The lateral filament looks like fungus or mold and not beneficial bacteria. I use myco and have never seen that on my roots. Root rot is a possibility too. Overwatering causes this. Letting the soil dry out to the point where the plant just begins to droop is best. This also helps with the root aphids and fungus gnats I describe below.
You say you don't have a bad bug problem. Do you have soil gnats? Fungus gnats or root aphids. When plants are watered or bumped the adults fly out of the pot. Both will destroy your root system. Reason I ask is because your roots are brown and not a vibrant white. This is a sign of gnats. Larvae eat the roots and damage them. It kinda looks like eggs in the third picture. I would suggest using a drench solution of GoGnats, Amebectin (avid) or Azamax (Azadirachtin). Yellow sticky fly traps placed at the pots height will help catch the adults and prevent future reproduction.