Effect of heat shock at 500 atm and pressure shock to 500 atm on Methanocaldococcus jannaschii

Growth and transcriptional profiles of the barophilic methanarchaeon Methanocaldococcus jannaschii were studied at temperatures up to 98C and pressures up to 500 atm. Application of 500 atm of hyperbaric pressure shifted the optimal growth temperature upwards, and heat shock from 88C to 98C at 500 atm resulted in termination of growth. Pressure shock of M. jannaschii from 7.8 to 500 atm over 15-min, the first pressure upshift reported for a barophile, did not accelerate growth. Transcriptional profiles indicated a similar pressure response under growth and heat shock at 500 atm and pressure shock to 500 atm suggesting that the commonly affected genes are important for high-pressure adaptation. Factorial microarray design allowed de-convolution of the interacting effect of elevated pressure and heat shock on expression profiles, thus suggesting genes that may contribute to the organism’s survival in the turbulent in situ conditions of deep-sea hydrothermal vents. Keywords: stress response, time course, high pressure, heat shock, pressure shock The cDNA arrays that were used contained three technical replicate spots for each ORF in the genome of M. jannaschii. Twenty-four sub-arrays were hybridized with the following pairs of samples: four biological-replicate pairs of samples extracted from 7.8 atm and 500 atm, both without heat shock, four biological-replicate pairs of samples extracted from 7.8 atm without heat shock and 7.8 atm with heat shock (0.5 h and 1.5h), four biological-replicate pairs of samples extracted from 500 atm without heat shock and 500 atm with heat shock (0.5 h and 1.5h), and four biological-replicate pairs of samples extracted from 7 atm and 500 atm, both heat shocked (0.5 h). Each of the four pairs of biological replicates included two pairs of dye-swapped samples. Six sub-arrays were hybridized with the following pairs of samples: three biological-replicate pairs of samples extracted from cells pressure shocked to 500 atm (0.5 h and 1.5 h) and from cells grown at 7 atm without heat shock.