Benzylpenicillin (Penicillin G)
M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson in Kucers’ The Use of Antibiotics, 2017
Pen G, similar to other beta-lactam agents, acts primarily on the bacterial cell wall, which is complex and unique to bacteria. Being relatively inelastic, it confers shape on the organism and protects it against damage due to osmotic pressure differences between the cell cytoplasm and the external environment (Koch, 1988). The cytoplasmic membrane lies immediately beneath the cell wall and is pressed up against it by osmotic forces within the cell. The cell wall and the cytoplasmic membrane together form the cell envelope. These component structures are interdependent, and alterations in one may render the other ineffective. The composition of the cell envelope, the complexity of which varies with different bacterial species, has an important role in modifying the action of antibiotics (Costerton and Cheng, 1975). Antibiotics act on protein synthesis within the cell or at a site within the envelope, so that they must pass through part or all of the envelope to reach their target.
Structure and function of skin
Roger L. McMullen in Antioxidants and the Skin, 2018
In addition to and following the series of events described thus far in the stratum granulosum, there are several more steps leading to the ultimate transformation of the keratinocyte to a cornified cell. First, the disintegration of ribosomes, mitochondria, and nuclei. In addition to these events, the plasma membrane is no longer able to survive and is replaced by a thick cornified cell envelope. Construction of the cell envelope takes place inside the boundaries of the plasma membrane. Two key proteins in the fabrication of the cell envelope include loricrin, derived from the keratohyalin granules, and involucrin from the cytoplasm. The contents of the cell envelope consist of these two proteins as well as a variety of other proteins, such as small proline-rich proteins, elafin, and envoplakin. The cell envelope is reinforced by epsilon-(gamma-glutamyl)lysine isopeptide cross-links, which are induced by transglutaminases. The resulting membrane is insoluble and impenetrable to polar substances. There are three known transglutaminases, expressed in the stratum granulosum, which carry out distinct functions.
Microbial resistance to preservative systems
R. M. Baird, S. F. Bloomfield in Microbial quality assurance in cosmetics, toiletries and non-sterile Pharmaceuticals, 2017
The cell envelope, an integral part of the cell, modulates access of nutrients and to some extent preservative compounds to the underlying cytoplasmic membrane. Two distinct mechanisms are thought to be involved in such action: The cytoplasmic membrane is bathed in a fluid continuous with that of the surrounding medium. The peptidoglycan matrix in Gram-positive bacteria (Scherrer and Gerhardt 1971) and in conjunction with the outer membrane in Gram-negative ones (Nikaido 1976, Nikaido and Nakae 1979) intercedes and functions as a molecular sieve, thereby preventing the ready access of large hydrophilic molecules to the cell membrane.Where such ready access to the membrane is denied, then a drug must interact with the cell wall in order to traverse it. With Gram-negative bacteria, this will involve sequential partitioning across the lipophilic layers that constitute the outer-membrane.
Yeast-inspired drug delivery: biotechnology meets bioengineering and synthetic biology
Published in Expert Opinion on Drug Delivery, 2019
Chinnu Sabu, Panakkal Mufeedha, Kannissery Pramod
Yeast cells are 2–3 µm ovoid or ellipsoidal structures covered by a thick cell wall. Saccharomyces is a Latin word which means sugar fungus, and cerevisiae is derived from two Latin words ceres and vise which means grain and strength. Cell envelope constitutes 15% of the total cell volume and is responsible for regulating the osmotic and permeability characteristics of the cell. The cytosol is further enveloped by a plasma membrane, periplasmic space, and the cell wall. Yeast cell wall which constitutes 25% of the total dry mass of cell is a rigid structure with a thickness of 200 nm. The four major macromolecules that constitute the cell wall are highly glycosylated glycoprotein or mannoproteins, two types of β-glucans and chitin. The cell wall constitution varies in accordance with growth condition of the cell. Spheroplasts or naked cells are formed by removing cell wall by reaction with a lytic enzyme in presence of osmotic stabilizers without causing any harm. They are susceptible to intergeneric and intrageneric cell fusions [8].
Molecular regulation of adhesion and biofilm formation in high and low biofilm producers of Bacillus licheniformis using RNA-Seq
Published in Biofouling, 2019
Faizan Ahmed Sadiq, Steve Flint, Hafiz Arbab Sakandar, GuoQing He
Increased peptidoglycan biosynthesis in biofilms may be related to the persistence of the cell wall. It is known that the cell envelope is a highly active component of bacterial cells in biofilms and plays an important role in biofilm development, resistance and sustainment (Resch et al. 2005; Bucher et al. 2015). Increased peptidoglycan biosynthesis has been reported in the biofilms formed by G. vaginalis (Castro et al. 2017), P. aeruginosa (El Zoeiby et al. 2001) and S. aureus (Resch et al. 2005). In the current study, it was found the ATP-binding cassette (ABC) transporters pathway was significantly enriched in the high biofilm forming strain only. This result shows that biofilm cells may be involved in transporting more solutes and small molecules compared to planktonic cells. An abundance of genes involved in ABS transporters has been reported in G. vaginalis (Castro et al. 2017), E. coli (Schembri et al. 2003), Desulfovibrio vulgaris (Clark et al. 2012) and biofilms formed by many other species. ABC transporter proteins have previously been reported to have a function in stress response in Streptococcus mutans (Nagayama et al. 2014). Increased amino sugar and nucleotide sugar metabolism in the high biofilm former indicates the role of amino sugars and nucleotide sugars (uracil-diphosphate glucose; UDP-glucose) in the biofilm matrix. Nucleotide sugars are important substrates for the enzyme glucosyltransferases (Gantt et al. 2013) which play an important role in polysaccharide synthesis (Li J and Wang 2012; Ren et al. 2016). It is important to mention that biofilm samples were obtained from 24 h biofilms in which bacterial cells may still be constructing biofilms thereby requiring more energy. For future studies, it will be equally important to study the metabolism of biofilm formation in B. licheniformis after 24 h.
Promoter orientation of the immunomodulatory Bacteroides fragilis capsular polysaccharide A (PSA) is off in individuals with inflammatory bowel disease (IBD)
Published in Gut Microbes, 2019
Lucy E. Blandford, Emma L. Johnston, Jeremy D. Sanderson, William G. Wade, Alistair J. Lax
Bacterial capsules are extracellular structures, typically comprised of polysaccharide, outside the cell envelope. Capsule possession appears to be part of a strategy to evade the host immune system, for example, by preventing the formation of a complement attack complex, and to avoid engulfment by phagocytosis.5 They also have roles in adhesion and colonization and for these reasons can be considered virulence factors; in addition, capsular mutants are often avirulent.6
Related Knowledge Centers
- Bacteria
- Bacterial Capsule
- Bacterial Outer Membrane
- Cell Wall
- Polysaccharide
- Prokaryote
- Cell Membrane
- Gram-Negative Bacteria
- Mollicutes
- Gram-Positive Bacteria