial population, before hitting them with the antibiotic again.
It had been assumed that the bacterial population would lose their resistance with this 'rest' period, but the scientists have shown that bacteria have been designed to 'hide' their resistance, so this assumptions needs to be reassessed and modified.
As the Copenhagen University press release accompanying the research published open access in the journal NPJ Biofilms and Microbiomes, explains:
One widespread strategy to combat antibiotic resistance has been to use antibiotics for a period of time and then take a break. The belief is that resistant bacteria will lose their resistance genes or be outcompeted during the break, after which the antibiotics will work again. But that approach doesn't seem to hold up.
In contrast to the active bacteria in biofilm, inactive bacteria in biofilm don’t grow. As such, they don’t compete. This allows space for them to carry plasmids. In this way, a reserve of resistance genes is built up into biofilm. Obviously, it’s a huge advantage for bacteria to be able to save resistance up to 'bad times' – in this case, when a bacterium meets an antibiotic.
In contrast to the active bacteria in biofilm, inactive bacteria in biofilm don’t grow. As such, they don’t compete. This allows space for them to carry plasmids. In this way, a reserve of resistance genes is built up into biofilm. Obviously, it’s a huge advantage for bacteria to be able to save resistance up to 'bad times' – in this case, when a bacterium meets an antibiotic.
Associate Professor Mette Burmølle, co-senior author
Section of Microbiology
Department of Biology
University of Copenhagen, Copenhagen, Denmark.
Antibiotic resistance is a race between us humans, who strive to find new antibiotics that can treat infectious diseases – and bacteria, which are becoming increasingly resistant. For now, bacteria are way ahead, which is why it is important for us to learn more about antibiotic resistance. A Danish research group has discovered a new piece of the puzzle that helps us better understand the 'enemy'.No doubt Creationists will be thrilling at the creative genius of their beloved sadist who has come up with this brilliant way to overcome the efforts medical science has been making to protect us from its nasty organisms. And such a simple strategy too - put those carrying the resistance plasmid into hibernation so there is no cost in carrying it, so it is ready when antibiotics are used again. And this will work in most environments and even turn harmless soil bacteria into pathogenic organisms with antibiotic resistance built in!
University of Copenhagen researchers have shown that the prevailing assumption that resistant bacteria lose their resistance capability when antibiotics are not present is a truth requiring significant modifications.
[…]
Biofilm deals resistance genes a strong card
Our study demonstrates that resistance genes are able to hide in inactive bacteria, where they form a hidden reserve of resistance that bacteria can rely on. In other words, they don't just disappear when antibiotics aren’t around.Most bacteria live and interact in what are known as biofilms – where microbial communities are encased in a matrix of mucus they form, often on the surface of a material. Biofilms are found everywhere from stones and plants, to plaque on the teeth, to implants. Biofilms contain both active and inactive bacteria. The mucus and hibernation of inactive bacteria make biofilms a fortress able to withstand large amounts of antibiotics. But the new study shows that biofilms deal bacteria another strong card.
Henriette Lyng Røder, co-first author
Section of Microbiology
Department of Biology
University of Copenhagen, Copenhagen, Denmark
We can see that the active bacteria living nearest the outer edge of the biofilm lose resistance genes when antibiotics aren’t present. However, deeper within the biofilm, there is a layer of inactive bacteria which hibernate away safely. These carry resistance genes even if they don’t need them. This is important because it means that biofilms can essentially act as a reserve for the storage of many types of resistance genes.[…]
Urvish Trivedi, co-first author
Section of Microbiology
Department of Biology
University of Copenhagen, Copenhagen, Denmark
Resistance genes are typically spread by small DNA molecules that transfer between the bacteria they use as hosts. Until now, it was thought that bacteria only keep plasmids for as long as they can benefit from them, e.g., by the resistance genes plasmids carry, or else lose them. Indeed, plasmids are no free lunch. They steal energy from a bacterium and cause it to grow more slowly. And since active bacteria are in constant competition with each other, it has been a mystery as to why many bacteria carry around plasmids without doing them much good – known as selection.
An enormous number of bacteria with antibiotic-resistant genes derived from humans and livestock end up in sewage and may spread along that path into the environment. One concern is that such bacteria could end up turning environmental bacteria into pathogens – bacteria that cause disease. In this way, everything is connected.The new study provides one of the answers. When it comes to inactive bacteria, conditions are different.
In the bigger picture, this means that if there are a lot of inactive bacteria in the environment, in soil for example, then resistant genes don’t just gradually disappear when antibiotics aren’t present. Therefore, we ought to consider abandoning the idea that we can get rid of resistance genes and instead assume that they are always present. Understanding these dynamics can better equip us to battle antibiotic-resistant bacteria.
All in all, the new findings inform us that resistant bacteria are even better at surviving than we thought.
Jonas Stenløkke Madsen, co-senior author.
Section of Microbiology
Department of Biology
University of Copenhagen, Copenhagen, Denmark
We're not getting rid of them
The researchers estimate that resistance stocks in biofilms are primarily built up in environmental bacteria, found in soil, air and wastewater among other places. However, it is well established that different species of bacteria can transmit resistance to each other. For example, resistance in environmental bacteria can be transmitted to the types of bacteria that make people sick.
Creationist mode: 
So much for the childish, superstitious view.
The real science is a more serious matter since this is not an arms race between medical science and an evil genius, hard though that might be for Creationist's with their infantile thinking processes to believe, but between medical science and natural selection acting on random mutations in a vast population of micro-organisms in which even a trillion to one chance mutation will occur regularly, and, with their ability to share plasmids even between species, will pass rapidly through the population.
The Danish team's findings can be read here:
AbstractThe driver of this process is the over-use of antibiotics for non-medical, economic reasons such as to increase the production of meat and dairy products. Without antibiotics in their environment, there is no advantage in being resistant, so nothing for natural selection to favour. Another cause is in failing to complete a course of prescribed antibiotics so the few remaining organisms will be more likely to be the resistant ones from which a resistant strain can develop, or demanding antibiotics for viral infections such as the common cold, since antibiotics don't work against viruses.
Plasmids facilitate rapid bacterial adaptation by shuttling a wide variety of beneficial traits across microbial communities. However, under non-selective conditions, maintaining a plasmid can be costly to the host cell. Nonetheless, plasmids are ubiquitous in nature where bacteria adopt their dominant mode of life - biofilms. Here, we demonstrate that biofilms can act as spatiotemporal reserves for plasmids, allowing them to persist even under non-selective conditions. However, under these conditions, spatial stratification of plasmid-carrying cells may promote the dispersal of cells without plasmids, and biofilms may thus act as plasmid sinks.
Røder, Henriette Lyng; Trivedi, Urvish; Russel, Jakob; Kragh, Kasper Nørskov; Herschend, Jakob; Thalsø-Madsen, Ida; Tolker-Nielsen, Tim; Bjarnsholt, Thomas; Burmølle, Mette; Madsen, Jonas Stenløkke
Biofilms can act as plasmid reserves in the absence of plasmid specific selection
npj Biofilms Microbiomes 7, 78 (2021). https://doi.org/10.1038/s41522-021-00249-w
Copyright: © 2021 The authors. Published by Springer Nature Ltd.
Open access
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
In other words, the real arms race here is that between medical science and human greed, ignorance and stupidity. Evolution by natural selection is simply the inevitable result of natural forces acting without purpose or intent in a conducive enviroment.
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