THE FATTY ACIDS OF BACTERIA

The role of membrane physiology in sHSP Lo18-lipid interaction and lipochaperone activity

To cope with environmental stresses, organisms, including lactic acid bacteria such as O. oeni, produce stress proteins called HSPs. In wine, O. oeni is constantly confronted by stress affecting its membrane fluidity. To survive through in these deleterious conditions, O. oeni synthesizes Lo18, a unique, small HSP which acts as a molecular chaperone and a lipochaperone. The molecular mechanism underlying its lipochaperone activity, particularly regarding membrane lipid composition, remains poorly understood. In this context, Lo18 lipochaperone activity and the associated modification in protein structure were studied during interaction with different liposomes from O. oeni cultures representing unstressed, stressed and stressed-adapted physiological states. The results showed that the presence of the membrane (whatever its nature) induces a modification of Lo18's structure. Also, the presence of oleic acid and/or phosphatidylglycerol is important to favor Lo18-membrane interaction, allowing lipochaperone activity. This research enhances understanding of sHSP-membrane interactions in bacterial systems.

Mycobacterium tuberculosis Rv3435c regulates inflammatory cytokines and promotes the intracellular survival of recombinant Mycobacteria

Mycobacterium tuberculosis is a pathogenic bacterium that is parasitic in macrophages and show high adaptation to the host's immune response. It can also trigger a complex immune response in the host. This relies on proteins encoded by a series of M. tuberculosis-encoded virulence genes. We found that the M. tuberculosis Rv3435c gene is highly conserved among pathogenic mycobacteria, and might be a virulence gene. To explore the gene function of Rv3435c, we used Mycobacterium smegmatis to construct a recombinant mycobacterium expressing Rv3435c heterologously. The results that Rv3435c is a cell wall-related protein that changes bacterial and colony morphology, inhibits the growth rate of recombinant mycobacteria, and enhances their resistance to various stresses. We also found that the fatty acid levels of the recombinant strain changed. Simultaneously, Rv3435c can inhibit the expression and secretion of inflammatory factors and host cell apoptosis, and enhance the survival of recombinant bacteria in macrophages. Experimental data indicated that Rv3435c might play an important role in Mycobacterium tuberculosis infection.

Structures of an unusual 3-hydroxyacyl dehydratase (FabZ) from a ladderane-producing organism with an unexpected substrate preference

The genomes of anaerobic ammonium-oxidizing (anammox) bacteria contain a gene cluster comprising genes of unusual fatty acid biosynthesis enzymes that were suggested to be involved in the synthesis of the unique "ladderane" lipids produced by these organisms. This cluster encodes an acyl carrier protein (denoted as "amxACP") and a variant of FabZ, an ACP-3-hydroxyacyl dehydratase. In this study, we characterize this enzyme, which we call anammox-specific FabZ ("amxFabZ"), to investigate the unresolved biosynthetic pathway of ladderane lipids. We find that amxFabZ displays distinct sequence differences to "canonical" FabZ, such as a bulky, apolar residue on the inside of the substrate binding tunnel, where the canonical enzyme has a glycine. Additionally, substrate screens suggest that amxFabZ efficiently converts substrates with acyl chain lengths of up to eight carbons, whereas longer substrates are converted much more slowly under the conditions used. We also present crystal structures of amxFabZs, mutational studies and the structure of a complex between amxFabZ and amxACP, which show that the structures alone cannot explain the apparent differences from canonical FabZ. Moreover, we find that while amxFabZ does dehydrate substrates bound to amxACP, it does not convert substrates bound to canonical ACP of the same anammox organism. We discuss the possible functional relevance of these observations in the light of proposals for the mechanism for ladderane biosynthesis.

Transformation of Cyanobacterial Biomolecules by Iron Oxides During Flash Pyrolysis: Implications for Mars Life-Detection Missions

Answering the question of whether life ever existed on Mars is a key goal of both NASA's and ESA's imminent Mars rover missions. The obfuscatory effects of oxidizing salts, such as perchlorates and sulfates, on organic matter during thermal decomposition analysis techniques are well established. Less well studied are the transformative effects of iron oxides and (oxy)hydroxides, which are present in great abundances in the martian regolith. We examined the products of flash pyrolysis-gas chromatography-mass spectrometry (a technique analogous to the thermal techniques employed by past, current, and future landed Mars missions) which form when the cyanobacteria Arthrospira platensis are heated in the presence of a variety of Mars-relevant iron-bearing minerals. We found that iron oxides/(oxy)hydroxides have transformative effects on the pyrolytic products of cyanobacterial biomolecules. Both the abundance and variety of molecular species detected were decreased as iron substrates transformed biomolecules, by both oxidative and reductive processes, into lower fidelity alkanes, aromatic and aryl-bonded hydrocarbons. Despite the loss of fidelity, a suite that contains mid-length alkanes and polyaromatic hydrocarbons and/or aryl-bonded molecules in iron-rich samples subjected to pyrolysis may allude to the transformation of cyanobacterially derived mid-long chain length fatty acids (particularly unsaturated fatty acids) originally present in the sample. Hematite was found to be the iron oxide with the lowest transformation potential, and because this iron oxide has a high affinity for codeposition of organic matter and preservation over geological timescales, sampling at Mars should target sediments/strata that have undergone a diagenetic history encouraging the dehydration, dihydroxylation, and oxidation of more reactive iron-bearing phases to hematite by looking for (mineralogical) evidence of the activity of oxidizing, acidic/neutral, and either hot or long-lived fluids.

Adaptation of Pseudomonas helmanticensis to fat hydrolysates and SDS: fatty acid response and aggregate formation

An essential part of designing any biotechnological process is examination of the physiological state of producer cells in different phases of cultivation. The main marker of a bacterial cell's state is its fatty acid (FA) profile, reflecting membrane lipid composition. Consideration of FA composition enables assessment of bacterial responses to cultivation conditions and helps biotechnologists understand the most significant factors impacting cellular metabolism. In this work, soil SDS-degrading Pseudomonas helmanticensis was studied at the fatty acid profile level, including analysis of rearrangement between planktonic and aggregated forms. The set of substrates included fat hydrolysates, SDS, and their mixtures with glucose. Such media are useful in bioplastic production since they can help incrementally lower overall costs. Conventional gas chromatography-mass spectrometry was used for FA analysis. Acridine orange-stained aggregates were observed by epifluorescence microscopy. The bacterium was shown to change fatty acid composition in the presence of hydrolyzed fats or SDS. These changes seem to be driven by the depletion of metabolizable substrates in the culture medium. Cell aggregation has also been found to be a defense strategy, particularly with anionic surfactant (SDS) exposure. It was shown that simple fluidity indices (such as saturated/unsaturated FA ratios) do not always sufficiently characterize a cell's physiological state, and morphological examination is essential in cases where complex carbon sources are used.

Pyrolysis of Carboxylic Acids in the Presence of Iron Oxides: Implications for Life Detection on Missions to Mars

The search for, and characterization of, organic matter on Mars is central to efforts in identifying habitable environments and detecting evidence of life in the martian surface and near surface. Iron oxides are ubiquitous in the martian regolith and are known to be associated with the deposition and preservation of organic matter in certain terrestrial environments, thus iron oxide-rich sediments are potential targets for life-detection missions. The most frequently used protocol for martian organic matter characterization (also planned for use on ExoMars) has been thermal extraction for the transfer of organic matter to gas chromatography-mass spectrometry (GC-MS) detectors. For the effective use of thermal extraction for martian samples, it is necessary to explore how potential biomarker organic molecules evolve during this process in the presence of iron oxides. We have thermally decomposed iron oxides simultaneously with (z)-octadec-9-enoic and n-octadecanoic acids and analyzed the products through pyrolysis-GC-MS. We found that the thermally driven dehydration, reduction, and recrystallization of iron oxides transformed fatty acids. Overall detectability of products greatly reduced, molecular diversity decreased, unsaturated products decreased, and aromatization increased. The severity of this effect increased as reduction potential of the iron oxide and inferred free radical formation increased. Of the iron oxides tested hematite showed the least transformative effects, followed by magnetite, goethite, then ferrihydrite. It was possible to identify the saturation state of the parent carboxylic acid at high (0.5 wt %) concentrations by the distribution of n-alkylbenzenes in the pyrolysis products. When selecting life-detection targets on Mars, localities where hematite is the dominant iron oxide could be targeted preferentially, otherwise thermal analysis of carboxylic acids, or similar biomarker molecules, will lead to enhanced polymerization, aromatization, and breakdown, which will in turn reduce the fidelity of the original biomarker, similar to changes normally observed during thermal maturation.

Detection of Species-Specific Lipids by Routine MALDI TOF Mass Spectrometry to Unlock the Challenges of Microbial Identification and Antimicrobial Susceptibility Testing

MALDI-TOF mass spectrometry has revolutionized clinical microbiology diagnostics by delivering accurate, fast, and reliable identification of microorganisms. It is conventionally based on the detection of intracellular molecules, mainly ribosomal proteins, for identification at the species-level and/or genus-level. Nevertheless, for some microorganisms (e.g., for mycobacteria) extensive protocols are necessary in order to extract intracellular proteins, and in some cases a protein-based approach cannot provide sufficient evidence to accurately identify the microorganisms within the same genus (e.g., Shigella sp. vs E. coli and the species of the M. tuberculosis complex). Consequently lipids, along with proteins are also molecules of interest. Lipids are ubiquitous, but their structural diversity delivers complementary information to the conventional protein-based clinical microbiology matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) based approaches currently used. Lipid modifications, such as the ones found on lipid A related to polymyxin resistance in Gram-negative pathogens (e.g., phosphoethanolamine and aminoarabinose), not only play a role in the detection of microorganisms by routine MALDI-TOF mass spectrometry but can also be used as a read-out of drug susceptibility. In this review, we will demonstrate that in combination with proteins, lipids are a game-changer in both the rapid detection of pathogens and the determination of their drug susceptibility using routine MALDI-TOF mass spectrometry systems.

High-Throughput Fingerprinting of Rhizobial Free Fatty Acids by Chemical Thin-Film Deposition and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Fatty acids (FAs) represent an important class of metabolites, impacting on membrane building blocks and signaling compounds in cellular regulatory networks. In nature, prokaryotes are characterized with the most impressing FA structural diversity and the highest relative content of free fatty acids (FFAs). In this context, nitrogen-fixing bacteria (order Rhizobiales), the symbionts of legumes, are particularly interesting. Indeed, the FA profiles influence the structure of rhizobial nodulation factors, required for successful infection of plant root. Although FA patterns can be assessed by gas chromatography-(GC-) and liquid chromatography-mass spectrometry (LC-MS), sample preparation for these methods is time-consuming and quantification suffers from compromised sensitivity, low stability of derivatives and artifacts. In contrast, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) represents an excellent platform for high-efficient metabolite fingerprinting, also applicable to FFAs. Therefore, here we propose a simple and straightforward protocol for high-throughput relative quantification of FFAs in rhizobia by combination of Langmuir technology and MALDI-TOF-MS featuring a high sensitivity, accuracy and precision of quantification. We describe a step-by-step procedure comprising rhizobia culturing, pre-cleaning, extraction, sample preparation, mass spectrometric analysis, data processing and post-processing. As a case study, a comparison of the FFA metabolomes of two rhizobia species-Rhizobium leguminosarum and Sinorhizobium meliloti, demonstrates the analytical potential of the protocol.

Exploring the potential of co-fermenting sewage sludge and lipids in a resource recovery scenario

In this study, co-fermentation of primary sludge (PS) or waste activated sludge (WAS) with lipids was explored to improve volatile fatty acid production. PS and WAS were used as base substrate to facilitate lipid fermentation at 20 °C under semi-aerobic conditions. Mono-fermentation tests showed higher VFA yields for PS (32-89 mgCOD gVS^-1) than for WAS (20-41 mgCOD gVS^-1) where propionate production was favoured. The principal component analysis showed that the base substrate had a notable influence on co-fermentation yields and profile. Co-fermentation with WAS resulted in a greater extent of oleic acid degradation (up to 4.7%) and evidence of chain elongation producing valerate. The occurrence of chain elongation suggests that co-fermentation can be engineered to favour medium-chain fatty acids without the addition of external commodity chemicals. BMP tests showed that neither mono-fermentation nor co-fermentation had an impact on downstream anaerobic digestion.

Evidence of defined temporal expression patterns that lead a gram-negative cell out of dormancy

Many bacterial species are capable of forming long-lived dormant cells. The best characterized are heat and desiccation resistant spores produced by many Gram-positive species. Less characterized are dormant cysts produced by several Gram-negative species that are somewhat tolerant to increased temperature and very resistant to desiccation. While there is progress in understanding regulatory circuits that control spore germination, there is scarce information on how Gram-negative organisms emerges from dormancy. In this study, we show that R. centenum cysts germinate by emerging a pair of motile vegetative cells from a thick cyst cell wall coat ~ 6 hrs post induction of germination. Time-lapse transcriptomic analysis reveals that there is a defined temporal pattern of gene expression changes during R. centenum cyst germination. The first observable changes are increases in expression of genes for protein synthesis, an increase in expression of genes involved in the generation of a membrane potential and the use of this potential for ATP synthesis via ATPase expression. These early events are followed by expression changes that affect the cell wall and membrane composition, followed by expression changes that promote chromosome replication. Midway through germination, expression changes occur that promote the flow of carbon through the TCA cycle to generate reducing power and parallel synthesis of electron transfer components involved in oxidative phosphorylation. Finally, late expression changes promote the synthesis of a photosystem as well as flagellar and chemotaxis components for motility.

Flavicella sediminum sp. nov., isolated from marine sediment

A novel, Gram-stain-negative, motile, flagellated, aerobic, rod-shaped (0.5-0.7 µm wide and 1.0-1.2 µm long) and faint-yellow strain, designated ALS 84^T, was isolated from marine sediment sampled at Ailian bay, Rongcheng, PR China. Growth occurred in the presence of 1-3 % (w/v) NaCl (optimum, 2 % NaCl), at pH 4.0-8.0 (pH 6.0-7.0) and at 8-30 °C (28 °C). The genome size was 4.37 Mbp. The G+C content of the genomic DNA was 33.6 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequences suggested that strain ALS 84^T belongs to the genus Flavicella within the family Flavobacteriaceae, and is most closely related to Flavicella marina (95.6 % similarity). The major fatty acids (>10 %) were iso-C_{15 : 0} 3-OH (22.9 %), iso-C_{15 : 0} (14.0 %) and C_{16 : 0} (10.9 %). The major polar lipids were phosphatidylethanolamine and three unidentified lipids. Menaquinone-6 (MK-6) was identified as the respiratory quinone. On the basis of the phenotypic, phylogenetic and chemotaxonomic data obtained in the study, strain ALS 84^T is considered to represent a novel species of the genus Flavicella, for which the name Flavicella sediminum sp. nov. is proposed. The type strain of the novel species is strain ALS 84^T (=KCTC 62398^T=MCCC 1K03480^T).

Solid Phase Micro Extraction: Potential for Organic Contamination Control for Planetary Protection of Life-Detection Missions to the Icy Moons of the Outer Solar System

Conclusively detecting, or ruling out the possibility of, life on the icy moons of the outer Solar System will require spacecraft missions to undergo rigorous planetary protection and contamination control procedures to achieve extremely low levels of organic terrestrial contamination. Contamination control is necessary to avoid forward contamination of the body of interest and to avoid the detection of false-positive signals, which could either mask indigenous organic chemistry of interest or cause an astrobiological false alarm. Here we test a new method for rapidly and inexpensively assessing the organic cleanliness of spaceflight hardware surfaces using solid phase micro extraction (SPME) fibers to directly swab surfaces. The results suggest that the method is both time and cost efficient. The SPME-gas chromatography-mass spectrometry (SPME-GC-MS) method is sensitive to common midweight, nonpolar contaminant compounds, for example, aliphatic and aromatic hydrocarbons, which are common contaminants in laboratory settings. While we demonstrate the potential of SPME for surface sampling, the GC-MS instrumentation restricts the SPME-GC-MS technique's sensitivity to larger polar and nonvolatile compounds. Although not used in this study, to increase the potential range of detectable compounds, SPME can also be used in conjunction with high-performance liquid chromatography/liquid chromatography-mass spectrometry systems suitable for polar analytes (Kataoka et al., 2000). Thus, our SPME method presents an opportunity to monitor organic contamination in a relatively rapid and routine way that produces information-rich data sets.

Effect of Prebiotics-Enhanced Probiotics on the Growth of Streptococcus mutans

Streptococcus mutans predominantly creates an acidic environment in an oral cavity. This results in dental demineralization and carious lesions. The probiotics are beneficial microorganisms that modulate the bacterial balance in the digestive system. Prebiotics are defined as nondigestible oligosaccharides that are utilized for the selective stimulation of the beneficial microorganisms. The objective of this study was to evaluate the efficacy of the prebiotics, galactooligosaccharides (GOS) and fructooligosaccharides (FOS), for enhancing the probiotic Lactobacillus acidophilus ATCC 4356, for inhibiting Streptococcus mutans (A32-2) for the prevention of dental caries. The growth rate of the S. mutans significantly decreased when cocultured with L. acidophilus in the GOS-supplemented medium at 3%, 4%, and 5%. In the FOS-supplemented medium, the growth rate of S. mutans significantly decreased in all concentrations when cocultured with L. acidophilus. There was no significant difference in the growth rate of L. acidophilus in all concentrations of either GOS or FOS. It can be concluded that the growth rate of S. mutans was significantly retarded when cocultured with L. acidophilus and the proper concentration of prebiotics. These prebiotics have potential for a clinical application to activate the function of the naturally intraoral L. acidophilus to inhibit S. mutans.

Effect of algal and bacterial diet on metal bioaccumulation in zooplankton from the Pearl River, South China

The biomagnification of metals (Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn) and the metalloid As in aquatic systems is a global health concern. In this study, concentrations of fatty acid biomarkers in zooplankton were analyzed from the Pearl River, South China between September 2016 and July 2017. The objective was to examine how particulate matter, algae and bacteria food sources affect metal bioaccumulation using fatty acid facilitation. In the zooplankton fraction, positive correlations were observed between Pb concentration and Eicosapentaenoic acid (EPA), Zn and Docosahexaenoic acid (DHA) (diatoms and Cryptophyceae biomarkers), Fe with Palmitoleic acid (C16:1n-7, diatom marker), and a weak association of Mn with α-linolenic acid (C18:3n-3). Cu concentration in the zooplankton increased significantly with an endogenous biotic biomarker Stearic acid (C18:0, bacteria biomarker), while Cd concentrations increased with increasing Oleic acid (C18:1n-9, green alga biomarker) concentration. There was a positive correlation between Cr concentration and the sum of Pentadecylic and Margaric acids (C15:0 + C17:0, bacteria biomarkers). Seven of the nine metals examined showed associations with fatty acids in the zooplankton. The bioaccumulation of Co, Cu, Pb, Fe, Mn and Zn concentration was correlated to the individual biomasses of Brachionus calyciflorus, Filinia longiseta, Schmackeria forbesi, Limnoithona sinenisis, Thermocyclops brevifurcatus, and Diaphanosoma dubium. For selected zooplankton taxa, the algal biomasses of Euglenophyceae, Chlorophyceae, Cryptophyceae, and Bacillariophyceae were correlated. Zooplankton were affected by selected species of phytoplankton and bacteria numbers in the Pearl River. These results show that metal accumulation in zooplankton is not only correlated with diet but is also in part, species specific with metal type. Thus, the bioaccumulation or scavenging of metals across trophic levels is a fundamental and complex component of metal cycling in aquatic environments.

Adaptive Metabolism in Staphylococci: Survival and Persistence in Environmental and Clinical Settings

Staphylococci are highly successful at colonizing a variety of dynamic environments, both nonpathogenic and those of clinical importance, and comprise the list of pathogens of global public health significance. Their remarkable survival and persistence can be attributed to a host of strategies, one of which is metabolic versatility—their ability to rapidly alter their metabolism in the presence of transient or long-term bacteriostatic and bactericidal conditions and facilitate cellular homeostasis. These attributes contribute to their widespread dissemination and challenging eradication particularly from clinical settings. The study of microbial behaviour at the metabolite level provides insight into mechanisms of survival and persistence under defined environmental and clinical conditions. This paper reviews the range of metabolic modulations that facilitate staphylococcal acclimatization and persistence in varying terrestrial and host conditions, and their public health ramifications in these settings.

The Fate of Lipid Biosignatures in a Mars-Analogue Sulfur Stream

Past life on Mars will have generated organic remains that may be preserved in present day Mars rocks. The most recent period in the history of Mars that retained widespread surface waters was the late Noachian and early Hesperian and thus possessed the potential to sustain the most evolved and widely distributed martian life. Guidance for investigating late Noachian and early Hesperian rocks is provided by studies of analogous acidic and sulfur-rich environments on Earth. Here we report organic responses for an acid stream containing acidophilic organisms whose post-mortem remains are entombed in iron sulphates and iron oxides. We find that, if life was present in the Hesperian, martian organic records will comprise microbial lipids. Lipids are a potential sizeable reservoir of fossil carbon on Mars, and can be used to distinguish between different domains of life. Concentrations of lipids, and particularly alkanoic or “fatty” acids, are highest in goethite layers that reflect high water-to-rock ratios and thus a greater potential for habitability. Goethite can dehydrate to hematite, which is widespread on Mars. Mars missions should seek to detect fatty acids or their diagenetic products in the oxides and hydroxides of iron associated with sulphur-rich environments.

A subclass of acylated anti-inflammatory mediators usurp Toll-like receptor 2 to inhibit neutrophil recruitment through peroxisome proliferator-activated receptor gamma

Toll-like receptors are host sentinel receptors that signal the presence of infectious nonself and initiate protective immunity. One of the primary immune defense mechanisms is the recruitment of neutrophils from the bloodstream into the infected tissue. Although neutrophils are important in host defense, they can also be responsible for damaging pathologies associated with excessive inflammation. Here, we report that the di-acylated TLR2 ligand lipoteichoic acid can directly inhibit neutrophil recruitment in vivo. This discovery allowed us to test the concept that conventional proinflammatory TLR2 ligands can be made to act as inhibitors through specific structural modifications. Indeed, lipopeptide TLR2 ligands, when modified at their acyl chains to contain linoleate, lose their capacity to induce inflammation and yield ligands that can directly inhibit the in vivo neutrophil recruitment initiated by a wide range of proinflammatory stimuli. The inhibitory capacity of LTA and these modified ligands requires the expression of TLR2, but is independent of the TLR2 signaling adaptor, MyD88. Instead, this inhibitory effect requires functional activity of the fatty acid and nuclear hormone receptor peroxisome proliferator-activated receptor γ (PPARγ). Therefore, these data support a model in TLR2 biology where structural modifications of these ligands can profoundly influence host-microbial interactions. These inhibitory TLR2 ligands also have broader implications with respect to their potential use in various inflammatory disease settings.

Aggregatibacter actinomycetemcomitans leukotoxin is post-translationally modified by addition of either saturated or hydroxylated fatty acyl chains

Aggregatibacter actinomycetemcomitans, a common inhabitant of the human upper aerodigestive tract, produces a repeat in toxin (RTX), leukotoxin (LtxA). The LtxA is transcribed as a 114-kDa inactive protoxin with activation being achieved by attachment of short chain fatty acyl groups to internal lysine residues. Methyl esters of LtxA that were isolated from A. actinomycetemcomitans strains JP2 and HK1651 and subjected to gas chromatography/mass spectrometry contained palmitoyl (C16:0, 27-29%) and palmitolyl (C16:1 cis Δ9, 43-44%) fatty acyl groups with smaller quantities of myristic (C14:0, 14%) and stearic (C18:0, 12-14%) fatty acids. Liquid chromatography/mass spectrometry of tryptic peptides from acylated and unacylated recombinant LtxA confirmed that Lys(562) and Lys(687) are the sites of acyl group attachment. During analysis of recombinant LtxA peptides, we observed peptide spectra that were not observed as part of the RTX acylation schemes of either Escherichia coliα-hemolysin or Bordetella pertussis cyclolysin. Mass calculations of these spectra suggested that LtxA was also modified by the addition of monohydroxylated forms of C14 and C16 acyl groups. Multiple reaction monitoring mass spectrometry identified hydroxymyristic and hydroxypalmitic acids in wild-type LtxA methyl esters. Single or tandem replacement of Lys(562) and Lys(687) with Arg blocks acylation, resulting in a >75% decrease in cytotoxicity when compared with wild-type toxin, suggesting that these post-translational modifications are playing a critical role in LtxA-mediated target cell cytotoxicity.

Temperature and food availability differentially affect the production of antimicrobial compounds in oral secretions produced by two species of burying beetle

Carrion beetles of the subfamily Nicrophorinae search and bury a carcass that they utilize for reproduction. After burial, the carcass is coated with oral secretions that delay its decomposition. Previously, oral secretions of Nicrophorus marginatus were found to show antimicrobial activity, whereas secretion of N. carolinus lacked significant activity. Here, we tested the effects of temperature, sex of the beetle, and food type on the antimicrobial properties of oral secretions of both species. Unlike previous findings, we found that oral secretions of N. carolinus had antimicrobial activity. Temperature had significant effects on the amount of secretion protein. When protein concentrations were standardized to 1 micro/ml, N. marginatus secretions had higher antimicrobial activity at cooler temperatures, while N. carolinus had higher activity at warmer ones. The sex of the beetle did not affect antimicrobial activity for either species. Beetles of both species that were fed whole rats contained more protein in their oral secretions than beetles fed with equally sized pieces of raw ground beef. After standardizing the resulting protein concentrations to 1 microg/ml, antimicrobial activity of oral secretion increased for N. carolinus after rat feeding, but not for N. marginatus. Our results highlight key ecological differences between these closely related species. In addition, they demonstrate the importance of experiments being conducted under varying environmental conditions when evaluating species for potential antimicrobial compounds.

The search for alien life in our solar system: strategies and priorities

With the assumption that future attempts to explore our Solar System for life will be limited by economic constraints, we have formulated a series of principles to guide future searches: (1) the discovery of life that has originated independently of our own would have greater significance than evidence for panspermia; (2) an unambiguous identification of living beings (or the fully preserved, intact remains of such beings) is more desirable than the discovery of markers or fossils that would inform us of the presence of life but not its composition; (3) we should initially seek carbon-based life that employs a set of monomers and polymers substantially different than our own, which would effectively balance the need for ease of detection with that of establishing a separate origin; (4) a "follow-the-carbon" strategy appears optimal for locating such alternative carbon-based life. In following this agenda, we judge that an intensive investigation of a small number of bodies in our Solar System is more likely to succeed than a broad-based survey of a great number of worlds. Our priority for investigation is (1) Titan, (2) Mars, (3) Europa. Titan displays a rich organic chemistry and offers several alternative possibilities for the discovery of extant life or the early stages that lead to life. Mars has already been subjected to considerable study through landers and orbiters. Although only small amounts of methane testify to the inventory of reduced carbon on the planet, a number of other indicators suggest that the presence of microbial life is a possibility. Care will be needed, of course, to distinguish indigenous life from that which may have spread by panspermia. Europa appears to contain a subsurface ocean with the possibility of hydrothermal vents as an energy source. Its inventory of organic carbon is not yet known.

LIPIDS OF SARCINA LUTEA. I. FATTY ACID COMPOSITION OF THE EXTRACTABLE LIPIDS

Huston, Charles K. (U.S. Army Biological Laboratories, Fort Detrick, Frederick, Md.), and Phillip W. Albro. Lipids of Sarcina lutea. I. Fatty acid composition of the extractable lipids. J. Bacteriol. 88:425-432. 1964.-The extractable lipids of Sarcina lutea were separated into several fractions by a combination of column and thin-layer chromatography. Qualitative and quantitative characterization of the fatty acid content of these lipid fractions was accomplished by means of gas-liquid chromatography and infrared analyses. Of the total extract, the lipids consisted of 2.1% free fatty acids, 51.0% glycerides, and 22.7% complex lipids; they had a fatty acid content with a complete spectrum of carbon numbers from C(8) to C(22). The fatty acids included a large component of branched-acids in addition to the normal straight-chain acids. The branched-acids, comprising 40% of the fatty acids analyzed, constituted a homologous series of iso-acids from C(12) to C(19). Two 18-carbon unsaturates were found cis-9-octadecenoate and cis-11-octadecenoate. A relatively high percentage (20.5%) of the extractable material from S. lutea was found to be hydrocarbon. This material was not further characterized.

Modified Feist broth as a serum-free alternative for enhanced production of protective antigen of Erysipelothrix rhusiopathiae

The production of protective antigen in modified serum-free nutrient broth (H. Feist, K.-D. Flossmann, and W. Erler, Arch. Exp. Veterinaermed. 30:49-57, 1976) and in brain heart infusion broth supplemented with 10% horse serum (BHIS) was evaluated for six strains of Erysipelothrix rhusiopathiae serotypes 1a, 2, 2b, 4, and N. All six strains grew to higher cell densities in modified Feist medium than in BHIS and produced larger amounts of 64,000- to 66,000- and 39,000- to 40,000-molecular-weight antigens involved in immunity to erysipelas. A vaccine produced in Feist medium from E. rhusiopathiae SE-9 (serotype 2) was highly effective in a mouse protection test. We therefore suggest that modified Feist medium is an excellent, if not superior, alternative to BHIS for production of erysipelas vaccine.

Analysis of fatty acids of the genus Rochalimaea by electron capture gas chromatography: detection of nonanoic acid

The fatty acid compositions of Rochalimaea quintana, strains Fuller and Guadalupe, and R. vinsonii, the Canadian vole agent, were determined in an effort to further characterize these bacteria. The cells were saponified with 5% NaOH in 50% methanol and acidified to pH 2. The methanolysates were extracted with chloroform, derivatized with 2,2,2-trichloroethanol, and analyzed using a Hewlett-Packard gas chromatograph equipped with a frequency pulse-modulated electron capture detector and a 3% OV-101 packed-glass column. The fatty acid profiles of the three Rochalimaea strains were similar, with octadecenoic acid (C18:1) the most abundant, followed by octadecanoic (C18:0) and hexadecanoic (C16:0) acids. Moderate to trace amounts of other acids were also present. Unexpectedly, well-defined peaks of nonanoic acid (C9) were found consistently. A portion of this acid, but not all, was extractable with chloroform. Since C9 is not reported as a usual component of bacteria and most analyses do not include a search for this fatty acid, this study was extended to three strains of Legionella and one of Campylobacter. Comparable results were obtained. Since these bacteria were grown in complex media which contain some C9, it is possible that the medium is the source of bacterial C9. Whether this compound can be synthesized by the bacteria remains to be investigated.

Antimicrobial effect of simple lipids with different branches at the methyl end group

Various fatty acids of branched nature possess fungistatic and bacteriostatic properties. Some of these, particularly those of iso-configuration, strongly enhance the effect of conventional antimicrobial agents that act inside the cell membrane. A relation between this biological effect and the collapse properties of the corresponding monomolecular surface film on water has been observed. In this work, a series of fatty acids with a slightly smaller end group than iso-propyl, the omega-cyclopropane fatty acids, as well as one possessing a somewhat larger end group, the neo-branched fatty acids, have been examined. The omega-cyclopropane fatty acids were found to be more fungistatic than the iso-acids studied earlier. Furthermore, both cyclopropane and neo-fatty acids of short chain lengths exhibited synergistic effects in combination with tetramethylthiuramdisulfide.

Evidence for the existence of an aerobic pathway for synthesis of monounsaturated fatty acids by Alcaligenes faecalis

Studies on the composition of total fatty acids of Alcaligenes faecalis harvested at different growth phases have been carried out. Ability of the organism to desaturate palmitic and stearic acid has also been tested. The organism contained palmitic (16:0), stearic (18:0), palmitoleic (16:1), cis-vaccenic (18:1), cyclopropane (17: big dn tri, open and 19: big dn tri, open), and three hydroxy acids. Increase in cyclopropane acids and corresponding decrease in monounsaturated acids in direct proportion to the age of the culture were observed, whereas other fatty acids remained relatively unaltered. A growing culture of the organism was found to desaturate [1-(14)C]palmitic acid supplied in the medium to hexadecanoic acid. Resting cells desaturated [1-(14)C]palmitic and [1-(14)C]stearic acid giving rise to about 50% of (14)C in the COOH group of corresponding monounsaturated fatty acids.

Effect of cultural conditions on the fatty acid composition of Thiobacillus novellus

The fatty acid content of Thiobacillus novellus was determined under various cultural conditions. Four fatty acids, C(16:0), C(18:0), C(18:1), and a C(19) cyclopropane acid (C(19:cyc)), generally accounted for 90 to 99% of the total acids. Phosphate concentration, temperature, culture agitation, and the presence of branch-chain precursors had no significant effect on cellular fatty acids. Autotrophically grown cells contained more saturated C(16) and C(18) acids than did heterotrophic ones, and the sum of the percentages of the C(18:1) and the C(19:cyc) acids was consistently higher in the heterotrophs. When the inorganic medium was supplemented with biotin, autotrophic cells produced more C(19:cyc) and much less C(18:1) than did autotrophs in unsupplemented medium. Heterotrophic cells grown with biotin also showed a marked reduction of the unsaturated acid and an increase in the cyclopropane acid, except when glutamatecitrate medium was employed, in which case the opposite effect was noted. Two different biotin-supplemented media yielded cells with 75 to 77% of the total fatty acids being the C(19) cyclopropane acid, one of the highest reported values for this class of acid.

Composition of fatty acids and carbohydrates in Leptospira

The fatty acid and monosaccharide composition of four pathogenic and two saprophytic strains of Leptospira was analyzed by gas chromatography (GC) and GC-mass spectrometry. Among the fatty acids, palmitic acid was most abundant and constituted 30 to 50% of the total fatty acids. Even-numbered unsaturated acids including octadecenoic, hexadecenoic, octadecadienoic, and tetradecadienoic acids comprised 40 to 60% of the total fatty acids. Tetradecanoic acid was about 5% in saprophytic strains, but 1% or less in pathogenic strains. The amount of chloroform-methanol extract of L. biflexa strain Ancona was 14 to 20% of the dry weight of the cell. Tetradecadienoic acid was found in the chloroform-methanol insoluble fraction, suggesting the presence of the acid in a bound form. GC analysis of monosaccharides revealed the existence of arabinose, xylose, rhamnose, mannose, galactose, glucose, glucosamine, and muramic acid in the cells. Among the neutral sugars, glucose was a minor component and was especially low in pathogenic strains. Total pentose content was about two to three times greater than total hexose.

Fatty acids of Thiobacillus thiooxidans

Fatty acid spectra were made on Thiobacillus thiooxidans cultures both in the presence and absence of organic compounds. Small additions of glucose or acetate had no significant effect either on growth or fatty acid content. The addition of biotin had no stimulatory effect but did result in slight quantitative changes in the fatty acid spectrum. The predominant fatty acid was a C(19) cyclopropane acid.

Fatty acids from vegetative cells and spores of Bacillus stearothermophilus

In spores of Bacillus stearothermophilus produced at 45 and 55 C, branched-chain fatty acids predominated in the former and straight-chain acids in the latter.

Effect of biotin on fatty acids and phospholipids of biotin-sensitive strains of Rhizobium japonicum

The effect of biotin on fatty acids and intact lipids was studied by comparing a biotin-requiring, a biotin-inhibited, and a biotin-indifferent strain of Rhizobium japonicum. These organisms were grown in a defined medium with added levels of 0, 0.3, and 0.5 mug of biotin per liter, and were analyzed for fatty acids and lipid components. Myristic, palmitic, and octadecenoic acids were found to be the major fatty acids in these strains. The indifferent strain also contained large amounts of C(19) cyclopropane acid and small amounts of a C(17) cyclopropane acid. Several unidentified acids were present in the other two strains. The percentages of fatty acids showed statistically significant changes corresponding with changes in level of biotin in the medium. When biotin concentration was increased in the medium, the C(18) monoenoic acids of the biotin-requiring strain increased significantly, and those of the biotin-inhibited and biotin-indifferent strains decreased significantly. Palmitic acid showed a statistically significant increase in the indifferent strain with increasing biotin concentration. The principal intact lipid components in these strains are phospholipids. The major phospholipids are phosphatidylserine, phosphatidylcholine, phosphatitidylethanolamine, and cardiolipin. These phospholipids were not affected by biotin level and were independent of medium composition.

Fatty acids and polar lipids of extremely thermophilic filamentous bacterial masses from two Yellowstone hot springs

The fatty acid composition of filamentous bacterial masses from two very hot Yellowstone Park springs is not unusual despite the extreme environment. Both populations have a series of C(14) to C(20) straight-chain acids with a maximum at C(18), and a series of saturated iso acids with a maximum at C(17) in one case and C(19) in the other. The fatty acid pattern of this anomalous group of organisms is like that of bacteria but not of blue-green algae. Both populations have similar polar lipids and identical carotenoids. It is speculated that these organisms may be adapted to their high-temperature environment by means of stable lipoprotein membrane systems.

Lipids of Pseudomonas aeruginosa cells grown on hydrocarbons and on trypticase soy broth

Lipids were extracted from cells of Pseudomonas aeruginosa grown on a pure hydrocarbon (tridecane), mixed hydrocarbons (JP-4 jet fuel), and on Trypticase Soy Broth. Total lipids produced from each substrate represented from 7.1 to 8.2% of cellular dry weight, of which 5.0 to 6.4% were obtained before cellular hydrolysis (free lipids) and 1.7 to 2.0% were extracted after cellular hydrolysis (bound lipids). Free lipids from cells grown on each medium were separated into four fractions by thin-layer chromatography. All fractions were present in cells from each type of medium, and the "neutral fraction" constituted the largest fraction. The fatty acid composition of free lipids was determined by gas-liquid chromatography. Cells grown on each medium contained saturated and unsaturated C(14) to C(20) fatty acids. Trace amounts of C(13) fatty acids were found in tridecane-grown cells. Saturated C(16) and C(18) were the major acids present in all cells. Quantitative differences were found in fatty acids produced on the three media, but specific correlations between substrate carbon sources and fatty acid content of cells were not evident. Tridecane-grown cells contained only traces of C(13) acid and small amounts of C(15) and C(17) acids, suggesting that the organism's fatty acids were derived from de novo synthesis rather than by direct incorporation of the hydrocarbon.

Aliphatic hydrocarbons and fatty acids of some marine and freshwater microorganisms

Gas chromatography and combined gas chromatography-mass spectrometry have been used to study the fatty acids and hydrocarbons of a bacterium from the Pacific Ocean, Vibrio marinus, a freshwater blue-green alga, Anacystis nidulans, and algal mat communities from the Gulf of Mexico. Both types of microorganisms (bacteria and algae) showed relatively simple hydrocarbon and fatty acid patterns, the hydrocarbons predominating in the region of C-17 and the fatty acids in the range of C-14 to C-18. The patterns of V. marinus were more comparable to those of the algal populations than to patterns reported for other bacteria. An incomplete correlation between fatty acids and hydrocarbons in both types of organisms was observed, making it difficult to accept the concept that the biosynthesis of hydrocarbons follows a simple fatty acid decarboxylation process.

Fatty acids in the genus Bacillus. I. Iso- and anteiso-fatty acids as characteristic constituents of lipids in 10 species

Fatty acids produced by 22 strains of 10 species of the genus Bacillus were analyzed on a very efficient and selective gas-liquid chromatographic column. All of the 10 species, alvei, brevis, cereus, circulans, licheniformis, macerans, megaterium, polymyxa, pumilus, and subtilis, produced eight fatty acids, six branched (anteiso-C(15), anteiso-C(17), iso-C(14), iso-C(15), iso-C(16), and iso-C(17)) and two normal (n-C(14) and n-C(16)). In all cases, the six branched-chain fatty acids made up over 60% of the total fatty acids. In addition to the eight fatty acids, B. cereus produced four extra fatty acids, three branched (anteiso-C(13), iso-C(12), and iso-C(13)) and one monoenoic-n-C(16). Furthermore, there were distinct differences in the relative amounts of fatty acids produced between B. cereus and the remaining nine species. B. cereus produced iso-C(15) fatty acid in the largest amount on a glucose-yeast extract medium as well as on Pennassay Broth. On the other hand, for the remaining nine species, anteiso-C(15) fatty acid was the major fatty acid from the glucose-yeast extract medium, whereas the amount of iso-C(15) fatty acid from Penassay Broth became comparable to that of anteiso-C(15) fatty acid. Mechanisms and various factors affecting the fatty acid distribution pattern in the 10 Bacillus species are discussed.

Indentification and localization of the fatty acids in Haemophilus parainfluenzae

Haemophilus parainfluenzae was capable of synthesizing 22 fatty acids. These fatty acids were equivalent to 4% of the bacterial dry weight. These fatty acids were localized in the membrane-wall complex, which contained the respiratory pigments, the quinone, and the phospholipids. The fatty acids which could be extracted with organic solvents comprised 86% of the total fatty acids of the cell. These fatty acids were distributed as 98% in the phospholipids and 1.9% in the neutral lipids, of which 0.5% were free fatty acids. Palmitic, palmitoleic, oleic, and vaccenic acids comprised 72% of the total fatty acids and were found almost exclusively in the phospholipids. The phospholipids also contained the cyclopropane fatty acids. The neutral lipids contained significant proportions of the odd-numbered branched and straight-chain fatty acids. The principal free fatty acids were n-dodecanoic and pentadecenoic acids. The nonextractable wall complex contained 14% of the total fatty acids. These wall fatty acids were rendered soluble only after saponification. The wall fraction contained all of the beta-hydroxymyristic acid and most of the myristoleic and pentadecenoic acids. The significance of the distribution of fatty acids between nonesterified, neutral lipid, phospholipid, and nonextractible wall remains to be determined.

Inhibition of microbial lipases by fatty acids

Addition of lard or sodium oleate to the medium used for lipase production by Pseudomonas fragi resulted in a decreased accumulation of lipase in the culture supernatant fluid without affecting cell growth. The production and activity of lipase was inhibited by lard, sodium oleate, and the salts of other unsaturated fatty acids. Some divalent cations, Tweens, lecithin, and bovine serum prevented oleate inhibition, but did not reverse it. Similar inhibitory actions were observed with Geotrichum candidum lipase, but not with a staphylococcal lipase or pancreatic lipase. A protective effect by protein in crude enzyme preparations is indicated. The ability of oleate to lower surface tension does not appear to be related to its ability to inhibit lipase.