China
Africa
Explore chapters and articles related to this topic
Mechanisms of Bacterial Heavy Metal Resistance and Homeostasis
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Pallavee Srivastava, Meenal Kowshik
Bacteria prevent the entry of the toxic metal into the cell and protect the intracellular metal sensitive machinery by creating a permeability barrier. This may be achieved by altering the cell-wall, membrane, or envelope as these are the primary sites of interaction. In Gram-negative bacteria, it is the outer membrane that provides this kind of protection. This is exemplified by E. coli B where porins present in the outer membrane, that control the transport of various hydrophilic substances including metal ions, are altered by genetic mutation in the presence of Cu2+ thereby preventing its influx (Bruins et al., 2000). Besides, the outer envelope may also confer natural resistance to a barrage of metals through non-specific binding, however, this kind of resistance is transient and holds true only till the saturation limit is reached (Rouch et al., 1995).
Protein, Cellular and Soft Tissue Interactions with Polyurethanes
Published in Nina M. K. Lamba, Kimberly A. Woodhouse, Stuart L. Cooper, Polyurethanes in Biomedical Applications, 2017
Nina M. K. Lamba, Kimberly A. Woodhouse, Stuart L. Cooper
Biomaterials, particularly in long-term implants are associated with bacterial infection. The implant appears to offer an attractive site for bacterial colonization. Indeed, after thrombosis, infection is the most common cause of implant failure in blood-contacting applications.203 In cardiovascular prostheses, thrombosis and infection are associated with protein adsorption and cellular adhesion to the surfaces, most likely involving similar mechanisms.138 Infection also is a serious problem for devices which are implanted in the abdomen including vascular grafts, ventriculoperitoneal shunts, and peritoneal dialysis catheters and feeding tubes.204,205 Mora et al.204 have shown that even when the biomaterial is sterile at the time of implantation into the peritoneal cavity (i.e., contamination did not occur during implantation), the material itself will cause bacteria to move from an intact normal bowel wall onto the prosthesis. Any contamination by bacteria in the peritoneal area is very hard to remove from the catheter material by any cleaning method.205 Certain types of bacteria, particularly gram negative bacteria, are associated with biomaterials infections.
Nanoparticles of Marine Origin and Their Potential Applications
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Fatemeh Sedaghat, Morteza Yousefzadi, Reza Sheikhakbari-Mehr
AgNPs exhibit potential antimicrobial properties against infectious microbes such as Escherichia coli, Bacillus subtilis, Vibrio cholerae, Pseudomonas aeruginosa, and Staphylococcus aureus. The application of nanomaterials as new antimicrobials provides novel modes of action on different cellular targets in comparison with existing antibiotics. Multiple drug resistance to traditional antibiotics has created a great requirement for the development of new antimicrobial agents. Bacteria are classified as gram-negative or gram-positive. The peptidoglycan is the key component of the bacterial cell wall. Gram-negative bacteria have only a thin peptidoglycan layer (~2–3 nm) between their two membranes, while Gram-positive bacteria lack the outer membrane (substituted by a thick peptidoglycan layer). Smaller sized NPs disrupt the function of the membrane (such as permeability or respiration) by attaching to its surface and subsequently, penetrating the cell and cause further damage by interacting with the DNA. The antimicrobial properties of Ag encourage its use in biomedical applications, animal husbandry, food packaging, water purification, cosmetics, clothing, and numerous household products. Now, Ag is the engineered nanomaterial most commonly used in consumer products. Clothing, respirators, household water filters, contraceptives, antibacterial sprays, cosmetics, detergent, dietary supplements, cutting boards, socks, shoes, cell phones laptop keyboards, and toys are among the retail products that purportedly exploit the antimicrobial properties of Ag nanomaterials. Several researchers investigated the antimicrobial efficacy against different bacterial and fungal pathogens [Ramkumara et al., 2016; Franci et al., 2015; Prabhu and Poulose, 2012].
A Review on Bioflotation of Coal and Minerals: Classification, Mechanisms, Challenges, and Future Perspectives
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Kaveh Asgari, Qingqing Huang, Hamid Khoshdast, Ahmad Hassanzadeh
Gram-negative bacteria refer to a group that cannot absorb violet crystals during Gram staining due to their wall type and outer membrane. In the second stage of Gram staining, when safranin is added, they show a red and pink color. The cell membrane of Gram-negative bacteria has a multi-layered and very complex structure. The inner membrane of Gram-negative bacteria, called the cytoplasmic membrane, is covered with a flat wall of Peptidoglycan (a huge polymer including sugar derivatives and amino acids), to which the outer membrane is attached. Among the Gram-negative bacteria are the fourth group of BV4 bacteria such as Chlamydia, Acidobacteria and Spirochetes and the three main branches of Proteobacteria. Gram-positive bacteria, meanwhile, refers to a group of bacteria that respond positively to Gram staining. The gram-positive bacteria absorb violet crystals by the Peptidoglycan in its wall and appear dark blue or purple. Gram-positive bacteria usually do not have an outer membrane in their cell wall and have a relatively simple cell wall consisting of two to three layers. Staphylococcus is one of the most important Gram-positive bacteria (Gram 1884; Sharma 2001).
Facile synthesis of metal nanoparticle-loaded polymer nanocomposite with highly efficient an optically enhanced biocidal and anticancer agents
Published in Journal of Biomaterials Science, Polymer Edition, 2021
M. Senthilkumar, R. Pandimurugan, S. Palanisamy, S. Mohandoss
Furthermore, silver-containing samples were found to be effective against E. coli, whereas polypyrrole alone did not affect [55]. Kelly et al. [56] studied in both silver-coated polypyrrole and polyaniline composites based on cellulose fibers performed similarly in terms of antibacterial activity, according to the researchers. Silver/polyaniline nanocomposites containing polyaniline nanofibers and silver were found to be effective against E. coli, S. aureus, and yeast. Moreover, the PDMA/Ag nanocomposite exhibited a superior inhibitory activity against E. coli (23.5 ± 2.8 mm) than S. aureus (20.5 ± 3.5 mm) (Figure 7(b)). At the same time, the positive control gentamicin showed 25.8 ± 2.1 and 22.4 ± 1.9 mm against E. coli than S. aureus, respectively. Generally, Gram-negative bacteria are more resistant to antibacterial agents than gram-positive bacteria, owing to the existence of an outer membrane containing lipopolysaccharides, which protects the bacteria more effectively from disturbance.
Application of antimicrobial plates in food packaging as an alternative way for food waste minimisation
Published in International Journal of Sustainable Engineering, 2021
Nawadon Petchwattana, Phisut Naknaen, Kamonchai Cha-Aim, Jakkid Sanetuntikul
To determine a suitable geraniol concentration, the blend compositions of PBS and geraniol were microbiologically measured via agar diffusion method. Figure 2 shows the inhibition clear zones detected from PBS/geraniol blends, at 0–10 wt%, against B. cereus and E. coli. Their quantitative data are clearly presented in Table 3. In Figure 2, geraniol was effectively inhibited the foodborne pathogens growth against both B. cereus and E. coli used in this study. However, geraniol appeared to have less effectiveness against E. coli with lower inhibition clear zone. Previous reports informed that the cell wall of Gram-positive bacteria is mostly comprised of peptidoglycan which allows the hydrophobic molecules to conveniently penetrate and disrupt their cells. On the other hand, Gram-negative bacteria have an outer membrane which comprises of a double-layer of phospholipids and lipopolysaccharides (Antunes et al. 2017). This makes the Gram-negative bacteria has more geraniol resistance than that of Gram-positive bacteria (Wiburanawong, Petchwattana, and Covavisaruch 2014; Petchwattana and Naknaen 2015; Antunes et al. 2017).