| The significance of surface colonization and changing thermal conditions in hydro-thermal environments motivated examination of biofilm formation and thermal stress response in the model heterotrophic hyperthermophilic microorganisms, Thermotoga maritima and Pyrococcus furiosus. Continuous culture, using maltose-based media and anaerobic conditions at 80°C for T. maritima and 95°C for P. furiosus, was employed to generate microbially-dense biofifims on nylon mesh and polycarbonate filters; significant amounts of wall growth were observed in the chemostats for both organisms. Transcriptional analysis of biofilm-bound cells showed that genetic mechanisms (e.g., response regulators, transcriptional regulators, and heat shock genes) observed for biofilm formation in less thermophilic bacteria applied to T. maritima.; Expression of stress-related genes in the T. maritima biofilm prompted a study of heat shock at 90°C. A 407-gene targeted cDNA microarray was used to study genetic differences between cells at 80°C and cells at 90°C after 0, 5, 10, 20, 30, 60, and 90 minutes. The major heat shock genes exhibited maximal induction at early times (∼5 minutes), subsequently decreasing to a steady-state level. Atypical of heat shock response, the majority of genes encoding ATP-dependent proteases were down-regulated. A number of other genes, not related to stress response, also showed significant changes in expression levels. These include transcriptional regulators, genes within the gluconate metabolic pathway, sugar transporters and glycosidases, and sigma factors. Homologs to sigmaE and sigma A were induced during heat shock at 90°C, suggesting that they are implicated in stress response regulation in T. maritima.; This work led to the development of chemostat-based methods for generating RNA from hyperthermophiles embedded in anaerobic biofilms that could be used for transcriptional analysis. Such analysis indicated possible connections between the genetic response of biofilm-bound cells and thermal stress response. The results here point to the significance of surface colonization and modification of cellular function arising from thermal changes in the microbial ecology of hydrothermal environments. |
