Effects of temperature on the macromolecular composition and fine structure of psychrophilic Arthrobacter species

A facultatively psychrophilic bacterium, Arthrobacter SI 55, grows at 20 degrees C, but growth, as measured by increase of viable cell count, is inhibited at 32 degrees C. Corresponding temperatures for an obligate psychrophile, Arthrobacter glacialis SI 137, are 10 degrees C and 19-20 degrees C. At the higher temperatures for each organism increases of cell mass, as measured by turbidity and of DNA, RNA, and protein, were not inhibited. At the upper temperatures, fewer septa were formed in Arthrobacter SI 55, and cells appeared as distorted filaments with irregular brancehs. Arthrobacter glacilis grew as single cells at the lower temperature, but as clumps of coccoid cells with well marked septa at the higher temperature. It appears that in Arthrobacter SI 55 septum formation may be inhibited at the higher temperature. In contrast, in A. glacialis septation occurs but the cells do not separate.