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Manganese-oxidizing bacteria (MnOB) produce Mn oxide minerals that can be used by humans for bioremediation, but the purpose for the bacterium is less clear. This study describes the isolation and characterization of cold-tolerant MnOB strains isolated from a compost pile in Morris, Minnesota, USA: Pseudomonas sp. MS-1 and DSV-1. The strains were preliminarily identified as members of species Pseudomonas psychrophila by 16S rRNA analysis and a multi-locus phylogenetic study using a database of 88 genomes from the Pseudomonas genus. However, the average nucleotide identity between these strains and the P. psychrophila sp. CF149 type strain was less than 93%. Thus, the two strains are members of a novel species that diverged from P. psychrophila. DSV-1 and MS-1 are cold tolerant; both grow at 4°C but faster at 24°C. Unlike the mesophilic MnOB P. putida GB-1, both strains are capable of robustly oxidizing Mn at low temperatures. Both DSV-1 and MS-1 genomes contain homologs of several Mn oxidation genes found in P. putida GB-1 (mnxG, mcoA, mnxS1, mnxS2, and mnxR). Random mutagenesis by transposon insertion was successfully performed in both strains and identified genes involved in Mn oxidation that were similar to those found in P. putida GB-1. Our results show that MnOB can be isolated from compost, supporting a role for Mn oxidation in plant waste degradation. The novel isolates Pseudomonas spp. DSV-1 and MS-1 both can oxidize Mn at low temperature and likely employ similar mechanisms and regulation as P. putida GB-1.IMPORTANCEBiogenic Mn oxides have high sorptive capacity and are strong oxidants. These two characteristics make these oxides and the microbes that make them attractive tools for the bioremediation of wastewater and contaminated environments. Identifying MnOB that can be used for bioremediation is an active area of research. As cold-tolerant MnOB, Pseudomonas sp. DSV-1 and MS-1 have the potential to expand the environmental conditions in which biogenic Mn oxide bioremediation can be performed. The similarity of these organisms to the well-characterized MnOB P. putida GB-1 and the ability to manipulate their genomes raise the possibility of modifying them to improve their bioremediation ability.

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The culturable yeast communities in temperate forest soils under the ornithogenic influence were studied in a seasonal dynamic. To investigate the intense ornithogenic influence, conventional and "live" feeders were used, which were attached to trees in the forest and constantly replenished throughout the year. It was found that the yeast abundance in the soil under strong ornithogenic influence reached the highest values in winter compared to the other seasons and amounted to 4.8 lg (cfu/g). This was almost an order of magnitude higher than the minimum value of yeast abundance in ornithogenic soils determined for summer. A total of 44 yeast species, 21 ascomycetes and 23 basidiomycetes, were detected in ornithogenic soil samples during the year. These included soil-related species (Barnettozyma californica, Cyberlindnera misumaiensis, Cutaneotrichosporon moniliiforme, Goffeauzyma gastrica, Holtermanniella festucosa, Leucosporidium creatinivorum, L. yakuticum, Naganishia adeliensis, N. albidosimilis, N. globosa, Tausonia pullulans, and Vanrija albida), eurybionts (yeast-like fungus Aureobasidium pullulans, Debaryomyces hansenii, and Rhodotorula mucilaginosa), inhabitants of plant substrates and litter (Cystofilobasidium capitatum, Cys. infirmominiatum, Cys. macerans, Filobasidium magnum, Hanseniaspora uvarum, Metschnikowia pulcherrima, and Rh. babjevae) as well as a group of pathogenic and opportunistic yeast species (Arxiozyma bovina, Candida albicans, C. parapsilosis, C. tropicalis, Clavispora lusitaniae, and Nakaseomyces glabratus). Under an ornithogenic influence, the diversity of soil yeasts was higher compared to the control, confirming the uneven distribution of yeasts in temperate forest soils and their dependence on natural hosts and vectors. Interestingly, the absolute dominant species in ornithogenic soils in winter (when the topsoil temperature was below zero) was the basidiomycetous psychrotolerant yeast T. pullulans. It is regularly observed in various soils in different geographical regions. Screening of the hydrolytic activity of 50 strains of this species at different temperatures (2, 4, 10, 15 and 20 °C) showed that the activity of esterases, lipases and proteases was significantly higher at the cultivation temperature. Ornithogenic soils could be a source for the relatively easy isolation of a large number of strains of the psychrotolerant yeast T. pullulans to test, study and optimize their potential for the production of cold-adapted enzymes for industry.

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The prolonged period of low temperatures in northern China poses a significant challenge to the bioremediation of antibiotic pollution. This study reports that a white-rot fungus Bjerkandera adusta DH0817, isolated from a poultry farm in Liaoning Province, can remove 60 % of SDZ within 20 days at 10°C and reduce the biotoxicity of SDZ. Six degradation pathways were proposed. SDZ biodegradation was primarily driven by cytochrome P450. Transcriptome analysis revealed that DH0817 upregulated genes associated with cell membrane, transcription factors and soluble sugars in response to low temperatures. Subsequently, genes associated with fatty acid, proteins and enzymes were upregulated to remove SDZ at low temperatures. This study provides valuable microbial resources and serves as a theoretical reference for addressing antibiotic pollution in livestock and poultry farms under low temperature conditions.

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The extremophile bacterium Deinococcus radiodurans is characterized by its ability to survive and sustain its activity at high levels of radiation and is considered an organism that might survive in extraterrestrial environments. In the present work, we studied the combined effects of temperature and chlorine-containing salts, with focus on perchlorate salts which have been detected at high concentrations in Martian regolith, on D. radiodurans activity (CO2 production rates) and viability after incubation in liquid cultures for up to 30 days. Reduced CO2 production capacity and viability was observed at high perchlorate concentrations (up to 10% w/v) during incubation at 0 or 25 °C. Both the metabolic activity and viability were reduced as the perchlorate and chloride salt concentration increased and temperature decreased, and an interactive effect of temperature and salt concentration on the metabolic activity was found. These results indicate the ability of D. radiodurans to remain metabolically active and survive in low temperature environments rich in perchlorate.

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Ten strains of psychrotolerant methylotrophic bacteria were isolated from the samples collected in Larsemann and Bunger Hills (Antarctica). Most of the isolates are assigned to the genus Pseudomonas, representatives of the genera Janthinobacterium, Massilia, Methylotenera and Flavobacterium were also found. Majority of isolates were able to grow on a wide range of sugars, methylamines and other substrates. Optimal growth temperatures for the isolated strains varied from 6 °C to 28 °C. The optimal concentration of NaCl was 0.5-2.0%. The optimal pH values of the medium were 6-7. It was found that three strains synthesized indole-3-acetic acid on a medium with L-tryptophan reaching 11-12 µg/ml. The values of intracellular carbohydrates in several strains exceeded 50 µg/ml. Presence of calcium-dependent and lanthanum-dependent methanol dehydrogenase have been shown for some isolates. Strains xBan7, xBan20, xBan37, xBan49, xPrg27, xPrg48, xPrg51 showed the presence of free amino acids. Bioprospection of Earth cryosphere for such microorganisms has a potential in biotechnology.

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Strain SED1T was isolated from glacial samples collected on Mount Deception, Washington, USA. Genome sequencing and assembly identified a DNA G + C content of 60.4 mol% with 6,125 predicted proteins. Analysis by the Type Strain Genome Server is consistent with the isolate representing a previously undescribed species in the genus Pseudomonas.

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Wheat is the second most important staple crop grown and consumed worldwide. Temperature fluctuations especially the cold stress during the winter season reduces wheat growth and grain yield. Psychrotolerant plant growth-promoting rhizobacteria (PGPR) may improve plant stress-tolerance in addition to serve as biofertilizer. The present study aimed to isolate and identify PGPR, with the potential to tolerate cold stress for subsequent use in supporting wheat growth under cold stress. Ten psychrotolerant bacteria were isolated from the wheat rhizosphere at 4 °C and tested for their ability to grow at wide range of temperature ranging from -8 °C to 36 °C and multiple plant beneficial traits. All bacteria were able to grow at 4 °C to 32 °C temperature range and solubilized phosphorus except WR23 at 4 °C, whereas all the bacteria solubilized phosphorus at 28 °C. Seven bacteria produced indole-3-acetic acid at 4 °C, whereas all produced indole-3-acetic acid at 28 °C. Seven bacteria showed the ability to fix nitrogen at 4 °C, while all the bacteria fixed nitrogen at 28 °C. Only one bacterium showed the potential to produce cellulase at 4 °C, whereas four bacteria showed the potential to produce cellulase at 28 °C. Seven bacteria produced pectinase at 4 °C, while one bacterium produced pectinase at 28 °C. Only one bacterium solubilized the zinc at 4 °C, whereas six bacteria solubilized the zinc at 28 °C using ZnO as the primary zinc source. Five bacteria solubilized the zinc at 4 °C, while seven bacteria solubilized the zinc at 28 °C using ZnCO3 as the primary zinc source. All the bacteria produced biofilm at 4 °C and 28 °C. In general, we noticed behavior of higher production of plant growth-promoting substances at 28 °C, except pectinase assay. Overall, in vitro testing confirms that microbes perform their inherent properties efficiently at optimum temperatures rather than the low temperatures due to high metabolic rate. Five potential rhizobacteria were selected based on the in vitro testing and evaluated for plant growth-promoting potential on wheat under controlled conditions. WR22 and WR24 significantly improved wheat growth, specifically increasing plant dry weight by 42% and 58%, respectively. 16S rRNA sequence analysis of WR22 showed 99.78% similarity with Cupriavidus campinensis and WR24 showed 99.9% similarity with Enterobacter ludwigii. This is the first report highlighting the association of C. campinensis and E. ludwigii with wheat rhizosphere. These bacteria can serve as potential candidates for biofertilizer to mitigate the chilling effect and improve wheat production after field-testing.

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A Gram-stain-positive rod, psychrotolerant, aerobic and bioemulsifier-producing strain, denoted as Val9T, was isolated from soil sampled at Vale Ulman, King George Island, Antarctica. The strain grew at up to 30 °C (optimum, 15 °C), at pH 6-9 (optimum, pH 8) and with up to 5 % w/v NaCl (optimum, 3 %). The strain was motile and positive for catalase, oxidase and H2S. It did not hydrolyse starch, casein or gelatin. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Val9T belonged to the genus Psychrobacillus and was closely related to Psychrobacillus psychrotolerans DSM 11706T (99.9 % similarity), Psychrobacillus psychrodurans DSM 11713T (99.8 %) and Psychrobacillus glaciei PB01T (99.2 %). Digital DNA-DNA hybridization and average nucleotide identity values were lower than 37.3 and 85.5 %, respectively, with the closest phylogenetic neighbours. The DNA G+C content of strain Val9T calculated from the complete genome sequence was 36.6 mol%. The predominant cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0 and anteiso-C17 : 1ω11c. Menaquinone-8 was the major respiratory quinone. The peptidoglycan type was A4ß l-Orn-d-glu. The novel strain contained diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol as predominant polar lipids. Based on 16S rRNA phylogenetic and multilocus sequence analyses (recA, rpoB and gyrB), as well as phylogenomic, chemotaxonomic and phenotypic tests, we demonstrate that strain Val9T represents a novel species of the genus Psychrobacillus, for which the name Psychrobacillus antarcticus sp. nov. is proposed. The type strain is Val9T (=DSM 115096T=CCGB 1952T=NRRL B-65674T).

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IMPORTANCE: Aerobic gammaproteobacterial methanotrophic bacteria (gMOB) play an important role in reducing methane emissions from freshwater ecosystems. In hypoxic conditions prevalent near oxic-anoxic interfaces, gMOB potentially shift their metabolism to fermentation, resulting in the conversion of methane to extracellular organic acids, which would serve as substrates for non-methanotrophic microbes. We intended to assess the prevalence of fermentation traits among freshwater gMOB. Therefore, we isolated two strains representing relevant freshwater gMOB genera, i.e., Methylovulum and Methylomonas, from boreal lakes, experimentally showed that they convert methane to organic acids and demonstrated via metagenomics that the fermentation potential is widely dispersed among lake and pond representatives of these genera. Combined with our recent study showing coherent results from another relevant freshwater gMOB genus, i.e., Methylobacter, we conclude that the conversion of methane to organic acids is a widely found trait among freshwater gMOB, highlighting their role as pivotal mediators of methane carbon into microbial food webs.

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An exopolysaccharide-producing bacterial strain GW4-15T, belonging to the genus Kaistella, was isolated from intertidal sediment from King George Island, Antarctic. The strain was Gram-stain-negative, aerobic, rod-shaped, non-motile and yellow-pigmented. The strain was able to grow in the presence of 0-2 % (w/v) NaCl (optimum, 0 %), at 4-30 °C (optimum, 20-28 °C) and at pH 5.0-10.0 (optimum, pH 8.0). A phylogenetic tree based on 16S rRNA gene sequences showed that strain GW4-15T formed a lineage within the genus Kaistella with the closest phylogenetic neighbours Kaistella carnis NCTC 13525T (98.3 %), Kaistella gelatinilytica G5-32T (97.7 %), Kaistella antarctica LMG 24720T (97.4 %) and Kaistella yonginensis HMD1043T (96.9 %). Digital DNA-DNA hybridization values of strain GW4-15T with K. carnis NCTC 13525T, K. antarctica LMG 24720T, K. gelatinilytica G5-32T and K. yonginensis HMD1043T were 22.8, 22.0, 21.7 and 21.6 %, respectively. The average nucleotide identity values between strain GW4-15T and K. carnis NCTC 13525T , K. antarctica LMG 24720T, K. gelatinilytica G5-32T and K. yonginensis HMD1043T were 79.3, 78.6, 77.5 and 77.2 %, respectively. The G+C content of the genome was 36.2 mol%. The major phospholipids were phosphatidylethanolamine and aminophospholipid. The predominant menaquinone was MK-6. The major fatty acids were anteiso-C15 : 0 (28.7 %), iso-C16 : 0 3-OH (15.7 %), iso-C16 : 0 H (10.0 %), iso-C16 : 0 (5.4 %), summed feature 9 (comprising iso-C17 : 1 ω9c and/or 10-methyl C16 : 0; 5.2 %) and iso-C15 : 0 (5.1 %). The monosaccharide composition of the new type of extracellular polymeric of GW4-15T was Glc, GalN, GlcN, Rha, Man and Gal with a molar ratio of 3.14 : 3.83 : 8.38 : 5.16 : 1 : 2.82. Based on phenotypic, phylogenetic and genotypic data, a novel species, Kaistella polysaccharea sp. nov., is proposed with the type strain GW4-15T (=CGMCC 1.19368T=KCTC 92753T).

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Cold-active lipases are presently employed extensively in the detergent, chemical intermediate, fine chemical, food, and pharmaceutical industries. Seven cold-adaptive bacteria were isolated from the Mediterranean Sea near Alexandria, Egypt, and tested for their ability to produce cold-active lipase, with the highest activity at 10 °C. The most potent isolate was Pseudomonas sp. A6. To determine the most important variables, the bacterium was exposed to a necessary medium component and environmental factor screening using a single factor-at-a-time approach, followed by a multifactorial Plackett-Burman design strategy. After purification and characterization, the optimal activity levels for the cold-active lipase were figured out. Inoculation of Pseudomonas A6 under near optimum conditions using medium consisting of (g/L) peptone 7.14; soybean oil 7.5% (v/v); K2HPO4, 0.4; MgSO4, 0.1; glucose 2; pH 8; and temperature 10 °C led to a maximum lipase activity anticipated to be 23.36 U/mL. Purified lipase showed the best activity and thermal stability at a pH of 8 and a temperature of 10 °C. The Pseudomonas A6 lipase tolerated the monovalent ions, while greater valence ions did not.

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A Continuously Stirred Tank Anaerobic Granular Reactor seeded with mesophilic biomass was studied for 1733 days analysing the impact of seasonal (12-23 °C) and controlled (8-15 °C) low temperatures on anaerobic treatment of sewage. Aided by intermittent dosing of 0.04% (v/v) methanol, the microbiota quickly adapted to temperature fluctuations. Chemical oxygen demand (COD) removal efficiency was high but low temperatures affected methane production. Under low-temperature stress, the Methanomythylovorans and Methanosaeta-dominated methanogenic community shifted focus to cellular repair and transport, with carbon diversion towards assimilative pathways, thereby decreasing methane yields. Specific methanogenic activity at 15 °C and 30 °C increased by five and four times, respectively, from their initial values indicating microbiota retained its mesophilic properties. Despite lower methane yield, stable and high COD removals, along with low dissolved methane and volatile fatty acids indicated that low-temperature anaerobic sewage treatment using mesophilic biomass in the long run is sustainable.

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BACKGROUND: Bacterial siderophores are chelating compounds with the potential of application in agriculture, due to their plant growth-promoting (PGP) properties, however, high production and purification costs are limiting factors for their wider application. Cost-efficiency of the production could be increased by omitting purification processes, especially since siderophores accompanying metabolites (SAM) often also possess PGP traits. In this study, the metabolism versatility of Pseudomonas sp. ANT_H12B was used for the optimization of siderophores production and the potential of these metabolites and SAM was characterized in the context of PGP properties. RESULTS: The metabolic diversity of ANT_H12B was examined through genomic analysis and phenotype microarrays. The strain was found to be able to use numerous C, N, P, and S sources, which allowed for the design of novel media suitable for efficient production of siderophores in the form of pyoverdine (223.50-512.60 µM). Moreover, depending on the culture medium, the pH of the siderophores and SAM solutions varied from acidic (pH < 5) to alkaline (pH > 8). In a germination test, siderophores and SAM were shown to have a positive effect on plants, with a significant increase in germination percentage observed in beetroot, pea, and tobacco. The PGP potential of SAM was further elucidated through GC/MS analysis, which revealed other compounds with PGP potential, such as indolic acetic acids, organic acids, fatty acids, sugars and alcohols. These compounds not only improved seed germination but could also potentially be beneficial for plant fitness and soil quality. CONCLUSIONS: Pseudomonas sp. ANT_H12B was presented as an efficient producer of siderophores and SAM which exhibit PGP potential. It was also shown that omitting downstream processes could not only limit the costs of siderophores production but also improve their agricultural potential.

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Here, we report the first complete genome of a psychrotolerant and yellow-pigmented rhizobacteria Chryseobacterium cucumeris PCH239. It was obtained from the rhizospheric soil of the Himalayan plant Bergenia ciliata. The genome consists of a single contig (5.098 Mb), 36.3% G + C content, and 4899 genes. The cold adaptation, stress response, and DNA repair genes promote survivability in a high-altitude environment. PCH239 grows in temperature (10-37 °C), pH (6.0-8.0), and NaCl (2.0%). The genome derived plant growth-promoting activities of siderophore production (siderophore units 53 ± 0.6), phosphate metabolism (PSI 5.0 ± 0.8), protease, indole acetic acid production (17.3 ± 0.5 µg/ml), and ammonia (2.89 ± 0.4 µmoles) were experimentally validated. Interestingly, PCH239 treatment of Arabidopsis seeds significantly enhances germination, primary, and hairy root growth. In contrast, Vigna radiata and Cicer arietinum seeds had healthy radicle and plumule elongation, suggesting varied plant growth-promotion effects. Our findings suggested the potential of PCH239 as a bio-fertilizer and biocontrol agent in the challenging conditions of cold and hilly regions.

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The nitrogen removal efficiency of heterotrophic nitrification and aerobic denitrification (HN-AD) bacteria can be seriously inhibited at low temperatures (< 15 °C). A novel psychrotolerant bacterium, Pseudomonas peli NR-5 (P. peli NR-5), with efficient HN-AD capability was isolated and screened from river sediments in cold areas. When P. peli NR-5 was aerobically cultivated for 60 h at 10 °C with NH4+-N, NO3--N, and NO2--N as the sole nitrogen sources (N 105 mg/L), the nitrogen removal efficiencies were 97.3, 95.3, and 87.8%, respectively, without nitrite accumulation, and the corresponding average nitrogen removal rates were 1.71, 1.67, and 1.55 mg/L/h, respectively. Meanwhile, P. peli NR-5 exhibited excellent simultaneous nitrification and denitrification capabilities at 10 °C. Sodium succinate was the most favorable carbon substrate for bacterial growth and ammonia removal by strain NR-5. The optimal culture conditions determined by the response surface methodology model were a carbon to nitrogen ratio of 5.9, temperature of 11.5 °C, pH of 7.0, and shaking speed of 144 rpm. Under these conditions, 99.1% of the total nitrogen was removed in the verification experiments, which was not significantly different from the predicted maximum removal in the model (99.6%). Six functional genes participating in the HN-AD process were successfully obtained by polymerase chain reaction amplification, which further confirmed the HN-AD capability of P. peli NR-5 and proposed the metabolic pathway of HN-AD. The above results provide a theoretical background of psychrotolerant HN-AD bacteria in wastewater purification under low-temperature conditions.

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Exploration of the novel species of the genus Paenibacillus with plant-growth promoting characteristics at the low-temperature environment is of great significance for the development of psychrotolerant biofertilizer in forestry and agriculture. During the course of isolation of root endophytes of Larix gmelinii in the island frozen soil, three strains designated as T3-5-0-4, N1-5-1-14 and N5-1-1-5 were isolated. The three strains showed plant growth-promoting properties at the low temperature, such as phosphate solubilization, indole-3-acetic acid biosynthesis and siderophore production. According to pairwise sequence analyses of the 16S rRNA genes, the three strains represent putatively novel taxa within the genus Paenibacillus. The strains have typical chemotaxonomic characteristics of the genus Paenibacillus by having meso-diaminopimelic acid as diagnostic diamino acid, anteiso-C15:0 as the predominant fatty acid and MK-7 as the predominant menaquinone. The polar lipid profiles of all strains contained diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The sizes of the genomes of the stains ranged from 5.66 to 9.07 Mb and the associated G+C contents ranged from 37.9% to 44.7%. Polyphasic taxonomic study including determination of genome relatedness indices revealed that the strains are representatives of three novel species in the genus Paenibacillus. Consequently, isolates T3-5-0-4, N1-5-1-14 and N5-1-1-5 are proposed as novel species for which the names of Paenibacillus endoradicis sp. nov. (CFCC15691T = KCTC43441T), Paenibacillus radicibacter sp. nov, (CFCC15694T = KCTC43442T) and Paenibacillus radicis sp. nov. (CFCC15710T = KCTC43173T), respectively. Moreover, analysis for biosynthetic genes showed that the strains have potential for plant growth-promoting characteristics, plant rhizospheres colonization and low-temperature adaption, most of which are consistent with the results of the bioactivity test.

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The impact of temperature on the biological removal of hydrogen sulfide (H2S) from air is critical to its effective application in cold regions or seasons. This study investigated the effect of seasonal temperature variations (7-30 °C) on the H2S removal performance of a biotrickling filter system, with an effective H2S elimination capacity of 98.1 g/m3/h (removal efficiency = 83.1 %) achieved at temperatures of 10-12 °C. Biofilm growth was found to be accelerated by increased secretion of extracellular polymeric substances, enhanced biofilm adhesion capacity and relatively high levels of elemental sulfur accumulation, which help to retain heat within the filter bed under cold conditions. High-throughput sequencing showed that the psychrotolerant sulfur-oxidizing bacterium (SOB) Metallibacterium was gradually enriched (54.8 %) at temperatures below 15 °C. The major pathways of sulfur metabolism under low temperature conditions were determined based on the detection of enzymes related to sulfur metabolism. Finally, a strategy to enrich Metallibacterium was proposed to promote the application of biodesulfurization under low temperature conditions.

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BACKGROUND: Rice straw (RS) is one of the largest sources of lignocellulosic, which is an abundant raw material for biofuels and chemicals. However, the natural degradation of RS under a low temperature environment is the biggest obstacle to returning straw to the field. RESULTS: In the present study, one bacillus strain W118 was isolated. Strain W118 was identified as Bacillus cereus through morphological and physiological characterization and 16S rDNA sequencing. The optimum growth temperature and pH of strain W118 were 20 °C and 6.5, respectively. Simultaneously, it was found that the strain W118 grew well at low temperature, even at a temperature of 4 °C (OD600  = 1.40 ± 0.01). The decrease of various compositions of RS after the fermentation process at a temperature of 20 °C and 4 °C for 14 days was 27.00 ± 0.02% and 23.70 ± 0.04%, respectively. The composition of RS decreased to 50.71 ± 0.02% after being fermented at 4 °C for 25 days. The results of scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction of RS showed that the compositions of RS were significant decreased. CONCLUSION: This test suggests that the strain W118 is efficient for degrading RS at low temperature, which has great application potential for straw degradation in a low temperature area. © 2022 Society of Chemical Industry.

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Yeasts provide attractive host/vector systems for heterologous gene expression. The currently used yeast-based expression platforms include mesophilic and thermotolerant species. A eukaryotic expression system working at low temperatures could be particularly useful for the production of thermolabile proteins and proteins that tend to form insoluble aggregates. For this purpose, an expression system based on an Antarctic psychrotolerant yeast Debaryomyces macquariensis strain D50 that is capable of growing at temperatures ranging from 0 to 30 °C has been developed. The optimal physical culture conditions for D. macquariensis D50 in a fermenter are as follows: temperature 20 °C, pH 5.5, aeration rate of 1.5 vvm, and a stirring speed of 300 rpm. Four integrative plasmid vectors equipped with an expression cassette containing the constitutive GAP promoter and CYC1 transcriptional terminator from D. macquariensis D50 were constructed and used to clone and express a gene-encoding cold-active ß-d-galactosidase of Paracoccus sp. 32d. The yield was 1150 U/L of recombinant yeast culture. Recombinant D. macquariensis D50 strains were mitotically stable under both selective and non-selective conditions. The D. macquariensis D50 host/vector system has been successfully utilized for the synthesis of heterologous thermolabile protein, and it can be an alternative to other microbial expression systems.

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Perchlorate is a contaminant that can persist in groundwater and soil, and is frequently detected in different ecosystems at concentrations relevant to human health. This study isolated and characterised halotolerant bacteria that can potentially perform perchlorate reduction. Bacterial microorganisms were isolated from marine sediments on Deception, Horseshoe and Half Moon Islands of Antarctica. The results of the 16S ribosomal RNA (rRNA) gene sequence analysis indicated that the isolates were phylogenetically related to Psychrobacter cryohalolentis, Psychrobacter urativorans, Idiomarina loihiensis, Psychrobacter nivimaris, Sporosarcina aquimarina and Pseudomonas lactis. The isolates grew at a sodium chloride concentration of up to 30% and a perchlorate concentration of up to 10,000 mg/L, which showed their ability to survive in saline conditions and high perchlorate concentrations. Between 21.6 and 40% of perchlorate was degraded by the isolated bacteria. P. cryohalolentis and P. urativorans degraded 30.3% and 32.6% of perchlorate, respectively. I. loihiensis degraded 40% of perchlorate, and P. nivimaris, S. aquimarina and P. lactis degraded 22%, 21.8% and 21.6% of perchlorate, respectively. I. loihiensis had the highest reduction in perchlorate, whereas P. lactis had the lowest reduction. This study is significant as it is the first finding of P. cryohalolentis and. P. lactis on the Antarctic continent. In conclusion, these bacteria isolated from marine sediments on Antarctica offer promising resources for the bioremediation of perchlorate contamination due to their ability to degrade perchlorate, showing their potential use as a biological system to reduce perchlorate in high-salinity ecosystems.

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