Effect of gas-substrate limitation on barophilic growth of Methanocaldocccus jannaschii at 500 atm.

Barophilic growth of the hyperthermophilic methanarchaeon Methanocaldococcus jannaschii occurred when gas-substrate availability did not limit growth. In contrast, when growth was limited by gas transfer, no enhancement of growth was evident and a stress response was exhibited at both high and low pressure. A pressure-induced transcriptional response was evident, regardless of whether growth was enhanced by pressure. High-pressure adaptation of a barophilic organism can thus occur at the transcriptional level, even though the cells are stressed by low substrate availability and do not exhibit accelerated growth. Keywords: stress response, gas substrate limitation, bioreactor volume, high pressure All RNA samples were extracted in the exponential phase of growth. The cDNA arrays that were used contained three technical replicate spots for each ORF in the genome of M. jannaschii. Samples from cells grown in 200 ml of medium at 500 atm and 88C were hybridized against samples from cells grown in 200 ml of medium at 7 atm and 88C in four different pairs of biological replicates (including two pairs of dye-swapped samples). All other samples were hybridized in three different pairs of biological replicates (including one pair of dye-swapped samples).