According to traditional poker rules (excluding Texas holdem),can the ace be used as the low card of a straight?
With standard rules the ace is the highest card in the deck so it completes straights that run 10 through ace. The ace is also used as the first card in the deck, as a one (like in Blackjack) to complete a five high straight. This does not exclude Texas Hold-em.
Yes, A2345 ("wheel") and 10JQKA ("broadway") are both straights in standard poker. In Deuce-to-seven lowball, a wheel is not a straight, but just A5432 high.