Boosting Geranyl Diphosphate Synthesis for Linalool Production in Engineered Yarrowia lipolytica

Linalool is a pleasant-smelling monoterpenoid widely found in the essential oils of most flowers. Due to its biologically active properties, linalool has considerable commercial potential, especially in the food and perfume industries. In this study, the oleaginous yeast Yarrowia lipolytica was successfully engineered to produce linalool de novo. The (S)-linalool synthase (LIS) gene from Actinidia argute was overexpressed to convert geranyl diphosphate (GPP) into linalool. Flux was diverted from farnesyl diphosphate (FPP) synthesis to GPP by introducing a mutated copy of the native ERG20F88W-N119W gene, and CrGPPS gene from Catharanthus roseus on its own and as part of a fusion with LIS. Disruption of native diacylglycerol kinase enzyme, DGK1, by oligo-mediated CRISPR-Cas9 inactivation further increased linalool production. The resulting strain accumulated 109.6 mg/L of linalool during cultivation in shake flasks with sucrose as a carbon source. CrGPPS expression in Yarrowia lipolytica increased linalool accumulation more efficiently than the ERG20F88W-N119W expression, suggesting that the increase in linalool production was predominantly influenced by the level of GPP precursor supply.

[Identification of Clinical Isolates of the Bacillus cereus Group and Their Characterization by Mass Spectrometry and Electron Microscopy]

Bacillus cereus is a spore-forming bacterium found in the environment mainly in soil. Bacillus spores are known to be extremely resistant not only to environmental factors, but also to various sanitation regimes. This leads to spore contamination of toxin-producing strains in hospital and food equipment and, therefore, poses a great threat to human health. Two clinical isolates identified as B. cereus and B. cytotoxicus were used in the present work. It was shown that their calcium ion content was significantly lower than that of the reference strains. According to electron microscopy, one of the SRCC 19/16 isolates has an enlarged exosporium, and the SRCC 1208 isolate has large electron-dense inclusions of an unclear nature during sporulation. We can assume that these contain a biologically active component with a cytotoxic effect and possibly play a role in pathogenesis. Comparative chemical, biochemical, physiological, and ultrastructural analysis of spores of clinical isolates and reference strains of B. cereus was performed. The results we obtained deepen our understanding of the properties of spores that contribute to the increased pathogenicity of B. cereus group species.

Biofilm matrix proteome of clinical strain of P. aeruginosa isolated from bronchoalveolar lavage of patient in intensive care unit

Extracellular matrix plays a pivotal role in biofilm biology and proposed as a potential target for therapeutics development. As matrix is responsible for some extracellular functions and influence bacterial cytotoxicity against eukaryotic cells, it must have unique protein composition. P. aeruginosa is one of the most important pathogens with emerging antibiotic resistance, but only a few studies were devoted to matrix proteomes and there are no studies describing matrix proteome for any clinical isolates except reference strains PAO1 and ATCC27853. Here we report the first biofilm matrix proteome of P. aeruginosa isolated from bronchoalveolar lavage of patient in intensive care unit. We have identified the largest number of proteins in the matrix among all published studies devoted to P. aeruginosa biofilms. Comparison of matrix proteome with proteome from embedded cells let us to identify several enriched bioprocess groups. Bioprocess groups with the largest number of overrepresented in matrix proteins were oxidation-reduction processes, proteolysis, and transmembrane transport. The top three represented in matrix bioprocesses concerning the size of the GO annotated database were cell redox homeostasis, nucleoside metabolism, and fatty acid synthesis. Finally, we discuss the obtained data in a prism of antibiofilm therapeutics development.

Development of a Platform for Producing Recombinant Protein Components of Epitope Vaccines for the Prevention of COVID-19

A new platform for creating anti-coronavirus epitope vaccines has been developed. Two loop-like epitopes with lengths of 22 and 42 amino acid residues were selected from the receptor-binding motif of the Spike protein from the SARS‑CoV‑2 virus that participate in a large number of protein-protein interactions in the complexes with ACE2 and neutralizing antibodies. Two types of hybrid proteins, including one of the two selected epitopes, were constructed. To fix conformation of the selected epitopes, an approach using protein scaffolds was used. The homologue of Rop protein from the Escherichia coli ColE1 plasmid containing helix-turn-helix motif was used as an epitope scaffold for the convergence of C- and N-termini of the loop-like epitopes. Loop epitopes were inserted into the turn region. The conformation was additionally fixed by a disulfide bond formed between the cysteine residues present within the epitopes. For the purpose of multimerization, either aldolase from Thermotogamaritima, which forms a trimer in solution, or alpha-helical trimerizer of the Spike protein from SARS‑CoV‑2, was attached to the epitopes incorporated into the Rop-like protein. To enable purification on the heparin-containing sorbents, a short fragment from the heparin-binding hemagglutinin of Mycobacterium tuberculosis was inserted at the C-terminus of the hybrid proteins. All the obtained proteins demonstrated high level of immunogenicity after triplicate parenteral administration to mice. Sera from the mice immunized with both aldolase-based hybrid proteins and the Spike protein SARS‑CoV‑2 trimerizer-based protein with a longer epitope interacted with both the inactivated SARS‑CoV‑2 virus and the Spike protein receptor-binding domain at high titers.

[Tropical malaria with a fatal outcome]

Tropical malaria is an acute infectious disease from a group of parasitic diseases transmitted by the vector-borne route. Russia registers deaths due to imported malaria. The paper gives brief information on the epidemiology, etiology, and clinical manifestations of the disease and describes the fatal outcome of cerebral tropical malaria, as well as morphological changes in organs and tissues. The K76T mutation associated with drug resistance in parasites was identified in the structure of the plasmodium gene.

Integrated into Environmental Biofilm Chromobacterium vaccinii Survives Winter with Support of Bacterial Community

Chromobacterium species are common in tropical and subtropical zones in environmental samples according to numerous studies. Here, we describe an environmental case of resident Chromobacterium vaccinii in biofilms associated with Carex spp. roots in Moscow region, Russia (warm-summer humid continental climate zone). We performed broad characterization of individual properties as well as surrounding context for better understanding of the premise of C. vaccinii survival during the winter season. Genome properties of isolated strains propose some insights into adaptation to habit and biofilm mode of life, including social cheaters carrying ΔluxR mutation. Isolated C. vaccinii differs from previously described strains in some biochemical properties and some basic characteristics like fatty acid composition as well as unique genome features. Despite potential to modulate membrane fluidity and presence of several genes responsible for cold shock response, isolated C. vaccinii did not survive during exposure to 4 °C, while in the complex biofilm sample, it was safely preserved for at least half a year in vitro at 4 °C. The surrounding bacterial community within the same biofilm with C. vaccinii represented a series of psychrophilic bacterial species, which may share resistance to low temperatures with other species within biofilm and provide C. vaccinii an opportunity to survive during the cold winter season.

[Hyper-Resistance of the Bacillus licheniformis 24 Strain to Oxidative Stress Is Associated with Overexpression of Enzymatic Antioxidant System Genes]

At the International Space Station (ISS), artificial living conditions are created and maintained to satisfy human needs, these conditions are also favorable for the growth of numerous microorganisms, molds and bacteria. Among the microorganisms detected on the ISS are those from the automicroflora of crew members, and a significant number of spore-forming bacteria. In most cases, this group of microorganisms gives rise to strains that are able to colonize, grow and reproduce on interior materials and equipment of stations, and may be involved in biodestructive processes. These bacteria show increased resistance to various stress factors, for example, DNA-damaging and oxidizing agents. The molecular mechanisms of this resistance to stress are poorly understood. As part of the sanitary-microbiological monitoring of the ISS habitat, the Bacillus licheniformis 24 strain was isolated. Here, we demonstrated that this strain has increased resistance to hydrogen peroxide and Paraquat when compared to the "terrestrial" B. licheniformis B-10956 strain. B. licheniformis 24 overexpressed genes encoding enzymes that neutralize reactive oxygen species, such as KatX catalase and the superoxide dismutases SodA and SodF. Apart from this, in comparison with B. licheniformis B-10956, of B. licheniformis 24 cells had lower hydrogen sulfide production that was associated with sharply reduced expression of the cysIJ operon that encodes sulfite reductase. The results indicate that enzymatic antioxidant protective systems make a more significant contribution to the hyper-resistance of Bacillus strains to oxidizing agents than components of non-enzymatic systems, such as hydrogen sulfide.

Camelid VHHs Fused to Human Fc Fragments Provide Long Term Protection Against Botulinum Neurotoxin A in Mice

The bacterium Clostridium botulinum is the causative agent of botulism-a severe intoxication caused by botulinum neurotoxin (BoNT) and characterized by damage to the nervous system. In an effort to develop novel C. botulinum immunotherapeutics, camelid single-domain antibodies (sdAbs, VHHs, or nanobodies) could be used due to their unique structure and characteristics. In this study, VHHs were produced using phage display technology. A total of 15 different monoclonal VHHs were selected based on their comlementarity-determining region 3 (CDR3) sequences. Different toxin lethal dose (LD50) challenges with each selected phage clone were conducted in vivo to check their neutralizing potency. We demonstrated that modification of neutralizing VHHs with a human immunoglobulin G (IgG)1 Fc (fragment crystallizable) fragment (fusionbody, VHH-Fc) significantly increased the circulation time in the blood (up to 14 days). At the same time, VHH-Fc showed the protective activity 1000 times higher than monomeric form when challenged with 5 LD50. Moreover, VHH-Fcs remained protective even 14 days after antibody administration. These results indicate that this VHH-Fc could be used as an effective long term antitoxin protection against botulinum type A.

Synthesis in Escherichia coli and Characterization of Human Recombinant Erythropoietin with Additional Heparin-Binding Domain

Recombinant human erythropoietin (EPO) with additional N-terminal heparin-binding protein domain (HBD) from bone morphogenetic protein 2 was synthesized in Escherichia coli cells. A procedure for HBD-EPO purification and refolding was developed for obtaining highly-purified HBD-EPO. The structure of recombinant HBD-EPO was close to that of the native EPO protein. HBD-EPO contained two disulfide bonds, as shown by MALDI-TOF mass spectrometry. The protein demonstrated in vitro biological activity in the proliferation of human erythroleukemia TF-1 cell test and in vivo activity in animal models. HBD-EPO increased the number of reticulocytes in the blood after subcutaneous injection and displayed local angiogenic activity after subcutaneous implantation of demineralized bone matrix (DBM) discs with immobilized HBD-EPO. We developed a quantitative sandwich ELISA method for measuring HBD-EPO concentration in solution using rabbit polyclonal serum and commercial monoclonal anti-EPO antibodies. Pharmacokinetic properties of HBD-EPO were typical for bacterially produced EPO. Under physiological conditions, HBD-EPO can reversibly bind to DBM, which is often used as an osteoplastic material for treatment of bone pathologies. The data on HBD-EPO binding to DBM and local angiogenic activity of this protein give hope for successful application of HBD-EPO immobilized on DBM in experiments on bone regeneration.