Chemoorganotrophic Bacteria From Lake Fryxell, Antarctica, Including Pseudomonas Strain LFY10, a Cold-Adapted, Halotolerant Bacterium Useful in Teaching Labs

Complete genome sequence data of an Antarctic bacterium Arthrobacter sp. EM1 from the freshwater lake of the King George Island

Arthrobacter sp. EM1 is a cold-adapted bacterium isolated from the Antarctic region, which was known to exhibit mannan-degrading activity. Accordingly, this strain not only promises a cell factory for mannan-degrading enzymes, widely used in industry but also serves as a model organism to decipher its cold adaptation mechanism. Accordingly, whole genome sequencing of the EM1 strain was performed via Single Molecule Real Time sequencing under the PacBio platform, followed by genome HGAP de novo assembly and genome annotation through Rapid Annotation System Technology (RAST) server. The chromosome of this strain is 3,885,750 bp in size with a GC content of 65.8. The annotation predicted a total of 3607 protein-coding genes and 65 RNA genes, which were classified under 398 subsystems. The subsystem with the highest number of genes is carbohydrate metabolism (397 genes), which includes two genes encoding mannan-degrading enzymes (endoglucanase and α-mannosidase). This confirmed that the EM1 strain is able to produce cold-adapted mannan degrading enzymes. The complete genome sequence data have been submitted to the National Center for Biotechnology Information (NCBI) and have been deposited at GenBank (Bioproject ID Accession Number: PRJNA963062; Biosample ID Accession Number: SAMN34434776; GenBank: CP124836.1; https://www.ncbi.nlm.nih.gov/nuccore/CP124836).

Efficacy of organic peroxyacids for eliminating biofilm preformed by microorganisms isolated from dairy processing plants

The aim of this study was to evaluate the ability of microorganisms isolated from the dairy industry to form biofilms and to investigate the efficacity of organic peroxyacids (peracetic, perpropionic and perlactic acids and BioDestroy®) to eradicate those biofilms. Eighteen microorganisms were isolated from Quebec dairy processing plants that have issues associated with biofilm formation and were presumptively identified by MALDI-TOF mass spectrometry. The single-species biofilm-producing ability of the isolates was then evaluated using 96-well microplates. Eight out of eighteen (8/18) of these isolates were identified as moderate or strong biofilm producers, and ten out of eighteen (10/18) resulted as negative or weak biofilm producers. The efficacy of above-mentioned disinfectants was tested on the stronger biofilm producing bacteria using the MBEC (Minimum Biofilm Eradication Concentration) assay. After 5 min, all the disinfectants tested successfully eradicated both the single and mixed biofilms when applied following the recommended concentration. However, the efficacy of organic peroxyacids was significantly variable at lower concentrations. For example, 25 ppm of BioDestroy® were sufficient to eradicate all the biofilms, except for Pseudomonas azotoformans PFl1A. Unfortunately, microscopic observations highlighted those dead cells were still attached to the surfaces. In conclusion, our results suggest that some microorganisms found in dairy plants can produce tenacious biofilms that are, however, still susceptible to disinfectants, including organic peroxyacids. Further studies would be needed in order to confirm these observations using a dynamic method to mimic in vivo conditions. IMPORTANCE Biofilm forming microorganisms are a major issue in the food industry, including dairy industry, because of their negative impact on products quality. Biofilms are difficult to remove by clean-in-place (CIP) procedures commonly used in processing plants and may be less sensitive to sanitizers. Therefore, it is important to identify these microorganisms, in order to develop biofilm control strategies. The results gathered in the present study could contribute to this aim, even though it was carried out using only static methods.

Cultivation and characterization of snowbound microorganisms from the South Pole

Little is known about microbial ecosystems of interior Antarctica, if indeed such ecosystems exist. Although considerable research has assessed microorganisms indigenous to coastal regions of Antarctica, particularly their lakes, ponds, and soils, to our knowledge only one characterized bacterium, a strain of Pseudomonas, has been isolated from South Pole ice or snow. Metagenomic community analyses described in this work and elsewhere reveal that a diversity of bacteria exists in inland polar snows, yet attempts to culture and characterize these microbes from this extreme environment have been few to date. In this molecular and culture-dependent investigation of the microbiology of inland Antarctica, we enriched and isolated two new strains of bacteria and one strain of yeast (Fungi) from South Pole snow samples. The bacteria were of the genera Methylobacterium and Sphingomonas, and the yeast grouped with species of Naganishia (class Tremellocytes). In addition to phylogenetic analyses, characterization of these isolates included determinations of cell morphology, growth as a function of temperature, salinity tolerance, and carbon and energy source versatility. All organisms were found to be cold-adapted, and the yeast strain additionally showed considerable halotolerance. These descriptions expand our understanding of the diversity and metabolic activities of snowbound microorganisms of interior Antarctica.

Pseudarthrobacter psychrotolerans sp. nov., a cold-adapted bacterium isolated from Antarctic soil

A novel cold-tolerant bacterium, designated strain YJ56T, was isolated from Antarctic soil collected from the Cape Burk area. Phylogenetic analysis through 16S rRNA gene sequence similarity revealed that strain YJ56T was most closely related to the genus Pseudarthrobacter , including Pseudarthrobacter oxydans DSM 20119T (99.06 % similarity), Pseudarthrobacter polychromogenes DSM 20136T (98.98 %) and Pseudarthrobacter sulfonivorans ALLT (98.76 %). The genome size (5.2 Mbp) of strain YJ56T was the largest among all the published genomes of Pseudarthrobacter type strains (4.2–5.0 Mbp). The genomic G+C content of strain YJ56T (64.7 mol%) was found to be consistent with those of other Pseudarthrobacter strains (62.0–71.0 mol%). The average nucleotide identity and average amino acid identity values between strain YJ56T and P. sulfonivorans ALLT were estimated at 84.1 and 84.2 %, respectively. The digital DNA–DNA hybridization value between the two strains was calculated to be 28.0 %. This rod-shaped and obligate aerobic strain exhibited no swimming or swarming motility. It had catalase activity but no oxidase activity. Cells grew at 4–28 °C (optimum, 13 °C) and pH 5.0–11.0 (optimum, pH 7.0) and with 0–6.0 % (w/v) NaCl (optimum, 0%) in Reasoner's 2A medium. MK-9 (H2) was the sole menaquinone. Two-dimensional TLC results revealed that the primary polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two glycolipids and phosphatidylinositol. Fatty acid methyl ester analysis showed that anteiso-C15 : 0, anteiso-C17 : 0, iso-C15 : 0, C16 : 0 and iso-C16 : 0 were the major cellular fatty acids in strain YJ56T. Based on phenotypic and genotypic characteristics, strain YJ56T represents a novel species of the genus Pseudarthrobacter , and thus the name Pseudarthrobacter psychrotolerans sp. nov is proposed. The type strain is YJ56T (=JCM 33881T=KACC 21510T).

Cultivable Bacterial Communities in Brines from Perennially Ice-Covered and Pristine Antarctic Lakes: Ecological and Biotechnological Implications

The diversity and biotechnological potentialities of bacterial isolates from brines of three Antarctic lakes of the Northern Victoria Land (namely Boulder Clay and Tarn Flat areas) were first explored. Cultivable bacterial communities were analysed mainly in terms of bacterial response to contaminants (i.e., antibiotics and heavy metals) and oxidation of contaminants (i.e., aliphatic and aromatic hydrocarbons and polychlorobiphenyls). Moreover, the biosynthesis of biomolecules (antibiotics, extracellular polymeric substances and enzymes) with applications for human health and environmental protection was assayed. A total of 74 and 141 isolates were retrieved from Boulder Clay and Tarn Flat brines, respectively. Based on 16S rRNA gene sequence similarities, bacterial isolates represented three phyla, namely Proteobacteria (i.e., Gamma- and Alphaproteobacteria), Bacteroidetes and Actinobacteria, with differences encountered among brines. At genus level, Rhodobacter, Pseudomonas, Psychrobacter and Leifsonia members were dominant. Results obtained from this study on the physiological and enzymatic features of cold-adapted isolates from Antarctic lake brines provide interesting prospects for possible applications in the biotechnological field through future targeted surveys. Finally, findings on contaminant occurrence and bacterial response suggest that bacteria might be used as bioindicators for tracking human footprints in these remote polar areas.