Bacterial lipases

Many different bacterial species produce lipases which hydrolyze esters of glycerol with preferably long-chain fatty acids. They act at the interface generated by a hydrophobic lipid substrate in a hydrophilic aqueous medium. A characteristic property of lipases is called interfacial activation, meaning a sharp increase in lipase activity observed when the substrate starts to form an emulsion, thereby presenting to the enzyme an interfacial area. As a consequence, the kinetics of a lipase reaction do not follow the classical Michaelis-Menten model. With only a few exceptions, bacterial lipases are able to completely hydrolyze a triacylglycerol substrate although a certain preference for primary ester bonds has been observed. Numerous lipase assay methods are available using coloured or fluorescent substrates which allow spectroscopic and fluorimetric detection of lipase activity. Another important assay is based on titration of fatty acids released from the substrate. Newly developed methods allow to exactly determine lipase activity via controlled surface pressure or by means of a computer-controlled oil drop tensiometer. The synthesis and secretion of lipases by bacteria is influenced by a variety of environmental factors like ions, carbon sources, or presence of non-metabolizable polysaccharides. The secretion pathway is known for Pseudomonas lipases with P. aeruginosa lipase using a two-step mechanism and P. fluorescens lipase using a one-step mechanism. Additionally, some Pseudomonas lipases need specific chaperone-like proteins assisting their correct folding in the periplasm. These lipase-specific foldases (Lif-proteins) which show a high degree of amino acid sequence homology among different Pseudomonas species are coded for by genes located immediately downstream the lipase structural genes. A comparison of different bacterial lipases on the basis of primary structure revealed only very limited sequence homology. However, determination of the three-dimensional structure of the P. glumae lipase indicated that at least some of the bacterial lipases will presumably reveal a conserved folding pattern called the α/β-hydrolase fold, which has been described for other microbial and human lipases. The catalytic site of lipases is buried inside the protein and contains a serine-protease-like catalytic triad consisting of the amino acids serine, histidine, and aspartate (or glutamate). The Ser-residue is located in a strictly conserved β-εSer-α motif. The active site is covered by a lid-like α-helical structure which moves away upon contact of the lipase with its substrate, thereby exposing hydrophobic residues at the protein's surface mediating the contact between protein and substrate. This movable lid-like α-helix explains at a molecular level the lipase-specific phenomenon of interfacial activation. At least some of the pathogenic bacterial species produce a lipase which has been studied with respect to its role as a virulence factor. Lipases of Propionibacterium acnes and Staphylococcus epidermidis may be involved in colonization and persistence of these bacteria on the human skin. Lipases of S. aureus and P. aeruginosa are produced during the bacterial infection process and, at least in vitro, considerably impair the function of different cell types involved in the human immune response like macrophages or platelets. The present state of knowledge suggests to classify the lipases as important bacterial virulence factors which exert their harmful effects in combination with other bacterial enzymes, in particular the phospholipases C. Most of the steadily increasing interest in bacterial lipases is based on their biotechnological applications which are partly based on their potential to catalyze not only hydrolysis but also synthesis of a variety of industrially valuable products. Optically active compounds, various esters and lactones are among the substances synthesized using bacterial lipases. Recently, an important application emerged with the addition of bacterial lipases to household detergents in order to reduce or even replace synthetic detergent chemicals which pose considerable environmental problems. As a main conclusion, lipases represent an extremely versatile group of bacterial extracellular enzymes that are capable of performing a variety of important reactions, thereby presenting a fascinating field tot future research.

Quantum cascade laser-based reflectance spectroscopy: a robust approach for the classification of plastic type

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Michel, A. P. M., Morrison, A. E., Colson, B. C., Pardis, W. A., Moya, X. A., Harb, C. C., & White, H. K. Quantum cascade laser-based reflectance spectroscopy: a robust approach for the classification of plastic type. Optics Express, 28(12), (2020): 17741-17756, doi:10.1364/OE.393231.The identification of plastic type is important for environmental applications ranging from recycling to understanding the fate of plastics in marine, atmospheric, and terrestrial environments. Infrared reflectance spectroscopy is a powerful approach for plastics identification, requiring only optical access to a sample. The use of visible and near-infrared wavelengths for plastics identification are limiting as dark colored plastics absorb at these wavelengths, producing no reflectance spectra. The use of mid-infrared wavelengths instead enables dark plastics to be identified. Here we demonstrate the capability to utilize a pulsed, widely-tunable (5.59 - 7.41 µm) mid-infrared quantum cascade laser, as the source for reflectance spectroscopy, for the rapid and robust identification of plastics. Through the application of linear discriminant analysis to the resulting spectral data set, we demonstrate that we can correctly classify five plastic types: polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS), with a 97% accuracy rate.Richard Saltonstall Charitable Foundation; National Academies Keck Futures Initiative (NAKFI DBS13)

Evidence for diversifying selection of genetic regions of encoding putative collagen-like host-adhesive fibers in Pasteuria penetrans

© FEMS 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Pasteuria spp. belong to a group of genetically diverse endospore-forming bacteria (phylum: Firmicutes) that are known to parasitize plant-parasitic nematodes and water fleas (Daphnia spp.). Collagen-like fibres form the nap on the surface of endospores and the genes encoding these sequences have been hypothesised to be involved in the adhesion of the endospores of Pasteuria spp. to their hosts. We report a group of 17 unique collagen-like genes putatively encoded by Pasteuria penetrans (strain: Res148) that formed five different phylogenetic clusters and suggest that collagen-like proteins are an important source of genetic diversity in animal pathogenic Firmicutes including Pasteuria. Additionally, and unexpectedly, we identified a putative collagen-like sequence which had a very different sequence structure to the other collagen-like proteins but was similar to the protein sequences in Megaviruses that are involved in host-parasite interactions. We, therefore, suggest that these diverse endospore surface proteins in Pasteuria are involved in biological functions, such as cellular adhesion; however, they are not of monophyletic origin and were possibly obtained de novo by mutation or possibly through selection acting upon several historic horizontal gene transfer events.Peer reviewedFinal Published versio

Stepped-wedge randomised trial of laparoscopic ventral mesh rectopexy in adults with chronic constipation:Study protocol for a randomized controlled trial

Funding was from the UK National Institute of Health Research, funding reference PGfAR: RP-PG-0612-20001 (£1,971,934). The calculation of all costs and contracting has been performed in conjunction with the sponsor. Indemnity: Queen Mary University London has agreed to act as study sponsor. Insurance and indemnity will be provided by the sponsor

Antibiotic research and development: business as usual?

This article contends that poor economic incentives are an important reason for the lack of new drugs and explains how the DRIVE-AB intends to change the landscape by harnessing the expertise, motivation and diversity of its partner

Current and prospective pharmacological targets in relation to antimigraine action

Migraine is a recurrent incapacitating neurovascular disorder characterized by unilateral and throbbing headaches associated with photophobia, phonophobia, nausea, and vomiting. Current specific drugs used in the acute treatment of migraine interact with vascular receptors, a fact that has raised concerns about their cardiovascular safety. In the past, α-adrenoceptor agonists (ergotamine, dihydroergotamine, isometheptene) were used. The last two decades have witnessed the advent of 5-HT1B/1D receptor agonists (sumatriptan and second-generation triptans), which have a well-established efficacy in the acute treatment of migraine. Moreover, current prophylactic treatments of migraine include 5-HT2 receptor antagonists, Ca2+ channel blockers, and β-adrenoceptor antagonists. Despite the progress in migraine research and in view of its complex etiology, this disease still remains underdiagnosed, and available therapies are underused. In this review, we have discussed pharmacological targets in migraine, with special emphasis on compounds acting on 5-HT (5-HT1-7), adrenergic (α1, α2, and β), calcitonin gene-related peptide (CGRP 1 and CGRP2), adenosine (A1, A2, and A3), glutamate (NMDA, AMPA, kainate, and metabotropic), dopamine, endothelin, and female hormone (estrogen and progesterone) receptors. In addition, we have considered some other targets, including gamma-aminobutyric acid, angiotensin, bradykinin, histamine, and ionotropic receptors, in relation to antimigraine therapy. Finally, the cardiovascular safety of current and prospective antimigraine therapies is touched upon