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Microbial Growth and Its Control
Published in Maria Csuros, Csaba Csuros, Klara Ver, Microbiological Examination of Water and Wastewater, 2018
Maria Csuros, Csaba Csuros, Klara Ver
Microbes obtain most of their nutrients in solution from the surrounding water. They, therefore, require water for growth and are actually about 80 to 90 percent water. When a microbial cell is in a solution that has a higher concentration of solute than in the cell (hypertonic), the cellular water passes out through the plasma membrane to the high salt concentration. This osmotic loss of water causes plasmolysis or shrinkage of the cell, and inhibits the growth of the cell. Thus, the addition of salt or other solutes to a solution and the resulting increase in osmotic pressure can be used to preserve food. For example, salted fish, honey, and sweetened condensed milk are preserved by this mechanism; the high salt or sugar concentrations draw water out from microbial cells that are present and, thus, prevent their growth.
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
Sydney et al. [137] investigated the effects of UVB on C. reinhardtii, Dunaliella salina, and Micractinium inermum. The cell wall of both C. reinhardtii and D. salina was influenced by UVB irradiation; it became swollen and bleached after 232 s of UVB irradiation, and the fatty acid methyl ester (FAME) recovery under these conditions was better than with the bead beating method (11.3% and 7.7% FAME yield, respectively). Micractinium inermum, in contrast, exhibits no apparent cell wall degradation during UVB irradiation due to its thick glycoprotein-based cell wall [137]. Moharikar et al. [138] conducted a UVC irradiation study on C. reinhardtii and discovered that cells subjected to 12–100 J m−2 of UVC irradiation began to shrink, which is indicative of apoptosis. Changes in nuclear morphology, phosphatidylserine flipping, and DNA fragmentation were also seen under this stress condition. El-Sheekh et al. [139] examined the effect of UVB irradiation on several microalgal species; Transmission Electron Microscopy (TEM) analysis revealed that the cell wall and cell membrane degrade and rupture, resulting in the release of intracellular chemicals; the formation of numerous gas vacuoles indicated the loss of cell inclusion; and plasmolysis developed, indicating that the cell was damaged. The majority of these characteristics were also observed in Dunaliella viridis, including cell swelling, organelle membrane rupture, mitochondrial condensation, and the formation of cytoplasmic blebs, intact cell membranes, and neat membrane blebbing [128].
Seripheidium quettense mediated green synthesis of biogenic silver nanoparticles and their theranostic applications
Published in Green Chemistry Letters and Reviews, 2019
Muhammad Qasim Nasar, Tanzeel Zohra, Ali Talha Khalil, Sadam Saqib, Muhammad Ayaz, Ashfaq Ahmad, Zabta Khan Shinwari
Antibiotics resistance is becoming a global issue and search for effective antibacterial drugs is the need of current time (32, 33). The antibacterial activity of synthesized Sq-AgNPs was studied against Gram-positive and Gram-negative pathogenic bacterial strains. Sq-AgNPs were most active against E. coli and B. subtilis with MICs of 11.1 and 33.3 μg/mL, respectively. Sq-AgNPs were moderately active against S. epidermidis, P. aeruginosa and was inactive against S. aureus(Table 2). According to previous reports, AgNPs synthesized from Chrysanthemum indicum flowers showed good activity against E. coli and K. pneumoniae (34). The exact bactericidal mechanism of AgNPs is not very well understood yet. Some researchers believe that AgNPs might interfere with bacterial cell wall synthesis, inhibit the synthesis of vital proteins implicated in cell division, inhibit the synthesis of nucleic acids and interfere metabolic pathways (35). It is also reported that AgNPs induce plasmolysis and disturb the permeability of cell membrane which effect the respiration process (36, 37).
Green biosynthesis of silver nanoparticles with Eryngium caucasicum Trautv aqueous extract
Published in Inorganic and Nano-Metal Chemistry, 2020
Matin Azizi, Sajjad Sedaghat, Kambiz Tahvildari, Pirouz Derakhshi, Ahad Ghaemi
The antibacterial activity of AgNPs might be as a result of the deliverance of silver ions plus the attached bioactive molecules such as flavonoids in the cells.[61,62] The interaction of silver ions with bacterial cell membranes, might lead to the cell membrane synthesis inhibition and plasmolysis,[63] cell division and finally death of bacteria.[64] The maximum zone of inhibition at extremely concentrated solution (stock AgNPs) μg/mL AgNPs is itemized in Table 1.