A combined fermentative-chemical approach for the scalable production of pure E. coli monophosphoryl lipid A

The Janus effect of colloidal self-assembly on the biological response of amphiphilic drugs

In aqueous environment amphiphilic molecules organize themselves into supramolecular structures deeply affecting the chemo-physical properties. Supramolecular assemby is also crucial in the pharmaceutical development of bioactive lipophilic molecules whose attitude to self-aggregate is a recognized factor affecting the in vivo pharmacokinetic, but can also play a crucial role in the interaction with the biological targets in in vitro tests. In aqueous solution, amphiphilic drugs exist in a complex equilibrium involving free monomers, oligomers and larger supramolecular aggregates held together by noncovalent bonds. In this review we focus our attention on the dual effect of drugs self-assembly, which can both reduce the availability of active compounds and create multivalent scaffolds, potentially improving binding affinity and avidity to cellular targets. We examine the effect of aggregation on different classes of amphiphatic molecules with significant biological activities, such as immunomodulatory, anti-tumor, antiviral, and antibiotic. Our purpose is to provide a comprehensive overview of how supramolecular chemistry influences the pharmacological and biological responses of amphiphilic molecules, emphasizing the need to consider these effects in early-stage drug development and in vitro testing. By elucidating these phenomena, this review aims to offer insights into optimizing drug design and formulation to overcome challenges posed by self-aggregation.

Vegan grade medium component screening and concentration optimization for the fermentation of the probiotic strain Lactobacillus paracasei IMC 502® using Design of Experiments

Lactobacillus paracasei IMC502® is a commercially successful probiotic strain. However, there are no reports that investigate growth medium composition in relation to improved biomass production for this strain. The major outcome of the present study is the design and optimization of a growth medium based on vegan components to be used in the cultivation of Lactobacillus paracasei IMC502®, by using Design of Experiments. Besides comparing different carbon sources, the use of plant-based peptones as nitrogen sources was considered. In particular, the use of guar peptone as the main nitrogen source, in the optimization of fermentation media for the production of probiotics, could replace other plant peptones (e.g. potato, rice, wheat, and soy) which are part of the human diet, thereby avoiding an increase in product and process prices. A model with R2 and adjusted R2 values higher than 95% was obtained. Model accuracy was equal to 94.11%. The vegan-optimized culture medium described in this study increased biomass production by about 65% compared to growth on De Man-Rogosa-Sharpe (MRS) medium. Moreover, this approach showed that most of the salts and trace elements generally present in MRS are not affecting biomass production, thus a simplified medium preparation can be proposed with higher probiotic biomass yield and titer. The possibility to obtain viable lactic acid bacteria at high density from vegetable derived nutrients will be of great interest to specific consumer communities, opening the way to follow this approach with other probiotics of impact for human health.

The outer membrane glycolipids of bacteria from cold environments: isolation, characterization, and biological activity

Lipopolysaccharides (LPSs) are the main components of the external leaflet of the outer membrane of Gram-negative bacteria. Microorganisms that colonize permanently or transiently cold habitats have evolved an array of structural adaptations, some of which involve components of bacterial membranes. These adaptations assure the perfect functionality of the membrane even at freezing or sub-freezing growth temperatures. This review summarizes the state-of-the-art information concerning the structural features of the LPSs produced by cold-adapted bacteria. The LPS structure has recently been elucidated from species mainly belonging to Gammaproteobacteria and Flavobacteriaceae. Although the reported structural heterogeneity may arise from the phylogenetic diversity of the analyzed source strains, some generalized trends can be deduced. For instance, it is clear that only a small portion of LPSs displays the O-chain. In addition, the biological activity of the lipid A portion from several cold-adapted strains is reported.

Rapid detection and discrimination of chromosome- and MCR-plasmid-mediated resistance to polymyxins by MALDI-TOF MS in Escherichia coli: the MALDIxin test

Background

Polymyxins are currently considered a last-resort treatment for infections caused by MDR Gram-negative bacteria. Recently, the emergence of carbapenemase-producing Enterobacteriaceae has accelerated the use of polymyxins in the clinic, resulting in an increase in polymyxin-resistant bacteria. Polymyxin resistance arises through modification of lipid A, such as the addition of phosphoethanolamine (pETN). The underlying mechanisms involve numerous chromosome-encoded genes or, more worryingly, a plasmid-encoded pETN transferase named MCR. Currently, detection of polymyxin resistance is difficult and time consuming.

Objectives

To develop a rapid diagnostic test that can identify polymyxin resistance and at the same time differentiate between chromosome- and plasmid-encoded resistances.

Methods

We developed a MALDI-TOF MS-based method, named the MALDIxin test, which allows the detection of polymyxin resistance-related modifications to lipid A (i.e. pETN addition), on intact bacteria, in <15 min.

Results

Using a characterized collection of polymyxin-susceptible and -resistant Escherichia coli, we demonstrated that our method is able to identify polymyxin-resistant isolates in 15 min whilst simultaneously discriminating between chromosome- and plasmid-encoded resistance. We validated the MALDIxin test on different media, using fresh and aged colonies and show that it successfully detects all MCR-1 producers in a blindly analysed set of carbapenemase-producing E. coli strains.

Conclusions

The MALDIxin test is an accurate, rapid, cost-effective and scalable method that represents a major advance in the diagnosis of polymyxin resistance by directly assessing lipid A modifications in intact bacteria.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

Characterization of complex, heterogeneous lipid A samples using HPLC-MS/MS technique I. Overall analysis with respect to acylation, phosphorylation and isobaric distribution

We established a new reversed phase-high performance liquid chromatography method combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry for the simultaneous determination and structural characterization of different lipid A types in bacteria (Escherichia coli O111, Salmonella adelaide O35 and Proteus morganii O34) showing serological cross-reactivity. The complex lipid A mixtures (obtained by simple extraction and acid hydrolysis of the outer membrane lipopolysaccharides) were separated and detected without phosphate derivatization. Several previously unidentified ions were detected, which differed in the number and type of acyl chains and number of phosphate groups. In several cases, we observed the different retention of isobaric lipid A species, which had different secondary fatty acyl distribution at the C2' or the C3' sites. The fragmentation of the various, C4' monophosphorylated lipid A species in deprotonated forms provided structural assignment for each component. Fragmentation pathways of the tri-acylated, tetra-acylated, penta-acylated, hexa-acylated and hepta-acylated lipid A components and of the lipid A partial structures are suggested. As standards, the hexa-acylated ion at m/z 1716 with the E. coli-type acyl distribution and the hepta-acylated ion at m/z 1954 with the Salmonella-type acyl distribution were used. The results confirmed the presence of multiple forms of lipid A in all strains analyzed. In addition, the negative-ion mode MS permitted efficient detection for non-phosphorylated lipid A components, too. Copyright © 2016 John Wiley & Sons, Ltd.

Structural characterization of the lipid A from the LPS of the haloalkaliphilic bacterium Halomonas pantelleriensis

Halomonas pantelleriensis DSM9661(Τ) is a Gram-negative haloalkaliphilic bacterium isolated from the sand of the volcanic Venus mirror lake, closed to seashore in the Pantelleria Island in the south of Italy. It is able to optimally grow in media containing 3-15 % (w/v) total salt and at pH between 9 and 10. To survive in these harsh conditions, the bacterium has developed several strategies that probably concern the bacteria outer membrane, a barrier regulating the exchange with the environment. In such a context, the lipopolysaccharides (LPSs), which are among the major constituent of the Gram-negative outer membrane, are thought to contribute to the restrictive membrane permeability properties. The structure of the lipid A family derived from the LPS of Halomonas pantelleriensis DSM 9661(T) is reported herein. The lipid A was obtained from the purified LPS by mild acid hydrolysis. The lipid A, which contains different numbers of fatty acids residues, and its partially deacylated derivatives were completely characterized by means of ESI FT-ICR mass spectrometry and chemical analysis. Preliminary immunological assays were performed, and a comparison with the lipid A structure of the phylogenetic proximal Halomonas magadiensis is also reported.