[The effect of temperature on the growth and lipopolysaccharide production of gram-negative bacteria].

5 strains of Pseudomonas and 7 of Enterobacteriaceae were cultivated in a Temperature Gradient Incubator (TGI) in intervals of 5 degrees C over a linear temperature gradient of 4 to 48 degrees C. After attaining the stationary growth phase the amount of lipopolysaccharides (LPS) formed was determined by means of the three LAL tests, i.e. the Capillary test, the "Mini" Endotoxin test and the Coatest endotoxin method. Simultaneously, the colony count was carried out. The same was done for one strain of E. coli in the exponential growth phase after continuous cultivation in 5 degrees C intervals over the range 10 to 35 degrees C. With the exception of the E. coli mutant P400, the lowest amounts of LPS produced in the stationary phase per 10(9) cfu was determined between 20 and 30 degrees C. Increasing or decreasing temperatures caused a more or less sharp rise in the quantity of LPS formed in the stationary phase. This was also demonstrated for E. coli in the exponential phase. For the E. coli mutant P400, however, the LPS content was highest at lower growth temperatures but decreased with increasing temperatures. Changes in the composition of fatty acids and sugars of the LPS and of membrane protein, which are dependent on the temperature of growth apparently alter the steric structure of the LPS which react with the LAL system, and could thus be responsible for the increased LPS found at the lower and higher growth temperatures. In the use of the LAL-tests methods for the assessment of the bacterial load of foods with gram negative bacteria, it is necessary, especially for cold stored products, to test for and determine the LPS-cfu relationship beforehand.