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Non-point source microbial pollution damages the overall health of marine ecosystems. Beyond their direct effects, contaminating microbes can introduce antimicrobial resistance and virulence genes into resident species by horizontal gene transfer, a process that may be enhanced by co-pollutants such as heavy metals. In this work, a number of heavy metal- and antimicrobial-resistant (AMR) strains of E. coli were isolated from water and sediment samples collected in the Causeway Bay, Hong Kong (22.2833 N, 114.1847 E) and their complete genomes obtained by hybrid assembly using both Illumina MiSeq and Oxford Nanopore MinION sequencing platforms. Genomic analysis showed an abundance of plasmids and mobile elements bearing heavy metal- and AMR genes, such as the mer operon and tetR-tetA efflux system, with these features frequently co-located. In addition, NCBIBLAST–using isolates collected from in-land soil, freshwater, and animal faeces in Hong Kong, as well as the NCBI database – showed that these genes, while common amongst human and animal-derived Enterobacteriaceae, could also be shown present in a number of strains of obligate halophilic Vibrio spp.. Previous water chemistry analysis at this location showed high levels of heavy metal contamination (98 ppm Pb, 0.12 ppm Hg, and 0.4 ppm Cd), which has been shown to promote AMR transfer by selecting for co- resistance. Further isolation and characterisation of marine bacterial species from Hong Kong coastal waters will help to determine the extent of this process.

Photodynamic inactivation of microorganisms known as antibacterial photodynamic therapy (APDT) is one of the most promising and innovative approaches for the destruction of pathogenic microorganisms. Among the photosensitizers (PSs), compounds based on cationic porphyrins/metalloporphyrins are most successfully used to inactivate microorganisms. Series of meso-substituted cationic pyridylporphyrins and metalloporphyrins with various peripheral groups in the third and fourth positions of the pyrrole ring have been synthesized in Armenia. The aim of this work was to determine and test the most effective cationic porphyrins and metalloporphyrins with high photoactivity against Gram negative and Gram positive microorganisms. It was shown that the synthesized cationic pyridylporphyrins/metalloporphyrins exhibit a high degree of phototoxicity towards both types of bacteria, including the methicillin-resistant S. aureus strain. Zinc complexes of porphyrins are more phototoxic than metal-free porphyrin analogs. The effectiveness of these Zn–metalloporphyrins on bacteria is consistent with the level of singlet oxygen generation. It was found that the high antibacterial activity of the studied cationic porphyrins/metalloporphyrins depends on four factors: the presence in the porphyrin macrocycle of a positive charge (+4), a central metal atom (Zn²⁺) and hydrophobic peripheral functional groups as well as high values of quantum yields of singlet oxygen. The results indicate that meso-substituted cationic pyridylporphyrins/metalloporphyrins can find wider application in photoinactivation of bacteria than anionic or neutral PSs usually used in APDT.

Bacterial resistance is today a matter of great medical concern, so it is urgent to investigate alternatives to alleviate it. Photodynamic inactivation (PDI) is a method that has been endorsed to inactivate different pathogens, including bacteria, fungi and viruses. PDI is achieved by using a photosensitizer (PS) molecule which generates reactive oxygen species under visible or UV radiation. We use visible light and UV-A radiation to excite four commercial PSs (methylene blue, rose bengal, riboflavin and curcumin), and nanoparticles synthesized in our laboratory. Despite these PSs having been thoroughly studied in the past by other research groups, in order to compare their effects in an appropriate way, we matched the number of photons they absorb. We found that methylene blue leads to the major inactivation of Escherichia coli. Furthermore, we evaluated the production of singlet oxygen and hydroxyl radicals in the photoinactivation process.

The development of an effective biological (bio) agent detection capability based upon terahertz (THz) frequency absorption spectra will require insight into how the constituent cellular components contribute to the overall THz signature. In this work, the specific contribution of ribonucleic acid (RNA) to THz spectra is analyzed in detail. Previously, it has only been possible to simulate partial fragments of the RNA (or DNA) structures due to the excessive computational demands. For the first time, the molecular structure of the entire transfer RNA (tRNA) molecule of E. coli was simulated and the associated THz signature was derived theoretically. The tRNA that binds amino acid tyrosine (tRNA_tyr) was studied. Here, the molecular structure was optimized using the potential energy minimization and molecular dynamical (MD) simulations. Solvation effects (water molecules) were also included explicitly in the MD simulations. To verify that realistic molecular signatures were simulated, a parallel experimental study of tRNAs of E. Coli was also conducted. Two very similar molecules, valine and tyrosine tRNA were investigated experimentally. Samples were prepared in the form of water solutions with the concentrations in the range 0.01-1 mg/ml. A strong correlation of the measured THz signatures associated with valine tRNA and tyrosine tRNA was observed. These findings are consistent with the structural similarity of the two tRNAs. The calculated THz signature of the tyrosine tRNA of E.coli reproduces many features of our measured spectra, and, therefore, provides valuable new insights into bio-agent detection.

The experimental and computational study of bacterial thioredoxin, an E. coli protein, at THz frequencies is presented. The absorption spectrum of the entire protein in water was studied numerically in the terahertz range (0.1 – 2 THz). In our work, the initial X-ray molecular structure of thioredoxin was optimized using the molecular dynamical (MD) simulations at room temperature and atmospheric pressure. The effect of a liquid content of a bacterial cell was taken into account explicitly via the simulation of water molecules using the TIP3P water model. Using atomic trajectories from the room-temperature MD simulations, thioredoxin's THz vibrational spectrum and the absorption coefficient were calculated in a quasi harmonic approximation.

For our terahertz transmission measurements, we used solutions of thioredoxin in distilled water obtained from Sigma. The experimental and simulated signatures are correlated and dominant peaks are close in frequencies. The results of this study demonstrate that terahertz spectroscopy is a promising tool in generating spectral data for cellular components of bio agents such as bacterial cells and spores.

The purpose of the present study was to asses the thermal inactivation of E. coli and coliform during the kneading step, in hot water, in the making process of Oaxaca cheese – a fresh pasta filata Mexican cheese. A three-strain cocktail of E. coli isolated from industrial Oaxaca cheeses was used for the assay. Three batches of pasteurised and, then, inoculated milk were processed into Oaxaca cheese following a traditional open-vat process until before the kneading step. At this point, the process was halted and a simulated kneading step at 55 °C for 15 min was carried out. Counts of E. coli and coliform were performed on the curd after 0, 5, 10 and 15 min of the begining of the sumulated kneading. The data of these counts were analysed using linear regression, and the correspondent D_55°C values were calculated. The heating taking place during the kneading can reduce considerably the population of E. coli and coliform of the curd. However, it did not eliminate entirely the risk of foodborne illness in Oaxaca cheese.

Cryo-EM analysis of a wild-type Escherichia coli pretranslocational sample has revealed the presence of previously unseen intermediate substates of the bacterial ribosome during the first phase of translocation, characterized by intermediate intersubunit rotations, L1 stalk positions, and tRNA configurations. Furthermore, we describe the domain rearrangements in quantitative terms, which has allowed us to characterize the processivity and coordination of the conformational reorganization of the ribosome, along with the associated changes in tRNA ribosome-binding configuration. The results are consistent with the view of the ribosome as a molecular machine employing Brownian motion to reach a functionally productive state via a series of substates with incremental changes in conformation.

Enteroccocus faecalis, a gram-positive bacterium ubiquitous in the environment and normal inhabitant of the human gastrointestinal tract, has emerged as a major health problem exacerbated by its ability at surviving adverse conditions, including prolonged stay on environmental surfaces. Here its tolerance to detergents that are routine household chemicals was investigated and compared to that of E. coli. A clinical isolate of E. faecalis with plasmid-mediated antibiotics resistance grown in the presence of increasing concentrations of sodium N-lauroylsarcosinate (sarkosyl) and sodium dodecyl sulphate (SDS) exhibited a sarkosyl minimum inhibitory concentration (MIC) of 0.1% (10% for E. coli) and a SDS MIC of 0.05% (6% for E. coli). A mutant with accrued sarkosyl resistance (MIC = 0.6%) was isolated after growth in the presence of 0.06% sarkosyl. While there was no cross-resistance to SDS, other mutant characteristics gave it advantages over the original strain, emphasizing the potential emergence of E. faecalis with increasing tolerance to common household detergents.

This study presents the first report on enhanced bacterial inactivation of E. coli by RF-plasma pretreated cotton with high surface area CuO powders compared with non-pretreated cotton textiles. The high surface area CuO (65 m/g) powder was fully characterized. The E. coli inactivation proceeded in the dark and was accelerated under visible and sunlight irradiation even at very low levels of visible light irradiation. The effect the RF-plasma pretreatment of the cotton on the binding of CuO, applied light dose, and initial E. coli concentration on the inactivation kinetics of E. coli is reported.

This study addresses unreported features for Cu DC-magnetron sputtering on cotton mediating inactivation of Escherichia coli K12 (from now on E. coli). The E. coli inactivation for cotton-Cu samples sputtered for 40 s was attained within 30 min under visible light (1.2 mW/cm²) and within 120 min in the dark. For a longer sputtering time of 180s, the bacterial inactivation kinetics under light was observed within 30 min, as was the case for the 40 s sputtered sample. This suggests that Cu-ionic species play a key role E. coli inactivation. The 40 s sputtered samples present the highest amount of Cu-sites held in exposed positions interacting on the cotton surface (or inside the cotton) with E. coli. Sputtering for 40 s deposited 4.10¹⁶ atoms Cu/cm² (taking ~10¹⁵ atoms/cm Cu per atomic layer) and this was the threshold amount of Cu necessary for complete E. coli inactivation. Cu DC-magnetron sputtering lead to thin metallic semi-transparent grey-brown Cu-coating presenting hydrophobic behavior as determined by contact angle measurements.

Antibacterial activity of alkaloids of two medicinal plants Fumaria bastardii and Fumaria capreolata was evaluated by two diffusion methods, wells method and disks method, against four bacterial stocks resistant to antibiotics isolated from infected patients in hospital. The tested strains are S.aureus S56, K. pneumoniae E47, P. aeruginosa 604 and E. coli. The contents of alkaloids were 2,42% and 1,17% in Fumaria bastardii and Fumaria capreolata respectively. Both alkaloid extracts showed a high antibacterial activity against the four strains tested. However P. aeruginosa was the least susceptible strain. Extract of F. bastardii was the most active one showing a higher activity excepted against P. aeruginosa which was most susceptible to F. capreolata extract. A synergy effect was observed between alkaloids of F. bastardii and the SXT on K. pneumonia and between alkaloids of F. capreolata and the SXT on P. aeruginosa 604.

Biofilms containing antimicrobial agents are gaining importance as environmentally-friendly food packaging systems to extend product shelf life. Biofilms based on calcium caseinate, plasticized with three different concentrations of glycerol (15, 25 and 35 wt%) and with 10 wt% of carvacrol, were prepared by solvent casting. Their biodegradation was tested under composting conditions by using Fourier transform infrared spectroscopy, while barrier properties were evaluated by determining oxygen transmission rate. Finally, antimicrobial effectiveness against Escherichia coli and Staphylococcus aureus was tested by using the agar diffusion method. Calcium caseinate based biofilms showed rapid degradation under composting conditions and excellent oxygen barrier properties in all cases. Formulations with carvacrol exhibited clear inhibitory effects against both bacteria tested. These results showed the potential of calcium caseinate as a matrix for bioactive packaging systems, leading to a possible increase in foodstuff shelf life by reducing oxidative degradation and decreasing microbial contamination.