SUMMARY—Salmonellae, normally grown at 3.5–37°C, can grow at much lower temperatures. Experimentally, minimum growth temperatbres were obtained when salmonellae were grown on the surface of agar in a temperature‐gradient incubator over a temperature range of 1.1 to 12.3°C. These minimum temperatures, as determined by visible growth for 7 serotypes, ranged from 5.5 to 6.8°C. The pattern of survival or growth of S. derby, S. heidelberg, and S. typhimurium was followed by inoculating the organisms into tubes of broth and incubating the tubes in a polythermostat over a temperature range of 1.1 to 12.3°C. Minimum growth temperature obtained for S. heidelberg after 19 days' incubation was 5.3°C. The minimum growth temperature for the same length of time for S. typhimurium and S. derby were 6.2 and 6.9°C respectively. The results indicate a growth temperature shift during extended incubation of Salmonella at low temperatures. This phenomenon and the low temperature. growth capability of Salmonella could be significant in foods stored for long periods of time at temperatures above 5°C.

Shrimp (Pandalus platyceros) were packed head-on and head-off in pouches with air or 50 or 100% CO2 and stored at 0 to 2°C for up to 23 d. Carbon dioxide in modified atmosphere pouches dissolved in the liquid phase and the pH decreased. As storage progressed, the pH increased. Only 100% CO2 was effective in extending the lag in bacterial growth, but the greatest weight or drip was also obtained with this atmosphere. The bacterial flora changed from mixed gram-negative and gram-positive organisms to a predominantly gram-positive flora. Ammonia was produced throughout storage in all atmospheres, but was delayed longer in head-off than in head-on shrimp. Indole was produced readily in air packs but only at low levels in CO2 packs.

Clostridium perfringens was isolated from samples collected in Puget Sound in the state of Washington and areas considered as possible sources of these organisms to Puget Sound. The distribution of C. perfringens in the total Clostridium population was determined for fish gut contents and sediments collected in highly polluted and less polluted areas, sewage samples, freshwater sediments, and soils. The greatest numbers of C. perfringens were obtained from marine sediments collected near the sewage outfall at West Point. Fewer isolates were made from fish collected from less polluted stations, although the number of C. perfringens remained high in sediments from other Puget Sound stations. The proportion of C. perfringens in the total Clostridium populations varied between 56 and 71% for sewage samples and only 0.4 to 4.1% for freshwater sediments and soil samples. Only 25 C. perfringens isolates out of 137 from fish guts, or 18%, were identifiable serologically and these fell into 12 groups. C. perfringens were fed to fish and the fish were sacrificed after varying lengths of time. The number of C. perfringens increased slightly in the gut during the first 24 h and then the numbers decreased rapidly for the next 120 h.

Shrimp (Pandalui jordani) were allowed to decompose at five temperatu!es (0, 5.6, 11.1, 16.7 and 22.2'C). Mean aerobic plate counts on the shrimp as received at the laboratory were 1.6 x 106/g. The most rapid growth was obtained at the higher temperatures but the highest maximum population was obtained at 0°C. A total of 638 bacteria were isolated and tested for identification. The heterogenous population at day 0 was composed of 38% Gram positives. The population changed becoming predominantly Gram negative by day 13. At the higher temperatures the indole producing fioteus emerged by day 7 and became an important component of the flora. Volatile base (N) and indole Increased both with increasing time and temperature during storage.

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