The measurement of bacterial respiration on pig skin with micro-respirometers

1. The respiration of bacteria normally present in thin slices of skin taken from pig's trotters has been measured in Cruickshank micro-respirometers. 2. These respirometers were originally designed to measure skin respiration in a medium including antibiotic to inhibit bacterial activity. The skin and medium was contained in a glass well. Using pig skin in a similar system without antibiotic, bacteria left the skin to grow independently in the medium. To overcome this difficulty polythene cups were made with an inner compartment for the tissue without medium and an outer compartment for water which provided a humid atmosphere. 3. Using polythene cups without medium the skin respiration was neglible, bacterial respiration was measured in situ and correlation between oxygen uptake and bacterial counts was obtained. This correlation was valid within experiments only. 4. Respiration of skin samples taken from adjacent areas of pig's trotter was similar, but there was large variation between samples from different trotters. 5. Respiration due to bacteria increased rapidly for 6–9 hr., followed by a slower increase. This may be due to a limited food supply or to a state of equilibrium.