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Enzyme Catalysis
Published in Harvey W. Blanch, Douglas S. Clark, Biochemical Engineering, 1997
Harvey W. Blanch, Douglas S. Clark
Many situations in nature are far removed from the spatially homogeneous case of a stirred tank reactor. In soils or in aquatic systems, significant gradients in nutrients may exist, resulting in spatially-varying cell concentrations. Approximately half of all bacterial orders contain at least one species which is motile. Cell movement results from the rotation of the flagellum (clockwise when viewed from the back of the bacterium) at speeds of up to 50 micron per second. The bacterial flagellum is composed of a filament, a hook and a basal structure. The filament is helical, composed of 11 parallel strands of the protein flagellin. The basal strucure is held in the cell envelope by a series of rings. The flagellum arises from the hook region. Bacteria may have a single flagellum at one of the poles of the cell, or may have many flagella distributed around the cell surface (peritrichate flagella). These peritrichously-flagellated bacteria typically move in a straight line for a short period of time (usually around 1 second), then stop and randomly change direction by a tumbling action (duration of 0.1 second).
Microbial Remediation of Persistent Organic Pollutants
Published in Narendra Kumar, Vertika Shukla, Persistent Organic Pollutants in the Environment, 2021
Some studies have revealed that bacteria also display chemotactic responses to substrate molecules. Chemotaxis is migration under the influence of a chemical gradient, either toward (positive chemotaxis) or against (negative chemotaxis) the gradient, and helps bacteria find optimum conditions for their growth and survival by swimming in a guided, nonrandom manner (Pandey and Jain, 2002). Chemotactic swimming is a result of rotation of flagella at speeds of around 18,000 rpm, powered by the proton motive force of protons or sodium ions across the cell’s membrane (DeRosier, 1998). Bacterial flagella are built from a protein called flagellin, and can be described as working like a rotary propeller that spins from a rod-and-ring structure embedded in a bacterial cell wall.
Proteomic analysis of secretomes from Bacillus sp. AR03: characterization of enzymatic cocktails active on complex carbohydrates for xylooligosaccharides production
Published in Preparative Biochemistry & Biotechnology, 2021
Johan S. Hero, José H. Pisa, Enzo E. Raimondo, M. Alejandra Martínez
Figure 2 shows the total number of proteins identified in each evaluated condition. Media supplemented with glucose and glucose + CMC showed similar amounts of identified proteins (172 and 167, respectively) and shared 147 proteins (85% and 88% of total proteins for glucose and glucose + CMC conditions, respectively). Furthermore, the Volcano plots denoted that some up-regulated proteins were found by comparing both media (Supplementary Material 3). Among them, only protein P02968 (flagellin) was up-regulated on glucose condition, while the proteins C0SP82 (probable oxidoreductase), P09339 (aconitate hydratase), P96579 (ribosomal N-acetyltransferase), and P04957 (β-glucanase) were up-regulated on glucose + CMC condition. On the other hand, medium containing CMC as the only carbon source presented the lowest number of proteins (147), with a higher number of unique and up-regulated proteins regarding the other two media (Fig. 2; Supplementary Material 3).
Irritable bowel syndrome and the gut microbiota
Published in Journal of the Royal Society of New Zealand, 2020
Phoebe E. Heenan, Jacqueline I. Keenan, Simone Bayer, Myrthe Simon, Richard B. Gearry
Evidence for microbial involvement in the BGA dates back to the 1970s when anatomical and immune system abnormalities of the GIT were noted in germ-free mouse models (Gustafsson and Maunsbach 1971; Wannemuehler et al. 1982), suggesting that the gut microbiota was directly affecting the tissues it came in close contact with. Altered GI motility was also noted in germ-free animal models which was ‘normalised’ by the introduction of conventional gut microbiota (Caenepeel et al. 1989; Husebye et al. 2001). Subsequently bacterial components, such as Flagellin, have been shown to induce an immune system reaction as well as ANS mediated altered motility (Vrees et al. 2002; Rhee et al. 2004). Another notable anatomical difference found in germ-free animal models in is the significantly increased EC density (Uribe et al. 1994), which could potentially explain the differences in GI motility observed in these models.
Antimicrobial properties of nanoparticles in the context of advantages and potential risks of their use
Published in Journal of Environmental Science and Health, Part A, 2021
Information on bacterial resistance to silver nanoparticles is becoming more and more frequent in the literature, however, most conclusions on this topic are formulated on the basis of mechanisms regarding silver ionic forms.[85,86] This is due to the fact that ionic silver is widely used in medical practice, and the reduced form was first used at the beginning of the 20th century, when colloidal silver was applied in the treatment of some diseases.[77] Further research revealed that isolates can reduce ionic silver to elemental silver and are resistant to the preparations containing silver available in the market.[87] Tests carried out on the Escherichia coli strain with using silver nitrate and silver nanoparticles have shown that in subsequent generations the MIC concentration increased almost 5-fold compared to the control sample. This was the result of a mutation in cuSgene coding for histidine kinase acting as a CusCFBA efflux pump sensor, in the purLgene encoding for an enzyme involved in de novopurine nucleotide biosynthesis and mutation in the rpoB gene, which is responsible for an RNA polymerase beta subunit.[84] A completely new mechanism of bacterial resistance to silver nanoparticles has been proposed by Panáček et al.[77] Studies carried out on the Escherichia coli strain have shown resistance of these bacteria to 28 nm AgNPs despite the lack of genetic changes in these microorganisms. According to researchers, bacteria that are primarily sensitive to AgNPs can gain resistance to the toxic effects of nanoparticles as a result of repeated exposure. The produced bacterial flagellum protein flagellin contributes to the aggregation of silver nanoparticles, which reduces the antibacterial effect against Gram-negative bacteria. The bacterial resistance produced can be weakened by using flagellin production inhibitors (e.g. PGRE). Pseudomonas aeruginosa bacteria build their resistance to nanoparticles by producing pyocyanine, pyocheline and pyoverdine.[88] Resistance of Enterococcus sp., Enterobacter cloacae, Klebsiella oxytoca, Proteus mirabilis, Klebsiella pneumoniae, and Staphylococcus aureus is the result of the production of efflux complexes.[87]