Chemical structure of the lipid A component of lipopolysaccharides of the genus Pectinatus

Pectinatus spp. - Unpleasant and recurrent brewing spoilage bacteria

Traditionally, beer has been recognised as a beverage with high microbiological stability because of the hostile growth environment posed by beer and increasing attention being paid to brewery hygiene. However, the microbiological risk has increased in recent years because of technological advances toward reducing oxygen in beers, besides the increase in novel beer styles production, such as non-pasteurised, flash pasteurised, cold sterilised, mid-strength, and alcoholic-free beer, that are more prone to spoilage bacteria. Moreover, using innovative beer ingredients like fruits and vegetables is an added cause of microbial spoilage. To maintain quality and good brand image, beer spoilage microorganisms are a critical concern for breweries worldwide. Pectinatus and Megasphaera are Gram-negative bacteria mostly found in improper brewing environments, leading to consumer complaints and financial losses. Because of the lack of compiled scientific knowledge on Pectinatus spoilage ability, this review provides a comprehensive overview of the occurrence, survival mechanisms, and the factors affecting beer spoilage Pectinatus species in the brewing process.

Pectinatus sottacetonis sp. nov., isolated from a commercial pickle spoilage tank

A strictly anaerobic, Gram-stain-negative, non-spore-forming, motile bacterium, designated strain FSRU B0405T, was isolated from a commercial pickle spoilage tank and characterized by biochemical, physiological and molecular biological methods. Analyses of the 16S rRNA gene sequence of strain FSRU B0405T showed affiliation to the class Negativicutes in the phylum Firmicutes , with the closest relatives being the type strains of Pectinatus haikarae (96 %) and Pectinatus brassicae (95 %). In maximum-likelihood and neighbour-joining phylogenetic trees, strain FSRU B0405T clustered definitively (in 100 % of bootstrapped trees) within the genus Pectinatus , but not specifically with any characterized species within this genus. Strain FSRU B0405T was a slightly curved rod, varying from 3 to 30 µm in length, motile with a distinctive X-wise movement, having flagella only on the concave side of the cell. The isolate produced acetate and propionate from fructose and glucose as major metabolites similar to type strains of species of the genus Pectinatus . The major fatty acids were C11 : 0, C13 : 0, C15 : 0, C13 : 0 3-OH, C17 : 1 and C18 : 1ω11t. Strain FSRU B0405T differed from the pickle wastewater strain, Pectinatus brassicae TYT, due to its lack of susceptibility to vancomycin, acetoin production, growth temperature range, acid production from adonitol, erythritol, glycerol, inositol, lactose, maltose, mannose, ribose, salicin, sorbitol, trehalose and xylitol and lack of hydrolysis of milk. Strain FSRU B0405T could be differentiated from other species of the genus Pectinatus both phenotypically and genetically. The results indicate that strain FSRU B0405T represents a novel species of the genus Pectinatus , for which the name Pectinatus sottacetonis sp. nov. is proposed. The type strain is FSRU B0405T ( = ATCC BAA-2501T = VTT E-113163T). An emended description of the genus Pectinatus is also provided.

Characterization of the microbial community in indoor environments by chemical marker analysis: an update and critical evaluation

We published recently an integrated procedure for applying chemical marker analysis to characterize the microbiology of indoor environments comprising a scheme for extraction and analysis of markers of endotoxin, peptidoglycan/bacterial biomass, and fungal biomass. In the present paper, we report some significant improvements and also new possibilities of the described approach. We found that while 3-hydroxy fatty acids (3-OH FAs) of 10-14 carbon chain lengths are useful endotoxin markers, longer 3-OH FAs (i.e. with 16 carbon atoms and more) may rather serve as markers of Actinobacteria. We introduced 13C-labeled 3-hydroxytridecanoic acid, from labeled Pectinatus cerevisiiphilus, as an internal standard to improve quantification of the 3-OH FAs in the gas chromatography-mass spectrometry analysis. Finally, in experiments aiming to identify a suitable method for collection of house dust for chemical marker analysis, we found that the marker compositions of dusts sedimented on plexiglass plates that were spatially well-distributed in a studied room at different heights above floor level, were undistinguishable. This type of sampling thus appears to be well suited for use, e.g. in epidemiological studies. In summary, the presented work describes important new capabilities of chemical marker analysis in defining human exposure to microorganisms in indoor environments.

PRACTICAL IMPLICATIONS

We are developing an integrated methodology for characterizing the microbiology of indoor environments where specific microbial monomeric constituents in building materials and inhalable house dust particles are determined by using mass spectrometry-based methods. The methodology should represent a firm basis in research aiming to relate microbial exposure indoors to well-being and health.

Lipopolysaccharides of anaerobic beer spoilage bacteria of the genusPectinatus– lipopolysaccharides of a Gram-positive genus

Bacteria of the genus Pectinatus emerged during the seventies as contaminants and spoilage organisms in packaged beer. This genus comprises two species, Pectinatus cerevisiiphilus and Pectinatus frisingensis; both are strict anaerobes. On the basis of genomic properties the genus is placed among low GC Gram-positive bacteria (phylum Firmicutes, class Clostridia, order Clostridiales, family Acidaminococcaceae). Despite this assignment, Pectinatus bacteria possess an outer membrane and lipopolysaccharide (LPS) typical of Gram-negative bacteria. The present review compiles the structural and compositional studies performed on Pectinatus LPS. These lipopolysaccharides exhibit extensive heterogeneity, i.e. several macromolecularly and structurally distinct LPS molecules are produced by each strain. Whereas heterogeneity is a common property in lipopolysaccharides, Pectinatus LPS have been shown to contain exceptional carbohydrate structures, consisting of a fairly conserved core region that carries a large non-repetitive saccharide that probably replaces the O-specific chain. Such structures represent a novel architectural principle of the LPS molecule.

Structure of the exceptionally large nonrepetitive carbohydrate backbone of the lipopolysaccharide of Pectinatus frisingensis strain VTT E-82164

The structures of the oligosaccharides obtained after acetic acid hydrolysis and alkaline deacylation of the rough-type lipopolysaccharide (LPS) from Pectinatus frisingensis strain VTT E-82164 were analysed using NMR spectroscopy, MS and chemical methods. The LPS contains two major structural variants, differing by a decasaccharide fragment, and some minor variants lacking the terminal glucose residue. The largest structure of the carbohydrate backbone of the LPS that could be deduced from experimental results consists of 25 monosaccharides (including the previously found Ara4NP residue in lipid A) arranged in a well-defined nonrepetitive structure: We presume that the shorter variant with R1 = H represents the core-lipid A part of the LPS, and the additional fragment is present instead of the O-specific polysaccharide. Structures of this type have not been previously described. Analysis of the deacylation products obtained from the LPS of the smooth strain, VTT E-79100T, showed that it contains a very similar core but with one different glycosidic linkage.

Structure elucidation of the O-chain from the major lipopolysaccharide of the Xanthomonas campestris strain 642

A novel O-polysaccharide consisting of D-Xylp and L-Rhap in the molar ratio of 1:2.5 was identified as the major component in the lipopolysaccharide fraction of Xanthomonas campestris strain 642, which is responsible for a new bacterial disease of the strawberry plant. Its structure was mainly determined using chemical analysis, Smith degradation and 1D and 2D NMR spectroscopy experiments as: carbohydrate sequence [see text].

Solution structure of polymyxins B and E and effect of binding to lipopolysaccharide: an NMR and molecular modeling study

The cyclic decapeptides polymyxin B (PmB) and E (PmE) (mo-K'TK'-cyclo-[K'K'XLK'K'T]; mo, methyl octanoate; K', diaminobutyric acid; X, D-Phe (PmB) or D-Leu (PmE)) display antimicrobial and lipopolysaccharide (LPS) antagonistic activities. We have investigated the conformational behavior of PmB and PmE in water solution, free and bound to LPS, by homonuclear NMR and molecular modeling methods. The free peptides exist in equilibria of fast exchanging conformations with local preferences for a distorted type II' beta-turn from residues 5-8, and/or a gamma-turn in residue 10. These two motifs are not present in the bound conformation of the peptides. The latter is amphiphilic separating the two hydrophobic residues in the cycle from the positively charged diaminobutyric acid side chains by an envelope-like fold of the cycle. The bound conformation is used for the derivation of a model of the PmB-lipid A complex based on electrostatic interactions and reduction of hydrophobic area. The proposed mode of binding breaks up the supramolecular structure of LPS connected with its toxicity. The model should contribute to the understanding of entropy-driven PmB-lipid A binding at the molecular level and assist the design of inhibitors of endotoxic activity.

Nisin, temperature and pH effects on growth and viability of pectinatus frisingensis, a gram-negative, strictly anaerobic beer-spoilage bacterium

Pectinatus frisingensis, a Gram-negative and strictly anaerobic beer spoilage bacterium is sensitive to nisin. An increase in nisin concentration (0 to 1100 IU ml-1) added to the culture medium prolonged the lag phase, and decreased the growth rate of the bacterium. In addition, late exponential cells of P. frisingensis exposed to low concentrations of nisin lost immediately a part of their intracellular K+. Presence of Mg2+ up to 15 mmol l-1 did not protect P. frisingensis from nisin-induced loss of viability and K+ efflux. Potassium leaks were also measured in P. frisingensis late exponential phase cells exposed to combined effects of nisin addition (100-500 IU ml-1), 10 min mild heat-treatment (50 degrees C) or rapid cooling (2 degrees C), and pH (4.0 and 6.2). Net K+ efflux from both starving and glucose-metabolizing cells, was more important at pH 6.2, whatever the temperature treatment and nisin addition. Reincubation at 30 degrees C of P. frisingensis glucose-metabolizing cells exposed to a preliminary combination of nisin addition and mild heat or cooling down treatment, showed that cells exposed to rapid cooling reaccumulated more K+ than heat-treated cells, whatever the pH conditions. A combination of nisin and mild heat-treatment could thus be of interest to prevent P. frisingensis growth in beers.

Structural characterization of the lipid A component of Helicobacter pylori rough- and smooth-form lipopolysaccharides

The chemical structure of free lipid A isolated from rough- and smooth-form lipopolysaccharides (R-LPS and S-LPS, respectively) of the human gastroduodenal pathogen Helicobacter pylori was elucidated by compositional and degradative analysis, nuclear magnetic resonance spectroscopy, and mass spectrometry. The predominant molecular species in both lipid A components are identical and tetraacylated, but a second molecular species which is hexaacylated is also present in lipid A from S-LPS. Despite differences in substitution by acyl chains, the hydrophilic backbone of the molecules consisted of beta(1,6)-linked D-glucosamine (GlcN) disaccharide 1-phosphate. Because of microheterogeneity, nonstoichiometric amounts of ethanolamine-phosphate were also linked to the glycosidic hydroxyl group. In S-LPS, but not in R-LPS, the hydroxyl group at position 4' was partially substituted by another phosphate group. Considerable variation in the distribution of fatty acids on the lipid A backbone was revealed by laser desorption mass spectrometry. In tetraacyl lipid A, the amino group of the reducing GlcN carried (R)-3-hydroxyoctadecanoic acid (position 2), that of the nonreducing GlcN carried (R)-3-(octadecanoyloxy)octadecanoic acid (position 2'), and ester-bound (R)-3-hydroxyhexadecanoic acid was attached at position 3. Hexaacyl lipid A had a similar substitution by fatty acids, but in addition, ester-bound (R)-3-(dodecanoyloxy)hexadecanoic acid or (R)-3(tetradecanoyloxy)hexadecanoic acid was attached at position 3'. The predominant absence of ester-bound 4'-phosphate and the presence of tetraacyl lipid A with fatty acids of 16 to 18 carbons in length differentiate H. pylori lipid A from that of other bacterial species and help explain the low endotoxic and biological activities of H. pylori LPS.

Characterization of lipopolysaccharides of polymyxin-resistant and polymyxin-sensitive Klebsiella pneumoniae O3

Lipopolysaccharides isolated from the polymyxin-resistant Klebsiella pneumoniae O3 mutant OM-5 and its polymyxin-sensitive parent LEN-1 were analyzed for chemical composition, and their lipid A portions were structurally characterized. The lipopolysaccharide of OM-5 contained approximately five times more 4-amino-4-deoxy-L-arabinopyranose than that of LEN-1. Other saccharide and phosphate components exhibited no significant differences. Structural characterization, including analyses by phosphorus magnetic resonance spectroscopy and by fast atom bombardment mass spectrometry, revealed a novel type of lipid A. In the OM-5 lipopolysaccharide, both phosphates of lipid A were almost totally present as phosphodiesters with 4-amino-4-deoxy-L-arabinopyranose. In the sensitive-type LEN-1 lipid A, the extent of this substitution was much lower, especially in the glycosidically linked phosphate. Phosphate in these K. pneumoniae lipopolysaccharides was almost exclusively found in lipid A. These results show that cationic substituents of phosphates of lipid A play a decisive role in determining polymyxin reactivity. OM-5 was also found to contain a large proportion of heptaacyl lipid A, which represented only a small fraction of lipid A in LEN-1.

Cellular fatty acyl and alkenyl residues in Megasphaera and Pectinatus species: contrasting profiles and detection of beer spoilage

The strictly anaerobic Gram-negative beer spoilage bacteria Megasphaera cerevisiae, Pectinatus cerevisiiphilus and P. frisingensis were subjected to cellular fatty acid analysis, employing acid- and base-catalysed cleavage, gas chromatography and mass spectrometry. M. cerevisiae contained 12:0, 16:0, 16:1, 18:1, 17:cyc, 19:cyc, 12:0(3OH), 14:0(3OH) as the main fatty acids, and alk-1-enyl chains instead of acyl chains were detected to a considerable extent (14% of total fatty acids), indicating the presence of plasmalogens. The fatty acid pattern of M. cerevisiae was almost identical to that of M. elsdenii, the only species previously assigned to this genus. P. cerevisiiphilus and P. frisingensis yielded fatty acids that were heavily dominated by odd-numbered chains; 11:0, 15:0, 17:1, 18:cyc and 13:0(3OH) were the main fatty acids detected in both species. Alk-1-enyl chains with similar chain lengths were also found. Both Pectinatus species contained six different 3-hydroxy fatty acids with chain lengths between 11 and 15 carbons, 13:0(3OH) being dominant and the others accounting for generally less than 1% of total fatty acids. Among the minor components, an unsaturated 3-hydroxy fatty acid was detected which was shown to be 13:1(30H). In addition, fatty acid analysis was shown to be applicable to detection of bacterial contamination of beer.

Lipopolysaccharides of polymyxin B-resistant mutants of Escherichia coli are extensively substituted by 2-aminoethyl pyrophosphate and contain aminoarabinose in lipid A

Lipopolysaccharides (LPS) of two polymyxin-resistant (pmr) mutants and the corresponding parent strain of Escherichia coli were chemically analysed for composition and subjected to 31P-NMR (nuclear magnetic resonance) for assessment of phosphate substitution. Whereas the saccharide portions, fatty acids, and phosphate contents were similar in wild-type and pmr LPS, the latter contained two- to threefold higher amounts of 2-aminoethanol. The pmr LPS also contained 4-amino-4-deoxy-L-arabinopyranose (L-Arap4N), which is normally not a component of E. coli LPS. This aminopentose has been assigned to be linked to the 4'-phosphate of lipid A. Comparative 31P-NMR analysis of the de-O-acylated LPS of the wild-type and pmr strains revealed that phosphate groups of the pmr LPS were mainly (71-79%) diphosphate diesters, which accounted for only 20% in the wild-type LPS. Diphosphate monoesters were virtually nonexistent in the pmr LPS, whereas they accounted for 42% of all phosphates in wild-type LPS. In the lipid A of the pmr strains, the 4'-phosphate was to a significant degree (35%) substituted by L-Arap4N, whereas in the wild-type LPS the L-ArapN was absent. In the pmr lipid A, 2-aminoethanol was completely substituting the glycosidic pyrophosphate but not the glycosidic monophosphate, forming a diphosphate diester linkage at this position in 40% of lipid A molecules. In the wild-type LPS the glycosidic position of lipid A carried mostly unsubstituted monophosphate and pyrophosphate. Thus the polymyxin resistance was shown to be associated, along with the esterification of the lipid A 4'-monophosphate by aminoarabinose, with extensive esterification of diphosphates in LPS by 2-aminoethanol.