How do bacteria gain immunities?

[Dominus Atheos]

How does bacteria become immune to things like penicillin? By what mechanism?

[Superman]

Bacteria will acquire the necessary genes to form resistances in one of three ways.

First, their DNA can spontaneously mutate. This is where drug resistant TB comes from. Another way is for one bacterium to pick up the DNA from another. This is basically microbial sex and is known as "transformation." In the third way, the bacterium acquires resistance from a circle of DNA called a plasmid. Plasmids can flit between bacteria of various types and carry multiple resistance.

Bacteria basically share resistances with one another.

[The Grim Squeaker]

They don't become immune to it.
What happens is that the few bacteria that may be resistant to penicillin/pesticides/etc' from each "Extermination" will survive and breed so that quickly the only existing bacteria will be the ones who resisted the penicillin with each additional "Culling" leaving only the most resistant bacteria to breed unhindered replacing the non resistant strains. Pure evolution in action.

[Raesene]

How does bacteria become immune to things like penicillin? By what mechanism?

Several possibilities: a mutation changes the structure of a protein so that the antibiotic cannot bind to it and thus prevent the protein from working (or reduces its efficacy), or (the other way) a mutation modifies an existing ABC-transport system which then can remove the antibiotic from the bacterial cell before it does its work.
(probably forgot some, but those mechanisms I can remember)

Afterwards, it's just evolution at work...

[mr friendly guy]

Most people have given the basics about bacterial resistance and evolution in action.

If you are specifically asking about penicillin resistance, it is because bacteria produces the enzyme betalactamase which allows it to break down parts of penicillin known as the beta-lactam ring. This grants it resistance to penicillins and related antibiotics like the cephalosporins.

One way we can overcome this betalactamase is to add another substance into the antibiotic to inhibit the activity of the betalactamase. For example with the antibiotic amoxycillin (type of penicillin) we add in clavulanic acid to inhibit the enzyme. This new antibiotic is called Augmentin.

[Admiral Valdemar]

There are a whole host of ways, but it only ever ends in mutation and natural selection playing out as it would in any other organism. Whether the bacterium that survives something like Triclosan is better able at pumping the drug out of its cytoplasm, or forming a better metabolic pathway to digest it is simply the basis for it perpetuating itself later on. There are far too many different antibiotics, drugs, radiation, solvents and immune defences to go over how each and every species can adapt to new extremes.

[Rye]

How does bacteria become immune to things like penicillin? By what mechanism?

Evolution, i.e. mutation, hereditation, natural selection. What happens is, you get an antibiotic that enters cells through the normal chemical pathways through the cell membranes, then it'll react with something in the cell that will in some manner harm it. Perhaps it will have a chemical part that denatures some critical proteins, or it blocks up vital holes in the cell membrane that it needs to get food and it dies.

Now, what happens is, the tiny organisms mutate quite often so it will be slightly different in physiology than its neighbours, and what might be 100% lethal in the others will do severe damage to this mutant strain, but its slightly different physiology will make it better than no difference at all, and it will survive long enough to replicate or share the new gene with any neighbours. The antibiotic could decay in the surroundings and more microbes grow in in short order. Many microbes share genetic material even outside their own type, so you can end up with monsters like MRSA that are resistent to almost everything.

Anyway, if you now have a gene in the environment that allows an organism to deal better with antibiotics and that gets passed around, you now havethe beginnings of a genetic defence against the antibiotic. The genes and how they're expressed can then be modified and apparently specialised by repeating the process over and over again until the organism becomes totally resistant to the antibiotic or perhaps even becomes reliant on the antibiotic in the environment as part of its normal life.

[Tasoth]

I remember this from microbio!

Bacteria can gain immunity from mutation, pick it up from dead bacteria, which is nifty when you consider the fact that they can absorb DNA that an exploded bacteria releases just by contact, or through the bacterial equivalent of sex (yes, sex is ubiquitous).

These genes are stored in plasmids, fun little rings of accessory DNA that they keep around and move back and forth out of their chromosomal DNA when they need the enzymes and cellular components they code for. These plasmids can also be transferred along with the HFr( I think...) plasmid via a specified pillus, a bacteria can have upto 34 of these at one time. So an immune bacterium can spread its resistance rapidly among non-immune bacteria, who then propagate the cycle and so forth and so on in an amazing wonderment that is biology.

Author's note: This is all drawn from memory and therefore may be prone to error.

[Admiral Valdemar]

Ugh, I hate drawing plasmid maps. It's fun talking about what all those genes do, but try making a detailed figure of the things. Pain in the arse.

[Trytostaydead]

Most people have given the basics about bacterial resistance and evolution in action.

If you are specifically asking about penicillin resistance, it is because bacteria produces the enzyme betalactamase which allows it to break down parts of penicillin known as the beta-lactam ring. This grants it resistance to penicillins and related antibiotics like the cephalosporins.

One way we can overcome this betalactamase is to add another substance into the antibiotic to inhibit the activity of the betalactamase. For example with the antibiotic amoxycillin (type of penicillin) we add in clavulanic acid to inhibit the enzyme. This new antibiotic is called Augmentin.

I hate the drug resistance chapters of pharm. Stupid tetracycline pumps, etc, etc.

[GrandMasterTerwynn]

How does bacteria become immune to things like penicillin? By what mechanism?

By evolution.

No, seriously. A few hours is a generation to a bacteria. When you breed that fast, natural selection can produce adaptations really quickly. Others have explained the dry technical details, but this is the gist of it.

[Master of Cards]

How does bacteria become immune to things like penicillin? By what mechanism?

Say theres 5000 Bacteria in a dish, Add in Penicllin and kill 4999 of them. But the one Bacteria that is left multiplys and you can't use pencillin on it because they are Super Bugs

[Raesene]

Ugh, I hate drawing plasmid maps. It's fun talking about what all those genes do, but try making a detailed figure of the things. Pain in the arse.

And checking for typos or in-frameness is so much fun...BLAST, another mismatch

[Darth Servo]

Random mutation creates diversity in a population. Some of that diversity produces greater resistance to a particular drug in the cells that possess that particular mutation.

Now apply antibiotic. Antibiotic kills off the cells that don't have the increased resistance, leaving behind the ones that do.

Repeat ad infinitium.

[mr friendly guy]

Most people have given the basics about bacterial resistance and evolution in action.

If you are specifically asking about penicillin resistance, it is because bacteria produces the enzyme betalactamase which allows it to break down parts of penicillin known as the beta-lactam ring. This grants it resistance to penicillins and related antibiotics like the cephalosporins.

One way we can overcome this betalactamase is to add another substance into the antibiotic to inhibit the activity of the betalactamase. For example with the antibiotic amoxycillin (type of penicillin) we add in clavulanic acid to inhibit the enzyme. This new antibiotic is called Augmentin.

I hate the drug resistance chapters of pharm. Stupid tetracycline pumps, etc, etc.

Heh heh heh. I barely remember the stuff, as in work I just prescribe antibiotics according to protocol and according to cultural and sensitivities. No doubt I will to learn the minutiae again if I sit the physicians written exam.

[Tasoth]

IIRC, bacteria, at least someone of them, reproduce every twenty minutes. If you kill off a shitload but leave, say 400, every 20 minutes that number doubles. And those are resistant bacteria. If the environment is still hostile, the ones that aren't as resistant in those generations die while the hardier ones survive and pass on their genes. When you start talking about staph and E.coli infections that get into the blood, you get horrifying results. E.coli alone is responsible for at least one type of infection per body system when it goes into the blood. It's kinda beautiful in a way.