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2 Coatings for Medical Applications
Published in Peerawatt Nunthavarawong, Sanjay Mavinkere Rangappa, Suchart Siengchin, Mathew Thoppil-Mathew, Antimicrobial and Antiviral Materials, 2022
Many studies show that gram-positive bacteria were more resistant to photocatalytic disinfection on TiO2 than gram-negative bacteria due to differences in the cell wall structure. Gram-positive bacteria have a thicker peptidoglycan layer and no outer membrane, whereas gram-negative bacteria have three layers of the cell wall; an inner membrane, a thin peptidoglycan layer, and an outer membrane [16, 22, 33-38]. There are some examples of gram-positive bacteria killed by photocatalytic disinfection on TiO2. For example, TiO2 suspension was studied to kill gram-positive bacteria as follows; Lactobacillus acidophilus [39-43], Listeria monocytogenes [22], Bacillus cereus [44], MRSA and Staphylococcus saprophyticus [45]. For TiO2 thin film application, there were some examples of studies as follows; Clostridium perfringens spores NCIMB 6125 [9], Staphylococcus aureus [46], Lactococcus lactis 411 [38], and Bacillus thuringiensis [47]. In addition, there were few TiO2 coating applications for killing organisms, for example, Actinobacillus actinomycetemcomitans [48] and Streptococcus iniae [49]. Nagame and colleagues [50] studied in killed Streptococcus cricetus by Kobe Steel TiO2 99.98% anatase. Tsuang and colleagues [29] studied the effect of TiO2 on orthopedic implants, and they found that TiO2 was the ability to kill Enterococcus hirae. TiO2 can kill gram-positive bacteria by photocatalytic disinfection [2].
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Bacillus anthracis, also called “woolsorters” disease, is a Gram-positive, spore-forming bacillus that can survive for over 100 years in the spore form. Bacteria are classified as Gram-positive or Gram-negative based upon their response to the Gram staining procedure. The primary difference between Gram-negative and Gram-positive bacteria occurs in the cell wall. Gram-positive cell walls are usually much thicker and more difficult to penetrate than Gram-negative cell walls. Bacillus is a genus of bacteria that is found everywhere in nature (soil, water and airborne dust). Spores are not formed in living tissue. When a host dies and the disease is exposed to oxygen during the decay of the corpse, the spores are formed. Development of spores is a survival system, which allows the bacteria to survive in nature until a suitable host is once again contacted. About 2,000–5,000 cases of naturally occurring anthrax are reported every year throughout the world. It most commonly occurs in South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean and the Middle East. About five cases are reported in the United States each year and occur mostly in five states: Texas, Louisiana, Mississippi, Oklahoma, and South Dakota.
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].
Design and synthesis of silver nanoparticle anchored poly(ionic liquid)s mesoporous for controlled anticancer drug delivery with antimicrobial effect
Published in International Journal of Environmental Health Research, 2022
Ehsan Aliakbari, Yahya Nural, Reza Eghdam Zamiri, Erdal Yabalak, Mehri Mahdavi, Vahid Yousefi
E.coli is a Gram-negative bacterium and S. aureus is a Gram-positive bacterium, and their difference is related to their structure. Gram-positive bacteria have a thick peptidoglycan network cell wall; Gram-negative bacteria have a thin peptidoglycan cell wall and an outer phospholipid bilayer membrane (Beveridge 2001). The fact that the MIC and MBC values obtained are the same for E. coli but different for S. aureus can be explained by the fact that the desired drug is stuck between the peptidoglycan strands and cannot pass much, but it easily passes through the phospholipid membrane. As a result, for E. coli, which has a thick phospholipid membrane wall, it passed easily and its MIC and MBC are the same, but in the case of S. aureus, because it has a thin phospholipid membrane wall, but instead has a thick peptidoglycan membrane, and the drug could not penetrate easily.
Biofilms formed on metallic materials by E. coli and S. epidermidis and their evaluation by crystal violet staining and its reflection
Published in Transactions of the IMF, 2022
M. Takayanagi, H. Kanematsu, H. Miura, T. Kogo, R. Kawai, A. Ogawa, N. Hirai, T. Kato, M. Yoshitake, T. Tanaka, D. M. Barry
The first step is the staining with crystal violet. All bacteria are stained a violet colour by this process. In the next step, a Gram’s iodine solution (composed of iodine and potassium iodide) is added to form a complex between the crystal violet and iodine. Through this process, the complex staining bacteria become insoluble in water. Then ethyl alcohol is added to the sample. The complex of crystal violet and iodine is trapped in the cell of gram-positive bacteria. On the other hand, the cell of gram-negative bacteria cannot retain the complex due to their thin peptidoglycan layer, and as a result, the colour is lost. Finally, they are stained with safranine. At this final stage, gram-positive bacteria do not change their violet colour, while gram-negative bacteria show a red colour. The colour difference is derived from the difference in a cell’s outer structure. Gram-positive bacteria have thick peptidoglycan layers, and these layers are the main reason for stained gram-positive bacteria showing a violet colour. However, the authors have also used crystal violet and their staining behaviours to evaluate biofilms, as described below. The crystal violet stains not only EPS, but also bacteria, and the staining extents are different between the two categories – gram-negative bacteria and gram-positive ones, as described above. The amount of stained parts for gram-positive bacteria is generally larger than that for gram-negative bacteria since the former has thick peptide glycan layers more susceptive to staining. Therefore, in this experiment, the authors chose E. coli and S. epidermidis, as representative models .
Screening, identification and optimization of Bacillus species isolated from textile effluents in malachite green degradation
Published in Bioremediation Journal, 2023
K. B. Roopa, S. Raj Surabhi, B. S. Gowrishankar
Gram’s staining was performed to confirm whether the organisms were Gram positive or Gram-negative bacteria. The results proved that both the organisms were Gram-positive bacilli (Figure 2a and b). Several biochemical tests like motility, Catalase activity, Starch hydrolysis, Indole test, MR-VP tests, Citrate utilization test and Carbohydrate fermentation test were performed to further characterize the organisms. Motility tests justified that both the organisms were motile (Table 2). Catalase activity validated that both the organisms produced catalase enzyme and were aerobic bacteria. Starch hydrolysis test proved that both the organisms were capable of producing amylase enzyme. Indole test showed that the organisms were negative for the production of compound Indole that has formed by the release of tryptophanase enzyme. SITBT1 was negative for acidic end product, but SITBT2 was positive, based on MR reaction. VP test corroborated that both the organisms were negative for the production of alkaline neutral product. Citrate utilization test proved that SITBT1 was positive for the production of citrase enzyme and SITBT2 was negative for the production of the enzyme. Different sugars like Glucose, Sucrose and Lactose were used as sources of carbohydrates in the carbohydrate fermentation test. SITBT1 was capable of utilizing glucose, sucrose and lactose for the fermentation process and proved that SITBT1 was aerobic bacterium. SITBT2 was capable of utilizing only glucose and sucrose but not lactose for their growth and proliferation and proved that it was aerobic bacterium (Table 3). Further, to confirm that the organisms belonged to different species, antibiotic susceptibility test were performed. Several antibiotic disks was used (Table 2) and based on the zone of clearance (MIC) it was confirmed that both the organisms belong to different species.