Molecular insights into the ecology of a psychrotolerant Pseudomonas syringae

Abstract

Low temperatures constrain cellular life due to reductions in nutrient uptake, enzyme kinetics, membrane permeability, and function of other biomacromolecules. This has implications for the biophysical limits of life on Earth, and the plausibility of life in extraterrestrial locations. Although most pseudomonads are mesophilic in nature, isolates such as the Antarctic Pseudomonas syringae Lz4W exhibit considerable psychrotolerance, with an ability to grow even between 4 and 0 C. In this review, we explore the molecular traits and characteristic phenotypes of P. syringae Lz4W that enable life at low temperatures. We describe adaptations that enhance membrane fluidity; examine genes involved in cellular function and survival in the cold; assess capability for energy generation at low temperature; and detail the mechanics of DNA repair and RNA processing at low temperature, and speculate that P. syringae Lz4W can also synthesize glycerol to maintain flexibility of macromolecular systems. In the range 4 to 0ºC, there are considerable changes in the properties and behaviour of water. Specifically, density can have adverse impacts on plasma-membrane functions, cytoplasmic viscosity, protein behaviour, and other essential properties of cellular system. We identified a combination of adaptations that may be peculiar to cold-tolerant P. syringae, including increase of unsaturated fatty acids in the plasma membrane; a RNA polymerase able to function at 0 C; RecBCD-and RuvAB-dependent reestablish ment of replication fork; and efficiencies of degradosome machinery and RNA processing by RNaseR at low temperature. Several unresolved questions are discussed in the context of astrobiology, and further work needed on the psychrotolerance of P. syringae.

Carbohydrate‐dependent sulfur respiration in halo(alkali)philic archaea

“…They possess two pathways [referred to the sn ‐glycerol‐3‐phosphate (G3P) and dihydroxyacetone (DHA) pathways] of its catabolism, likely acquired from bacteria as part of their evolutionary transformation to heterotrophic nutrition (Nelson‐Sathi et al ., 2012). There is circumstantial evidence that some haloarchaea may use glycerol as a stress metabolite (Pavankumar et al ., 2020). Prior to the present study, however, there was no direct evidence of anaerobic growth of haloarchaea on glycerol, and a potential for this kind of metabolism was only suggested for Halalkalicoccus jeotgali , isolated from fermented food (Roh et al ., 2007; Williams et al ., 2017).…”

Microbiology of a NaCl stalactite ‘salticle’ in Triassic halite

“…The most‐commonly utilized organic compatible solutes that are produced by most Bacteria include trehalose, ectoine, proline, glycine betaine, glucosylglycerol, and dimethylsulfoniopropionate (León et al ., 2018). There is evidence that some bacterial species may also utilize glycerol for osmotic adjustment and other stress‐protection roles (Pavankumar et al ., 2021).…”

Water is a preservative of microbes

“…Furthermore, cells within mineral oil were likely contained within an aqueous extracellular layer so they too were effectively preserved in water. Interestingly, at 4°C survival was poor in water (or mineral oil), a phenomenon which may relate to changes in the density of water—and associated cellular damage—that are peculiar to this temperature (Pavankumar et al ., 2021). In general, however, water has proved the most effective preservative of fungi in studies where comparisons were carried out (for further examples, see the review of Castro‐Rios and Bermeo‐Escobar, 2021).…”