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Mechanism of Drug Resistance in Staphylococcus aureus and Future Drug Discovery
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Felipe Wakasuqui, Ana Leticia Gori Lusa, Sven Falke, Christian Betzel, Carsten Wrenger
Drug discovery and development investigations combine mainly the following methods, computer assisted drug design, structure-based drug discovery and screening of substances, as shown as in Fig. 9.1. Today investigating and screening natural products continues to be one of the most important and approaches in drug discovery. Until now, most of the drug classes discovered originated from natural sources. Even after two decades of combinatorial chemistry, no increase of lead structures was reached, despite the increase of chemical substances (Newman and Cragg, 2007). One possible explanation is the structural diversity of natural products which cannot be reached by synthetic techniques. One obstacle to identify new natural compounds is that the vast majority of bacteria cannot be cultivated in conventional conditions. New cultivation techniques allowed the prospection of previously uncultivated bacteria. One of them is a microfluidic reactor, which allows to cultivate even slow growing bacteria (Zang et al., 2013). Another revolutionary technique is the iChip, a multichannel device with hundreds of microdiffusion chambers, each with an environmental cell. It can be put in a natural environment to increase colony count, and therefore allows efficient cultivation (Nichols et al., 2010). Screening of soil bacteria allowed the discovery of Teixobactin, an inhibitor of cell wall synthesis, binding in a precursor of peptidoglycan and cell wall teichoic acid (Ling et al., 2015). Using a new method to screen the soil microbiome malacidins were discovered. They are macrocyclic lipopeptides with activities against multidrug resistant Gram-positive pathogens (Hover et al., 2018). Prospection of new environments also rendered molecules. The nasal commensal bacteria Staphylococcus lugdunensis produces a non-ribosomally synthesized thiazolidine-containing cyclic peptide called Lugdunin, which prevents colonization by S. aureus and has distinct bactericidal properties (Zipperer et al., 2016).
Development and characterization of antimicrobial alginate hydrogel beads filled with cinnamon essential oil nanoemulsion
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Mahsa Mostaghimi, Marjan Majdinasab, Mohammad-Taghi Golmakani, Mohammad Hadian, Seyed Mohammad Hashem Hosseini
The beads filled with CEO nanoemulsion reduced the viable bacteria of E. coli and B. cereus by about 1.67 and 1.6 log CFU/mL, respectively. According to the figures, the reduction in the number of total viable bacteria exposed to the filled beads is quite evident compared to the control samples, indicating the good antimicrobial activity of the beads against Gram-positive and Gram-negative bacteria. The beads led to a further reduction in the population of B. cereus compared with E. coli. This means the greater effect of the encapsulated CEO on the Gram-positive bacteria. This can be due to the differences in the composition of cell membrane of two kinds of bacteria and the difference in their sensitivity to the active compounds in the CEO. Gram-negative bacteria have a complex structure and an external lipopolysaccharide layer around their peptidoglycan cell wall which limits the penetration of hydrophobic compounds through their lipopolysaccharide layer; while Gram-positive bacteria contain a layer of teichoic acid or glycoprotein membrane. In Gram-positive bacteria, the hydrophobic molecules can easily access the cell membrane through the weakly peptidoglycan layer [28].
Preparation of graphene oxide nanoparticles and their derivatives: Evaluation of their antimicrobial and anti-proliferative activity against 3T3 cell line
Published in Journal of Dispersion Science and Technology, 2022
Mohammadamin Saedi, Vahid Shirshahi, Mehdi Mirzaii, Mohammad Nikbakht
The difference in the effect of nanomaterials on gram-negative and gram-positive bacteria can also be seen in a study by Deokar et al.[42] They explain this difference by saying that these nanomaterials interact with gram-positive bacteria through physical interaction (perforation) and electrostatic or hydrogen bond interactions. However, gram-negative bacteria interact only through direct physical contact. The thick layer of peptidoglycan and the presence of lipids, teichoic acid, and amino acids on its surface in gram-positive bacteria play an essential role in the interaction with nanomaterials. Peptidoglycan layers also have adhesion properties due to the presence of proteins such as teichoic acid. These factors can cause the adsorption of nanomaterials, such as GO and chemical interactions.[43]
Heavy metal remediation and resistance mechanism of Aeromonas, Bacillus, and Pseudomonas: A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Ali Fakhar, Bushra Gul, Ali Raza Gurmani, Shah Masaud Khan, Shafaqat Ali, Tariq Sultan, Hassan Javed Chaudhary, Mazhar Rafique, Muhammad Rizwan
All bacterial species have a cell wall composed of peptidoglycan, which is a linear polymer. In Gram-positive bacteria, the peptidoglycan cell wall is composed of glutamic acid, alanine, meso-di-amino pimelic acid, and a polymer of glycerol and teichoic acid. The cell wall of Gram-negative bacteria includes enzymes, lipoproteins, phospholipids, glycoproteins, and lipopolysaccharides that are actively involved as binding sites for metals (Gupta, Nayak, et al., 2015). Once heavy metals become bound to cellular compounds, microbial cells transform their oxidation state and reduce their toxicity (Chaturvedi et al., 2015). To harness heavy metal pollution, various approaches other than physical remediation have been developed. These include bioremediation (Mohamed, 2016). Bacteria can be used for bioreduction and biorecovery of heavy metal ions (Iravani & Varma, 2020). Herbaspirillum sp. GW103 and Paenibacillus sp. RM are bacterial diazotrophs, which have been assessed for bioleaching and bioremediation, respectively. Copper (Cu) resistance has been confirmed by locating the copA and copB genes (Govarthanan et al., 2014, 2016).