Penetration of bacteria into meat.

@article{Gill1977PenetrationOB,
  title={Penetration of bacteria into meat.},
  author={Colin O Gill and N Penney},
  journal={Applied and environmental microbiology},
  year={1977},
  volume={33 6},
  pages={1284-6}
}
Bacteria are confined to the surface of meat during the logarithmic phase of growth. When proteolytic bacteria approach their maximum cell density, extracellular proteases secreted by the bacteria apparently break down the connective tissue between muscle fibers, allowing the bacteria to penetrate the meat. Non-proteolytic bacteria do not penetrate meat, even when grown in association with proteolytic species.