Originally posted by jford I'm curious why you say this. I work with fungi professionally - although not specifically those that grow on lenses - and know that the growth rate is tied to the nutrient availability and "hospitality" of the environment. Concluding that it's dead simply because the lens isn't a fluffy ball seems a bit of a leap. Likewise, as stevebrot (correctly) says, the fungal spores exist long after the mycellia has become inactive. And at least for the species I use, sporulation is more likely when the fungi grows on a "lean" media - which, likely, lens' glues are. I agree that the likelihood of one lens infecting another is small, I don't agree that "This is an internet myth." I have too much trouble with Neurospora contaminations in our Trichoderma cultures. I don't have proof, but I believe the Neurospora comes from ten-year old spores from a now-retired colleague's work with that species. I'm not trying to cause a war - I'm just curious why you made the conclusions you stated. Thanks.
My background is also in biology, and my answer was perhaps less than precise. It is just that this myth of lenses infecting others seems to come up again and again and it is untrue. Layman seem to think the mycellium will grow out of the lens across their camera bag and into another lens. My reference to a fluffy ball, while an attempt to be humorous, was simply trying to point out that fungus does not stop growing until it runs out of something it needs to grow. So if it was 'live' then it would still be growing. The spores are indeed another story.
As both you and Steve pointed out spores last a very long time. In addition they are present in most environments. So it is safe to say that spores of one type or another are already in the lenses and other equipment we have. As you correctly stated the growth is almost exclusively governed by the presence of water and nutrients. In lenses, the regulating condition is almost always water as it is used up before potential nutrients are. In my experience with camera lenses the fungus continues to grow as long as water and nutrients are present and then it stops. The mycellium then dies although of course spores are still going to be present.
New spores, formed by the fungus growing in the lens, are rare, in fact I have never seen fruiting bodies present in any lens infected with fungus because usually the fungus uses up the available moisture quite quickly and dies before it reaches a fruiting stage. I am not saying this is not possible, only that I have not observed or seen pictures of such an event.
My primary point is that all lenses are already, probably, infected by fungal spores and only keeping your gear dry will prevent it from growing. The new WR lenses may be sealed better and may have less of an opportunity to become infected with spores but even they I suspect will have spores present if tested. My DA*16-50 pumps air in and out with each actuation of the zoom thus moving air and the dust & spores it contains into the lens.
Like all myths there is a grain of truth here but saying that having a fungus infected lens in close proximity to another lens will increase the possibility that it will be infected is just not true. There is a high probability that the other lens is already infected, but as long as it stays dry, you will never see any fungal growth.
I think the reason this is one of my hot buttons is that keeping your gear dry is the only thing needed to prevent fungus growth, and allowing people to think that keeping infected lenses away from their gear will keep it from being infected is just giving them a false sense of security. If they get water in their gear there is a high probability that fungus will grow, whether it has been near an 'infected' lens or not. I have bought a number of old camera kits at estate sales and often there will be a lens with fungus growth. Some of these kits have been stored away for 10 or more years with a number of lenses all packed together in the same bag, but only one has fungus. If close proximity to an infected lens had any relationship to a lens getting fungus surely these lenses would all have fungus?
Sorry for the long post, I hope that explains my thoughts. And I will try to be more precise in the future instead of dashing off a careless reply.