Bacterial Cell Debris Research Articles

Application of non-thermal plasma as an alternative for purification of bacterial cellulose membranes

During the production of cellulose a purification process is applied, which is essential for its safe application in certain contexts, such as skin replacement, as it removes metabolites and bacterial cell debris. Currently, the most frequently adopted methodology is the immersion of the membranes in NaOH solution and this generates chemical residues. Also, the lack of consensus on the ideal methodology has led to discrepancies between results obtained by different authors. In the study reported herein, the action of non-thermal plasma (NTP) technology when applied in the bacterial cellulose (BC) purification process was investigated. The BC was synthesized using Gluconacetobacter hansenii. It was removed from the culture medium and immediately exposed to the NTP reactor in sterile distilled water for different treatment periods (10–30 min). The production capacity was determined and the BC obtained was subjected to physical-chemical characterization, morphological analysis, live/dead fluorescent microscopy and surface characterization via contact angle measurements. The results showed that after 15 min of treatment with NTP, no new membranes appeared when the BC samples were placed back in the culture medium. Micrographs of the membranes subjected to 10 min of plasma treatment showed bacteria or bacterial remnants (in both inner and outer areas) while after 15 min a significant decrease in bacterial cells was observed, mainly in the inner area. This demonstrates that the plasma can be used for the superficial and internal reduction of colonies present in BC membranes, to levels of almost complete elimination. The results reported herein demonstrate the potential of NTP application in the bacterial cellulose purification process, optimizing the production time and avoiding the generation of aggressive chemical residues.

Kelp inspired bio-hydrogel with high antibiofouling activity and super-toughness for ultrafast uranium extraction from seawater

Highly efficient extraction of uranium from seawater is vital for meeting the growth demands of uranium resources for the development of nuclear energy industry. However, currently available uranium adsorbents encounter multiple challenges, including the ultralong extraction period, severe marine biofouling, and violent impact of ocean motions. Targeting on these challenges and inspiring by the high tolerance of kelp to marine biofouling and motions, a kelp inspired super-toughness (KIST) bio-hydrogel is fabricated for uranium extraction from seawater. The hydrogel KIST is prepared by compositing the biofriendly and low-cost bacterial cell debris with polyvinyl alcohol, making the KIST hydrogel possesses high environment friendly. Attributing to the fast uranium adsorption rate of the bacterial cell debris, the KIST hydrogel realizes a uranium extraction capacity of 1.18 mg g−1 in biofouling-containing natural seawater with an ultrafast equilibrium adsorption time of 28 h, which is the shortest among all available uranium adsorbents in natural seawater. The antimicrobial activity of the bacterial cell debris empowers KIST hydrogel with as high as 99.21% inhibition rate to the growth of a broad range marine biofouling microorganisms, including the marine bacteria and marine algae. The KIST hydrogel also possesses outstanding tensile ability, flexibility, and rheological property, endowing the hydrogel with high resistance to the ocean current. Taking into consideration these advantages, the KIST hydrogel would be a promising adsorbent for practical uranium extraction.

Optimization of industrial-scale centrifugal separation of biological products: comparing the performance of tubular and disc stack centrifuges

It is reported for the first time, the selection of an industrial centrifuge with the optimized geometry and operational conditions to efficiently separate the diphtheria bacterial cell debris from the culture medium and particularly to harvest the purified bacterial toxin by using the computational fluid dynamics (CFD) simulation and experimental approaches. The industrial-scale tubular and disc stack centrifuges each with two different sizes were first simulated to quantify their complex hydrodynamics. An optimal balance among the rotational speed, feed flow rate, and possible cell damages was required to efficiently separate the bacterial cells. It was also revealed that both large-sized tubular and disc stack centrifuges perform remarkably better than the smaller ones. Ultimately, according to the CFD simulation results, among four centrifuges, the large-sized disc stack centrifuge with the rotational speeds upper than 5500 rpm and the feed flow rates lower than 100 L h−1 was a potential candidate to utilize in the real process. Through performing experiments by using an industrial disc stack centrifuge, a good agreement was found between the CFD and experimental data in terms of the optimized rotational speed and feed flow rate required for the separation of cells. The Ramon flocculation assay confirmed the preserved quality and quantity of the main product of this bioseparation process, ‘the bacterial toxin purified from the bacterial cell debris’.

Troger's Base Derived Butterfly Shaped Contorted AIEgens for Dead Bacterial Cell‐Imaging

AbstractThis work describes the design and synthesis of contorted dual emissive luminogen based on Tröger's base scaffold. The underlying principle of our design strategy was to use Tröger's base as the core scaffold and functionalize appropriately to avoid the detrimental π‐π stacking responsible for the emission quenching and induce RIR in the aggregated state and thereafter investigate their photophysical, electrochemical, and thermal properties. The unique white light emission of the fluorophores in the solid‐state together with excellent biocompatibility, photo, and thermal stabilities provided an opportunity for the application of one of the molecules for bacterial cell imaging. The luminogen was biocompatible and surprisingly possess an ability to selectively stain the dead bacterial cell debris, a unique property that can be exploited for the confirmation of cell lysis.

Polymer-Based Surfaces Designed to Reduce Biofilm Formation: From Antimicrobial Polymers to Strategies for Long-Term Applications.

Contact-active antimicrobial polymer surfaces bear cationic charges and kill or deactivate bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). The exact mechanism of this interaction is still under debate. While cationic antimicrobial polymer surfaces can be very useful for short-term applications, they lose their activity once they are contaminated by a sufficiently thick layer of adhering biomolecules or bacterial cell debris. This layer shields incoming bacteria from the antimicrobially active cationic surface moieties. Besides discussing antimicrobial surfaces, this feature article focuses on recent strategies that were developed to overcome the contamination problem. This includes bifunctional materials with simultaneously presented antimicrobial and protein-repellent moieties; polymer surfaces that can be switched from an antimicrobial, cell-attractive to a cell-repellent state; polymer surfaces that can be regenerated by enzyme action; degradable antimicrobial polymers; and antimicrobial polymer surfaces with removable top layers.

Streptococcus pneumoniae resists intracellular killing by olfactory ensheathing cells but not by microglia.

Olfactory ensheathing cells (OECs) are a type of specialized glial cell currently considered as having a double function in the nervous system: one regenerative, and another immune. Streptococcus pneumoniae is a major agent of severe infections in humans, including meningitis. It is commonly found in the nasopharynx of asymptomatic carriers, and, under certain still unknown conditions, can invade the brain. We evaluated whether pneumococcal cells recovered from lysed OECs and microglia are able to survive by manipulating the host cell activation. An intracellular-survival assay of S. pneumoniae in OECs showed a significant number of bacterial CFU recovered after 3 h of infection. In contrast, microglia assays resulted in a reduced number of CFU. Electron-microscopy analysis revealed a large number of pneumococci with apparently intact morphology. However, microglia cells showed endocytic vesicles containing only bacterial cell debris. Infection of OEC cultures resulted in continuous NF-κB activation. The IFN-γ-induced increase of iNOS expression was reversed in infected OECs. OECs are susceptible to S. pneumoniae infection, which can suppress their cytotoxic mechanisms in order to survive. We suggest that, in contrast to microglia, OECs might serve as safe targets for pneumococci, providing a more stable environment for evasion of the immune system.

The Uptake of Soluble and Particulate Antigens by Epithelial Cells in the Mouse Small Intestine

Intestinal epithelial cells (IECs) overlying the villi play a prominent role in absorption of digested nutrients and establish a barrier that separates the internal milieu from potentially harmful microbial antigens. Several mechanisms by which antigens of dietary and microbial origin enter the body have been identified; however whether IECs play a role in antigen uptake is not known. Using in vivo imaging of the mouse small intestine, we investigated whether epithelial cells (enterocytes) play an active role in the uptake (sampling) of lumen antigens. We found that small molecular weight antigens such as chicken ovalbumin, dextran, and bacterial LPS enter the lamina propria, the loose connective tissue which lies beneath the epithelium via goblet cell associated passageways. However, epithelial cells overlying the villi can internalize particulate antigens such as bacterial cell debris and inert nanoparticles (NPs), which are then found co-localizing with the CD11c+ dendritic cells in the lamina propria. The extent of NP uptake by IECs depends on their size: 20–40 nm NPs are taken up readily, while NPs larger than 100 nm are taken up mainly by the epithelial cells overlying Peyer's patches. Blocking NPs with small proteins or conjugating them with ovalbumin does not inhibit their uptake. However, the uptake of 40 nm NPs can be inhibited when they are administered with an endocytosis inhibitor (chlorpromazine). Delineating the mechanisms of antigen uptake in the gut is essential for understanding how tolerance and immunity to lumen antigens are generated, and for the development of mucosal vaccines and therapies.

Persistence of bacterial proteolytic enzymes in lake ecosystems

This study analyzes proteolytic enzyme persistence and the role of dead (or metabolically inactive) aquatic bacteria in organic matter cycling. Samples from four lakes of different trophic status were used. Irrespective of the trophic status of the examined lakes, bacterial aminopeptidases remained active even 72h after the death of the bacteria that produced them. The total pool of proteolytic enzymes in natural lake water samples was also stable. We found that the rates of amino acid enzymatic release from proteinaceous matter added to preserved lake water sample were constant for at least 96h (r(2) =0.99, n=17, P≤0.0001, V(max) =84.6nMh(-1) ). We also observed that proteases built into bacterial cell debris fragments remained active for a long time, even after the total destruction of cells. Moreover, during 24h of incubation time, about 20% of these enzymatically active fragments adsorbed onto natural seston particles, becoming a part of the 'attached enzymes system' that is regarded as the 'hot-spot' of protein degradation in aquatic ecosystems.

Spontaneous bacterial cell lysis and biofilm formation in the colon of the Cape Dune mole-rat and the laboratory rabbit

A wide range of techniques, including high-throughput DNA sequencing methods, have been applied to the evaluation of the normal intestinal flora. However, the inability to grow many of those species in culture imposes substantial constraints on the techniques used to evaluate this important community. The presence of biofilms in the normal gut adds further complexity to the issue. In this study, a flow cytometric analysis was used to separate intact bacterial cells, cell debris, and other particulate matter based on bacteria-specific staining and particle size. In addition, an analysis of biofilm formation using fluorescent light microscopy was conducted. Using these approaches, the ratio of bacterial cell debris to intact bacterial cells as a measure of spontaneous lysis of bacterial cells in the gut of the Cape dune mole-rat (Bathyergus suillus) and the laboratory rabbit (Oryctolagus cuniculus) was examined, and the degree of biofilm formation was semi-quantitatively assessed. The results suggest that the degree of spontaneous cell lysis was greater in the appendix than in the cecum in both the mole-rat and the rabbit. Further, the results point toward extensive epithelial-associated biofilm formation in the proximal mole-rat and rabbit large bowel, although the biofilms may be less structured than those found in laboratory rodents and in humans.

Introducing a new paradigm for bioburden management

The prevention and management of infection relies largely on the use of topical antimicrobial dressings. These treatments achieve their effects by killing bacteria, but this results in the presence of bacterial cell debris in the wound and the release of endotoxins, which may prolong inflammation. An alternative approach, where bacteria and fungi bind irreversibly to the wound dressing as a result of a hydrophobic interaction and are then removed at dressing change, avoids the risk of prolonged inflammation and the potential for resistance. A further benefit is that there is no risk of toxicity to healthy tissue or systemic absorption

Bioengineering Bacterial Cellulose/Poly(ethylene oxide) Nanocomposites

By adding poly(ethylene oxide) (PEO) to the growth medium of Acetobacter xylinum, finely dispersed bacterial cellulose (BC)/PEO nanocomposites were produced in a wide range of compositions and morphologies. As the BC/PEO w/w ratio increased from 15:85 to 59:41, the cellulose nanofibers aggregated in larger bundles, indicating that PEO mixed with the cellulose on the nanometer scale [corrected]. Fourier transform infrared spectroscopy suggested intermolecular hydrogen bonding and also preferred crystallization into cellulose Ibeta in the BC/PEO nanocomposites. The fine dispersion of cellulose nanofibers hindered the crystallization of PEO, lowering its melting point and crystallinity in the nanocomposites although remaining bacterial cell debris also contributed to the melting point depression. The decomposition temperature of PEO also increased by approximately 15 degrees C, and the tensile storage modulus of PEO improved significantly especially above 50 degrees C in the nanocomposites. It is argued that this integrated manufacturing approach to fiber-reinforced thermoplastic nanocomposites affords a good flexibility for tailoring morphology and properties. These results further pose the question of the necessity to remove bacterial cells to achieve desirable materials properties in biologically derived products.

Application of enzymes, sodium tripolyphosphate and cation exchange resin for the release of extracellular polymeric substances from sewage sludge

The study describes extraction of extracellular polymeric substances (EPS) from sewage sludge by applying enzymes and enzymes combined with sodium tripolyphosphate (STPP). Additionally, a systematic study of two non-enzymatic extraction agents is described. The assessment of the released products is made by colorimetrical methods and polysaccharides/glycoconjugates identification by the interaction with four immobilized lectins. Bio-sludge from Helsingborg (Sweden) and Damhusåen (Denmark) were used as two case studies for testing enzymatic extractability and thereby to make useful prediction of sludge bio-digestibility. From Helsingborg sludge the enzymes extracted about 40% more of EPS than from Damhusåen. The polysaccharides/glycoconjugates in both sludges maintained the same level, and showed substantial different interaction motifs with lectins panel. Damhusåen enzymatic extracted EPS had an enhanced amount of suspended material that was post-hydrolysed by the use of polygalacturonase and lysozyme resulting in pectin like polymers and petiptidoglycans. Petiptidoglycan is a marker from bacterial cell debris. STPP and cation exchange resin (CER) released different quantities of EPS. The CER released polysaccharides/glycoconjugates had higher molecular weight and stronger affinity towards Concanavalin A than the one released by the action of STPP. Independent of the extraction conditions, STPP released elevated amounts of polyvalent cations and humic substances in contrast to the very low amounts of released by CER.

Protein recovery from bacterial cell debris using crossflow microfiltration with backpulsing

Protein recovery from a bacterial lysate was accomplished using crossflow microfiltration with rapid backpulsing. The net flux with backpulsing was found to increase with increasing forward and backpulse pressures, increase to a maximum and then decrease with increasing forward filtration time between backpulses (or decreasing backpulse frequency), increase weakly with increasing shear rate, and decrease strongly with increasing concentration in the feed. Variation of the operating conditions for a dilute feed of 0.0025 g cell debris/g suspension on a wet cell mass basis yielded net flux values as high as 4.5×10 −3 cm/s (160 1/m 2 h) with backpulsing, compared to a steady-state value of 4.0×10 −4 cm/s (14 1/m 2 h) for similar conditions without backpulsing. The optimal backpulse frequency was found to be very high, about 2.5 times per second, for the minimum backpulse duration of 0.09 s. However, the performance of the backpulsing operation declined with increasing concentration of cell debris, with no flux improvement achieved for concentrations greater than 0.01 g cell debris/g suspension. Nevertheless, 100% protein transmission with backpulsing was achieved for all conditions investigated, compared to an average value of 60% transmission in the absence of backpulsing. Thus, rapid backpulsing is an effective method for the recovery of protein from dilute cell debris.

Determination of muramic acid by high-performance liquid chromatography-plasma spray mass spectrometry

A high-performance liquid chromatographic-plasma spray mass spectrometric method was developed for the determination of muramic acid, a unique compound present in bacterial peptidoglycan. The method included hydrolysis of bacterial samples by hydrochloric acid, purification using a disposable extraction column, and separation using cation-exchange chromatography with a mobile phase composed of ammonium acetate-trifluoroacetic acid-water. Muramic acid was detected in cells of Bacillus subtilis; the presence of yeast cells ( Saccharomyces cerevisiae) in excess amounts did not interfere with the analyses. In contrast to currently applied liquid and gas chromatographic methods, the described method permits highly selective determination of underivatized muramic acid, and may therefore be useful for detecting bacterial and bacterial cell debris in complex biological matrices.

Studies on the separation of intracellular soluble enzymes from bacterial cell debris by tangential flow membrane filtration

The recoveries of genetically engineered human growth hormone (hGH), carboxypeptidase and β-galactosidase, fromE. coli broths have been studied, using the process of microfiltration. The suspension superficial velocity was found to significantly influence the yields obtained. However, the molecular weight of the product could be an important factor in microfiltration. Simple washing procedures seem to be adequate for effective rejuvenation of the membrane.

Xanthan Polysaccharide Plugging Behavior in Porous Media - Preferential Use of Fermentation Broth

Summary Xanthan polysaccharides are shown to contain some large but deformable multimolecular translucid aggregates called microgels, causing partial plugging at some distance from injection wells. A new laboratory procedure has been developed for testing the filterability of available products, among which fermentation broths are preferred to powder polymers. Introduction Xanthangums, which are biologically produced polysaccharides, are considered viable alternatives to hydrolyzed polyacrylamides fot use in enhanced oil recovery operations. Contrary to polyacrylamides, xanthan gums are less sensitive to salinity changes and mechanical degradation. Nevertheless, industrially available products are known to have plugging tendencies. High cost and poor processing efficiency for. improving their injectability also explain why only a few pilot tests with xanthan gums have been extended to a field scale. The origin of this formation plugging has been attributed either to residual bacterial cell debris coming from the fermentation process1–5 or to clumps of poorly dissolved polymer aggregates, called microgels,3–5 created by interactions with multivalent ions existing in field brines. So far, no publication has dealt with microgels in polysaccharide powder and with their plugging behavior. This, paper aims to contribute to a better understanding of microgel plugging mechanisms. A previously developed testing method6 was used to compare the flow properties of various industrial products or laboratory samples through porous media. Special attention also has been paid to the advantages of the. direct use of clarified and diluted fermentation broths rather than polysaccharides isolated in powder form. Polysaccharide Plugging Behavior Plugging Process With any mixing conditions and salt content, polysaccharide solutions exhibit a turbid appearance which has been related to cellular debris or undissolved polymer particles. Many methods have been proposed for removing these insoluble particles from biopolymer solutions - i.e., flocculation processes, enzyme clarification,8 chemical treatments,1 diatomaceous earth, or Millipore™ filter filtration.2,3,5,9 A clarification procedure is recommended before injecting polysaccharide solutions into wells. Filtration tests of unclarified solutions through Millipore filters,2,4,5,10 and sometimes through Berea sandstone cores,4,5 were carried out at extremely high pressure gradients, probably to simulate hydrodynamic conditions in the vicinity of injection wells. Plugging Process With any mixing conditions and salt content, polysaccharide solutions exhibit a turbid appearance which has been related to cellular debris or undissolved polymer particles. Many methods have been proposed for removing these insoluble particles from biopolymer solutions - i.e., flocculation processes, enzyme clarification,8 chemical treatments,1 diatomaceous earth, or Millipore™ filter filtration.2,3,5,9 A clarification procedure is recommended before injecting polysaccharide solutions into wells. Filtration tests of unclarified solutions through Millipore filters,2,4,5,10 and sometimes through Berea sandstone cores,4,5 were carried out at extremely high pressure gradients, probably to simulate hydrodynamic conditions in the vicinity of injection wells.