As Axelsaurus already pointed out, monitor lizards and helodermatids (the gila monster and the beaded lizard) are both venomous. The Komodo dragon is the largest extant monitor lizard, and like other monitors, possesses a venom that acts primarily as an anticoagulant, causing prey with heavy bite wounds to simply bleed out until they either die or are too weak to escape. Humans who have been bitten by lace monitors, perenties, and tree monitors in Australia have been documented to suffer heavy bleeding relative to the size of the wound, intense pain, and localized swelling.
The major issues with the bacteria theory are likely that it did not take the target's immune system into account and that bacteria found on carrion that a Komodo might be eating are also found everywhere else; the Komodo does not have symbiotic "mouth bacteria" that are exclusive/endemic to them.
More on-topic, I hope that mega evolutions have been removed from Sun/Moon, for the following reasons:
1) They've overcentralized the metagame.
2) Too many of them are too powerful, in some cases so powerful that the boosts to defensive teams/strategies introduced in X/Y don't matter.
3) They aren't even evolutions, because they aren't permanent.
4) Pokemon like Mawile, Absol, and Medicham needed a permanent evolution, not a mega evolution. They would have been better served with permanent evolutions so that they could use a hold item.
5) Many of the pokemon that received mega evolutions simply did not need them, because they already had high BSTs/good movepools, etc.
6) They take up slots for new pokemon. X/Y could have had more type diversity if slots for new pokemon weren't used to develop megas.
6) Most of the megas have terrible concept design flaws. Admittedly, this is somewhat subjective, but I think that part of the reason Pokemon became popular and stayed popular is because Sugimori's art style and skillful balance of complexity and simplicity made the art very appealing. A number of the mega evolutions break the "Sugimori rules" of simplicity vs. complexity, and cease to be aesthetically pleasing or simply don't make much sense (sense being defined as relative to other aspects of the game, which may not make sense relative to the real world).
Probably gonna get flamed to hell for all of this, but bring it on. Megas were a terrible idea and I hope gamefreak came to their senses and removed them.