How long can mycobacteria tuberculosis culture survive in 4 degrees incubation? - (Sep/17/2013 )

how long can mycobacteria tuberculosis culture survive in 4 degrees incubation and what simple method is used to keep Mtb in -80 degrees as stock? Thanks

http://www.ncbi.nlm.nih.gov/pubmed/6799264

You can keep them at -80C in 50% glycerol for many months (even years). Don't keep them at -20C.

why not, will be also frozen at -20°C ?

Cultures in 50% glycerol will not freeze at -20, and are not stable at that temperature.

I was used to keep E.coli culture at -20C and I never had problems. I did that with different mycobacterial strains: sometimes it was fine, sometimes they didn't grow after thawing. They I began to keep mycobacteria at -80C and every times they were perfectly viable.