CoBG-11 preparation v1

CoBG-11 is a coculture medium used to coculture cyanobacteria and E. coli by Zhang et al (2020). It is optimized for E. coli growth. Here are its components: 1. 150 mM NaCl, 2. 4 mM NH4Cl 3. 3 g/L 2-[[1,3-dihydroxy-2-(hydroxymethyl) propan-2-yl] amino] ethanesulfonic acid (TES) The pH value is adjusted with NaOH to 8.3. The protocol below describes the preparation of 100ml of coBG-11.

E. coli growth curve assay in BG-11 + sucrose v1

To obtain growth curves of KJK01 and pCSCX-KJK01 in BG-11 + sucrose and to characterize their growth. This also serves to estimate sucrose consumption and butanol production over time. This can be adapted for any other bacteria as well by giveing proper growth conditions, and using appropriate wavelength to measure the OD and giving proper time intervals based on whether the bacteria is slow growing or fast growing.

Bacterial growth inhibitory effects of Calotropis procera’s latex, leaves and roots extracts

This study was conducted to evaluate in vitro antibacterial potential of water and ethanolic extracts from Calotropis procera roots, leaves and latex. The growth inhibitory effects of the extracts were tested against Escherichia coli using disc diffusion method. Amoxicillin was used as positive control, whereas ethanol and distilled water were used as negative controls. Results showed that water extracts from root, latex and leaves had 3.27 ± 0.14, 3.1 ± 0.21 and 2.38 ± 0.24 cm of maximum inhibition zones, while the ethanolic extracts showed 2.91 ± 0.19, 3.02 ± 0.16 and 0.84 ± 0.31 cm, respectively of maximum inhibition zones. The positive control; amoxicillin had 3.56 ± 0.09 cm of maximum inhibition zone. Post hoc tests revealed that roots, latex and conventional amoxicillin were equally effective in inhibiting E. coli growth. It further revealed that water extracts exhibited more growth inhibitory effects than ethanol extracts. No significant variations were observed on the E. coli growth inhibition due to the locations from where C. procera were collected. Generally, results indicated that C. procera inhibited the growth of E. coli. Thus its uses for the development of traditional and complementary medicines and further investigation on its biological activity on other microbes are highly recommended. Keywords: Antibacterial, Calotropis procera, Diameter of inhibition zone. Escherichia coli, Plant crude extract, Traditional medicine.

Dependence of the Ripeness Stage on the Antioxidant and Antimicrobial Properties of Walnut (Juglans regia L.) Green Husk Extracts from Industrial By-Products

Walnut green husk (WGH) is a waste generated by the walnut (Juglans regia L.) harvest industry. It represents a natural source of polyphenols, compounds with antioxidant and antimicrobial activities, but their activity could be dependent on the ripeness stage of the raw material. In this study, the effect of the different ripeness stages—open (OH) and closed (CH) husks—on the antioxidant and antimicrobial properties of WGH extracts were analyzed, emphasizing the influence of the extracts in inhibiting Escherichia coli growth. The ripeness stage of WGH significantly affected the antioxidant activity of the extracts. This was attributed to the different polyphenol profiles related to the mechanical stress when the husk opened compared to the closed sample. The antimicrobial activity showed inhibition of E. coli growth. OH-extracts at 96 µg/mL caused the lowest specific growth rate (µmax = 0.003 h−1) and the greatest inhibition percentage (I = 93%) compared to CH-extract (µmax = 0.01 h−1; I = 69%). The obtained results showed the potential of the walnut green husk, principally open husk, as an economical source of antioxidant and antimicrobial agents with potential use in the food industry.

Influence of Polymer Solvents on the Properties of Halloysite-Modified Polyethersulfone Membranes Prepared by Wet Phase Inversion

Ultrafiltration polyethersulfone (PES) membranes were prepared by wet phase inversion. Commercial halloysite nanotubes (HNTs) in the quantities of 0.5 wt% vs. PES (15 wt%) were introduced into the casting solution containing the polymer and different solvents: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), or 1-methyl-2-pyrrolidinone (NMP). The type of solvent influenced the membranes’ morphology and topography, as well as permeability, separation characteristics, and antifouling and antibacterial properties. The membranes prepared using DMA exhibited the loosest cross-section structure with the thinnest skin and the roughest surface, while the densest and smoothest were the DMF-based membranes. The advanced contact angles were visibly lower in the case of the membranes prepared using DMF compared to the other solvents. The highest water permeability was observed for the DMA-based membranes, however, the most significant effect of the modification with HNTs was found for the NMP-based series. Regardless of the solvent, the introduction of HNTs resulted in an improvement of the separation properties of membranes. A noticeable enhancement of antifouling performance upon application of HNTs was found only in the case of DMF-based membranes. The study of the antibacterial properties showed that the increase in surface roughness had a positive effect on the inhibition of E. coli growth.

Suppression of Escherichia coli Growth Dynamics via RNAs Secreted by Competing Bacteria

With the discovery of secreted RNAs, it has become apparent that the biological role of regulatory oligonucleotides likely goes beyond the borders of individual cells. However, the mechanisms of their action are still comprehended only in general terms and mainly for eukaryotic microRNAs, which can interfere with mRNAs even in distant recipient cells. It has recently become clear that bacterial cells lacking interference systems can also respond to eukaryotic microRNAs that have targets in their genomes. However, the question of whether bacteria can perceive information transmitted by oligonucleotides secreted by other prokaryotes remained open. Here we evaluated the fraction of short RNAs secreted by Escherichia coli during individual and mixed growth with Rhodospirillum rubrum or Prevotella copri, and found that in the presence of other bacteria E. coli tends to excrete oligonucleotides homologous to alien genomes. Based on this observation, we selected four RNAs secreted by either R. rubrum or P. copri, together with one E. coli-specific oligonucleotide. Both fragments of R. rubrum 23S-RNA suppressed the growth of E. coli. Of the two fragments secreted by P. copri, one abolished the stimulatory effect of E. coli RNA derived from the 3′-UTR of ProA mRNA, while the other inhibited bacterial growth only in the double-stranded state with complementary RNA. The ability of two RNAs secreted by cohabiting bacteria to enter E. coli cells was demonstrated using confocal microscopy. Since selected E. coli-specific RNA also affected the growth of this bacterium, we conclude that bacterial RNAs can participate in inter- and intraspecies signaling.