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Chemical Structure of Lipid A: Recent Advances in Structural Analysis of Biologically Active Molecules
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Ulrich Zähringer, Buko Lindner, Ernst T. Rietschel
LD-MS contributed to the structural elucidation of a variety of lipid A structures; these analyses have been performed on dephosphorylated or methylated monophosphoryl lipid A of R. sphaeroides (28), N. gonorrhoeae (64), Campylobacter jejuni (76), Rhodocyclus gelatinosus (77), Rhodobacter capsulatus (51), Por-phyromonas (Bacteroides) fragilis (78), Rhizobium meliloti (41), Neisseria meningitidis (79), Sphaerotilus natans (80), P. aeruginosa (68), Rhodospirillum salinarum (36), Klebsiella pneumoniae (81), Rhodospirillum fulvum (82), Pectinatus cerevisiiphilus (83), and Helicobacter pylori (84). The results of those and other studies are summarized in Table 3.
The role of iron-oxidizing bacteria in biocorrosion: a review
Published in Biofouling, 2018
As mentioned above, this review will focus on those microbes, primarily bacteria, capable of lithoautotrophic or chemosynthetic growth on ferrous iron, Fe(II); however, it is important to consider the other reactions between microbes and iron as well, since they can be important, and also the source of some confusion. Table 1 presents metabolic reactions relevant to iron that are important for biocorrosion. Lithoautotrophy refers to microbes that gain energy from the oxidation of ferrous iron to ferric iron (Fe(III)), and use this energy to fix carbon dioxide (CO2) as the cell’s primary source of carbon. Heterotrophic Fe-oxidation refers to microbes that actively catalyze the oxidation of Fe(II), but do not gain energy from the process, nor do they fix CO2, instead using organic matter as a carbon and energy source. Exemplars of this process are organisms like Leptothrix discophora and Sphaerotilus natans that produce proteins or enzyme systems that actively catalyze Fe-oxidation, or Mn-oxidation, yet derive no energetic benefit from it (Ghiorse 1984). It is also important to remember that at circumneutral pH, Fe(II) readily oxidizes in the presence of O2 resulting in the spontaneous precipitation of Fe-oxyhydroxides (rust). These oxides can passively adsorb bacteria, thus the mere association of a bacterium with Fe-oxyhydroxides does not prove whether it is catalytically oxidizing Fe(II), or playing a more passive role (Small et al. 1999). One potential example of this are Sediminibacterium spp., a genus within the Bacteroidetes, a bacterial phylum best known for its capacity to grow on complex organic matter (Fernández-Gómez et al. 2013). In the corrosion literature a number of papers refer to Sediminibacterium as a member of the iron-oxidizing bacteria (Wang et al. 2012; Li et al. 2014, 2015; Jin et al. 2015) in part due to the finding of 16S rRNA genes related to this organism being found in DNA extracted from corrosion products. Yet the original description of S. salmoneum, isolated from a eutrophic lake (Qu & Yuan 2008), or subsequent descriptions of newly isolated Sediminibacterium species (Kim et al. 2016), do not make any mention of the capacity to either oxidize Fe(II), or use it as a sole electron donor. Additional issues arise when, in the course of laboratory experiments, cells are grown with compounds like ferrous citrate, where citrate may serve as a carbon/energy source, and it can then be difficult to assess if oxidation of Fe(II) is actually catalyzed by the bacteria or occurring spontaneously (Xu et al. 2007; Liu et al. 2017).