Chemotaxis In Bacteria Research Articles

A Microscale Model of Bacterial Swimming, Chemotaxis and Substrate Transport

In this paper, we introduce a mathematical and computational model at the microscale level of bacterial motility and chemotaxis coupled with the advection and diffusion of a biologically reacting substrate. The hydrodynamic interaction of a small bacterial population is explicitly modelled through the use of discrete representations of individual microbes. We use the immersed boundary method to couple microbial motion and the advection-diffusion of substrate with the full incompressible Navier–Stokes equations. Simulations using a preliminary two-dimensional model are presented, demonstrating the mutual dependence through the fluid media of several swimming bacteria. A run and tumble mechanism is introduced for simulating the chemotaxis of swimming bacteria.

Effects of butyltins and inorganic tin on chemotaxis of aquatic bacteria

Tributyltin (TBT) and its degradation products dibutyltin (DBT), monobutyltin (MBT) and SnIV were toxic toPseudomonas fluorescens SHC-6 andSerratia sp. Gil-1 with EC50 values in the range of 10−3 to 10−4M. These four compounds were negative chemotactic agents forP. fluorescens, and the butyltins were negatively chemotactic forSerratia sp. at concentrations over four orders of magnitude lower than the EC50 values.l-Aspartate was a positive chemotactic agent for both organisms. TBT, DBT and MBT negated the effect ofl-aspartate onP. fluorescens but not onSerratia sp. Thus, TBT has the potential to affect microbial populations at concentrations much lower than those which prevent growth, and degradation of TBT does not always detoxify it. SnCl4 was less toxic than TBT or DBT to these organisms and it was not chemotactic forSerratia sp. Gil-1. Tributylamine and tributylphosphate were less than 1/10th as toxic as TBT and they did not have a chemotactic effect on either organism at concentrations at which TBT had a significant effect. Therefore, both the Sn-and butyl-moieties contribute to the toxic and chemotactic properties of TBT.

Identification of a fliG homologue in treponema denticola

Using a bacteriophage λ, library of Treponema denticola (Td) ATCC 35405 DNA, and, as a reagent, sera derived from individuals with advanced adult periodontal disease, a variety of recombinant clones producing antigens of this oral spirochete have been isolated. Nucleotide sequence analysis of a clone expressing three immunoreactive antigens has revealed the presence of an open reading frame highly homologous to the flagellar switch/motor protein, FliG, which is known to be essential for flagellar assembly and rotation, and chemotaxis in enteric bacteria. The deduced amino-acid sequence of the treponemal FliG protein had 73% similarity (55% identity) to the Bacillus subtilis FliG protein, and showed significant, but lesser homologies to Gram - FliG proteins. Sequence analysis of regions flanking fliG indicated that this gene is immediately preceded by a fliF homologue, further supporting that the cloned DNA encodes FliG of Td. The findings imply that although the signals for control of chemotaxis may be distinctly different in spirochetes, at least some of the molecules involved in torque generation, control of flagellar rotation and signal transduction are highly conserved with other bacteria. The stronger homology of the spirochete FliG with those of Gram + bacteria is also consistent with recent analyses of other spirochetal genes.

Effect of different environmental conditions on bacterial chemotaxis toward fungal spores

The chemotactic response of four common soil bacteria, Agrobacterium radiobacter, Bacillus subtilis, Pseudomonas fluorescens, and Xanthomonas malvacearum, was observed in natural soil to conidia of Cochliobolus sativus, chlamydospores of Fusarium oxysporum f.sp. ciceri, sclerotia of Macrophomina phaseolina, and oospores of Phytophthora drechsleri f.sp. cajani. All bacteria migrated through soil toward fungal spores. Chemical analysis of fungal exudates demonstrated the presence of various amino acids and sugars that served as chemoattractants. The effect of temperature, pH, soil water matric potential, and soil texture on bacterial chemotaxis toward fungal spores was also investigated. In general, the response of bacteria to different types of fungal spores was significantly greater (P = 0.05) at higher water matric potential (0 and −5 kPa) than at lower soil water potential (−10 and −20 kPa). The chemotactic response was greatest in sandy soil, followed by sandy loam and clay loam soil. High temperature (40 °C) was not favourable for bacterial chemotaxis. The chemotactic response decreased by 4 to 28 times when soil pH decreased from 7 to 5 or increased from 7 to 9. The relative concentration response of the exudate of fungal spores and the motility or chemotaxis of bacteria were assessed. A significant positive correlation (P = 0.05; r = 0.89–0.92) was recorded between motility and relative concentrations of exudate. The swimming speed and tumbling frequency of Pseudomonas fluorescens cells was observed at different pH values and temperatures. The swimming speed of bacteria increased with increasing temperature, but decreased with an increase in pH from 5 to 7. The tumbling frequency had a sharp peak at 30 °C and pH 7. Bacteria were able to stimulate the release of exudate from the fungal spores. The amount of exudation was also affected by temperature, pH, and soil texture. A positive significant correlation (P = 0.05; r = 0.79–0.85) was recorded between exudation and a progressive increase in temperature. The amount of exudation also increased with an increase in soil pH from 5 to 8, but further increases in pH decreased the rate of exudation. In general, fungal spores exuded the greatest amounts of carbon compounds in sandy soil, followed by sandy loam and clay loam soil. Exudation in sandy soil was often greatest in the presence of A. radiobacter cells, while the greatest exudation in sandy loam and clay loam soils was induced by B. subtilis cells.Key words: chemotaxis, chemoattractants, fungal spores, motility.

On the Relationship Between Cell Balance Equations for Chemotactic Cell Populations

This paper considers several cell balance equations describing the time and spatial evolution of the number density of chemotactic cell populations. The conditions are determined under which the three-dimensional cell balance equations of Alt reduce to the simpler, one-dimensional equations of Segel that have been used by Lauffenberger and colleagues to describe chemotaxis of flagellar bacteria and polymorphonuclear leukocytes, and to interpret experimental measurements on such systems.

Effect of apocynin on the induction of ulcerative lesions in rat skin injected with tubercle bacteria

Apocynin is an effective and selective inhibitor of the neutrophil oxidative burst in vitro. Other neutrophil functions, tested in vitro, such as chemotaxis, exocytosis, phagocytosis and intracellular killing of bacteria are unaffected by apocynin. These properties make apocynin a potential anti-inflammatory agent in vivo. This was tested in WAG/Rij rats, injected intracutaneously with tubercle bacteria in oil (complete Freund's adjuvant). We show here that continuous administration of apocynin via the drinking water prevents the formation of ulcerative lesions in the inflamed skin. No effects on humoral and cellular immunity were observed after treatment with apocynin (between 1 and 100 μg/ml drinking water) measuring serum antibodies and delayed-type hypersensitivity, respectively.

Swimming against the tide: Chemotaxis in Agrobacterium

Chemotaxis in bacteria is an excellent model for signal transduction processes. In Agrobacterium tumefaciens, the causative agent of crown gall tumour on wounded plants, it is a vital part of the organism's biology. A chromosomally-determined chemotaxis system causes the bacterium to be attracted into the rhizosphere by chemoattractants in plant exudates. By interfacing with this system, the multifunctional products of two Ti-plasmid encoded genes, virA and virG, allow the sensing of specific wound phenolics such as acetosyringone. This attracts Ti-plasmid harbouring A. tumefaciens to wound sites, where the higher acetosyringone concentrations lead to virA and virG-mediated induction of the vir-genes. The products of the induced genes, act in concert to effect transfer of the T-DNA to the plant cell.

Chemotaxis of bacteria in glass capillary arrays. Escherichia coli, motility, microchannel plate, and light scattering

Random and directed motility of bacterial populations were assayed by monitoring the flux of bacteria through a microchannel plate (a porous glass plate comprising a fused array of capillary tubes) separating two identical stirred chambers. Cells, washed free of growth medium by a new filtration method, were added to one chamber at a low density. Their number in the other chamber was determined from the amount of light scattered from a beam of a laser diode and recorded on a strip chart. Diffusion coefficients were computed from fluxes observed in the absence of chemical gradients, and chemotaxis drift velocities were computed from fluxes observed in their presence. Cells migrated through tubes of diam 10 microns more rapidly than through tubes of diam 50 microns, suggesting that the straight segments of their tracks were aligned with the axes of the smaller tubes. Mutants that are motile but nonchemotactic could be selected because they move through the microchannel plate in the face of an adverse gradient. Weak chemotactic responses were assessed from ratios of fluxes observed in paired experiments in which the sign of the gradient of attractant was reversed. Studies were made of wild-type Escherichia coli and mutants that are nonmotile, tumblely, smooth-swimming, aspartate-blind, or defective in methylation and demethylation. Chemotaxis drift velocities for the latter mutants (cheRcheB) were quite small.

Acetylcholine Inhibition of Escherichia coli Chemotaxis for Aspartate

Though acetylcholine per se was not attractant or repellent for Escherichia coli, it was found that acetylcholine inhibits the chemotaxis of the bacteria for aspartate. The inhibition appeared at 10(-5) M of acetylcholine and at 10(-2) M the inhibition reached 50%.

Random-walk chemotaxis: trial and error as a control process.

The biased random-walk chemotaxis of the bacterium Escherichia coli is a remarkably effective method of navigation based on random trial-and-error responding rather than steering. Humans restricted to the same mode of responding are able to navigate to target locations, just like the bacterium. This mode of navigation can be modeled as an input control process that selectively retains favorable and rejects unfavorable consequences of the random responses. The selection process is determined by the internal organization of the system rather than the external influence of the environment (as in natural selection or reinforcement).

Methyl-accepting protein associated with bacterial sensory rhodopsin I.

In vivo radiolabeling of Halobacterium halobium phototaxis mutants and revertants with L-[methyl-3H] methionine implicated seven methyl-accepting protein bands with apparent molecular masses from 65 to 150 kilodaltons (kDa) in adaptation of the organism to chemo and photo stimuli, and one of these (94 kDa) was specifically implicated in phototaxis. The lability of the radiolabeled bands to mild base treatment indicated that the methyl linkages are carboxylmethylesters, as is the case in the eubacterial chemotaxis receptor-transducers. The 94-kDa protein was present in increased amounts in an overproducer of the apoprotein of sensory rhodopsin I, one of two retinal-containing phototaxis receptors in H. halobium. It was absent in a strain that contained sensory rhodopsin II and that lacked sensory rhodopsin I and was also absent in a mutant that lacked both photoreceptors. Based on the role of methyl-accepting proteins in chemotaxis in other bacteria, we suggest that the 94-kDa protein is the signal transducer for sensory rhodopsin I. By [3H]retinal labeling studies, we previously identified a 25-kDa retinal-binding polypeptide that was derived from photochemically reactive sensory rhodopsin I. When H. halobium membranes containing sensory rhodopsin I were treated by a procedure that stably reduced [3H]retinal onto the 25-kDa apoprotein, a 94-kDa protein was also found to be radiolabeled. Protease digestion confirmed that the 94-kDa retinal-labeled protein was the same as the methyl-accepting protein that was suggested above to be the signal transducer for sensory rhodopsin I. Possible models are that the 25- and 94-kDa proteins are tightly interacting components of the photosensory signaling machinery or that both are forms of sensory rhodopsin I.

Chemotaxis of bacteria to extracellular products of marine bloom algae.

The chemotactic response of bacteria to extracellular products of two bloom algae, Asterionella glacialis (Bacillariophycea) and Chattonellamarina (Rhaphidophycea) was measured using the quantitative capillary tube technique. Genus Vibrio did not show chemotactic response to either algal extracellular product. Pseudomonas 022 which was isolated as a dominant bacterium during the A. glacialis bloom was chemotactic to A. glacialis extracellular product, but not to C. marina extracellular product. The chemotactic response of Pseudomonas 022 was great when the bacterium was preincubated on A. glacialis extracellular product. The chemotactic substance(s) in the extracellular product of A. glacialis has a molecular weight in the range 5, 000-1, 000 daltons with cationic charge and is composed by amino acids.

Molecular mechanisms of beta-adrenergic receptor desensitization.

Multiple mechanisms seem to be involved in regulating the responsiveness of hormone receptor-coupled adenylate cyclase systems. These mechanisms at least involve the receptors and nucleotide regulatory proteins. With the recent development of methods for purifying the catalytic unit of the enzyme it will be possible to assess whether it is also a locus for such regulatory phenomena. At least two major pathways of receptor regulation have been uncovered. Homologous desensitization (Fig. 9) involves the uncoupling and translocation of the receptors out of their normal plasma membrane environment. This process sequesters the receptors away from their effector, the regulatory and catalytic components of adenylate cyclase. The site of receptor sequestration is unclear and might lie within the plasma membrane or within the cell. The sequestered receptors can recycle to the cell surface or become down-regulated, perhaps being destroyed within the cell. Phosphorylation of the receptors through a beta-adrenergic receptor kinase appears to be associated with homologous desensitization. This phosphorylation event may serve either to uncouple functionally the receptors or to trigger their sequestration from the cell surface or both. In heterologous desensitization (Fig. 10), receptor function is regulated by phosphorylation in the absence of receptor sequestration or down-regulation. This covalent modification serves to functionally uncouple the receptors, that is, to impair their interactions with the guanine nucleotide regulatory proteins. Several protein kinases seem to be capable of promoting phosphorylation of the receptors including the cAMP-dependent kinase and protein kinase C. In addition to the receptor modification, heterologous desensitization seems to be associated with functional modifications (phosphorylation?) at the level of nucleotide regulatory proteins (Ns and Ni), (Fig. 10). Further studies of the mechanisms of desensitization of adenylate cyclase-coupled receptors are thus likely to help elucidate modes of regulation of a wide variety of receptor-coupled functions in diverse types of cells.

Ultrastructure of Bacterial Penetration in Plants

Successful infection of a host plant by a pathogen involves the movement of the pathogen toward the host, attachment of the pathogen to the plant surface, penetration of the host by the pathogen, and the proliferation of the pathogen inside the host immediately following entrance. Thus, the motility of plant­ pathogenic bacteria (63), as well as the aerotaxis and chemotaxis of bacteria toward plant exudates and leachates (10,21,65), helps bacteria land on host plants. Electric charges (45) and surface structures of the plant and bacteria (29, 42, 74) determine the recognition and adsorption between host and bacteria. Bacterial proliferation following entrance aids establishment of bacteria in infection courts. For a general account of these phases of the infection process, the reader is referred to reviews by Goodman (27, 28) and Billing (7). This review focuses primarily on spatial relationships and ul­ trastructural interactions between bacteria and host tissues at sites of infection with special emphasis on scanning electron microscopy (SEM) and transmis­ sion electron microscopy (TEM) of the movement of bacteria from the outside to the inside of a plant tissue.

Surface structure recognized for covalent modification of the aspartate receptor in chemotaxis.

The aspartate receptor involved in chemotaxis is modified by methyl esterification at four distinct glutamate residues during the adaptive response of this receptor. To explain the high degree of specificity of this modification, it has been proposed that the methyltransferase recognizes the sequence Glu-Glu-Xaa-Xaa-Ala-Ser/Thr in an alpha-helical conformation and methylates the second glutamate in this sequence. This hypothesis is strengthened here by localized mutagenesis studies. By reversing the alanine-threonine sequence to threonine-alanine at the principal site of methylation, Glu-309, a factor of 4 decrease in reactivity was achieved. Thus, the rate of methylation of this site is sensitive to the reversal of two residues of similar structure. These residues are somewhat distant in sequence from the glutamate that is modified but are adjacent in space if an alpha-helical structure is present. The other sites of modification, Glu-295, Glu-302, and Glu-491, are slightly increased in reactivity in the mutant. The 4-fold change in reactivity of the major site of methylation obtained with a relatively subtle change supports the recognition sequence hypothesis, including its structural implications. It is noted, in addition, that chemotaxis of bacteria expressing the mutant receptor does not seem to be greatly altered. This might be explained by the observation that the overall methylation levels of the mutant and wild-type receptors are similar.

A mechanism for exact sensory adaptation based on receptor modification

We provide a theoretical explanation for the observation that in many sensory systems a step increase in stimulus triggers a response that goes through a maximum and then returns to the basal level. Considered here is a receptor molecule that in the absence of ligand can be found in either of two states R and D. Two more states, RL and DL, are formed upon the addition of ligand L. It is assumed that the receptor triggers activity in a sensory system, and that the activity is proportional to a weighted combination of the fractions of molecules that are in each of the four states. It is shown that judicious choice of the weights can provide both an adequate response and exact adaptation to step increases in stimuli. The interconversion between states may operate without energy expenditure or through covalent modification. In both cases, adaptation is associated with receptor modification that acts as a counterweight to changed external conditions. Application to cAMP secretion in Dictyostelium discoideum and to chemotaxis in bacteria is discussed.

EXCESSIVE INTAKE OF ZINC IMPAIRS IMMUNE RESPONSES

The effect of administration of large amounts of zinc on immune response and serum lipoproteins was examined. Eleven healthy adult men ingested 150 mg of elemental zinc twice a day for six weeks. This was associated with a reduction in lymphocyte stimulation response to phytohemagglutinin as well as chemotaxis and phagocytosis of bacteria by polymorphonuclear leukocytes. Serum high-density lipoprotein concentration decreased significantly and low-density lipoprotein level increased slightly. The common food fad of zinc supplementation with resultant excessive intake could have deleterious effects in healthy persons. ( JAMA 1984;252:1443-1446)

Immunotherapy in burn patients

Infection remains the leading cause of death following hospitalization of patients with major burn injury. This susceptibility is due not only to the loss of the skin barrier, but also, and perhaps more importantly, to acquired immunodeficiencies. Virtually every variable of immunologic resistance to infection has been studied and reported to be abnormal following severe thermal injury (5). Neutrophils have been reported to show impairment in chemotaxis, phagocytosis, and intracellular killing of bacteria. T lymphocytes show a diminished response both to specific and nonspecific activators, such as phytohemagglutinin (PHA), and suppressor T cells show increased activity in the thermally injured patient. B-cell function, as measured by antibody synthesis, has been shown to be diminished in severely burned patients. Complement levels are variable, depending on the complement factor measured. Certain inhibitory complement degradation products, such as C3b and C5a, are markedly elevated following severe thermal injury, and the opsonic index also is markedly depressed. The fixed macrophages of the reticuloendothelial system (RES) demonstrate a markedly diminished phagocytic ability within 24 hr of burn injury. To determine which of these abnormalities was most predictive of the development of an infection, a sequential prospective analysis of immunologic abnormalities in infections following severe thermal injuries was undertaken at this institution (4). Twenty consenting patients with burn injuries involving more than 45% of the total body surface area (TBSA) were studied. The average burn size x~Tas 59.5% TBSA, and 44.0% were third degree burns. All patients received routine therapy, including topical antibiotics; systemic antibiotics were administered only on specific indications, primarily bacteremia. The caloric needs were met using nasogastric tube feedings, if necessary, to meet the requirements. Blood samples were obtained on all patients three times per week until the patient's wounds were totally closed, or until the patient died. The following tests were run on all samples: measurements of antibacterial function of neutrophils using Staphylococcus attretts and Escherichia coli, chemotaxis of neutrophils, serum levels of C3 and IgG, measurement of opsonic activity of the serum, and lymphocyte response to PHA. For analysis, all patients were divided into two groups, infected and noninfected, based on the presence or absence of a positive blood culture during the period of the study. Of the 20 patients, 13 developed positive blood cultures at some time during the period of observation. The average burn size for these patients was 62% TBSA. The seven patients without positive blood cultures had an average 54% TBSA burn. All tests showed an impairment of function, both in those patients who developed bacteremias and in those who did not. There were no differences between the infected and noninfected patients in any of these variables, except for the neutrophil bactericidal index (NBI). NBI is a measurement of the neutrophil's ability to phagocytose and kill bacteria, with numbers greater than one indicating impairment in these abilities. Infected patients had significantly worse neutrophil function (p < 0.01) against S. aureus, overall, than noninfected patients (Fig. 1). The NBI for E. coli in the infected group was worse compared with the noninfected group, but not significantly so.

Excessive Intake of Zinc Impairs Immune Responses

The effect of administration of large amounts of zinc on immune response and serum lipoproteins was examined. Eleven healthy adult men ingested 150 mg of elemental zinc twice a day for six weeks. This was associated with a reduction in lymphocyte stimulation response to phytohemagglutinin as well as chemotaxis and phagocytosis of bacteria by polymorphonuclear leukocytes. Serum high-density lipoprotein concentration decreased significantly and low-density lipoprotein level increased slightly. The common food fad of zinc supplementation with resultant excessive intake could have deleterious effects in healthy persons.

Transport and fate of microorganisms in porous media: A theoretical investigation

Bacteria and viruses found in groundwater are a proven health hazard as evidenced by the large number of outbreaks of water-borne diseases caused by contaminated groundwater. To analyze the fate of biological contaminants in soils and groundwater, we studied various transport processes including dispersion, convection, Brownian motion, chemotaxis and tumbling of bacteria. The differences between bacteria and viruses in their transport mechanisms, decay and growth kinetics have also been investigated. It has been shown that the rate of deposition terms can be incorporated by a first-order and an adsorption isotherm for bacteria and viruses, respectively. The movement of bacteria is coupled with the transport of a bacterial nutrient present in seeping wastewater.