Talk:Phage

Size
This was extremely informative but I still want to know the size of the virus in nanometers

WikiProject

 * WikiProject Viruses


 * the project is tagged inactive. 132.205.94.174 23:35, 24 July 2005 (UTC)

Size of Bacteriophage
Structure - Bacteriophage come in many different sizes and shapes. The basic structural features of bacteriophages are illustrated in Figure 1, which depicts the phage called T4.

1. Size - T4 is among the largest phages; it is approximately 200 nm long and 80-100 nm wide. Other phages are smaller. Most phages range in size from 24-200 nm in length.

2. Head or Capsid - All phages contain a head structure which can vary in size and shape. Some are icosahedral (20 sides) others are filamentous. The head or capsid is composed of many copies of one or more different proteins. Inside the head is found the nucleic acid. The head acts as the protective covering for the nucleic acid.

3. Tail - Many but not all phages have tails attached to the phage head. The tail is a hollow tube through which the nucleic acid passes during infection. The size of the tail can vary and some phages do not even have a tail structure. In the more complex phages like T4 the tail is surrounded by a contractile sheath which contracts during infection of the bacterium. At the end of the tail the more complex phages like T4 have a base plate and one or more tail fibers attached to it. The base plate and tail fibers are involved in the binding of the phage to the bacterial cell. Not all phages have base plates and tail fibers. In these instances other structures are involved in binding of the phage particle to the bacterium.

This is an article from BACTERIOLOGY > CHAPTER SEVEN - BACTERIOPHAGE

I hope this is of use to you.

Phage therapy
The current text for phage therapy needs to be streamlined and balanced. Phage therapy made it back into the media recently but most scientists in the field (me being one of them) do not think that phages are therapeutically relevant. There is only anecdotal evidence for their use in human therapies. Rather starting editing this back an forth, we should try to find a consensus. The West did not forget about phages - they were the most important tool early researchers had but clinical trials simply failed. There is no need to mention the Tbilisi three times in the current text.

Spitshine 16:50, 22 November 2005 (UTC)


 * I am certainly no expert in the field. The edits I made were based on something I saw on tv. If any of that is wrong, remove it. But is it? The fact that, unlike antibiotics, which is a mere substance, a phage remains active until all the bacteria it feeds on are gone seems plausible and, if true, certainly worth a mention. By the way, an advantage of ingested or injected antibiotics (though at the same time a disadvantage) is that it doesn't only work locally.
 * Saying eitherA specific type of phage infects only one specific type of bacterium or A specific type of phage infects only within a very limited range of bacterial species is largely a different way of saying the same thing, though ironically the first sounds positive and the second negative. Maybe it has both positive and negative aspects. One approach might be to say that a phage is similar to a narrow spectrum antibiotic in this sense, which does have the advantage that other bacteria are left in peace, right? I mean, isn't that what narrow spectrum antibiotics are used for?
 * The focus on antibiotics in the West may be a bit of an overstatement, but as I understood it, there was so much focus on antibiotics that phages were were put largely on a sidetrack, as opposed to the Soviet Union. So there will be more knowledge there. Might there be a communication problem here? I've heard on several accounts that certain things (especially medical and in China) were developed in the East, which were totally ignored by the West because the results weren't translated. Might that be a problem here?
 * Saying 'to test' or 'proving' makes quite a difference. Your phrasing suggest that there have been tests. Have there? And in the West or in the former Soviet Union? In the latter case, there may be the aforementioned problem.
 * But in the (former) Soviet Union many people have been treated successfully where other therapies have failed. Is this not true? DirkvdM 13:08, 23 November 2005 (UTC)

I work with enterobacteria every day and phage therapy was discussed on an expert meeting I went to. Phage therapy was exhumed recently but most of us see the therapeutic potential overrated particular by the mass media. That is not to say that there is no potential but there is too much evidence against a widespread use. I think we all would like to have good handle in the light of multiresistant strains.

There is no real track record of tests that were carried out in the west but as far as we know some attempts were made in early years (failures are rarely published). There are newer test in the literature carried out in the food industry and in mice. The idea that things were "forgotten in the West" is often used to give weight to arguments but in modern research there is hardly anything left that is not written in English. There is a lot of information on the web that we should take into account, including positive arguments for phage therapy, for instance this review.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16258815 However, even in the postive light that the review draws, one should not forget about the severe problems that need to be tackled. Note that the problems of resistance also present phage therapy, the added amount of time to find the course of the infection and the massive allergic reactions you could provoke by phage particles.

I'll assemble some more data and will edit the article soon, more comments too. Spitshine 10:20, 24 November 2005 (UTC)

Hope the edit is balanced - I take questions :-)

Spitshine 17:24, 24 November 2005 (UTC)


 * You have the adavantage of knowing more about the subject, but that is also a disadvantage because what you write is not as intelligible to non-experts. That is always a problem. Since a layman like me can't edit such stuff, it's up to you to take this into account, which I can imagine is not too easy.
 * I understood that Tblisi is the major centre for knowledge of phage therapy and that it is therefore also the best place to go for treatment. If so, that deserves a mention, not just mentioning Tbilisi in connection with d'Herellle.
 * I'm not sure anymore now, but I thought it was said that phage therapy was largely used where other treatments had failed, so I reinserted that.
 * You removed  Unlike antibiotics, phages adapt along with the bacteria, as they have done for millions of years, so resistance is unlikely. That sounds very plausible and relevant. Same for when an effective phage has been found, it will continue to kill bacteria of that type until they are all gone. At which point, I might add, they will probably disappear. And it also seems logical that phages 'seek out' bacteria, whereas antibiotics have to 'chance upon them'. This is about a very central difference - phages are biological (I won't say 'alive') and have been around for quite some time. This is also in keeping with the more modern approach of not going against nature, but using it against itself, such as the use of biological in stead of chemical agents to fight crop diseases (although 'modern' doesn't necessarily mean it's better). DirkvdM 10:24, 25 November 2005 (UTC)
 * No reaction after a while, so I'll put those things back. I'm just not sure about the 'millions of years' bit. How old are phages? The article should say that (if known). DirkvdM 07:51, 6 December 2005 (UTC)

phages are probably as old as life itself, so the millions could be changends to billions of years. — Preceding unsigned comment added by 137.224.252.10 (talk) 14:25, 2 December 2011 (UTC)

There is probably a phage for every species of bacterium.

Any sources or reasons for such a claim? --Lorenzarius 20:20, 27 December 2005 (UTC)

History reference
I note the paragraph:
 * One of the most prolific natural sources for phages is common seawater. There can be as many as 2.5x10^11 virions per liter (See references).

but the only refence to number given is the second one 2, but that only associates this with "natural waters", whatever that is supposed to refer to. Can anyone with access to the full Nature article clarify whether this was meant to be a particular fresh-water or sea-water source. On a (brief) search, I found this reference here that gave a figure fifty times lower in seawater, namely 5 x10^9 per litre. David Ruben Talk 09:37, 4 February 2006 (UTC)

I checked the papers you refer to. The numbers you have refer to two publications examining sea water in Germany and California respectively. They are more than 10 years apart and use very different methods, (microscopic vs genetic). The number give a good view of the possible density of phages, but most likely, we don't have enough sampling to give an upper bound yet. We can safely cite the original Natue paper. I'll change the densitiy back to per millilitre though. Spitshine 14:11, 6 February 2006 (UTC)

Relationship between phages and bacteria
I am a layman, and I was just wondering... do phages tend to eliminate all their target bacteria? Doesn't there exist a natural countermechanism that prevents that from happening?

Why I think there should exist a natural countermechanism: If phages tend to eliminate all their target bacteria, they themselves would perish, having no device that will replicate them (note I assume 1 class of phages kills 1 class bacteria). I'm speculating that, in general, bacteria should not fear being totally wiped out by phages that target them, because the reason that phages exist up to this time is because of the fact that they do not successfully lyse all their existing target bacteria out of existence.

Maybe that's why phages aren't used for treatment?

Or maybe they do lyse all bacteria they come in contact with, but that applies to a small locality, and the size of the earth containing similar bacteria is so large that it is practically impossible for these bacteria to be wiped out by their phages, So that from the point of view of phages, they have unlimited natural resource for reproduction/replication?

Or maybe phages actually do become extinct because of this exhaustion of their target bacterial resources (or remain dormant until a slightly similar bacteria comes along, then they go for the kill? That is if phages actually settle for a similar bacteria)

Maybe it's not right for me to assume that there SHOULD be a natural counter mechanism. Maybe phages do become extinct because of that "negative feedback" effect, or stay dormant for millions of years if they can survive the elements.


 * Phage definetly need bacteria to survive, and if phage succesfully killed all the bacteria around, they themselves would cease to exist, but isn't that the way of life? Phage are no difference to viruses that infect us, some of the truly deadly viruses are self limiting because they don't let any live long enough to pass them around (Ebola?), I believe phage are the same way. The most successful viruses don't kill anyone(cold?) or have no effect at all(the thousands of retroviruses in our genome!). Bacteria's only defense against phage is mutation, some microbes naturally will change in to resistant strains. If you ever had the chance to work with phage you'd see some interesting stuff. Phage don't kill off entire plates of bacteria, they kill off small areas near where they are introduced. I don't know the mechanisms of there retarded virulence, but it is apparent. plus  on some virally killed areas, you may notice spots of bacteria that resisted the virus probably from natural mutation. On the counter point, a bad phage infection will shut down huge fermentation plants, some indefintely. I think phage have but one task, kill every bacteria they can, and do so quickly, it's nature and circumstance that keep the balance. Keep in mind the specificty of some phage. Lambda phage need to bind to maltose resecptors on bacteria, no maltose around = no receptors; and P1 phage require an F plasmid pilius to infect, the F plasimd itself being another form of infection. Anything that's too successful will probably just burn themselves out. Just my thought, anyone else?! Adenosine | Talk 08:58, 9 March 2006 (UTC)

Soviets?
I heard instead of deeper research into penecilin-type products, the Soviets worked on bateriophages and did most of the research into the subject, is this true?

Why Phage?
Considering phage is the shortened version of the true name of bacteriophage, shouldn't Phage redirect to Bacteriophage instead of the other way around? While updating the article I switched the redirection -- Serephine / talk - 15:23, 10 June 2006 (UTC)