Survival of Salmonella anatum Heated in Various Media

Survival of Salmonella anatum heated at 55 C for 35 min was determined in solutions of various chemical constituents of foods including salts, carbohydrates, amino acids, peptides, nucleic acids, gums, and stabilizers and compared with survival in 0.1 m phosphate buffer (pH 7.0). Commercially sterilized whole milk gave the most protection against heat. Trypticase Soy Broth, various peptide mixtures, and some amino acids gave substantial protection. Results with carbohydrates were variable, with mannitol, sucrose, and rhamnose providing substantial protection and glucose decreasing heat resistance. A few other substances, cysteine, glutathione, and sodium citrate, also decreased heat resistance. Pure proteins had little effect. Results show that water activity is of little significance under the test conditions. Protection from heat probably results from complexing of substances with heat-sensitive proteins in the cells. Autoclaved milk should not be considered equivalent to raw milk for studies of survival of bacteria during heating.     

Fine Structure of Thermus aquaticus, an Extreme Thermophile

Electron microscopic studies using thin sections revealed that Thermus aquaticus has a structure similar to that of most other gram-negative bacteria. The cell envelope is tripartite: plasma membrane, thin middle layer, and a thicker and irregular outer layer. The outer layer appears to be joined to the plasma membrane by a series of connections and, when seen in tangential section, the outer layer appears as a series of parallel bands. The cell division mechanism resembles that of typical gram-negative bacteria. Large spherical bodies designated “rotund bodies” are formed as a result of the association of a number of separate cells. In this association the outer envelope layers of the cells fuse and pull away from the middle layer. The rotund body thus appears as a series of rods, usually lying in parallel around the periphery of the sphere, completely connected by means of the fused outer layer.     

Potassium Fluxes during Potassium Absorption by Intact Barley Plants of Increasing Potassium Content

The presence of previously absorbed K in plants caused a marked reduction in the short term influx of ⁸⁶Rb-labeled K into roots of barley seedlings. The influx values agreed with net K absorption rates into intact plants, thus suggesting that K efflux was negligible in comparison with influx.     

The aggregation States of phytochrome from etiolated rye and oat seedings

Initial extracts from etiolated plants contained two aggregates of phytochrome. A major fraction was almost excluded by Sephadex G-200 and was within the fractionation range of Sepharose 4 B. A minor fraction was within the fractionation range of Sephadex G-200. Modifications of a previous isolation procedure which allowed retention of this aggregation state are reported. With respect to gel filtration, the major fraction of phytochrome from oat and rye seedlings was identical. The aggregates of rye and oat phytochrome were also separated by diethylaminoethyl cellulose chromatography.     

Growth of Pseudomonas fluorescens with Sodium Maleate as a Carbon Source

The growth of Pseudomonas fluorescens (ATCC 11150) on sodium maleate was observed, and the composition of the media was monitored in batch culture. Utilization of the maleate as the sole organic carbon source proceeded by stepwise conversion to fumarate and then to malate. Respiration rates of P. fluorescens on maleate, mixtures of maleate and fumarate salts, and mixtures of maleate and malate salts were measured. Complex effects, possibly due to a change in metabolic mechanism, were observed.