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R M Stevenson

Publications and source records attributed to R M Stevenson.

29 records · Page 2Linked to original sources
PubMed1981

Extracellular virulence factors of Aeromonas hydrophila in fish infections.

Aeromonas hydrophila NRC 505 produced extracellular substances which were capable of causing pathological effects when injected into trout. Proteolytic activity and haemolytic activity of the extracellular products, and the effect on fish, were lost on heating. The extracellular substances from strain G35, a protease-deficient mutant, were significantly more toxic to both rainbow trout (Salmo gairdneri) and speckled trout (Salvelinus fontinalis) than the analogous preparation from the parental strain NRC 505. The response of speckled trout injected intraperitoneally with dilutions of the extracellular preparations implicates haemolytic activity as a significant lethality factor.

Aeromonas↗
PubMed1979

Amino acid uptake systems in Bacteroides ruminicola.

Uptake of amino acids by Bacteroides ruminicola was observed in cells grown in a complete defined medium, containing ammonia as the nitrogen source. A high rate of uptake occurred only in fresh medium, as an inhibitory substance, possibly acetate, apparently accumulated during growth. All amino acids except proline were taken up and incorporated into cold trichloroacetic acid precipitable material. Different patterns of incorporation and different responses to 2,4-dinitrophenol and potassium ferricyanide indicated multiple uptake systems were involved. Kinetic inhibition patterns suggested six distinct systems were present for amino acid uptake, with specificities related to the chemical structures of the amino acids. Thus, the failure of free amino acids to act as sole nitrogen sources for growth of B. ruminicola is not due to the absence of transport systems for these compounds.

Amino Acids↗