Comparative Transcriptomics of Cold Growth and Adaptive Features of a Eury- and Steno-Psychrophile

Abstract

Permafrost subzero environments harbor diverse, active communities of microorganisms. However, our understanding of the subzero growth, metabolisms, and adaptive properties of these microbes remains very limited. We performed transcriptomic analyses on two subzero-growing permafrost isolates with different growth profiles in order to characterize and compare their cold temperature growth and cold-adaptive strategies. The two organisms, Rhodococcus sp. JG3 (-5 to 30°C) and Polaromonas sp. Eur3 1.2.1 (-5 to 22°C), shared several common responses during low temperature growth, including induction of translation and ribosomal processes, upregulation of nutrient transport, increased oxidative and osmotic stress responses, and stimulation of polysaccharide capsule synthesis. Recombination appeared to be an important adaptive strategy for both isolates at low temperatures, likely as a mechanism to increase genetic diversity and the potential for survival in cold systems. While Rhodococcus sp. JG3 favored upregulating iron and amino acid transport, sustaining redox potential, and modulating fatty acid synthesis and composition during growth at -5°C compared to 25°C, Polaromonas sp. Eur3 1.2.1 increased the relative abundance of transcripts involved in primary energy metabolism and the electron transport chain, in addition to signal transduction and peptidoglycan synthesis at 0°C compared to 20°C. The increase in energy metabolism may explain why Polaromonas sp. Eur3 1.2.1 is able to sustain growth rates at 0°C comparable to those at higher temperatures. For Rhodococcus sp. JG3, flexibility in use of carbon sources, iron acquisition, control of membrane fatty acid composition, and modulating redox and co-factor potential may be ways in which this organism is able to sustain growth over a wider range of temperatures. Increasing our understanding of the microbes in these habitats helps us better understand active pathways and metabolisms in extreme environments. Identifying novel, thermolabile, and cold-active enzymes from studies such as this is also of great interest to the biotechnology and food industries.

Culture-Dependent Bioprospecting of Bacterial Isolates From the Canadian High Arctic Displaying Antibacterial Activity

“…GHCE.5.JVZL.12) were capable of growing at 37°C. This observation suggests that these isolates are eurypsychrophiles which are typically characterized by their tolerance to subzero temperatures and display optimal growth at ∼20°C (Raymond-Bouchard et al, 2018). Previous studies conducted with similar soil samples from the MARS site have led to the isolation of eurypsychrophillic strains including Planococcus halocryophilus Or1 that is capable of growth at –15°C (Mykytczuk et al, 2016).…”

“…Previous studies conducted with similar soil samples from the MARS site have led to the isolation of eurypsychrophillic strains including Planococcus halocryophilus Or1 that is capable of growth at –15°C (Mykytczuk et al, 2016). The initial incubation of the bulk soil plates was performed at room temperature precluded the isolation of stenopsychrophiles that would have required lower cultivation temperatures (Raymond-Bouchard et al, 2018).…”

16S rRNA gene sequencing and MALDI-TOF mass spectrometry based comparative assessment and bioprospection of psychrotolerant bacteria isolated from high altitudes under mountain ecosystem

“…The last category is further subdivided into psychrophiles with optimal growth temperatures below 15 °C and an upper limit of 20 °C, and psychrotrophs (psychrotolerants) with the ability to grow at 0 °C or below but grow optimally at temperatures around 20-25 °C [27]. In the recent literature, the cold-adapted microorganisms have also been classified as stenopsychrophiles that grow in a narrow range of low temperature (T max ~ 20 °C and T opt 5-15 °C) and eurypsychrophiles that can grow at the broad range of temperature (psychrotrophs/psychrotolerants; T max > 20 °C and T min < 0 °C with T opt > 20 °C) [35]. Both psychrophiles and psychrotrophs are important in global ecology as the majority of aquatic and terrestrial ecosystems of our planet are permanently or seasonally submitted to low temperatures [14].…”

Transporters and Efflux Pumps Are the Main Mechanisms Involved in Staphylococcus epidermidis Adaptation and Tolerance to Didecyldimethylammonium Chloride

“…Another adaptation response identified here for SE11Ad was reduced production of secondary metabolites, as in this way cells can save energy to 'streamline' their primary metabolism [29,30]. The down-regulated Ipk gene (SE2288, -21.7-fold) is involved in terpenoid biosynthesis, which is essential for cell survival.…”