Complete genome sequence of Psychrobacter cibarius AOSW16051, a trimeric autotransporter adhesin synthesizing bacterium isolated from the Baltic Sea.

Bacteria of the genus Psychrobacter are widely distributed in the global low-temperature marine environment and have been studied for their effects on the settlement and metamorphosis of marine invertebrates. Psychrobacter cibarius AOSW16051 was isolated from the surface water samples of the Baltic Sea on the edge of the Arctic Ocean. Here, we present the complete genome of strain AOSW16051, which consists of a circular chromosome composed of 3,425,040 nucleotides with 42.98% G + C content and a circular plasmid composed of 5846 nucleotides with 38.66% G + C content. The genes predicted in this strain showed its strong outer membrane system, type VI secretion system and adhesion system. Trimeric autotransporter adhesins (TAAs) has been identified in the genome of P. cibarius AOSW16051, which has a variety of biological functions in interacting with host cells. However, there are no reports on TAAs in marine bacteria and aquatic pathogenic bacteria. By analyzing the genomic data, we can gain valuable insights to enhance our understanding of the physiological characteristics of P. cibarius, as well as the biological functions of TAAs and their role in triggering metamorphosis of invertebrate larvae.

Silicone-geranium essential oil blend for long-term antifouling coatings.

This study explores the potential of geranium essential oil as a natural solution for combating marine biofouling, addressing the environmental concerns associated with commercial antifouling coatings. Compounds with bactericidal activities were identified by 13Carbon nuclear magnetic resonance (13C NMR). Thermogravimetric analysis (TGA) revealed minimal impact on film thermal stability, maintaining suitability for antifouling applications. The addition of essential oil induced changes in the morphology of the film and Fourier transform infrared spectroscopy (FTIR) analysis indicated that oil remained within the film. Optical microscopy showed an increase in coating porosity after immersion in a marine environment. A total of 18 bacterial colonies were isolated, with Psychrobacter adeliensis and Shewanella algidipiscicola being the predominant biofilm-forming species. The geranium essential oil-based coating demonstrated the ability to reduce the formation of Psychrobacter adeliensis biofilms and effectively inhibit macrofouling adhesion for a duration of 11 months.

A new family of bacterial ribosome hibernation factors.

To conserve energy during starvation and stress, many organisms use hibernation factor proteins to inhibit protein synthesis and protect their ribosomes from damage1,2. In bacteria, two families of hibernation factors have been described, but the low conservation of these proteins and the huge diversity of species, habitats and environmental stressors have confounded their discovery3-6. Here, by combining cryogenic electron microscopy, genetics and biochemistry, we identify Balon, a new hibernation factor in the cold-adapted bacterium Psychrobacter urativorans. We show that Balon is a distant homologue of the archaeo-eukaryotic translation factor aeRF1 and is found in 20% of representative bacteria. During cold shock or stationary phase, Balon occupies the ribosomal A site in both vacant and actively translating ribosomes in complex with EF-Tu, highlighting an unexpected role for EF-Tu in the cellular stress response. Unlike typical A-site substrates, Balon binds to ribosomes in an mRNA-independent manner, initiating a new mode of ribosome hibernation that can commence while ribosomes are still engaged in protein synthesis. Our work suggests that Balon-EF-Tu-regulated ribosome hibernation is a ubiquitous bacterial stress-response mechanism, and we demonstrate that putative Balon homologues in Mycobacteria bind to ribosomes in a similar fashion. This finding calls for a revision of the current model of ribosome hibernation inferred from common model organisms and holds numerous implications for how we understand and study ribosome hibernation.

Psychrobacter species enrichment as potential microplastic degrader and the putative biodegradation mechanism in Shenzhen Bay sediment, China.

Microplastic (MP) pollution has emerged as a pressing environmental concern due to its ubiquity and longevity. Biodegradation of MPs has garnered significant attention in combatting global MP contamination. This study focused on MPs within sediments near the sewage outlet of Shenzhen Bay. The objective was to elucidate the microbial communities in sediments with varying MPs, particularly those with high MP loads, and to identify microorganisms associated with MP degradation. The results revealed varying MP abundance, ranging from 211 to 4140 items kg-1 dry weight (d. w.), with the highest concentration observed near the outfall. Metagenomic analysis confirmed the enrichment of Psychrobacter species in sediments with high MP content. Psychrobacter accounted for ∼16.71% of the total bacterial community and 41.71% of hydrocarbon degrading bacteria at the S3 site, exhibiting a higher abundance than at other sampling sites. Psychrobacter contributed significantly to bacterial function at S3, as evidenced by the Kyoto Encyclopedia of Genes and Genomes pathway and enzyme analysis. Notably, 28 enzymes involved in MP biodegradation were identified, predominantly comprising oxidoreductases, hydrolases, transferases, ligases, lyases, and isomerases. We propose a putative mechanism for MP biodegradation, involving the breakdown of long-chain plastic polymers and subsequent oxidation of short-chain oligomers, ultimately leading to thorough mineralization.

Heterologous protein production using Psychrobacter sp. PAMC 21119 analyzed with a green fluorescent protein-based reporter system.

Insolubility and low expression are typical bottlenecks in the production of proteins for studying their function and structure using X-ray crystallography or nuclear magnetic resonance spectroscopy. Cold-active enzymes from polar microorganisms have unique structural features that render them unstable and thermolabile, and are responsible for decreased protein yield in heterologous expression systems. To address these challenges, we developed a heterologous protein expression system using a psychrophilic organism, Psychrobacter sp. PAMC 21119, as a protein expression host with its own promoter. We screened 11 promoters and evaluated their strength using quantitative real-time polymerase chain reaction and a reporter system harboring the SfGFP gene. The highest expression was achieved using promoters RH96_RS13655 (P21119_20930) and RH96_RS15090 (P21119_23410), regardless of the temperature used. The p20930 strain exhibited a maximum expression level 19.6-fold higher than that of its control at 20 °C and produced approximately 0.5 mg of protein per gram of dry cell weight. To our knowledge, this is the first report of a low-temperature recombinant protein expression system developed using Psychrobacter sp. that can be used to express various difficult-to-express and cold-active proteins.

Phylogenomics-based reclassifications in the genus Psychrobacter including emended descriptions of Psychrobacter pacificensis, Psychrobacter proteolyticus and Psychrobacter submarinus.

The taxonomic status of 43 Psychrobacter species was examined based upon the genome sequences of their type strains. Three groups of type strains were found to be conspecific, Psychrobacter salsus Shivaji et al. (Syst Appl Microbiol 27:628-635, 2004. 10.1078/0723202042369956) and Psychrobacter submarinus Romanenko et al. (Int J Syst Evol Microbiol 52:1291-1297, 2002. 10.1099/00207713-52-4-1291); Psychrobacter oceani Matsuyama et al. (Int J Syst Evol Microbiol 65:1450-1455, 2015. 10.1099/ijs.0.000118) and Psychrobacter pacificensis Maruyama et al. (Int J Syst Evol Microbiol 50:835-846, 2000. 10.1099/00207713-50-2-835); and Psychrobacter proteolyticus Denner et al. (Syst Appl Microbiol 24:44-53, 2001. 10.1078/0723-2020-00006), Psychrobacter marincola Romanenko et al. (Int J Syst Evol Microbiol 52:1291-1297, 2002. 10.1099/00207713-52-4-1291) and Psychrobacter adeliensis Shivaji et al. (Syst Appl Microbiol 27:628-635, 2004. 10.1078/0723202042369956). For all three groups, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values are > 97.69% and > 80.2%, respectively. This conclusion is supported by similarities in morphology, growth properties, and fatty acid compositions. Based on this evidence, we propose the reclassification of Psychrobacter salsus Shivaji et al. (Syst Appl Microbiol 27:628-635, 2004. 10.1078/0723202042369956) as a later heterotypic synonym of Psychrobacter submarinus Romanenko et al. (Int J Syst Evol Microbiol 52:1291-1297, 2002. 10.1099/00207713-52-4-1291); Psychrobacter oceani Matsuyama et al. (Int J Syst Evol Microbiol 65:1450-1455, 2015. 10.1099/ijs.0.000118) as a later heterotypic synonym of Psychrobacter pacificensis Maruyama et al. (Int J Syst Evol Microbiol 50:835-846, 2000. 10.1099/00207713-50-2-835), and Psychrobacter marincola Romanenko et al. (Int J Syst Evol Microbiol 52:1291-1297, 2002. 10.1099/00207713-52-4-1291) and Psychrobacter adeliensis Shivaji et al. (Syst Appl Microbiol 27:628-635, 2004. 10.1078/0723202042369956) as later heterotypic synonyms of Psychrobacter proteolyticus Denner et al. (Syst Appl Microbiol 24:44-53, 2001. 10.1078/0723-2020-00006).

Psychrobacter Phage Encoding an Antibiotics Resistance Gene Represents a Novel Caudoviral Family.

Psychrobacter is an important bacterial genus that is widespread in Antarctic and marine environments. However, to date, only two complete Psychrobacter phage sequences have been deposited in the NCBI database. Here, the novel Psychrobacter phage vB_PmaS_Y8A, infecting Psychrobacter HM08A, was isolated from sewage in the Qingdao area, China. The morphology of vB_PmaS_Y8A was characterized by transmission electron microscopy, revealing an icosahedral head and long tail. The genomic sequence of vB_PmaS_Y8A is linear, double-stranded DNA with a length of 40,226 bp and 44.1% G+C content, and encodes 69 putative open reading frames. Two auxiliary metabolic genes (AMGs) were identified, encoding phosphoadenosine phosphosulfate reductase and MarR protein. The first AMG uses thioredoxin as an electron donor for the reduction of phosphoadenosine phosphosulfate to phosphoadenosine phosphate. MarR regulates multiple antibiotic resistance mechanisms in Escherichia coli and is rarely found in viruses. No tRNA genes were identified and no lysogeny-related feature genes were detected. However, many similar open reading frames (ORFs) were found in the host genome, which may indicate that Y8A also has a lysogenic stage. Phylogenetic analysis based on the amino acid sequences of whole genomes and comparative genomic analysis indicate that vB_PmaS_Y8A contains a novel genomic architecture similar only to that of Psychrobacter phage pOW20-A, although at a low similarity. vB_PmaS_Y8A represents a new family-level virus cluster with 22 metagenomic assembled viral genomes, here named Minviridae. IMPORTANCE Although Psychrobacter is a well-known and important bacterial genus that is widespread in Antarctic and marine environments, genetic characterization of its phages is still rare. This study describes a novel Psychrobacter phage containing an uncharacterized antibiotic resistance gene and representing a new virus family, Minviridae. The characterization provided here will bolster current understanding of genomes, diversity, evolution, and phage-host interactions in Psychrobacter populations.

Structure and functions of a multireplicon genome of Antarctic Psychrobacter sp. ANT_H3: characterization of the genetic modules suitable for the construction of the plasmid-vectors for cold-active bacteria.

Among Psychrobacter spp., there are several multireplicon strains, carrying more than two plasmids. Psychrobacter sp. ANT_H3 carries as many as 11 extrachromosomal replicons, which is the highest number in Psychrobacter spp. Plasmids of this strain were subjected to detailed genomic analysis, which enables an insight into the structure and functioning of this multireplicon genome. The replication and conjugal transfer modules of ANT_H3 plasmids were analyzed functionally to discover their potential for being used as building blocks for the construction of novel plasmid-vectors for cold-active bacteria. It was shown that two plasmids have a narrow host range as they were not able to replicate in species other than Psychrobacter, while remaining plasmids had a wider host range and were functional in various Alpha- and Gammaproteobacteria. Moreover, it was confirmed that mobilization modules of seven plasmids were functional, i.e., could be mobilized for conjugal transfer by the RK2 conjugation system. Auxiliary genes were also distinguished in ANT_H3 plasmids, including these encoding putative DNA-protecting protein DprA, multidrug efflux SMR transporter of EmrE family, glycine cleavage system T protein, MscS small-conductance mechanosensitive channel protein, and two type II restriction-modification systems. Finally, all genome-retrieved plasmids of Psychrobacter spp. were subjected to complex genome- and proteome-based comparative analyses showing that Antarctic replicons are significantly different from plasmids from other locations.

Detection and description of a novel Psychrobacter glacincola infection in some Red Sea marine fishes in Hurghada, Egypt.

An important food-producing sector in Egypt is aquaculture and fisheries; however, several pathogenic microorganisms lead to high mortalities and significant economic losses. The occurrence of Psychrobacter glacincola infection among 180 wild marine fishes collected from the Red sea at Hurghada, Egypt were investigated in the present study. The disease prevalence rate was 6.7%. The recovered isolates were subjected to biochemical and molecular identification. The study also investigated pathogenicity and the antibiogram profile of the recovered isolates. The clinical examination of the infected fish revealed various signs that included lethargy and sluggish movement, hemorrhages and ulcers on the body and the operculum, scale loss, and fin congestion and rot, especially at the tail fin. Furthermore, during postmortem examination, congestion of the liver, spleen, and kidney was observed. Interestingly, 12 isolates were recovered and were homogenous bacteriologically and biochemically. The phylogenetic analysis based on 16S rRNA gene confirmed that MRB62 identified strain was closely related the genus Psychrobacter and identified as P. glacincola and was pathogenic to Rhabdosargus haffara fish, causing 23.3% mortality combined with reporting a series of clinical signs similar to that found in naturally infected fishes. The present study also showed that P. glacincola isolates were sensitive to all antibiotics used for sensitivity testing. Our findings add to the body of knowledge regarding the occurrence of pathogenic P. glacincola infection in Egyptian marine fishes and its potential effects on fish. Future large-scale surveys exploring this bacterium among other freshwater and marine fishes in Egypt would be helpful for the implementation of effective strategies for the prevention and control of this infection are warranted.

Effects of the Probiotic Psychrobacter sp. B6 on the Growth, Digestive Enzymes, Antioxidant Capacity, Immunity, and Resistance of Exopalaemon carinicauda to Aeromonas hydrophila.

Probiotics, known to improve the water quality and the host's intestinal microbial balance, has gained more and more attention in recent years. The effects of Psychrobacter sp. B6 on the growth and immunity of Exopalaemon carinicauda were investigated in this study. Psychrobacter sp. B6 was sprayed to the basal diet with four different levels (0 [basal diet], 5 × 105, 5 × 107, and 5 × 109 CFU/100 g diet) and were fed to E. carinicauda (average weight 1.15 ± 0.04 g) for 30 days. At the end of the feeding trial, shrimps were immersed in seawater contaminated with 106 CFU/mL pathogenic Aeromonas hydrophila for 2 h and then the cumulative mortality was calculated after 14 days observation. The results showed that the weight gain rate, survival rate, and specific growth rate of E. carinicauda were significantly increased with the increasing dietary level of Psychrobacter sp. B6. The activities of digestive enzymes (α-amylase and chymotrypsin) were significantly increased (P < 0.05) in the groups fed with Psychrobacter sp. B6, and the highest activities of digestive enzymes were detected in the 5 × 109 CFU/100 g diet group. The activities of antioxidant enzymes (catalase, peroxidase, and superoxide dismutase) in probiotics treated shrimp were significantly higher than those in the control shrimp, with the highest activity in 5 × 109 and 5 × 107 CFU/100 g diet group separately. At the same time, the activities of immune-related enzymes (alkaline phosphatase and lysozyme) were significantly affected by the dietary B6 content, and the highest activity of immune-related enzymes was found in shrimps fed with 5 × 107 CFU/100 g diet. The relative expression levels of CTL (C-type lectin), MBL (mannose-binding lectin), SPI (serine protease inhibitor), and ProPo (prophenoloxidase) in hepatopancreas of E. carinicauda with 5 × 109 CFU/100 g diet were significantly higher than those in the control. Moreover, cumulative mortality (22.22%) post-challenge with A. hydrophila was the lowest in 5 × 109 CFU/100 g diet. The results suggested that Psychrobacter sp. B6 could effectively promote the growth, immunity, antioxidant capacity, and disease resistance of E. carinicauda. This study provided a reference for the study on the artificial breeding of E. carinicauda.

A Plasmid-Borne Gene Cluster Flanked by Two Restriction-Modification Systems Enables an Arctic Strain of Psychrobacter sp. to Decompose SDS.

The cold-adapted Psychrobacter sp. strain DAB_AL62B, isolated from ornithogenic deposits on the Arctic island of Spitsbergen, harbors a 34.5 kb plasmid, pP62BP1, which carries a genetic SLF module predicted to enable the host bacterium to metabolize alkyl sulfates including sodium dodecyl sulfate (SDS), a common anionic surfactant. In this work, we experimentally confirmed that the pP62BP1-harboring strain is capable of SDS degradation. The slfCHSL genes were shown to form an operon whose main promoter, PslfC, is negatively regulated by the product of the slfR gene in the absence of potential substrates. We showed that lauryl aldehyde acts as an inducer of the operon. The analysis of the draft genome sequence of the DAB_AL62B strain revealed that the crucial enzyme of the SDS degradation pathway-an alkyl sulfatase-is encoded only within the plasmid. The SLF module is flanked by two restriction-modification systems, which were shown to exhibit the same sequence specificity. We hypothesize that the maintenance of pP62BP1 may be dependent on this unique genetic organization.

CATASAN Is a New Anti-Biofilm Agent Produced by the Marine Antarctic Bacterium Psychrobacter sp. TAE2020.

The development of new approaches to prevent microbial surface adhesion and biofilm formation is an emerging need following the growing understanding of the impact of biofilm-related infections on human health. Staphylococcus epidermidis, with its ability to form biofilm and colonize biomaterials, represents the most frequent causative agent involved in infections of medical devices. In the research of new anti-biofilm agents against S. epidermidis biofilm, Antarctic marine bacteria represent an untapped reservoir of biodiversity. In the present study, the attention was focused on Psychrobacter sp. TAE2020, an Antarctic marine bacterium that produces molecules able to impair the initial attachment of S. epidermidis strains to the polystyrene surface. The setup of suitable purification protocols allowed the identification by NMR spectroscopy and LC-MS/MS analysis of a protein-polysaccharide complex named CATASAN. This complex proved to be a very effective anti-biofilm agent. Indeed, it not only interferes with cell surface attachment, but also prevents biofilm formation and affects the mature biofilm matrix structure of S. epidermidis. Moreover, CATASAN is endowed with a good emulsification activity in a wide range of pH and temperature. Therefore, its use can be easily extended to different biotechnological applications.

Deletion Variants of Autotransporter from Psychrobacter cryohalolentis Increase Efficiency of 10FN3 Exposure on the Surface of Escherichia coli Cells.

The autotransporter AT877 from Psychrobacter cryohalolentis belongs to the family of outer membrane proteins containing N-terminal passenger and C-terminal translocator domains that form the basis for the design of display systems on the surface of bacterial cells. It was shown in our previous study that the passenger domain of AT877 can be replaced by the cold-active esterase EstPc or the tenth domain of fibronectin type III (10Fn3). In order to increase efficiency of the 10Fn3 surface display in Escherichia coli cells, four deletion variants of the Fn877 hybrid autotransporter were obtained. It was demonstrated that all variants are present in the membrane of bacterial cells and facilitate binding of the antibodies specific against 10Fn3 on the cell surface. The highest level of binding is provided by the variants Δ239 and Δ310, containing four and seven beta-strands out of twelve that comprise the structure of the translocator domain. Using electrophoresis under semi-native conditions, presence of heat modifiability in the full-size Fn877 and its deletion variants was demonstrated, which indicated preservation of beta structure in their molecules. The obtained results could be used to optimize the bacterial display systems of 10Fn3, as well as of other heterologous passenger domains.

Comparative structural insight into the unidirectional catalysis of ornithine carbamoyltransferases from Psychrobacter sp. PAMC 21119.

Ornithine carbamoyltransferases (OTCs) are involved in the arginine deiminase (ADI) pathway and in arginine biosynthesis. Two OTCs in a pair are named catalytic OTC (cOTC) and anabolic OTC (aOTC). The cOTC is responsible for catalyzing the third step of the ADI pathway to catabolize citrulline into carbamoyl phosphate (CP), as well as ornithine, and displays CP cooperativity. In contrast, aOTC catalyzes the biosynthesis of citrulline from CP and ornithine in vivo and is thus involved in arginine biosynthesis. Structural and biochemical analyses were employed to investigate the CP cooperativity and unidirectional function of two sequentially similar OTCs (32.4% identity) named Ps_cOTC and Ps_aOTC from Psychrobacter sp. PAMC 21119. Comparison of the trimeric structure of these two OTCs indicated that the 80s loop of Ps_cOTC has a unique conformation that may influence cooperativity by connecting the CP binding site and the center of the trimer. The corresponding 80s loop region of in Ps_aOTC was neither close to the CP binding site nor connected to the trimer center. In addition, results from the thermal shift assay indicate that each OTC prefers the substrate for the unidirectional process. The active site exhibited a blocked binding site for CP in the Ps_cOTC structure, whereas residues at the active site in Ps_aOTC established a binding site to facilitate CP binding. Our data provide novel insights into the unidirectional catalysis of OTCs and cooperativity, which are distinguishable features of two metabolically specialized proteins.

Characteristics and polyethylene biodegradation function of a novel cold-adapted bacterial laccase from Antarctic sea ice psychrophile Psychrobacter sp. NJ228.

Biotreatment of polyethylene (PE) waste is an emerging topic in environmental remediation; in particular, the degrading enzymes requires further exploration. This study described a novel cold-adapted laccase (PsLAC) from an Antarctic psychrophile and characterized its PE-degradation ability. Homology modeling revealed that PsLAC possessed a typical bacterial laccase catalytic structure and unique cold adaptation structural characteristics such as few hydrogen bonds. Recombinant PsLAC (rPsLAC) retained 54.3% residual activity at 0 â„ƒ and presented increased Km values at low temperatures and a relatively high kcat value (42.65 s-1). Collectively, these factors help resist cold stress. rPsLAC possessed substantial salt tolerance at 1.5 M NaCl, with 119.80% activity, and Cu2+ enhanced its activity to 127.10%. PE-degradation experiments indicated that 13.2% weight was lost, and the water contact angle was decreased to 74.6°. Polar functional groups such as carbonyl and carboxyl groups on PE surface were detected in Fourier transform infrared spectroscopy; X-ray diffraction exhibited that crystallinity reduced by 25%. Enormous damage to PE surface and interior was observed via scanning electron microscopy. Overall, PsLAC, with its unique cold-adapted catalytic structure and biochemical characteristics, could supplement the diversity of sources and properties of bacterial laccases and ensure PE-degradation with a novel cold-adapted enzyme resource.

Molecular cloning, characterization, and homology modeling of serine hydroxymethyltransferase from psychrophilic bacterium Psychrobacter sp.

Serine hydroxymethyltransferase (SHMT) plays a significant role in the synthesis of l-serine, purine, and thymidylate, which could be extensively applied in the treatment of cancers and the development of antibiotics. In this study, cloned from Psychrobacter sp. ANT206, a novel cold-adapted SHMT gene (psshmt, 1257 bp) encoding a protein of 418 amino acids was expressed in Escherichia coli. The homology modeling result revealed that PsSHMT owned fewer Proline (Pro) residues and hydrogen bonds compared with its homologs from mesophilic E. coli and thermophilic Geobacillus stearothermophilus. In addition, the molecular weight of the purified recombinant PsSHMT (rPsSHMT) was identified to be 45 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis, approximately. The enzymatic characteristics of the cold-adapted rPsSHMT displayed that its optimum temperature and pH were 30°C and 7.5, respectively, and its enzymatic activity could be inhibited by Cu2+ , significantly. rPsSHMT also showed a high kcat value and low ΔG at low temperatures. Furthermore, arginine (Arg) could affect the activity of rPsSHMT and be vital to its active sites. The results of this study reflected that these characteristics of the cold-adapted rPsSHMT made it a remarkable candidate that could be utilized in multiple industrial fields under low temperatures.

Functional and molecular characterization of a cold-active lipase from Psychrobacter celer PU3 with potential antibiofilm property.

The lipase gene from Psychrobacter celer PU3 was cloned into pET-28a(+) expression vector and overexpressed in E. coli BL21 (DE3) pLysS cells. The purified Psychrobacter celer lipase (PCL) was characterized as an alkaline active enzyme and has a molecular mass of around 30 kDa. The PCL was active even at a low temperature and the optimum range was observed between 10 and 40 °C temperatures. MALDI-TOF and phylogenetic analysis ensured that Psychrobacter celer PU3 lipase (PCL) was closely related to P. aureginosa lipase (PAL). MD simulation results suggest that temperature change did not affect the overall structure of PCL, but it might altered the temperature-dependent PCL functional changes. R1 (129-135 AA) and R2 (187-191 AA) regions could be important for temperature-dependent PCL function and they fluctuated much at 35 °C temperature. PMSF completely inhibited PCL lipase activity and it demonstrates the presence of serine residues in the active site of PCL. PCL is moderately halophilic and most of the tested organic solvents found to be inhibiting the lipase activity except the solvents ethanol and methanol. PCL activity was increased with surfactants (SDS and CTAB) and bleaching agents (hydrogen peroxide). The effect of different metal ions on PCL resulted that only mercuric chloride was found as the enhancer of the lipase activity. Antibiofilm property of PCL was evaluated against pathogenic Vibrio parahaemolyticus isolated from the diseased shrimp and MIC value was 500 U. PCL significantly altered the morphology and biofilm density of V. parahaemolyticus and the same was observed through scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) imaging. RT-PCR analysis revealed that the mRNA expression level of biofilm, colony morphology and major toxin-related (aphA, luxS, opaR, tolC, toxR) genes of V. parahaemolyticus were significantly downregulated with PCL treatment.

Immobilization of psychrophile Psychrobacter sp. ANT206 onto novel reusable magnetic nanoparticles and its application for nitro-aromatic compounds biodegradation under low temperature.

Efficient biodegradation may offer a solution for the treatment of nitro-aromatic compounds (NACs) with toxicity, mutagenicity and persistence in the environment. In this study, dopamine (DA) functionalized magnetic nanoparticles with biocompatibility and hydrophilicity were synthesized and utilized for the immobilization of nitro-aromatic compounds degrading psychrophile Psychrobacter sp. ANT206 harboring the cold-adapted nitroreductase. The prepared nanocarriers were characterized using multiple methods. The highest immobilization yield of cells immobilized by Fe3O4@SiO2@DA was 90.67% under the optimized conditions of 10 °C, pH 7.5, 2 h and cell/support 1.2 mg/mg, and the activity recovery was 89.41%. In addition, the obtained immobilized cells displayed excellent salinity stability and reusability. Moreover, immobilized P. sp. ANT206 strains showed remarkable biodegradation capability on nitrobenzene and p-nitrophenol. This study introduced those novel Fe3O4@SiO2@DA nanoparticles could be applied as ideal and low-cost nanocarriers for the immobilization of cells and large-scale bioremediation of hazardous NACs with perspective applications under low temperature.

Glutaredoxin Interacts with GR and AhpC to Enhance Low-Temperature Tolerance of Antarctic Psychrophile Psychrobacter sp. ANT206.

Glutaredoxin (Grx) is an important oxidoreductase to maintain the redox homoeostasis of cells. In our previous study, cold-adapted Grx from Psychrobacter sp. ANT206 (PsGrx) has been characterized. Here, we constructed an in-frame deletion mutant of psgrx (Δpsgrx). Mutant Δpsgrx was more sensitive to low temperature, demonstrating that psgrx was conducive to the growth of ANT206. Mutant Δpsgrx also had more malondialdehyde (MDA) and protein carbonylation content, suggesting that PsGrx could play a part in the regulation of tolerance against low temperature. A yeast two-hybrid system was adopted to screen interacting proteins of 26 components. Furthermore, two target proteins, glutathione reductase (GR) and alkyl hydroperoxide reductase subunit C (AhpC), were regulated by PsGrx under low temperature, and the interactions were confirmed via bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (Co-IP). Moreover, PsGrx could enhance GR activity. trxR expression in Δpsgrx, Δahpc, and ANT206 were illustrated 3.7, 2.4, and 10-fold more than mutant Δpsgrx Δahpc, indicating that PsGrx might increase the expression of trxR by interacting with AhpC. In conclusion, PsGrx may participate in glutathione metabolism and ROS-scavenging by regulating GR and AhpC to protect the growth of ANT206. These findings preliminarily suggest the role of PsGrx in the regulation of oxidative stress, which could improve the low-temperature tolerance of ANT206.

Genome analysis of a new biosurfactants source: The Antarctic bacterium Psychrobacter sp. TAE2020.

Biosurfactants are considered a possible green alternative to chemical surfactants for countless commercial products including detergents and cleaners, personal care products, cosmetics, pharmaceuticals and therapeutics, food additives, emulsifiers, and dispersants for bioremediation. Organisms from extreme environments are well-adapted to the harsh conditions and represent an exciting avenue of discovery of naturally occurring biosurfactants. In this study, we report the genome analysis of Psychrobacter sp. TAE2020, an aerobic Æ´-proteobacterium isolated from an Antarctic coastal seawater sample collected in the vicinity of the French Antarctic station Dumont d'Urville, Terre Adelie (66°40' S; 140° 01' E) which has been shown to produce biosurfactants. Biochemical assays indicate that Psychrobacter sp. TAE2020 can produce one or more excellent emulsifiers and a biosurfactant which is able to reduce the surface tension of a Gut medium. Next generation sequencing and genome mining allowed the identification of a plethora of biosynthetic gene clusters possibly involved in the production of emulsifying agents, just waiting to be isolated and characterized. This study paves the way for a more thorough investigation into the potential biotechnological applications of this new Antarctic strain.