Related: I tried a search for "gingivalis" and it turned up the following 3 submissions, all from 5 years ago and related to Alzheimer's.

P. gingivalis in Alzheimer's disease brains - https://news.ycombinator.com/item?id=19596915 (49 comments)

Cause of Alzheimer’s: gingivalis, the key bacteria in chronic gum disease - https://news.ycombinator.com/item?id=18984054 (12 comments)

Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for causation - https://news.ycombinator.com/item?id=18989630 (1 comment)