Exploring the role of antimicrobials in the selective growth of purple phototrophic bacteria through genome mining and agar spot assays

Purple non-sulphur bacteria (PNSB) are an emerging group of microbes attractive for applied microbiology applications such as wastewater treatment, plant biostimulants, microbial protein, polyhydroxyalkanoates and H₂ production. These photoorganoheterotrophic microbes have the unique ability to grow selectively on organic carbon in anaerobic photobioreactors. This so-called selectivity implies that the microbial community will have a low diversity and a high abundance of a particular PNSB species. Recently, it has been shown that certain PNSB strains can produce antimicrobials, yet it remains unclear whether these contribute to competitive inhibition. This research aimed to understand which type of antimicrobial PNSB produce and identify whether these compounds contribute to their selective growth. Mining 166 publicly-available PNSB genomes using the computational tool BAGEL showed that 59% contained antimicrobial encoding regions, more specifically biosynthetic clusters of bacteriocins and non-ribosomal peptide synthetases. Inter- and intra-species inhibition was observed in agar spot assays for Rhodobacter blasticus EBR2 and Rhodopseudomonas palustris EBE1 with inhibition zones of, respectively, 5.1 and 1.5-5.7 mm. Peptidomic analysis detected a peptide fragment in the supernatant (SVLQLLR) that had a 100% percentage identity match with a known non-ribosomal peptide synthetase with antimicrobial activity.

Photochemical regeneration of flavoenzymes - An Old Yellow Enzyme case-study

Direct, NAD(P)H-independent regeneration of Old Yellow Enzymes represents an interesting approach for simplified reaction schemes for the stereoselective reduction of conjugated C=C-double bonds. Simply by illuminating the reaction mixtures with blue light in the presence of sacrificial electron donors enables to circumvent the costly and unstable nicotinamide cofactors and a corresponding regeneration system. In the present study, we characterise the parameters determining the efficiency of this approach and outline the current limitations. Particularly, the photolability of the flavin photocatalyst and the (flavin-containing) biocatalyst represent the major limitation en route to preparative application.

Improved analysis of ultra-high molecular mass polystyrenes in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using DCTB matrix and caesium salts

RATIONALE

The ionization of polystyrenes in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is typically achieved by the use of silver salts. Since silver salts can cause severe problems, such as cluster formation, fragmentation of polymer chains and end group cleavage, their substitution by alkali salts is highly desirable.

METHODS

The influence of various cations (Ag(+), Cs(+) and Rb(+)) on the MALDI process of polystyrene (PS) mixtures and high mass polystyrenes was examined. The sample preparation was kept as straightforward as possible. Consequently, no recrystallization or other cleaning procedures were applied.

RESULTS

The investigation of a polystyrene mixture showed that higher molecular polystyrenes could be more easily ionized using caesium, rather than rubidium or silver salts. In combination with the use of DCTB as matrix a high-mass polymer analysis could be achieved, which was demonstrated by the detection of a 1.1 MDa PS.

CONCLUSIONS

A fast, simple and robust MALDI sample preparation method for the analysis of ultra-high molecular weight polystyrenes based on the use of DCTB and caesium salts has been presented. The suitability of the presented method has been validated by using different mass spectrometers and detectors.

Patterned self-assembly of gold nanoparticles on chemical templates fabricated by soft UV nanoimprint lithography

Chemical templates for the patterned immobilization of gold nanoparticles were fabricated by soft UV nanoimprint lithography. The template structures were fabricated by means of the consecutively performed process steps of nanoimprint lithography, reactive ion etching, chemical functionalization with amino groups, and lift-off of imprint resist. These chemical templates were used for the defined assembly of 20 nm diameter citrate stabilized gold nanoparticles from aqueous solution. By reducing the ionic strength of the solution, one- and zero-dimensional particle assemblies were generated on sub-100-nm template structures. By this means, the pattern resolution predefined by the lithography process could be easily enhanced by dilution of the nanoparticle solution.

Phenotype-related differential alpha-2,6- or alpha-2,3-sialylation of glycoprotein N-glycans in human chondrocytes

OBJECTIVE

Sialic acids frequently occur at the terminal positions of glycoprotein N-glycans present at chondrocyte surfaces or in the cartilage matrix. Sialic acids are transferred to glycoproteins in either alpha-2,3 or alpha-2,6 linkage by specific sialyltransferases (SiaTs) and can potentially affect cell functions and cell-matrix interactions. The present study aimed to assess the relationship between the expression of the human chondrocyte phenotype and the sialylation of chondrocyte glycoprotein N-glycans.

METHODS

The transcription of 5 SiaT was quantified using real-time Reverse transcription polymerase chain reaction (RT-PCR) assays. N-glycan analysis was performed using LC-ESI-MS. Primary human chondrocytes were cultured in monolayer or alginate beads and compared to the chondrocyte cell lines C-28/I2 and SW1353. In addition, effects of interleukin-1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha) on primary cells were assessed.

RESULTS

Primary human chondrocytes predominantly express alpha-2,6-specific SiaTs and accordingly, alpha-2,6-linked sialic acid residues in glycoprotein N-glycans. In contrast, the preponderance of alpha-2,3-linked sialyl residues and, correspondingly, reduced levels of alpha-2,6-specific SiaTs are associated with the altered chondrocyte phenotype of C-28/I2 and SW1353 cells. Importantly, a considerable shift towards alpha-2,3-linked sialic acids and alpha-2,3-specific SiaT mRNA levels occurred in primary chondrocytes treated with IL-1beta or tumour necrosis factor-alpha (TNF-alpha).

CONCLUSION

The expression of the differentiated chondrocyte phenotype is linked to the ratio of alpha-2,6- to alpha-2,3-linked sialic acids in chondrocyte glycoprotein N-glycans. A shift towards altered sialylation might contribute to impaired cell-matrix interactions in disease conditions.

The HSG procedure for modelling integrated urban wastewater systems

Whilst the importance of integrated modelling of urban wastewater systems is ever increasing, there is still no concise procedure regarding how to carry out such modelling studies. After briefly discussing some earlier approaches, the guideline for integrated modelling developed by the Central European Simulation Research Group (HSG - Hochschulgruppe) is presented. This contribution suggests a six-step standardised procedure to integrated modelling. This commences with an analysis of the system and definition of objectives and criteria, covers selection of modelling approaches, analysis of data availability, calibration and validation and also includes the steps of scenario analysis and reporting. Recent research findings as well as experience gained from several application projects from Central Europe have been integrated in this guideline.

Solution of the Poisson-Nernst-Planck equations in the cell-substrate interface

Electrogenic cells are able to generate electrical signals which can be measured by various invasive electrophysiological methods such as patch-clamp or sharp microelectrode recordings. Growing cells on the surfaces of e.g. metal microelectrodes or field-effect transistors allows the recording of an extracellular component of these signals. For an understanding of such extracellular signals it is mandatory to get detailed topographical as well as electrical information about the cell-sensor interface. In a first approximation, this interface can be described by a flat disk between cell membrane and sensor surface. For a correct description of the signals, the electrodiffusion of ions in this interface is modeled by using the stationary Poisson-Nernst-Planck equations. We solve the equations analytically, and derive expressions for the potential, the ionic charge densities, and the seal resistance. The results provide a method for determining the distance h between sensor surface and cell membrane. For human embryonic kidney cells, we receive h approximately 70 nm. Comparison with literature shows good agreement.

Transanal treatment of strictured rectal anastomosis with a circular stapler device: simple and safe

BACKGROUND

Several methods of treatment for benign anastomotic strictures after low anterior resection have been described. We report and illustrate a simple, safe, and effective method for treating benign rectal anastomotic strictures by means of a transanal circular stapling device.

METHODS

Three patients with a clinically significant rectal stricture underwent transanal resection of the fibrous stenosis by a circular stapler device (CEEA stapler 29 or 31 mm calibre; Tyco Co., USA).

RESULTS

No complications occurred. Patients were discharged from the hospital on the first postoperative day. After a follow-up period of 8, 12 and 14 months respectively, no recurrence of the stricture was observed. The stool habits of all 3 patients were normal with 1-3 formed, asymptomatic fecal passages per day.

CONCLUSION

Transanal reanastomosis by means of a circular stapler device is a simple and effective method. However, a larger number of patients need to be treated with this relatively new method to draw further conclusions.

Phonon dispersion curves in wurtzite-structure GaN determined by inelastic x-ray scattering

We have investigated the lattice dynamics of a wurtzite GaN single crystal by inelastic x-ray scattering. Several dispersion branches and phonons at high-symmetry points have been measured, including the two zone-center Raman- and infrared-inactive silent modes. The experiments have been complemented by ab initio calculations. They are in very good agreement with our measurements, not only for phonon energies, but also for scattering intensities, thus validating the correctness of the eigenvectors. Other phenomenological and ab initio theories exhibit significant differences.

Deposits of different origin in the lungs of the 5,300-year-old Tyrolean Iceman

Deposits in the lung of the Late Neolithic Tyrolean Iceman were studied with a combination of different methods of analytical electron microscopy. Numerous anthracotic areas with plentiful inhaled soot particles were found in the lung; these most probably derived from open fires in houses. Between the soot particles tiny mineral crystals (mainly muscovite) were identified, which may indicate that the Tyrolean Iceman lived in a muscoviterich area. Furthermore, illite, quartz, and a plagioclase (andesine), which are also minerals in the crystalline rocks of the Otztal Alps, were found. Additionally, organic material, which may represent inhaled threshing residues, was present in the anthracotic areas. As threshing residues and seeds in husk also were detected in the Iceman's belongings, some kind of rustic occupation seems probable. Outside of the anthracotic areas, vivianite and hydroxyapatite crystals were detected. Because of their separate location, and as vivianite is also described in the Iceman's skin, these minerals seem to have crystallized during his 5,300 years of storage in the high mountains.

Proprioceptive contribution to distance estimation by motion parallax in a praying mantid

The behavioural experiments described here examined, in the praying mantis Tenodera sinensis, the manner in which the proprioceptive cervical hair plate sensilla are involved in the measurement of the distance to a jump target with the aid of motion parallax actively produced by translatory head motion. Various combinations of surgical deafferentation of the cervical hair plate sensilla had no influence on the linearisation of head motion. However, the measurement of relative and absolute distance and the jump frequency were impaired by these interventions. From the results, it is concluded that the cervical hair plate sensilla are involved in the distance measurement mechanism, probably by allowing the nervous system to compare retinal image motion with head motion. <P>

Induction of acute pancreatitis in germ-free rats: evidence of a primary role for tumor necrosis factor-alpha

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) has been implicated as a mediator of the systemic manifestations associated with acute pancreatitis. The purpose of this study was to show that TNF-alpha expression in pancreatitis is a primary response and is not the result of endotoxemia.

METHODS

Severe acute pancreatitis was induced in germ-free rats, which have no source of endogenous endotoxin, by ductal infusion of artificial bile. Control animals underwent sham operation and ductal infusion of saline solution. TNF-alpha levels were measured by the WEHI bioassay. Endotoxin was measured by the Limulus assay.

RESULTS

TNF-alpha levels remained low in the sham group (mean, 24.6 +/- 8.0 pg/ml) but were significantly elevated in normal rats with pancreatitis (181 +/- 26.8 pg/ml; p < 0.001 versus sham group) and in germ-free rats with pancreatitis (213 +/- 90 pg/ml; p < 0.002 versus sham group). No endotoxin was detected in any of the experimental rats.

CONCLUSIONS

Our results indicate that TNF-alpha levels are elevated in acute pancreatitis despite the absence of endotoxin, indicating a primary role of TNF-alpha in this disease.

NADPH and "cocktails" containing polyarginine reactivate superoxide generation in leukocytes lysed by membrane-damaging agents

Human blood leukocytes generated large amounts of superoxide (O2-) following stimulation by certain "cocktails" of soluble agents consisting of poly-L-arginine (PARG), phytohemagglutinin, the chemotactic peptide formyl-methionyl-leucyl-phenylalanine and polyanethole sulfanote (liquoid). A variety of cytochalasins, which markedly boosted O2- generation by the soluble cocktails, markedly depressed luminol-dependent chemiluminescence (LDCL) which had been induced either by opsonized streptococci or by soluble agents. Glutathione, which totally reversed the inhibition of LDCL induced by cytochalasin A, failed to reverse the inhibition of LDCL induced by cytochalasin B. Generation of O2- by all the soluble agents employed, except PMA, was strongly inhibited either by the omission of extracellular calcium and magnesium or by treatment with the calcium blocker TMB-8. Generation of O2- was enhanced following stimulation of leukocytes with soluble agents if the cells had been exposed to slightly hypotonic buffers. Leukocytes, which had been preincubated for short periods (5 min) with PARG, saponin, digitonin, or lysolecithin (LL) and which lost their viability, and their O2- and LDCL-generating capacities following stimulation by soluble agents containing cytochalasin B, nevertheless regained these activities by the addition of NADPH. It is suggested that the lytic agents induced the leakage out of NADPH rather than acting as inactivators of the oxidase in the leukocyte membranes. Prolonged incubation of leukocytes with lytic agents failed to allow restoration, by NADPH, of the generation of SOD-inhibitable O2- generation. Since PARG acted both as a cytolytic agent and as a inducer of O2- generation, we postulate that lytic agents might also act as "primers" of the nascent membrane oxidase which could, however, be further potentiated and activated by soluble agents acting in "multiple hits," PARG could be totally replaced either by LL or by digitonin in the generation of O2- provided that both PHA and cytochalasin B were present in the reaction mixtures. We suggest that the various ingredients of the soluble "cocktails" may help to assemble components of the NADPH oxidase. Such an assembly and regulations are prerequisite for stimulation of the NADPH oxidase and the generation of oxygen radicals in leukocytes.

Studies of the behaviour of isolated cells in an open system

A computer-aided arrangement was used to study the time function of lactate output of isolated intestinal epithelial cells in an open system. The results indicate better viability of the cells than in a closed system.

Regional distribution and biochemical properties of 125I-Tyr8-substance P binding sites in synaptic vesicles

1. Binding of 125I-Tyr8-substance P (SP) to synaptic vesicles shows an uneven distribution within the brain and the spinal cord. The regional distribution has a positive correlation with the SP-content, except in the hypothalamus. 2. Ca2+ and MG2+-ions (1 and 10 mM) decrease the number of binding sites without alteration of affinity. EDTA and EGTA enhance SP-binding which is interpreted as being due to removal of the inhibitory influence of endogenous Ca2+ and Mg2+ through chelation with these agents. No significant inhibition of SP binding was observed by Na+ or K+ in concentrations below 100 mM. 3. Pretreatment of synaptic vesicles with trypsin or with phospholipase A2, C and D leads to a total loss of SP binding showing a proteolipid or a joint protein-phospholipid nature of these binding sites. SH groups do not contribute to SP binding since no effect of N-ethylmaleimide and monoidoacetic acid on SP binding was found.