| The synthesis of heat shock protein (HSP) in cells is a universal response to unfavorable environmental conditions. Each class of HSP likely performs specific functions that enhance cell survival. Diatoms (Chrysophyta) are a diverse group of algae that are ubiquitous and their distributions are often associated with specific environments. These attributes may make diatoms useful as bioindicators. Also, diatoms have potential in biotechnology since many produce fine chemicals and lipids that may be exploitable as medicines and renewable energy. However, to utilize diatoms, it is helpful to understand how they respond to environmental conditions. The response of thermo-intolerant (Phaeodactylum tricornutum) and thermo-tolerant ( Chaetoceros muelleri) diatoms to heat stress was investigated, with focus on protein induction, characterization of some key stress genes and changes in fatty acids.; SDS polyacrylamide gel electrophoresis (PAGE) and total protein assays revealed that P. tricornutum, unlike C. muelleri , exhibited a typical response to heat stress. Nonetheless, small heat shock proteins (smHSP) may play a role in the response in both diatoms. Western blot analysis revealed that HSP70, a putative stress response regulator, may be present only in undetectable amounts in P. tricornutum and was invariable among treatments of C. muelleri. These results suggest that greater basal levels of HSP may correspond to greater thermo-tolerance in cells.; The 70-kDa stress genes are a multi-gene family with cytosolic (hsp70) and chloroplast (dnaK) isoforms. Probes specific to hsp70 gene types in P. tricornutum and C. muelleri were generated using polymerase chain reaction (PCR). DNA hybridizations using the probes suggest that DnaK may be nuclear encoded only in P. tricornutum and nuclear and chloroplast encoded in C. muelleri. The probes generated in this study may be useful in future studies involving DNA library screening and Northern blot analysis.; Changes in fatty acids varied between diatoms in response to temperature with a particular temperature, and not treatment duration, likely responsible for changes. Since changes occurred rapidly (2 hours) compared to nutrient starvation (2 days), the mechanism governing lipid mobilization during heat stress may differ from those acting during other stresses.; The results of this study may improve our understanding of how diatoms respond to stress and may increase their usefulness in biotechnology. |
