Novel Psychrophiles and Exopolymers from Permafrost Thaw Lake Sediments

Abstract

Thermokarst lakes are one of the most abundant types of microbial ecosystems in the circumpolar North. These shallow basins are formed by the thawing and collapse of ice-rich permafrost, with subsequent filling by snow and ice melt. Until now, permafrost thaw lakes have received little attention for isolation of microorganisms by culture-based analysis. The discovery of novel psychrophiles and their biomolecules makes these extreme environments suitable sources for the isolation of new strains, including for potential biotechnological applications. In this study, samples of bottom sediments were collected from three permafrost thaw lakes in subarctic Québec, Canada. Their diverse microbial communities were characterized by 16S rRNA gene amplicon analysis, and subsamples were cultured for the isolation of bacterial strains. Phenotypic and genetic characterization of the isolates revealed affinities to the genera Pseudomonas, Paenibacillus, Acinetobacter,Staphylococcus and Sphingomonas. The isolates were then evaluated for their production of extracellular enzymes and exopolymers. Enzymes of potential biotechnological interest included α and β-glucosidase, α and β-maltosidase, β-xylosidase and cellobiohydrolase. One isolate, Pseudomonas extremaustralis strain 2ASCA, also showed the capability to produce, in the loosely bound cell fraction, a levan-type polysaccharide with a yield of 613 mg/L of culture, suggesting its suitability as a candidate for eco-sustainable alternatives to commercial polymers.

Genomic Analysis Provides New Insights Into Biotechnological and Industrial Potential of Parageobacillus thermantarcticus M1

“…In order to precipitate exopolymer, the mixture was centrifuged for 30 min at 10,000 rpm at 4°C. Warm distilled water was used to dissolve the pellet and it was dialyzed against water in dialysis tubes (Spectra/Por MWCO; molecular weight cut-off 12–14 kDa) for 3 days, then lyophilized (Hetodrywinner) and weighed ( Finore et al, 2020 ). Phenol/sulfuric acid method ( Dubois et al, 1956 ) was used to assay the total carbohydrate content of exopolymers.…”

Prokaryotic Diversity of the Composting Thermophilic Phase: The Case of Ground Coffee Compost

“…Xylan and cellulose hydrolysis were tested by flooding cultures with 0.1% Congo Red dye, followed by rinsing with a 1.0 M NaCl solution on a solid medium containing 0.2% ( w / v ) xylan and carboxymethyl cellulose (CMC), respectively. Gelatine hydrolysis was tested in the appropriate medium enriched with 1.0% ( w / v ) gelatine [ 15 , 18 ]. Detection of enzymatic activities in the cytosol fraction of three isolates was performed by suspending their cells in a 50 mM Tris-HCl buffer pH 7.0 containing lysozyme (3 mg of lysozyme per gram of wet cell) at 37 °C for 1 h. The cytosolic samples obtained through centrifugation at 10,000 rpm for 30 min were tested for endoxylanase, β-xylosidase, and α-arabinofuranosidase, as previously reported [ 15 , 16 , 17 , 18 , 19 ].…”

“…Gelatine hydrolysis was tested in the appropriate medium enriched with 1.0% (w/v) gelatine [15,18]. Detection of enzymatic activities in the cytosol fraction of three isolates was performed by suspending their cells in a 50 mM Tris-HCl buffer pH 7.0 containing lysozyme (3 mg of lysozyme per gram of wet cell) at 37 • C for 1 h. The cytosolic samples obtained through centrifugation at 10,000 rpm for 30 min were tested for endoxylanase, β-xylosidase, and α-arabinofuranosidase, as previously reported [15][16][17][18][19].…”

Biomass Valorization: Sustainable Methods for the Production of Hemicellulolytic Catalysts from Thermoanaerobacterium thermostercoris strain BUFF

“…One unit of xylanase activity was expressed as µmol of reducing sugars (xylose equivalent) released in 1 min under the abovementioned conditions. β-xylosidase, α-arabinofuranosidase, β-glucosidase, α-galactosidase, β-galactosidase and β-fucosidase assays were based on the release of p-nitrophenol from 1 mM of p-nitrophenyl-β-D-xylopyranoside, p-nitrophenyl-α-Larabinofuranoside, p-nitrophenyl-β-D-glucopyranoside, p-nitrophenyl-α-D-galactopyranoside, p-nitrophenyl-β-D-galactopyranoside and p-nitrophenyl-β-D-fucopyranoside, respectively, using appropriately diluted enzyme solution at 60 • C for 20 min in 1 mL of 50 mM sodium acetate buffer pH 5.6 as final volume [28]. The acetyl-xylan esterase assay was based on the release of p-nitrophenol from 0.1 mM of p-nitrophenyl-acetate by the enzyme solution at 60 • C in 50 mM sodium acetate buffer at pH 5.6 for 20 min in 2 mL as final volume [29].…”