Solid medium for the direct isolation of bacterial colonies growing with polycyclic aromatic hydrocarbons or 2,4,6-trinitrotoluene (TNT)

Pseudomonas and Pseudarthrobacter are the key players in synergistic phenanthrene biodegradation at low temperatures

Hydrocarbon contamination, including contamination with polycyclic aromatic hydrocarbons (PAHs), is a major concern in Antarctica due to the toxicity, recalcitrance and persistence of these compounds. Under the Antarctic Treaty, nonindigenous species are not permitted for use in bioremediation at polluted sites in the Antarctic region. In this study, three bacterial consortia (C13, C15, and C23) were isolated from Antarctic soils for phenanthrene degradation. All isolated bacterial consortia demonstrated phenanthrene degradation percentages ranging from 45 to 85% for 50 mg/L phenanthrene at 15 ℃ within 5 days. Furthermore, consortium C13 exhibited efficient phenanthrene degradation potential across a wide range of environmental conditions, including different temperature (4-30 ℃) and water availability (without polyethylene glycol (PEG) 6000 or 30% PEG 6000 (w/v)) conditions. Sequencing analysis of 16S rRNA genes revealed that Pseudomonas and Pseudarthrobacter were the dominant genera in the phenanthrene-degrading consortia. Moreover, six cultivable strains were isolated from these consortia, comprising four strains of Pseudomonas, one strain of Pseudarthrobacter, and one strain of Paeniglutamicibacter. These isolated strains exhibited the ability to degrade 50 mg/L phenanthrene, with degradation percentages ranging from 4 to 22% at 15 ℃ within 15 days. Additionally, the constructed consortia containing Pseudomonas spp. and Pseudarthrobacter sp. exhibited more effective phenanthrene degradation (43-52%) than did the individual strains. These results provide evidence that Pseudomonas and Pseudarthrobacter can be potential candidates for synergistic phenanthrene degradation at low temperatures. Overall, our study offers valuable information for the bioremediation of PAH contamination in Antarctic environments.

Pseudomonas violetae sp. nov. and Pseudomonas emilianonis sp. nov., two new species with the ability to degrade TNT isolated from soil samples at Deception Island, maritime Antarctica

Two motile, rod-shaped, Gram-stain-negative bacterial strains, TNT11T and TNT19T, were isolated from soil samples collected at Deception Island, Antarctica. According to the 16S rRNA gene sequence similarity, both strains belong to the genus Pseudomonas. Further genomic analyses based on ANI and dDDH suggested that these strains were new species. Growth of strain TNT11T is observed at 0-30 ℃ (optimum, 20 ℃), pH 4.0-9.0 (optimum, pH 6.0) and in the presence of 0-5.0% NaCl (optimum, 1% NaCl), while for TNT19T is observed at 0-30 ℃ (optimum between 15 and 20 ℃), pH 5.0-9.0 (optimum, pH 6.0) and in the presence of 0-5.0% NaCl (optimum between 0 and 1% NaCl). The fatty acid profile consists of the major compounds; C16:0 and C16:1 ω6 for TNT11T, and C16:0 and C12:0 for TNT19T. Based on the draft genome sequences, the DNA G + C content for TNT11T is 60.43 mol% and 58.60 mol% for TNT19T. Based on this polyphasic study, TNT11T and TNT19T represent two novel species of the genus Pseudomonas, for which the proposed names are Pseudomonas violetae sp. nov. and Pseudomonas emilianonis sp. nov., respectively. The type strains are Pseudomonas violetae TNT11T (= RGM 3443T = LMG 32959T) and Pseudomonas emilianonis TNT19T (= RGM 3442T = LMG 32960T). Strains TNT11T and TNT19T were deposited to CChRGM and BCCM/LMG with entry numbers RGM 3443/LMG 32959 and RGM 3442/LMG 32960, respectively.

Arthrobacter vasquezii sp. nov., isolated from a soil sample from Union Glacier, Antarctica

A Gram-stain-positive, catalase-positive, non-motile bacteria, with a rod-coccus cycle (designated as EH-1B-1T) was isolated from a soil sample from Union Glacier in Ellsworth Mountains, Antarctica. Strain EH-1B-1T had an optimal growth temperature of 28 °C and grew at pH 7-10. The major cellular fatty acids were anteiso-C15 : 0, iso-C15 : 0, C16 : 0 and anteiso-C17 : 0. The G+C content based on the whole genome sequence was 63.1 mol%. Strain EH-1B-1T was most closely related to members of the genus Arthrobacter, namely Arthrobacter subterraneus and Arthrobacter tumbae. The strain grew on tryptic soy agar, Reasoner's 2A agar, lysogeny broth agar and nutrient agar. The average nucleotide identity and digital DNA-DNA hybridization values between strain EH-1B-1T and its closest reference type strains ranged from 78 to 88 % and from 20.9 to 36.3 %, respectively. Based on phenotypic, chemotypic and genotypic evidence, it is proposed that strain EH-1B-1T represents a novel species of Arthrobacter, for which the name Arthrobacter vasquezii sp. nov. is proposed, with strain EH-1B-1T (RGM 3386T=LMG 32961T) as the type strain.