Pseudomonas petrae sp. nov. isolated from regolith samples in Antarctica

The number of known Pseudomonas species has increased exponentially in the last few decades. The genus Pseudomonas currently includes more than 290 validly described names (http://www.bacterio.net, May 2022) (Parte et al., 2020). They are characterized by their ubiquity and have been isolated from various sources worldwide, including fresh water, marine environments, soil, plants, and animals (Palleroni et al., 1992), and they have been detected in various environmental samples, including ones from Antarctica. For example, Pseudomonas extremaustralis has been isolated from a temporary pond in Antarctica (López et al., 2009); Pseudomonas pelagia from an Antarctic green alga (Hwang et al., 2009), and the psychrophilic species Pseudomonas antarctica, Pseudomonas meridiana, and Pseudomonas proteolytica have been found as co-inhabitants in cyanobacterial mats in this region (Reddy et al., 2004). One of the recently described Antarctic pseudomonads is Pseudomonas neustonica, which was found in a microlayer sample of the sea surface (Jang et al., 2020). Pseudomonas spp. are characterized by their low nutrient requirements, which allow them to colonize extremely nutrient-poor environments such as oligotrophic soil or rocks. Examples of such cold-adapted and oligotolerant species found in such environments in Antarctica are Pseudomonas guineae (Bozal et al., 2007); Pseudomonas prosekii (Kosina et al., 2013); Pseudomonas versuta (See-Too et al., 2017), or the recently discovered Pseudomonas fildesensis (Pavlov et al., 2020).

Microorganisms living in environments with persistently low temperatures have often evolved diverse adaptation at all levels within their cells, from the adaptation of the cell envelope, cell membrane and enzymes to the production of cryoprotectants and chaperones or novel metabolic traits (Collin and Margesin, 2019). The ability to accumulate bacterial polyhydroxyalkanoates, especially polyhydroxybutyrate, was found to be essential for coping with cold and oxidative stress in P. extremaustralis isolated in Antarctica (Tribelli and López, 2018, Tribelli et al., 2020). Certain Pseudomonas strains isolated from maritime Antarctica were found to have higher enzymatic activity of amylase, caseinase, lipase or gelatinase at low temperatures of 4 °C than at 20 °C (Loperena et al., 2012). A higher production of those extracellular enzymes seems to be beneficial in cold environments.

The aim of this study is to provide a thorough phylogenetic analysis and comprehensive characterization of a novel Pseudomonas species, characterized these cold tolerant strains, isolated from Antarctic regoliths.

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