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Introduction to the Biological System
Published in Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu, Interdisciplinary Engineering Sciences, 2020
Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu
As shown in Figure 8.6, the bacterial cell is enclosed by a lipid membrane, which houses proteins, ribosomes, and other necessary components of the cytosol. As mentioned earlier in this chapter, membrane-bound organelles are absent in bacteria and thus have few intracellular structures. The nucleoid is an area of the bacterial cells, which is composed of chromosomes associated with small amounts of RNA and proteins. Like monkeys have tails, the tail-like structures of bacteria are known as flagella, which help in motility or migration on a material substrate. The flagella are proteinaceous structures of about 20 μm in length and up to 20 nm in diameter. Pili are essentially extracellular structures, which can transfer DNA/RNA from one bacterial cell to the other, in the process of bacterial conjugation.
Microbial Biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
In many bacteria, an S-layer of rigidly arrayed protein molecules covers the outside of the cell. This layer provides chemical and physical protection for the cell surface and can act as a macromolecular diffusion barrier. S-layers have diverse but mostly poorly understood functions, although they are known to act as virulence factors in Campylobacter and contain surface enzymes in Bacillus stearothermophilus. Flagella are rigid protein structures, approximately 20 nm in diameter and up to 20 μm in length, that are used for motility. Flagella are driven by the energy released by the transfer of ions down an electrochemical gradient across the cell membrane. Fimbriae are fine filaments of protein, just 2–10 nm in diameter and up to several micrometers in length. They are distributed over the surface of the cell and resemble fine hairs when seen under the electron microscope. Fimbriae are believed to be involved in attachment to solid surfaces or to other cells and are essential for the virulence of some bacterial pathogens. Pili (pilus in the singular) are cellular appendages slightly larger than fimbriae, which can transfer genetic material between bacterial cells in a process called conjugation.
Microbial biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
In many bacteria, an S-layer of rigidly arrayed protein molecules covers the outside of the cell. This layer provides chemical and physical protection for the cell surface and can act as a macromolecular diffusion barrier. S-layers have diverse but mostly poorly understood functions, although they are known to act as virulence factors in Campylobacter and contain surface enzymes in Bacillus stearothermophilus. Flagella are rigid protein structures, approximately 20 nm in diameter and up to 20 gm in length, that are used for motility. Flagella are driven by the energy released by the transfer of ions down an electrochemical gradient across the cell membrane. Fimbriae are fine filaments of protein, just 2–10 nm in diameter and up to several micrometers in length. They are distributed over the surface of the cell and resemble fine hairs when seen under the electron microscope. Fimbriae are believed to be involved in attachment to solid surfaces or to other cells and are essential for the virulence of some bacterial pathogens. Pili (pilus in the singular) are cellular appendages slightly larger than fimbriae, which can transfer genetic material between bacterial cells in a process called conjugation.
A state of the art review on electron transfer mechanisms, characteristics, applications and recent advancements in microbial fuel cells technology
Published in Green Chemistry Letters and Reviews, 2020
Ali Nawaz, Atiatul Hafeez, Syed Zaghum Abbas, Ikram ul Haq, Hamid Mukhtar, Mohd Rafatullah
In the case of monolayer biofilms, the majority cells are in the close vicinity of electrodes and thus involved in the production of current. In multilayer biofilms, long-range electron transport mechanisms such as nanowires (pili) are used because only a few cells can directly access electrodes. The dense pili network possesses metal-like conductivity, which is greatly responsible for the large current generation by conductive biofilms (19). A wide range of microorganisms are known to produce conductive pili including G. sulfurreducens. pili; i.e. type IV pili are the nanowires that are involved in the transportation of electrons between cells in the biofilm and to the surface of the electrode. It has been recently confirmed by electrostatic force microscopy that charge propagation from cell to cell along pili is similar to that of carbon nanotubes (19).
The purification and functional study of new compounds produced by Escherichia coli that influence the growth of sulfate reducing bacteria
Published in Egyptian Journal of Basic and Applied Sciences, 2020
Oluwafemi Adebayo Oyewole, Julian Mitchell, Sarah Thresh, Vitaly Zinkevich
According to Liu et al. [64], the cell membranes of bacteria are semi-permeable and this may allow the inflow of the growth promoter thereby enriching the cells and encouraging biofilm formation. The more abundant viable cells observed with SGE correlate to the more rapid growth observed in the liquid medium of the bioassay result. During purification of SGE, the inhibitor of SRB growth (SGI) was discovered. The development of biofilms follows three stages and includes irreversible attachment of single bacteria colonies on biotic or abiotic surfaces using structures such as pili, extracellular polymeric substances (EPS) and fimbriae. The next stage is growth. Once bacterial colonies are attached to surfaces, the bacteria replicate actively to form a complex structure referred to as glycocalyx [65] and the cycle continues following dispersion of planktonic cells from the biofilm matrix [66,67,68]. However, if the initiation of SRB colonization on surfaces is prevented or if their growth is impeded, this will inhibit biofilm formation and eventually lead to the limitation of damage such as biocorrosion, equipment failure, biofouling, hydrocarbon degradation and reservoir souring facilitated by SRB. Meanwhile, the cell deformity, bulge and elliptical changes observed in SGI-treated SRB cells are similar to reports obtained when Mn2+ and Cd2+ were incubated with cultures of SRB strain Salmonella daqing, isolated from Daqing oil-field [64]. Similarly, Mishra and Malik [68] reported changes in the physiology and morphology of bacterial cells when exposed to heavy metal.