Non-canonical nucleic acid structures play important roles in the regulation of molecular processes. Considering the importance of the ongoing coronavirus crisis, we decided to evaluate genomes of all coronaviruses sequenced to date (stated more broadly, the order Nidovirales) to determine if they contain non-canonical nucleic acid structures. We discovered much evidence of putative G-quadruplex sites and even much more of inverted repeats (IRs) loci, which in fact are ubiquitous along the whole genomic sequence and indicate a possible mechanism for genomic RNA packaging. The most notable enrichment of IRs was found inside 5 ′ UTR for IRs of size 12+ nucleotides, and the most notable enrichment of putative quadruplex sites (PQSs) was located before 3 ′ UTR, inside 5 ′ UTR, and before mRNA. This indicates crucial regulatory roles for both IRs and PQSs. Moreover, we found multiple G-quadruplex binding motifs in human proteins having potential for binding of SARS-CoV-2 RNA. Non-canonical nucleic acids structures in Nidovirales and in novel SARS-CoV-2 are therefore promising druggable structures that can be targeted and utilized in the future.

No abstract

Antimicrobial materials are widely used for inhibition of microorganisms in the environment. It has been established that bacterial growth can be restrained by silver nanoparticles. Combining these with other antimicrobial agents, such as ZnO, may increase the antimicrobial activity and the use of carrier substrate makes the material easier to handle. In the paper, we present an antimicrobial nanocomposite based on silver nanoparticles nucleated in general silicate nanostructure ZnO·mSiO2. First, we prepared the silicate fine net nanostructure ZnO·mSiO2 with zinc content up to 30 wt% by precipitation of sodium water glass in zinc acetate solution. Silver nanoparticles were then formed within the material by photoreduction of AgNO3 on photoactive ZnO. This resulted into an Ag-ZnO·mSiO2 composite with silica gel-like morphology and the specific surface area of 250 m2/g. The composite, alongside with pure AgNO3 and clear ZnO·mSiO2, were successfully tested for antimicrobial activity on both gram-positive and gram-negative bacterial strains and yeast Candida albicans. With respect to the silver content, the minimal inhibition concentration of Ag-ZnO·mSiO2 was worse than AgNO3 only for gram-negative strains. Moreover, we found a positive synergistic antimicrobial effect between Ag and Zn agents. These properties create an efficient and easily applicable antimicrobial material in the form of powder.

The study monitored the effect of tetracycline on bacterial biofilm formation and compared biofilm formation by resistant bacterial strains in different phases of the wastewater treatment process in wastewater treatment plant (WWTP). The crystal violet staining method was used to evaluate the biofilm formation. Biofilm-related bacterial properties were characterized by hydrophobicity, autoaggregation and motility tests. The relative abundance of tetracycline resistance genes (tetW, tetM, tetO, tetA and tetB) in wastewaters were subsequently quantified using qPCR. The results show that the isolates from the nitrification tank produce biofilm with up to 10 times greater intensity relative to the isolates from the sedimentation tank. In isolates of Aeromonas sp. from the nitrification tank, increased biofilm production in the occurrence of tetracycline from a concentration of 0.03125 µg/mL was observed. The tetW gene showed the highest relative abundance out of all the tested genes. From the sampling points, its abundance was the highest in the sedimentation tank of the WWTP. Based on these results, it can be assumed that resistant bacteria are able to form a biofilm and sub-inhibitory tetracycline concentrations induce biofilm formation. WWTPs thus represent a reservoir of antibiotic resistance genes and contribute to the spread of resistance in the natural environment.

Noncanonical nucleic acid structures play important roles in the regulation of molecular processes.Considering the importance of the ongoing coronavirus crisis, we decided to evaluate genomes of all coronaviruses sequenced to date (stated more broadly, the order Nidovirales) to determine if they contain noncanonical nucleic acid structures. We discovered much evidence of putative G-quadruplex sites and even much more of inverted repeats (IRs) loci, which in fact are ubiquitous along the whole genomic sequence and indicate a possible mechanism for genomic RNA packaging. The most notable enrichment of IRs was found inside 5′UTR for IRs of size 12+ nucleotides, and the most notable enrichment of putative quadruplex sites (PQSs) was located before 3′UTR, inside 5′UTR, and before mRNA. This indicates crucial regulatory roles for both IRs and PQSs. Moreover, we found multiple G-quadruplex binding motifs in human proteins having potential for binding of SARS-CoV-2 RNA.Noncanonical nucleic acids structures in Nidovirales and in novel SARS-CoV-2 are therefore promising druggable structures that can be targeted and utilized in the future.

Wastewater is considered the most serious source of the spread of antibiotic resistance in the environment. This work, therefore, focuses on the fate and spread of antibiotic resistance genes (ARGs) in wastewater and the monitoring of multidrug-resistant strains. ARGs were monitored in the nitrification and sedimentation tanks of the wastewater treatment plant (WWTP) and in the dam into which this WWTP flows, at various times. The highest relative abundance was found for the blaTEM > tetW > blaNDM-1 > vanA resistance genes, respectively. An increased concentration of tetracycline (up to 96.00 ng/L) and ampicillin (up to 19.00 ng/L) was found in water samples compared to other antibiotics detected. The increased incidence of seven ARGs and four antibiotics was observed in the November and December sampling times. Isolated ampicillin-resistant strains showed a high degree of resistance to ampicillin (61.2% of the total isolates had a minimum inhibitory concentration (MIC) ≥ 20 mg/mL). In 87.8% of isolates, out of the total number, the occurrence of two or more ARGs was confirmed. These multidrug-resistant strains were most often identified as Aeromonas sp. This strain could represent a significant role in the spread of multidrug resistance through wastewater in the environment.

No abstract

Polylactide (PLA) materials treated with antimicrobial fillers represent a suitable alternative to the production of medical devices. Their advantage is that they can prevent the growth of microorganisms and the formation of microbial biofilms on the surface and around composites. The work is focused on the evaluation of biocompatibility and biocide effect of PLA composite films filled with vermiculite and graphene oxide modified with silver (Ag+ and Ag nanoparticles), hexadecylpyridinium (HDP) and hexadecyltrimethylammonium (HDTMA) cations and their degradation leachates monitored at 1–3–6-month intervals. The antimicrobial effect of the leachates was detected by microdilution methods on gram-negative (Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis), gram-positive (Staphylococcus aureus, Streptococcus salivarius) bacteria and yeast (Candida albicans). The biocidal effect of composites on biofilm formation on the surface of composites was monitored by Christensen method and autoaggregation and motility tests. The biocompatibility of the composite and the leachates was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) cytotoxicity assay. The evaluation of the antimicrobial effect of the leachates demonstrated that leachates of PLA composite filled with graphene oxide and Ag+ showed a stronger antimicrobial effect than leachates of PLA composite filled with vermiculite and Ag+ and Ag nanoparticles. The leachates of PLA composites containing vermiculite with HDP and HDTMA cations had a higher antimicrobial effect on G+ bacteria and yeast than G– bacteria. Bacterial growth, biofilm formation, autoaggregation and motility of the tested bacteria were most inhibited by the composite with vermiculite and Ag+ and Ag nanoparticles. Even after a 6-month degradation of this composite, bacterial growth and biofilm formation continued to be strongly inhibited up to 42 and 91%, respectively. The cytotoxic effect was proved only in the leachate of the composite with vermiculite containing HDP after 6 months of its degradation. Tests evaluating the biocompatibility of materials have shown that the vermiculite is the most preferred carrier and can be used in the future to bind other compounds. The study confirmed that PLA composite filled with vermiculite and Ag+ and Ag nanoparticles was the most stable and effective composite with the best biocompatible and biocidal properties.