Project description:Cold shock adaptability is a key survival skill of gut bacteria of warm-blooded animals. Escherichia coli cold shock responses are controlled by a complex multi-gene, timely-ordered transcriptional program. We investigated its underlying mechanisms. Having identified short-term, cold shock repressed genes, we show that their responsiveness is unrelated to their transcription factors or global regulators, while their single-cell protein numbers’ variability increases after cold shock. We hypothesized that some cold shock repressed genes could be triggered by high propensity for transcription locking due to changes in DNA supercoiling (likely due to DNA relaxation caused by an overall reduction in negative supercoiling). Concomitantly, we found that nearly half of cold shock repressed genes are also highly responsive to gyrase inhibition (albeit most genes responsive to gyrase inhibition are not cold shock responsive). Further, their response strengths to cold shock and gyrase inhibition correlate. Meanwhile, under cold shock, nucleoid density increases, and gyrases and nucleoid become more colocalized. Moreover, the cellular energy decreases, which may hinder positive supercoils resolution. Overall, we conclude that sensitivity to diminished negative supercoiling is a core feature of E. coli’s short-term, cold shock transcriptional program, and could be used to regulate the temperature sensitivity of synthetic circuits.
Project description:The cold shock response of B. subtilis was defined after 0.5 hr and 2 hr cold shock using RNA sequencing. We identified novel RNAs (including non-coding RNAs) that play a role during growth at low temperatures. Deletion of the cold induced protein YplP results in a cold sensitive phenotype, and a comparative RNA sequencing analysis suggests that YplP induces pftAB expression after prolonged incubation at low temperatures, thereby optimizing pyruvate transport under cold shock conditions.
Project description:The ability to rapidly respond to changes in temperature is critical for insects and other ectotherms living in variable environments. In a physiological process termed rapid cold-hardening (RCH), exposure to non-lethal low temperature allows many insects to significantly increase their cold tolerance in a matter of minutes to hours. Additionally, there are rapid changes in gene expression and cell physiology during recovery from cold injury, and we hypothesize that RCH may modulate some of these processes during recovery. In this study, we used a cDNA microarray to examine the molecular mechanisms of RCH and cold shock (CS) recovery in the flesh fly, Sarcophaga bullata. With our custom 2-color array, we measured expression of ~15,000 ESTs during RCH and during recovery from cold shock. Surprisingly, no transcripts were upregulated during RCH, and likewise, RCH had a minimal effect on the transcript signature during recovery from cold shock. However, during recovery from cold shock, we observed differential expression of ~1,400 ESTs, including a number of heat shock proteins, cytoskeletal components, and genes from several cell signaling pathways. Several gene pathways correlated well with metabolomics data, indicating that coordinated changes in gene expression and metabolism contribute to recovery from cold shock.
