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Mechanisms of phytoremediation and microbial remediation of heavy metals
Published in Rym Salah-Tazdaït, Djaber Tazdaït, Phyto and Microbial Remediation of Heavy Metals and Radionuclides in the Environment, 2022
Rym Salah-Tazdaït, Djaber Tazdaït
The following are the main reactive sites: Lipopolysaccharides (LPS) are chains of molecules evolving outside of cells. They are composed of a common lipid A on which is fixed a polysaccharide, which contains carboxyl groups and phosphomonoesters.Phospholipids are composed of hydrophobic chains attached to a glycerol unit on which is attached a hydrophilic group. On the latter, there are two reactive sites (amine and phosphodiester functions).The peptidoglycan (PG) network is a rigid structure composed of two sugar molecules (N-acetylglucosamine and N-acetylmuramic acid) linked to a short peptide (tetrapeptide to octapeptide). It contains three carboxyl functions and an amine(Cox, Smith, Warren, and Ferris 1999, 4514; Yee and Fein 2001, 2037). It should be noted that the constitutive wall differences between Gram-positive and Gram-negative cells seem to have a minor influence on the sorption capacities of metals (Yee and Fein 2001, 2037; Ngwenya, Sutherland, and Kennedy 2003, 537).
Penicillin, Cephalosporin, and Streptomycin Production
Published in Debabrata Das, Soumya Pandit, Industrial Biotechnology, 2021
The composition of beta-lactam is not very typical and apart from the antibiotic classes to be listed, it is present only in certain alkaloids and some anti-metabolite toxins, including pachystermines from Pachystradra terminals (Chang et al., 2000), Pseudomonas tabici producing wild-fire poison (Yi et al., 1990) and even Streptomyces verticillus producing anti-tumour antibiotics, phleomycins and bleomycin (Kawano et al., 2000). The commonly used beta-lactam antibiotics are penicillins and cephalosporins whereas some fairly recent members are cephamycins, nocardicins, thienamycins. Apart from nocardicins, the above antibiotics are derivatives of bicyclic core structures wherein the lactam ring unifies with the ring molecule employing a nitrogen atom and a carbon atom (Figure 12.2). This ring compound is 5-membered in penicillins (thiazolidine), thienamycins (pyrroline), and clavulanic acid (oxazolidine). It is 6-membered in cephalosporins and cephamycins (dihydro-thiazolidine). Beta-lactam antibiotics prevent the development of the bacterial cell membrane's peptidoglycan. Given the absence of this factor in mammalian cells, beta-lactam antibiotics have low toxicity to mammals (Bruggink et al., 1998).
Indoor Microbial Pollutants
Published in Rafał L. Górny, Microbiological Corrosion of Buildings, 2020
Marcin Cyprowski, Anna Ławniczek-Wałczyk, Rafał L. Górny, Agata Stobnicka-Kupiec
The importance of bacteria, including Gram-positive bacteria (from the cocci, corynebacteria or bacilli group), as factors determining human well-being in the environment has not been fully understood so far, although these bacteria clearly dominate in the indoor microbiota [Gołofit-Szymczak and Górny 2018]. It should be emphasised that their potential health harmfulness cannot be assessed solely on the basis of infectious or allergic properties. An equally important and still underestimated route of exposure is inhalation of immunologically active airborne peptidoglycans. Peptidoglycans are an important structural component of the bacterial cell wall, consisting of a muramic acid biopolymer and N-acetylglucosamine, connected by β-(1→4)-glycosidic and pentapeptide bonds. It is estimated that in Gram-positive bacteria, peptidoglycans constitute about 70% of the whole cell wall, whereas the respective percentage in Gram-negative bacteria is about 25% [Sigsgaard et al. 2005].
A review of microalgal cell wall composition and degradation to enhance the recovery of biomolecules for biofuel production
Published in Biofuels, 2023
Syafiqah Md Nadzir, Norjan Yusof, Norazela Nordin, Azlan Kamari, Mohd Zulkhairi Mohd Yusoff
Most microalgal species that have been studied as potential feedstock for biofuel production have a Type 2 cell surface [17–19]. Compared to the other forms of cell surface, the Type 2 extracellular material of some microalgae and cyanobacteria is the most complicated (Figure 1). Depending on the type of species, it can appear as a cell wall, mucilage sheath, scales, frustule, lorica, or skeleton [20,21]. In both prokaryotic and eukaryotic algae, the cell wall is a semi-permeable, rigid, and frequently multilayered protective covering. The peptidoglycan-based cell wall of cyanobacteria resembles that of Gram-negative bacteria, in which the cell wall is placed exterior to the cell membrane. The peptidoglycan consists of two sugar derivatives, N-acetylglucosamine and N-acetylmuramic acid, linked by β-1,4-glycosidic bonds [22]. The three most important functions of peptidoglycan are maintaining osmotic pressure between the cell and its external environment, preserving cell shape, and providing rigidity.
Overview of methodologies for the culturing, recovery and detection of Campylobacter
Published in International Journal of Environmental Health Research, 2023
Marcela Soto-Beltrán, Bertram G. Lee, Bianca A. Amézquita-López, Beatriz Quiñones
Broad spectrum tetracycline and beta-lactams have been used for treating gastrointestinal infections. Resistance to tetracycline in Campylobacter is moderate to high and is generally mediated by the tet(O) gene, commonly found on the pTet plasmid but also on a genomic island. Beta-Lactam antibiotics act by binding to penicillin-binding proteins and disrupting peptidoglycan cross-linking during cell wall synthesis. Resistance through beta-lactamase, blaOXA-61, is widespread in C. jejuni and C. coli. The Campylobacter multidrug efflux pump CmeABC has also worked synergistically to provide resistance to beta-lactams as well as tetracyclines, macrolides and fluoroquinolones (Whitehouse et al. 2018). Campylobacter infections that are resistant to less toxic antibiotics may be treated with aminoglycosides, such as gentamicin (Fair and Tor 2014). Aminoglycosides bind to prokaryotic ribosomes impairing protein synthesis, and over 24 genes, encoding aminoglycoside-modifying enzymes, have been identified in Campylobacter. A gene cluster aadE-sat4-aphA-3 confers multidrug resistance including aminoglycosides and has been found in C. jejuni and C. coli, recovered from food and human. This gene cluster has been detected on a plasmid and integrated in the chromosome (Zhao et al. 2016). Finally, an intrinsic resistance in some C. jejuni and C. coli isolates has been described against penicillin, older cephalosporins, trimethoprim, sulfamethoxazole, rifampicin, and vancomycin (Fitzgerald et al. 2008).
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).