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Special Issue "Lipopolysaccharide: Bacterial Endotoxin"

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Bacterial Toxins".

Deadline for manuscript submissions: 30 June 2018

Special Issue Editor

Guest Editor
Prof. Susana Merino Montero

Department of Genetic, Microbiology and Statistics, Section Microbiology, Virology and Biotechnology; Faculty of Biology; University of Barcelona, Barcelona 08028, Spain

Special Issue Information

Dear Colleagues,

It is my pleasure to invite you to submit an original or review article for publication in a Special Issue on “Lipopolysaccharide: Bacterial Endotoxin”.

Lipopolysaccharide (LPS) is the major molecular surface component of the outer membrane of Gram-negative bacteria. LPSs are negatively-charged molecules exposed to the external environment and that provide a physical barrier that protects bacteria from antibacterial agents. They are amphiphilic molecules, consisting of a hydrophilic polysaccharide or oligosaccharide portion, covalently linked to a hydrophobic and high conserved lipid portion, termed lipid A, which is embedded in the external face of the outer membrane. The saccharide portion is diverse in terms of length and composition among different Gram-negative bacterial species, and can be divided in two domains: The core, which can be subdivided into inner and outer cores, and the O-antigen chain. The inner core is proximal to lipid A, which is required for bacterial viability, and contains unusual sugars, such as 3-deoxy-D-manno-octulosonic acid (Kdo) and heptoses. However, the outer core typically contains hexose sugars. The O-antigen chain is the most external domain, is highly variable, and is composed of repeating oligosaccharide units.

The LPS lipid A released from cell surfaces of bacteria during multiplication, lysis or death can be recognized by specific host cell receptors and is responsible for the activation of the innate immune system via the induction of inflammatory cytokines release. The uncontrolled activation of innate immune response triggers the development of septic shock and multiple-organ failure. Thus, lipid A is one of the most potent immune-stimulators, of which the toxicity depends on its primary structure and the severity of infection. Although lipid A is highly conserved biochemically, some bacteria show an impressive amount of diversity. Variations of the lipid A serve to promote survival by providing resistance to components of the innate immune system and help to evade recognition by Toll-like receptors.

The set of articles proposed for this Special Issue will examine the structure and composition, biological activity, host interaction, and induction of innate immunity of the Gram-negative bacterial endotoxin.

Prof. Susana Merino Montero
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


  • Lipid A
  • Core LPS
  • O-antigen LPS
  • Glycoconjugates
  • Chemical structure
  • Biological significance
  • Host interaction
  • Immune evasion
  • vaccines

Published Papers (1 paper)

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Open AccessFeature PaperArticle Cyanobacteria Scytonema javanicum and Scytonema ocellatum Lipopolysaccharides Elicit Release of Superoxide Anion, Matrix-Metalloproteinase-9, Cytokines and Chemokines by Rat Microglia In Vitro
Toxins 2018, 10(4), 130; doi:10.3390/toxins10040130
Received: 9 January 2018 / Revised: 23 February 2018 / Accepted: 14 March 2018 / Published: 21 March 2018
PDF Full-text (1413 KB) | HTML Full-text | XML Full-text | Supplementary Files
Cosmopolitan Gram-negative cyanobacteria may affect human and animal health by contaminating terrestrial, marine and freshwater environments with toxins, such as lipopolysaccharide (LPS). The cyanobacterial genus Scytonema (S) produces several toxins, but to our knowledge the bioactivity of genus Scytonema LPS has
[...] Read more.
Cosmopolitan Gram-negative cyanobacteria may affect human and animal health by contaminating terrestrial, marine and freshwater environments with toxins, such as lipopolysaccharide (LPS). The cyanobacterial genus Scytonema (S) produces several toxins, but to our knowledge the bioactivity of genus Scytonema LPS has not been investigated. We recently reported that cyanobacterium Oscillatoria sp. LPS elicited classical and alternative activation of rat microglia in vitro. Thus, we hypothesized that treatment of brain microglia in vitro with either cyanobacteria S. javanicum or S. ocellatum LPS might stimulate classical and alternative activation with concomitant release of superoxide anion (O2), matrix metalloproteinase-9 (MMP-9), cytokines and chemokines. Microglia were isolated from neonatal rats and treated in vitro with either S. javanicum LPS, S. ocellatum LPS, or E. coli LPS (positive control), in a concentration-dependent manner, for 18 h at 35.9 °C. We observed that treatment of microglia with either E. coli LPS, S. javanicum or S. ocellatum LPS generated statistically significant and concentration-dependent O2, MMP-9 and pro-inflammatory cytokines IL-6 and TNF-α, pro-inflammatory chemokines MIP-2/CXCL-2, CINC-1/CXCL-1 and MIP-1α/CCL3, and the anti-inflammatory cytokine IL-10. Thus, our results provide experimental support for our working hypothesis because both S. javanicum and S. ocellatum LPS elicited classical and alternative activation of microglia and concomitant release of O2, MMP-9, cytokines and chemokines in a concentration-dependent manner in vitro. To our knowledge this is the first report on the toxicity of cyanobacteria S. javanicum and S. ocellatum LPS to microglia, an immune cell type involved in neuroinflammation and neurotoxicity in the central nervous system. Full article
(This article belongs to the Special Issue Lipopolysaccharide: Bacterial Endotoxin)

Figure 1

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Content of β-hydroxy acids of Gram-negative bacterial strains: correlation between biological and chemical methods

Paba, A. Chiominto, A.M. Marcelloni, E. Paci, F. Tombolini, G. Tranfo

Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, National Institute for Insurance against Accidents at Work (INAIL), Monte Porzio Catone (Rome), Italy

Assessment of occupational exposure to airborne endotoxins has been studied for several years but a large number of procedures are used for sampling and analysis. Among analytical methods, the most widely used is the Limulus Amebocyte Lysate (LAL) test, in its kinetic-chromogenic version. However, some critical aspects of this test are reported in literature.

A different approach is represented by biochemical analyses, which are based on the release and detection of the-hydroxy fatty acids, as chemical markers of LPS. Several methods involving Gas Chromatography coupled with Mass Spectrometry (GC/MS) have developed, but its comparison with the LAL test reveals relatively weak correlations. In this paper a new analytical method in HPLC-MS/MS, previously developed and validated [Chiominto et al., 2014], was used to detect β-hydroxy-dodecanoic (3-OH C12) and β-hydroxy-tetradecanoic (3-OH C14) acids in thirteen ATCC Gram-negative bacterial strains. The choice of the two fatty acids is due to the fact that previous reports indicate that shorterchains (C10-C14) are positively correlated with endotoxin activity in the Limulus bioassay and they may elicit more significant potent immunological effects in humans.

The Pearson’s correlation between pairs of EU/ml, 3-OH C12, 3-OH C14 and 3-OH C12+3-OH C14 was studied. 3-OH C12/3-OH C14 sum correlate positively with Lal Test (r= 0.785); 3-OH C12, when present, seems to correlate even better than 3-OH C14 (r=0.750). Also loading plot evidences that, moving along PC1, endotoxin levels positively correlate with the sum of the fatty acids measured. PCA results provides additional information. PC2 divides the chart plane into two distinct parts: the positive PC2 axis takes into account the prevalence of 3-OH C12, while the negative PC2 axis identifies the species with greater quantities of 3-OH C14: in this group, with the highest content of 3-OH C14, we find Enterobacteriaceae and Aeromonadaceae, opportunistic pathogens to humans, in which they can cause a range of intestinal and/or extra-intestinal infections.

In conclusion, data confirm our previous results [Paci et al., 2017]: the sum of 3-hydroxytetradecanoic and 3-hydroxydodecanoic acids concentration can be considered a reliable chemical marker of endotoxin contamination. The predominance of 3-hydroxytetradecanoic acid (>97%) seems to identify a group of species of clinical and occupational interest, while in the group of species with a significant content of 3-OH C12 four out of the six bacterial strains considered belong to the Pseudomonaceae. Moreover, chemometrics is a suitable statistical tool for analyzing this type of experimental data.

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