The idea of silica sticking to the latice-like exosporium just popped out of the blue because arguments from others didn't make complete scientific sense. Maybe I'm wrong, but bits of silica being pounded into the latice-like exosporium and sticking there seems to make PERFECT sense.
I contacted the co-author of the Aerosol science article to see what he and the other authors think.
Figure 7a shows a particle potentially containing a single BG spore; since no uncoated single spores were observed, this suggests that virtually all single spores remained coated with silica. The coating apparently solidified from exposure to water in the air over the years of sample storage and use. However, multiple spores or clumps were found frequently and these were often largely uncoated as indicated in Figure 7b. The reason for the difference in coating adherence to different sized particles is unclear.
Pounding silica particles into the exosporium isn't possible without breaking up the clumps into single spores. Either something prevented the clumps from being broken up, or there's something about the larger object that exceeds some kind of threshold for adherence.
Here's Figure 7b:
Looking at the scale on Figure 7b, I notice that the spores in the clump are smaller than the 1 micron by 1.5 micron size of a typical Bacillus spore. The spores seem to be about .5 micron in diameter and 1 micron in length. That could mean they're lighter than other spores and somehow float near the top of the silica/spore mixture and don't get pounded through the mesh until the very last. Or, because they're smaller than other spores, they go through the mesh most easily and get less pounding.
Whatever the explanation, there doesn't seem to be ANY explanation for van der Waals forces binding silica to single spores but NOT to the spores in the clumps.
Or, of course, you could just take the time to read the article I posted yesterday. The one that shows that the silica nanoparticles adhere to large particles of powder by van der Waals forces.
Then you wouldn’t need to go into your own private fantasies about chunks of silica being pounded into spore surfaces.