Exploring the genome of Arctic Psychrobacter sp. DAB_AL32B and construction of novel Psychrobacter-specific cloning vectors of an increased carrying capacity

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.

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.

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.

Deep Hypersaline Anoxic Basins as Untapped Reservoir of Polyextremophilic Prokaryotes of Biotechnological Interest

Deep-sea hypersaline anoxic basins (DHABs) are considered to be among the most extreme ecosystems on our planet, allowing only the life of polyextremophilic organisms. DHABs’ prokaryotes exhibit extraordinary metabolic capabilities, representing a hot topic for microbiologists and biotechnologists. These are a source of enzymes and new secondary metabolites with valuable applications in different biotechnological fields. Here, we review the current knowledge on prokaryotic diversity in DHABs, highlighting the biotechnological applications of identified taxa and isolated species. The discovery of new species and molecules from these ecosystems is expanding our understanding of life limits and is expected to have a strong impact on biotechnological applications.

Benefits and Drawbacks of Harboring Plasmid pP32BP2, Identified in Arctic Psychrophilic Bacterium Psychrobacter sp. DAB_AL32B

Psychrobacter sp. DAB_AL32B, originating from Spitsbergen island (Arctic), carries the large plasmid pP32BP2 (54,438 bp). Analysis of the pP32BP2 nucleotide sequence revealed the presence of three predicted phenotypic modules that comprise nearly 30% of the plasmid genome. These modules appear to be involved in fimbriae synthesis via the chaperone-usher pathway (FIM module) and the aerobic and anaerobic metabolism of carnitine (CAR and CAI modules, respectively). The FIM module was found to be functional in diverse hosts since it facilitated the attachment of bacterial cells to abiotic surfaces, enhancing biofilm formation. The CAI module did not show measurable activity in any of the tested strains. Interestingly, the CAR module enabled the enzymatic breakdown of carnitine, but this led to the formation of the toxic by-product trimethylamine, which inhibited bacterial growth. Thus, on the one hand, pP32BP2 can enhance biofilm formation, a highly advantageous feature in cold environments, while on the other, it may prevent bacterial growth under certain environmental conditions. The detrimental effect of harboring pP32BP2 (and its CAR module) seems to be conditional, since this replicon may also confer the ability to use carnitine as an alternative carbon source, although a pathway to utilize trimethylamine is most probably necessary to make this beneficial. Therefore, the phenotype determined by this CAR-containing plasmid depends on the metabolic background of the host strain.