RT Journal Article SR Electronic T1 Genomic insights and temperature-dependent transcriptional responses of Kosmotoga olearia, a deep-biosphere bacterium that can grow from 20ºC to 79ºC JF bioRxiv FD Cold Spring Harbor Laboratory SP 060053 DO 10.1101/060053 A1 Stephen M. J. Pollo A1 Abigail A. Adebusuyi A1 Timothy J. Straub A1 Julia M. Foght A1 Olga Zhaxybayeva A1 Camilla L. Nesbø YR 2017 UL http://biorxiv.org/content/early/2017/02/02/060053.abstract AB Temperature is one of the defining parameters of an ecological niche, and ambient temperature change is a physiological challenge faced by all living cells. Most organisms are adapted to growing within a temperature range that rarely exceeds ~ 30°C, but the anaerobic thermophilic deep subsurface bacterium Kosmotoga olearia is capable of growing over an extremely wide temperature range (20°C - 79°C). To identify genes with expression patterns correlated with this flexible phenotype, we compared transcriptomes of K. olearia cultures grown at its optimal 65°C to those at 30°C, 40°C, and 77°C. In addition to expected differences in growth rate we found that the temperature treatments significantly affected expression of 573 of 2,224 K. olearia’s genes. At different temperatures K. olearia remodels its metabolism dramatically, with increased expression of genes involved in energy and carbohydrate metabolism at high temperatures and up-regulation of amino acid metabolism at lower temperatures. At sub-optimal temperatures, many transcriptional changes were similar to those observed in mesophilic bacteria at physiologically low temperatures, including up-regulation of genes encoding enzymes for fatty acid synthesis, typical cold stress genes and ribosomal proteins. In comparison to other Thermotogae, K. olearia has multiple copies of some cold-associated genes, consistent with observations that increase in gene copy number is a strategy for adaptation to low temperature environments. Many of these cold response genes are predicted to have been laterally acquired and, particularly among the transferred genes shared with Mesotoga, a larger portion are up-regulated at low temperatures, suggesting that gene exchange plays a role in bacterial thermoadaptation. Notably, at 77°C one-third of the up-regulated genes encode proteins with hypothetical functions, indicating that many features of response to high temperature and stress may still be unknown. Our finding of coordinated temperature-specific gene expression patterns, and by extension temperature specific metabolism, suggests that Kosmotoga populations encounter variable environments, probably through migration. Therefore, we conjecture that deep subsurface microbial communities are more dynamic than currently perceived.