How possible is it that a prokaryotic cell with hardened pili exists and that microorganisms use them as a way of hunting?

Question

I'm creating prokaryotes for my speculative evolution project and I was wondering if it's possible for them to develop a hardened pili that would allow them to be used either as a defense or, in this case, for predation. For example, I was thinking of two prokaryotes, one spiral-shaped with a hardened pili in front and this one perforating the biofilms like a biological drill, and then another predatory cell that moves at high speed when it detects prey using its chemoreceptors, launching itself like a dart and piercing its prey and thus feeding on its remains.

Answer 1

I would expect that structures such as these wouldn't be pili any more. A pilus is a very thin, flexible tubule, whereas the OP's 'hardened pili' would need to be much thicker, and probably much shorter, since objects that would seem to look 'stiff' or 'hard' to us in our macroscopic world are in fact quite flexible at the micro or nano scale of single cells.

In general, protozoa are physically quite robust at their scale, and a 'spike' would be unlikely to affect them the way that a scaled-up spike would affect us. At the nano-scale, the spike would either bend or the victim would be pushed aside. In the unlikely event that it did penetrate, when the spike was withdrawn, the hole would close up.

Consider that microbiologists use micro-scale glass pipettes to penetrate single-celled prokaryotic organisms, the cells must be held in place, they deform very considerably before the pipette penetrates., and when the pipette is withdrawn, the organism doesn't spill its contents everywhere.

ICSI footage from Fertility Associates

So, for a single-celled organism to penetrate and thus feed upon another cell, it would need something other than an inert spike. The modified pilus would need to be tipped with some means of penetrating the cell membrane, and would also need some way of 'digesting' the prey cell's contents so that it didn't end up hybridising with it, since pili are used in bacterial conjugation.

However, as long as these 'spikes' have the appropriate chemical properties, they are quite feasible. They could be considered to be modified fimbriae.