For Safer Food, Just Add Viruses(pbs.org)
pbs.org
For Safer Food, Just Add Viruses
http://www.pbs.org/wgbh/nova/next/nature/phages-for-food-safety/
5 comments
Viruses seem so weird to me. They're naturally emergent nanobots.
> naturally emergent nanobots
That's an astonishing thought. "Look at all those bacteria that we cannot possibly eliminate with conventional means!" - "Well, maybe in the future, we could build nanobots that kill them individually...".
Yep, already there. Viruses. Really seems like a terrific shortcut.
That's an astonishing thought. "Look at all those bacteria that we cannot possibly eliminate with conventional means!" - "Well, maybe in the future, we could build nanobots that kill them individually...".
Yep, already there. Viruses. Really seems like a terrific shortcut.
I wouldn't really call them nanobots; they don't function in any active manner. They're really just like their digital counterparts--malicious program data that gets executed by our cellular machinery.
They are not pure code. They come with a protein coat and a bunch of proteins/enzymes to bring the code to the cell or nucleus, and sometimes more functions.
Sure, but those are produced by the cell at the behest of the viral code; not produced by the virus. The freshly-minted copy of the virus doesn't get to react to stimuli by producing proteins once it has left its host cell. It's a lot more like the relationship between, say, pollen spores and the gametophytes they contain.
To put it another way--a post-code and stamp on an envelope will get the postal system to deliver its contents to the right destination. That doesn't mean the contents are functioning to deliver themselves there; they're relying on a working mail-transport system that wants to take them there.
To put it another way--a post-code and stamp on an envelope will get the postal system to deliver its contents to the right destination. That doesn't mean the contents are functioning to deliver themselves there; they're relying on a working mail-transport system that wants to take them there.
Given that the human digestive tract (reportedly) contains more bacteria than the human body has cells, and they are vital to our survival, how can spraying bacteria-killers on food not be harmful?
According to this link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3278644/ phages target specific pathogenic bacteria, and "[...]phages only minimally impact non-target bacteria or body tissues". So that would mean that even though they target bacteria, they would only target a specific bacteria and not all.
You do have to wonder if they aren't over-stating the specificity. The older I get, the more I come to expect the unstated "but..." on claims like that. As the saying goes, "When it's too good to be true, it probably is."
I don't think they're overstating this claim. It's a double-edged sword.
If you have an infection your doctor can give you antibiotics and send you home. Antibiotics tend to be wide spectrum and kill entire classes of bacteria, like gram-positive, indiscriminately.
A phage that kills one strain of E.coli might be completely incapable of infecting a closely related E.coli strain. Thinking that a single phage could be effective against closely relate pathogens, for example E.coli AND Salmonella, is wishful thinking. This might have the upside of preserving gut flora, but it's easy to see how it would confound treatment: some things are very difficult to grow in vitro.
If you have an infection your doctor can give you antibiotics and send you home. Antibiotics tend to be wide spectrum and kill entire classes of bacteria, like gram-positive, indiscriminately.
A phage that kills one strain of E.coli might be completely incapable of infecting a closely related E.coli strain. Thinking that a single phage could be effective against closely relate pathogens, for example E.coli AND Salmonella, is wishful thinking. This might have the upside of preserving gut flora, but it's easy to see how it would confound treatment: some things are very difficult to grow in vitro.
Phages will and do target E. Coli and other "pathogenic" bacterium that do in fact reside in your digestive system
Exactly my concern. There are special (very expensive) bacterial supplements (e.g. Mutaflor) which reportedly help people with Colitis Ulcerosa and other inflammatory disease, and they are nothing other than special E. Coli strains. I wouldn't want a supplier to silently introduce something that can kill beneficial gut flora. This is the kind of stuff that lifestyle diseases are made of.
I've read phages are very specialized and tied to their target type of cell.
Elanco, sells a liquid phage product called Finalyse that is sprayed on the hides of cattle before they’re slaughtered.
I'm thinking that name is just a little too on the button.
I'm thinking that name is just a little too on the button.
This was fascinating. Could phages be engineered to attack mrsa and other superbugs we see in hospitals?
It depends.
There are extant phage that predate staph, like Phage K. There are some hurdles you'd need to overcome. Foremost among these is when compared to antibiotics, phage suck for treating disease. This is a big part of the reason everyone beat a path to antibiotics
Phage are extremely narrow spectrum. You can select for a high-fitness phage with serial passages: Plate the host bacterium along with some phage. Find the largest region of dead host (a plaque), pick it and repeat for several hundred generations. The good news is that you'll have a high-fitness phage. The bad news is that it will probably only infect the particular strain of bacteria you've been using to select it. I worked with a fitness optimized E.coli phage that wild-type E.coli probably would have laughed off. I haven't read the therapeutic phage literature, but my assumption would be that you may need to optimize
Phage have some issues with immune clearance. The immune system really loves to eliminate foreign looking viruses. The concentration of phage injected intramusucularly falls very fast. Again, this might be something you can overcome with serial passages. There was some work in rabbits where the authors found an enrichment for mutations in the capsid (the phage's head). I don't recall if they quantified the fitness impact of these mutations.
If I ever get out of software development, it'll probably be to work on phage.
There are extant phage that predate staph, like Phage K. There are some hurdles you'd need to overcome. Foremost among these is when compared to antibiotics, phage suck for treating disease. This is a big part of the reason everyone beat a path to antibiotics
Phage are extremely narrow spectrum. You can select for a high-fitness phage with serial passages: Plate the host bacterium along with some phage. Find the largest region of dead host (a plaque), pick it and repeat for several hundred generations. The good news is that you'll have a high-fitness phage. The bad news is that it will probably only infect the particular strain of bacteria you've been using to select it. I worked with a fitness optimized E.coli phage that wild-type E.coli probably would have laughed off. I haven't read the therapeutic phage literature, but my assumption would be that you may need to optimize
Phage have some issues with immune clearance. The immune system really loves to eliminate foreign looking viruses. The concentration of phage injected intramusucularly falls very fast. Again, this might be something you can overcome with serial passages. There was some work in rabbits where the authors found an enrichment for mutations in the capsid (the phage's head). I don't recall if they quantified the fitness impact of these mutations.
If I ever get out of software development, it'll probably be to work on phage.
This could be a replacement for antibiotics once they become completely ineffective