Aggregation Of Bacteria Research Articles

Autoaggregation and Coaggregation of Bacteria Associated with Acute Endodontic Infections

Biofilms and microbial aggregates are a common mechanism for the survival of bacteria in nature. Microbial aggregates have been associated with intraradicular and extraradicular endodontic disease. One objective of this study was to assess bacteria isolated from acute endodontic infections for autoaggregation and coaggregation. Another objective was to use both a conventional visual assay and a novel fluorescent dye-staining technique to study bacterial aggregation. Sixty-two strains of bacteria were isolated from 10 clinical samples of endodontic abscesses or cellulitis. Autoaggregation was detected in 35/62 (56.45%) of the bacteria using the visual assay. Coaggregation of bacteria from each of the samples was demonstrated for 29/183 (15.85%) bacterial pairs using the visual assay and 148/183 (80.87%) using the dye-staining assay. Coaggregation was observed for each of the 15 genera assayed, especially Prevotella, Streptococcus, and Fusobacterium. The dye-staining assay using a confocal microscope was a highly sensitive method to detect aggregation of bacteria.

Aggregation of ammonia-oxidizing bacteria in microbial biofilm on oyster shell surface

Formation and activity of bacterial nitrifying biofilms play an important role in the closed seawater systems for shrimp cultivation. The structure of microbial biofilm on empty oyster shells, used as a biofilm carrier in biofiltration of aquacultural water, was studied using fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy. FISH was performed with specific oligonucleotide probes for Bacteria and ammonia-oxidizing Nitrosomonas spp. The bacterial cells were arranged within the biofilm as a layer of vertically elongated aggregates. Aggregates of ammonia-oxidizing bacteria were embedded within the matrix formed by other bacteria. Vertically elongated cell aggregates may be ecologically important in bacterial biofilms because they have a higher surface-to-volume ratio than that of laminated biofilms.

Global existence results for complex hyperbolic models of bacterial chemotaxis

Bacteria are able to respond to environmental signals by changing their rules of movement. When we take into account chemical signals in the environment, this behaviour is often called chemotaxis. At the individual-level, chemotaxis consists of several steps. First, the cell detects the extracellular signal using receptors on its membrane. Then, the cell processes the signal information through the intracellular signal transduction network, and finally it responds by altering its motile behaviour accordingly. At the population level, chemotaxis can lead to aggregation of bacteria, travelling waves or pattern formation, and the important task is to explain the population-level behaviour in terms of individual-based models. It has been previously shown that the transport equation framework [12, 13] is suitable for connecting different levels of modelling of bacterial chemotaxis. In this paper, we couple the transport equation for bacteria with the (parabolic/elliptic) equation for the extracellular signals. We prove global existence of solutions for the general hyperbolic chemotaxis models of cells which process the information about the extracellular signal through the intracellular biochemical network and interact by altering the extracellular signal as well. Working in one spatial dimension with multi-dimensional internal dynamics, conditions for global existence in terms of the properties of the signal transduction model are given.

Bioflocculent algal–bacterial biomass improves low-cost wastewater treatment

An innovative technology for the biological treatment of wastewater in regions with sufficient solar radiation based on the simultaneous growth and degradation processes of algal and bacterial biomass is presented. The aim of the work is the improvement of pond technology through the formation of stable algae-bacteria aggregates, which a) permit a simple separation of the algal biomass by gravity sedimentation, b) enable a high removal efficiency for organic carbon and nutrients, and c) are independent in terms of oxygen provision through algal photosynthesis. Algae-bacteria aggregates could be developed with a suitable algal species (Chlorella vulgaris, Strain Hamburg) as a 'model organism' in a wastewater environment. The morphology of algal-bacterial flocs is similar to activated sludge flocs. They are stable and settle quickly. Floc size ranged between 400 and 800 microm. Results of our experiments with an artificially irradiated lab-scale system, operated in continuous flow mode, revealed that even at a relatively short hydraulic detention time of two days, a high elimination capacity of 9.96 g N m(-2) d(-1) and 0.87g Pm(-2) d(-1) can be achieved. Recent investigations confirmed that floc formation of unicellular algae and wastewater bacteria also could be developed and maintained in a pilot-scale system with a water depth of 0.5 m.

Lactoferrin: an important host defence against microbial and viral attack.

The first function attributed to lactoferrin (Lf), an iron binding protein belonging to the non-immune natural defences, was antimicrobial activity that depended on its capacity to sequester iron. Iron-independent microbicidal activities, requiring direct interaction between this cationic protein and microbial surface components, were later demonstrated. Many other anti-microbial and anti-viral functions have since been ascribed to Lf. In mucosal secretions, iron and Lf modulate the motility and aggregation of pathogenic bacteria. Lf inhibits bacterial adhesion on abiotic surfaces through ionic binding to biomaterials, or specific binding to bacterial structures or both. Lf inhibition of bacterial adhesion to host cells requires Lf binding to bacteria and/or host cells. Lf hinders microbial internalization by binding to both glycosaminoglycans and bacterial proteins which can be degraded by Lf-mediated proteolysis. Moreover, Lf internalisation and localisation to the host cell nuclei could modulate bacterial entry into cells through gene regulation. Finally, the capability of Lf to exert antiviral activity, through its binding to host cells and/or viral particles, strengthens the idea that it is an important brick in the mucosal wall, effective against both microbial and viral attacks.

Aggregation as bacterial inclusion bodies does not imply inactivation of enzymes and fluorescent proteins

BackgroundMany enzymes of industrial interest are not in the market since they are bio-produced as bacterial inclusion bodies, believed to be biologically inert aggregates of insoluble protein.ResultsBy using two structurally and functionally different model enzymes and two fluorescent proteins we show that physiological aggregation in bacteria might only result in a moderate loss of biological activity and that inclusion bodies can be used in reaction mixtures for efficient catalysis.ConclusionThis observation offers promising possibilities for the exploration of inclusion bodies as catalysts for industrial purposes, without any previous protein-refolding step.

Evaluation of Nonculture Methods for the Detection of Prosthetic Hip Biofilms

Authors of previous studies have found that culture-based detection of prosthetic hip infections can be improved by adherence to strict anaerobic protocols and mild ultrasonication of retrieved prostheses to remove bacteria growing as an adherent biofilm. Furthermore, direct analyses of sonicate samples by immunofluorescence microscopy (with genus-specific and species-specific monoclonal antibodies or polyclonal antisera) produces significantly greater and more rapid detection rates for infection compared with culture alone. Despite its diagnostic value within a research setting, the practical advantages and limitations of immunofluorescence microscopy for a busy diagnostic laboratory needs consideration. In addition, the method must be evaluated against other nonculture-based techniques that may prove more appropriate. In this review, we describe how immunofluorescence microscopy presents an attractive and reliable method for routine detection of prosthetic hip biofilms compared, primarily, to polymerase chain reaction, although other nonculture methods of diagnosis based on fluorescent in situ hybridization and serologic analysis are considered. We describe how the immunofluorescence microscopy technique is robust, relatively simple and, in contrast to broad-range 16S recombinant-deoxyribonucleic-acid-based polymerase chain reaction, does not require a separate clean-room facility or strict adherence to aseptic techniques. More importantly we highlight how dislodged biofilm, which appears as large aggregates of bacteria, easily can be identified from skin contaminants that occur as single cells or small aggregates of only a few cells.

Sequence determinants of protein aggregation: tools to increase protein solubility

Escherichia coli is one of the most widely used hosts for the production of recombinant proteins. However, very often the target protein accumulates into insoluble aggregates in a misfolded and biologically inactive form. Bacterial inclusion bodies are major bottlenecks in protein production and are hampering the development of top priority research areas such structural genomics. Inclusion body formation was formerly considered to occur via non-specific association of hydrophobic surfaces in folding intermediates. Increasing evidence, however, indicates that protein aggregation in bacteria resembles to the well-studied process of amyloid fibril formation. Both processes appear to rely on the formation of specific, sequence-dependent, intermolecular interactions driving the formation of structured protein aggregates. This similarity in the mechanisms of aggregation will probably allow applying anti-aggregational strategies already tested in the amyloid context to the less explored area of protein aggregation inside bacteria. Specifically, new sequence-based approaches appear as promising tools to tune protein aggregation in biotechnological processes.

Aggregates of Resident Bacteria Facilitate Survival of Immigrant Bacteria on Leaf Surfaces

The fate of immigrant bacterial cells on leaves under stressful conditions was determined as a function of the anatomical features and the local spatial density of resident cells at their landing site. Pantoea agglomerans 299R was established on bean leaves and the survival of immigrant cells of Pseudomonas fluorescens A506 and Pseudomonas syringae B728a, as well as P. agglomerans itself, was determined by epifluorescence microscopy following subsequent exposure of plants to desiccation stress. Resident and immigrant bacterial strains constitutively expressed the cyan and the green fluorescent protein, respectively, and the viability of individual cells was assessed directly on leaf surfaces following propidium iodide staining. Although only a small fraction of the immigrant cells landed on established bacterial aggregates, their fate was usually strongly influenced by the presence of indigenous bacteria at the site at which they landed. Immigrants of P. agglomerans 299R or P. fluorescens A506 that arrived as solitary cells had about double the probability of survival when landing on aggregates formed by P. agglomerans 299R than when landing on uncolonized areas of the leaf surface. In contrast, the survival of P. syringae B728a was similar irrespective of whether it landed on colonized or uncolonized parts of a leaf. The nature of plant anatomical features at which immigrant bacteria landed also strongly influenced the fate of immigrant bacteria. The fraction of immigrant cells of each species tested that landed on veins, glandular trichomes, or epidermal cells altered by P. agglomerans that died was always less than when they landed on normal epidermal cells or at the base of hooked trichomes. Depending on the process by which immigrants arrive at a leaf, only a small fraction of cells may be deposited on existing bacterial aggregates. Although uncolonized sites differed greatly in their ability to influence the survival of immigrant cells, the fate of an immigrant bacterium will depend on the nature of the leaf structure on which it is deposited, and apparently indirectly on the amount of nutrients and water available at that site to support the development of bacterial aggregates.

Effects of SEM Preparation Techniques on the Appearance of Bacteria and Biofilms in the Carter Sandstone

Abstract When biofilms (aggregations of bacteria and extracellular polymer secretions) in samples from the Carter Sandstone of Alabama were prepared for scanning electron microscopy (SEM) using different dehydration techniques, the organic material had visibly different textures and distributions. In order to assess whether the variation was attributable to sample preparation or to inherent biofilm heterogeneity, each of five techniques were tested 3 to 10 times on small (1 cm) pieces of the Carter Sandstone containing either a strain of bacteria cultured from and reintroduced into the rock, or an in situ biofilm grown by injection of nutrients through core samples. The techniques tested were (1) air drying alone; (2) fixation in 10% glutaraldehyde with air drying; (3) ethanol dehydration with hexamethyldisilazane (HMDS) drying [2.5% glutaraldehyde, ethanol dehydration, and HMDS]; (4) ethanol dehydration with critical-point drying; and (5) ethanol and acetone dehydration with critical-point drying. Unpreserved control samples were either imaged wet in an environmental scanning electron microscope (ESEM) or vacuum-dried for SEM. Observations were based on SEM microscopy of over 60 samples and study of over 150 photomicrographs. In both experiments, the original morphology of individual bacteria was best preserved by ethanol dehydration with HMDS drying, ethanol dehydration with critical-point drying, or ethanol-acetone dehydration with critical-point drying. Critical-point drying preserved bacteria but stripped away mucilaginous material, revealing filamentous structures within the biofilm. These filaments, along with masses of microspheres (nannobacteria?) and the smooth mucilaginous outer layer, also occur in wet samples studied by ESEM, and are, therefore, not dehydration artifacts. However, different sample preparation techniques accentuated different components of the heterogeneous biofilm, thus resulting in vastly different textures. The cultured bacteria produced a biofilm that had a different surface texture and was more susceptible to sample preparation artifacts than the in situ biofilm. Use of more than one sample preparation technique is recommended in order to avoid bias.

Precipitation and Growth Morphology of Calcium Carbonate Induced by Myxococcus Xanthus: Implications for Recognition of Bacterial Carbonates

Abstract It is thought that morphologies of bacterial carbonates can be used to identify microbial fossils and/or precipitates in sediments and rocks. This study shows that calcite and vaterite formed in a gel medium in the presence of Myxococcus xanthus display a range of morphologies that depend on whether the bacteria are live or dead. Metabolic activity of the bacteria induced: (1) aggregates of calcified bacteria formed at maximum supersaturation; (2) vaterite spheres (final growth stage of dumbbell fibrous-radiated aggregates); and (3) dipyramid- and disphenoid-like calcite crystals (combination of {011} and {0001} forms). Morphologies (2) and (3) developed at a lower supersaturation and are typically found in gel-like media. Dipyrimidal-like calcite crystals were also obtained abiotically in gel medium. Dead M. xanthus cells induced heterogeneous precipitation of calcite with rhombohedral morphologies at low supersaturation. A growth mechanism resulting from self-assembly of calcium carbonate nanocrystals may account for the observed morphologies, crystal microstructure, and crystallite size measurements. All of the above-mentioned morphologies of bacterial carbonate have been observed in other laboratory experiments and in continental and marine environments. However, all of them have also been produced abiotically, with the exception of calcified bacterial cells. This may make it more difficult to identify bacterial activity in the rock record. Nonetheless, bacterially induced alkalinization appears to be a prerequisite for the development of spherulitic and dipyramid- or disphenoid-like forms in natural mucilaginous biofilms and microbial mats. The morphologies reported here may facilitate the recognition of early and recent marine and continental microcrystalline bacterial carbonates and cements.

Anatomy of Cranberry Stem Gall and Localization of Bacteria in Galls

ABSTRACT Cranberry stem gall is characterized by tumors that girdle stems, thereby killing all distal leaves, flowers, and fruit. Bacteria that produce high levels of the plant growth hormone indole-3-acetic acid (IAA) are associated with and believed to cause cranberry stem gall. The anatomy of naturally occurring galls on woody cranberry plants and galls caused by inoculation of micropropagated cranberry plants with Pantoea agglomerans strain 4/99 was consistent with elevated levels of IAA in plants. Field galls exhibited hypertrophy and hyperplasia of tissue external to the vascular cambium, resulting in extensive stem swelling and splitting of the periderm. Similarly, galls on micropropagated plants contained enlarged cortical parenchyma cells. The current year's xylem vessels in field galls were narrow and dense compared with xylem vessels of healthy stems. Curved xylem elements apparently developed de novo within field galls and galls on inoculated plants. Cavities and fissures in both types of galls contained dense aggregates of bacteria. Treatment of micropropagated plants with synthetic IAA caused hypertrophy of cortical parenchyma and formation of adventitious roots. The results support the hypothesis that IAA-producing bacteria cause cranberry stem gall.

Detection of bacteria with carbohydrate-functionalized fluorescent polymers.

Many pathogens that infect humans use cell surface carbohydrates as receptors to facilitate cell-cell adhesion. The hallmark of these interactions is their multivalency, or the simultaneous occurrence of multiple interactions. We have used a carbohydrate-functionalized fluorescent polymer, which displays many carbohydrate ligands on a single polymer chain, to allow for multivalent detection of pathogens. Incubation of a mannose-functionalized polymer with Escherichia coli yields brightly fluorescent aggregates of bacteria. These results show that carbohydrate-functionalized fluorescent polymers are a versatile detection method for bacteria. Future design of detectors for other pathogens only requires information on the carbohydrates bound by the organisms, which has been exhaustively reported in the literature.

Turning Yersinia pathogenesis outside in: subversion of macrophage function by intracellular yersiniae

Three bacterial species within the genus Yersinia are causative agents of human disease. Yersinia pestis is transmitted by fleas or in aerosols, infects regional lymph nodes or lungs, and causes the highly lethal disease known as plague. Yersinia enterocolitica and Yersinia pseudotuberculosis are enteric pathogens most commonly associated with self-limiting infections of the mesenteric lymph nodes. Although Y. pestis and the enteropathogenic Yersinia species utilize different modes of transmission and cause different diseases, they rely on a common set of “core” virulence determinants to successfully infect a mammalian host. These virulence factors are encoded on the bacterial chromosome and on an approximately 70-kb plasmid. Once established in lymphoid tissue, all three Yersinia species replicate as aggregates of extracellular bacteria within necrotic lesions or abscesses. At this stage of the infectious process, the bacteria resist phagocytosis by neutrophils, which are able to destroy the bacteria if they are internalized. A type III secretion system encoded on the 70-kb plasmid functions to export multiple proteins (the Yops and LcrV) that are delivered to the extracellular milieu, the plasma membrane, or the cytosol of a host target cell. The Yops and LcrV act in concert to inhibit phagocytosis and downregulate inflammation. Although it is clear that the bulk of bacterial multiplication occurs in an extracellular phase, there is also evidence that all three pathogenic Yersinia survive and multiply in macrophages. Survival and replication of Yersinia in macrophages may occur throughout the infection, but is likely to be of greatest importance at early stages of colonization. That macrophages can serve as permissive sites for bacterial replication in vivo is supported by in vitro experiments, which demonstrate that Y. pestis, Y. peudotuberculosis, and Y. enterocolitica share the ability to survive and multiply in macrophage phagosomes. There is also evidence that the bacteria can subvert the functions of macrophages from within, by inhibiting phagosome acidification ( Y. pseudotuberculosis) and the production of nitric oxide ( Y. pestis and Y. pseudotuberculosis). Although considerable attention has been focused on how Yersinia subverts the functions of phagocytes from the outside, the study of how these bacteria subvert macrophage functions from the inside will lead to a better overall understanding of Yersinia pathogenesis.

An improved fluorescence in situ hybridization protocol for the identification of bacteria and archaea in marine sediments

In situ identification of prokaryotic cells in subsurface sediments is hampered by the low cellular rRNA contents of the target organisms. Fluorescence in situ hybridization with catalyzed reporter deposition (CARD–FISH) has the potential to overcome this limitation, and was therefore optimized for a 40 cm deep sediment core sampled from a tidal sandy flat of the German Wadden Sea. Treatment with methanol and H 2O 2 inactivated endogenous peroxidases and effectively reduced the background signal. Percentage of DAPI stained cells detected with the probe combination EUB(I-III), targeting nearly all the Bacteria, were comparable for CARD–FISH with a horseradish peroxidase (HRP)-labeled probe and FISH with a fluorescently monolabeled probe in the 2–3 cm depth interval (92% and 82%, respectively), but significantly higher with the HRP-labeled probe at 35–40 cm, the deepest layer sampled (63% with HRP vs. 26% with monolabeled probe). With CARD–FISH Alphaproteobacteria and the Desulfobulbaceae group of sulfate-reducing bacteria were detected only in the upper layers. In contrast, Desulfosarcinales, the Bacteroidetes group, Planctomycetes, Betaproteobacteria, and Gammaproteobacteria were found at all depths. Archaea were detectable with ARCH915-HRP after achromopeptidase treatment. Surprisingly, aggregates of Bacteria and Archaea were found, below 12 cm depth, that strongly resemble consortia involved in anoxic oxidation of methane that have previously been found in sediments near methane hydrate deposits. With the optimized CARD–FISH protocol, microbial populations could also be detected in deeper sediment horizons. Furthermore, the intensity of the CARD–FISH signals improved detection of rare organisms such as Archaea.

Arabinose content of extracellular polysaccharide plays a role in cell aggregation of Azospirillum brasilense

Extracellular polysaccharides play an important role in aggregation and surface colonization of plant-associated bacteria. In this work, we report the time course production and monomer composition of the exopolysaccharide (EPS) produced by wild type strain and several mutants of the plant growth promoting rhizobacterium (PGPR) Azospirillum brasilense. In a fructose synthetic medium, wild type strain Sp7 produced a glucose-rich EPS during exponential phase growth and an arabinose-rich EPS during stationary and death phase growth. d-glucose or l-arabinose did not support cell growth as sole carbon sources. However, glucose and arabinose-rich EPSs, when used as carbon source, supported bacterial growth. Cell aggregation of Sp7 correlated with the synthesis of arabinose-rich EPS. exoB (UDP-glucose 4′-epimerase), exoC (phosphomannomutase) and phbC (poly-β-hydroxyburyrate synthase) mutant strains, under tested conditions, produced arabinose-rich EPS and exhibited highly cell aggregation capability. A mutant defective in LPS production (dTDP 4-rhamnose reductase; rmlD) produced glucose-rich EPS and did not aggregate. These results support that arabinose content of EPS plays an important role in cell aggregation. Cell aggregation appears to be a time course phenomenon that takes place during reduced metabolic cell activity. Thus, aggregation could constitute a protected model of growth that allows survival in a hostile environment. The occurrence of exoC and rmlD was detected in several species of Azospirillum.

Arabinose content of extracellular polysaccharide plays a role in cell aggregation of Azospirillum brasilense

Extracellular polysaccharides play an important role in aggregation and surface colonization of plant-associated bacteria. In this work, we report the time course production and monomer composition of the exopolysaccharide (EPS) produced by wild type strain and several mutants of the plant growth promoting rhizobacterium (PGPR) Azospirillum brasilense. In a fructose synthetic medium, wild type strain Sp7 produced a glucose-rich EPS during exponential phase growth and an arabinose-rich EPS during stationary and death phase growth. d-glucose or l-arabinose did not support cell growth as sole carbon sources. However, glucose and arabinose-rich EPSs, when used as carbon source, supported bacterial growth. Cell aggregation of Sp7 correlated with the synthesis of arabinose-rich EPS. exoB (UDP-glucose 4′-epimerase), exoC (phosphomannomutase) and phbC (poly-β-hydroxyburyrate synthase) mutant strains, under tested conditions, produced arabinose-rich EPS and exhibited highly cell aggregation capability. A mutant defective in LPS production (dTDP 4-rhamnose reductase; rmlD) produced glucose-rich EPS and did not aggregate. These results support that arabinose content of EPS plays an important role in cell aggregation. Cell aggregation appears to be a time course phenomenon that takes place during reduced metabolic cell activity. Thus, aggregation could constitute a protected model of growth that allows survival in a hostile environment. The occurrence of exoC and rmlD was detected in several species of Azospirillum.

Glycodendriproteins: a synthetic glycoprotein mimic enzyme with branched sugar-display potently inhibits bacterial aggregation.

The continuing ability of bacteria to resist current antibiotic treatments highlights the need for alternative strategies for inhibiting their pathogenicity. Bacterial attachment is a major factor in infectivity and virulence. This key binding phase of bacteria to any potential host is mediated by adhesin proteins and so these present an attractive therapeutic target for antiinfective blocking strategies. However, the natural ligands to adhesins are large, typically complex molecules that are difficult to mimic with small molecules. We describe here a method that creates precise synthetic mimics of glycoproteins that are designed to bind adhesins. By using protein-degrading enzymes as the basis for these mimics we have created large-molecule protein ligands that inhibit aggregation of pathogenic bacteria at levels greater than a million-fold higher than small-molecule inhibitors of adhesins.

Lung and salivary scavenger receptor glycoprotein-340 contribute to the host defense against influenza A viruses.

The lung scavenger receptor-rich protein glycoprotein-340 (gp-340) is present in bronchoalveolar lavage (BAL) fluids and saliva and mediates specific adhesion to and aggregation of bacteria. It also binds to surfactant proteins A and D (SP-A and -D). Prior studies demonstrated that SP-A and SP-D contribute to innate defense against influenza A virus (IAV). We now show that lung and salivary gp-340 inhibit the hemagglutination activity and infectivity of IAV and agglutinate the virions through a mechanism distinct from that of SP-D. As in the case of SP-A, the antiviral effects of gp-340 are mediated by noncalcium-dependent interactions between the virus and sialic acid-bearing carbohydrates on gp-340. Gp-340 inhibits IAV strains that are resistant to SP-D. Concentrations of gp-340 present in saliva and BAL fluid of healthy donors are sufficient to bind to IAV and inhibit viral infectivity. On the basis of competition experiments using competing saccharide ligands, it appears that SP-D does not entirely mediate that anti-IAV activity of BAL fluid and contributes little to that of saliva. Furthermore, removal of gp-340 from BAL fluid and saliva significantly reduced anti-IAV activity. Hence, gp-340 contributes to defense against IAV and may be particularly relevant to defense against SP-D-resistant viral strains.

Numerical simulation of chemotactic bacteria aggregation via mixed finite elements

We start from a mathematical model which describes the collective motion of bacteria taking into account the underlying biochemistry. This model was first introduced by Keller-Segel [13]. A new formulation of the system of partial differential equations is obtained by the introduction of a new variable (this new variable is similar to the quasi-Fermi level in the framework of semiconductor modelling). This new system of P.D.E. is approximated via a mixed finite element technique. The solution algorithm is then described and finally we give some preliminary numerical results. Especially our method is well adapted to compute the concentration of bacteria.