China
Africa
Explore chapters and articles related to this topic
Preservative Resistance
Published in Philip A. Geis, Cosmetic Microbiology, 2020
Overexpression of flagellin components has been reported in triclosan-resistant E. coli isolates (53,54). Flagellin is a globular protein that forms a filament in the bacterial flagellum. By having a modification in the flagellin expression, there was a decrease in the levels of intracellular ethylenediaminetetraacetic acid (EDTA) and sodium deoxycholate uptake which indicates the involvement of the outer membrane of the cell as a permeability barrier to preservatives as mentioned for Pseudomonas aeruginosa (55). It has been previously speculated that changes to the outer membrane of the cell can cause antimicrobial resistance by changing the permeability of the cell to the entry of compounds (56). In a separate study, it was found that high concentrations of sodium benzoate did not limit proliferation and control adaptability of Enterobacter gergoviae in cosmetic product formulations (57). It was speculated that outer membrane changes in Enterobacter gergoviae could be responsible for this sodium benzoate resistance.
Biology of microbes
Published in Philip A. Geis, Cosmetic Microbiology, 2006
A little more complexity appears when we look at the basal body of the bacterial flagellum. It is embedded within the bacterial cell wall and consists of a number of rings that vary, depending on whether the bacterium is Gram-negative or Gram-positive. A hook links the filament and the basal body. The basic difference between Gram-negative and Gram-positive flagella is the number of basal body rings. Gram-negative bacteria usually have four basal body rings. The first two rings are attached to the outer membrane (L-ring) and peptidoglycan layer (P-ring). The inner two rings contact the periplasmic space (S-ring) and the plasma membrane (M-ring). The Gram-positive flagellum has only two rings: one attached to the plasma membrane and the other attached to the peptidoglycan.
Beyond Enzyme Kinetics
Published in Clive R. Bagshaw, Biomolecular Kinetics, 2017
Photobleaching of fluorophores, which is often a technical limitation for following reactions in cells, can be exploited in the technique of fluorescence recovery after photobleaching (FRAP) [297–299]. The dynamic nature of cellular structures can be established by bleaching fluorophores in a small (micrometer) region using a focused laser beam and following the recovery as molecules outside the bleached region diffuse back into the bleached region to replenish the original molecules (Figure 5.15). Recovery of fluorescence by diffusion of individual proteins can occur on the millisecond time scale, consistent with their known diffusion constants (Table 3.1). However, recovery times are usually slower than in aqueous solution because protein must navigate through a web of cytoskeletal elements. Perhaps, more surprising is the recovery of many protein assemblies that involve not only diffusion but also the exchange of subunits on the seconds to minutes time scale and that demonstrate such complexes are highly dynamic. These include molecular motors, such as the bacterial flagellum, whose components are in continuous exchange while they operate [300]. These measurements demonstrate that self-assembly constitutes a series of reversible reactions and the resultant nanomachines are distinct from man-made macroscopic machines. We could not replace a damaged piston ring while a car is firing on the other three cylinders. FRAP has been used to elucidate the kinetic mechanism of transcription by RNA polymerases in vivo [301,302]. However, care is required in these studies because of reversible photobleaching of the fluorophores, particularly those involving green fluorescence protein (GFP) variants [303,304], may give rise to apparent recovery.
Regulation of flagellar motility and biosynthesis in enterohemorrhagic Escherichia coli O157:H7
Published in Gut Microbes, 2022
Hongmin Sun, Min Wang, Yutao Liu, Pan Wu, Ting Yao, Wen Yang, Qian Yang, Jun Yan, Bin Yang
The bacterial flagellum is a macromolecular machine that consists of a basal body (rotary motor), a hook (universal joint), and a filament (propeller).8 Flagellar-mediated motility confers an important advantage for bacteria in moving toward favorable conditions or in avoiding detrimental environments and allows bacteria to pursue nutrients and to reach and maintain their preferred niches for survival.9 In addition to having locomotive properties, flagellum-mediated motility plays diverse roles in the pathogenesis and progression of EHEC O157:H7 infection. Upon entering the host intestine, EHEC O157:H7 relies on flagellum-mediated motility to reach and adhere to optimal colonization sites in the host.10 Subsequently, EHEC O157:H7 inhibits flagellar biosynthesis to save energy and minimize host immunity (Figure 1).10
Differential transformation and antibacterial effects of silver nanoparticles in aerobic and anaerobic environment
Published in Nanotoxicology, 2019
Consistent with the SPR spectrum profiles, more AgNPs were formed under the exposure of higher concentration of Ag+ (Figure 4). Many AgNPs bound to the EPS that wrapped the cells (Figure 4(a-i)). As mentioned before, most of the newly formed AgNPs did not present as individuals but clustered together (Figure 4(a-i)). Some nanoparticles were preferably embedded in EPS matrix (Figure 4(b-i,b-ii)). Accumulating high density of AgNPs on the surface stressed the cells (Figure 4(c-i)), which may damage bacterial membrane, resulting in cytoplasm release as indicated by the arrow in Figure 4(c-i). The leaked cytoplasm exhibited strong attraction for Ag+ to produce AgNPs (Figure 4(c-ii)). When more AgNPs were formed, stronger aggregation occurred (Figure 4(d-i,d-ii)). EPS and cell lysate might mediate the gathering of formed AgNPs because of the high complexation activity between Ag and biomolecules. Large numbers of AgNPs can fully cover cell surface (Figure 4(e-i,e-ii)). Interestingly, although the bacterial cell was killed, its shape was maintained. The bacterial flagellum was clearly present (Figure 4(e-ii)). Much larger AgNPs were formed under the treatment of 25 mg/L of Ag+. EDS data confirmed the chemical composition of these nanoparticles and aggregates. The dark particles in the TEM model corresponded to the white area in STEM image. By focusing on the nanoparticle-packed area (marked by the arrow), Ag signal substantially increased (Figure 4(f-i)). Apparent Ag signal was detected for the micro-size aggregates (Figure 4(f-ii)). The Ag counts associated with the cells or aggregates were considerably larger than those in the surrounding area.
Host acid signal controls Salmonella flagella biogenesis through CadC-YdiV axis
Published in Gut Microbes, 2022
Weiwei Wang, Yingying Yue, Min Zhang, Nannan Song, Haihong Jia, Yuanji Dai, Fengyu Zhang, Cuiling Li, Bingqing Li
Once ingested, flagella allows Salmonella to cross the intestinal barrier and adhere to the intestinal epithelial cells.7–9 The bacterial flagellum is a complex macromolecular machine whose construction requires proteins encoded by three classes of genes.10,11 Class I comprises two genes in a single operon, flhDC, the“master switch” of all other flagellar genes. The FlhD4C2 complex acts as the transcription factor for class II genes.12,13 Products of class II flagellar genes form the flagellar basal structure and the hook-basal body complex, and class III flagellar protein are related to filament formation, flagellar rotation, and chemotaxis.11,14–16 After Salmonella enters host cells, the flagellum becomes a prime target antigen for the host immune system. Previous studies showed that the expression of flagellar antigen FliC decreased to 1/10 the original level upon Salmonella entry into host cells.17,18 Previously, three regulators were identified to be responsible for this process, YdiV, STM1697, and YdiU. YdiV, a post-transcriptional regulator, disrupts FlhDC complex structure by binding to FlhD, thereby preventing it binding to class II promoters and targeting it for proteolysis.19–21 STM1697, another post-transcriptional anti-FlhDC factor, represses flagellar synthesis by preventing FlhDC from recruiting RNA polymerase to the promoter.22 The function of FlhDC is also regulated by post-translational modification by YdiU, a modifying enzyme that catalyzes the UMPylation of the FlhC subunit to prevent FlhDC binding to flagellar genes, thus switching off flagellar biogenesis.23 Although these regulators control flagella biogenesis, it is not clear which host signals Salmonella perceives to turn on this flagella control process.