Full-back Skarz was an ever-present in the Shakers' League Two promotion side last term after joining on a free transfer from Huddersfield in summer 2010.
The 22-year-old has made 79 appearances for Richie Barker's side and is now committed to the Gigg Lane outfit until the end of the 2013/14 season after agreeing a new two-and-a-half year deal.
John-Lewis, who has earned a reputation as an impact sub since joining the Shakers, will remain with the League One team until the end of the 2012/13 season with the option of a further 12 months in his new contract.
Following his release by Lincoln, the striker initially joined Bury on trial in summer 2010 before signing for a year and extending after last term's promotion campaign.
John-Lewis, 22, has made 53 of his 65 Bury appearances from the bench but marked a rare start against league leaders Charlton with a goal in a 1-1 draw last time out.
