I have a collection of Takumars, I love the ones I have.
I recently bought two Auto Takumar 55/2.2 both "has no fungus". I bought two because I messed up - I forgot that I had bought the first when I bid for the second. No matter, they are very cheap lenses (I got one for £7 the other for £11). I believe that the vendors honestly thought that there was no fungus.
When I got the lenses I looked at them carefully and saw no fungus myself. I have bought lenses before with fungus and know what it looks like (see below for a horrible infection). After I got them, I wanted to choose between these two lenses, keep the best one and sell the other one.
Anyway, today I was at a lose end and I shone a very bright LED flashlight through the lenses and used a desktop magnifying lens (one of those on an arm with a light) to inspect what I could see. First, you have to be careful doing this, because it can dazzle you! Second, when you get the angle right, the light will show various elements within the lens.
I found that the first lens I had bought did have fungus on one internal element. Just a bit, but it was there. The other lens did not have fungus as far as I could see, but I noticed some very light scratches on the front element. Swings and roundabouts. Incidentally, these defects do not show up on images I have taken using the lenses. I have one lens that is (as far as I can tell) fungus-free, and the other has some minor fungus infection (it is older than me! and dates from around 1961, of course there will be a good chance that it may has fungus).
Then I did the same inspection with some of my other cherished Takumars, and found that my Super Takumar 105/2.8 has a few whispy fungus on an inner element. I hadn't noticed this before, and frankly I do not care.
So my message to you is this:
1) every lens has some fungus internally and you can never have a lens that is fungus free
2) most fungus will have zero effect on the images taken with the lens
3) most fungus will not spread to your other lenses - DO NOT WORRY!
4) a 40 year old lens is bound to have fungus somewhere, and you will not normally see this
5) let me reiterate this - most people do not know that their lenses have fungus, and will get wonderful images even with fungus
I will not re-sell the Auto Tak 55/2.2 that has fungus. There is no point because it is so cheap that I will not benefit from re-selling, and equally so, there is no point me making an issue with the vendor who I think was honest about their view. My reason for considering reselling was simply to give someone else the benefit of owning a wonderful lens.
Just for the record, here is a lens with a serious fungus infection. (SMC Takumar 55/2) I knew this was the case when I bought it (I wanted the Spotmatic it was attached to), because the infection was so obvious. When I get the time, I will take some photographs of the Auto-Tak with fungus and show how the vendor thought it was fungus-free and how I found it was not. But for now, here's an obvious example.