Rheotactic behavior of a gliding mycoplasma.

Mycoplasma mobile, a new gliding mycoplasma isolated from the gills of a fish, was capable of positive rheotaxis; the cells glided upstream in a moving fluid. To our knowledge this is the first demonstration of rheotactic behavior among the procaryotes.     

Chemotactic activity of L-forms and mycoplasma.

L-forms of Streptococcus faecalis, Escherichia coli and Proteus mirabilis showed significantly less chemotactic activity for normal human leucocytes than did parent bacterial forms which were strongly chemotactic. Mycoplasma pneumoniae and Mycoplasma hominis did not demonstrate chemotactic activity.     

Force and velocity of mycoplasma mobile gliding

The effects of temperature and force on the gliding speed of Mycoplasma mobile were examined. Gliding speed increased linearly as a function of temperature from 0.46 microm/s at 11.5 degrees C to 4.0 microm/s at 36.5 degrees C. A polystyrene bead was attached to the tail of M. mobile using a polyclonal antibody raised against whole M. mobile cells. Cells attached to beads glided at the same speed as cells without beads. When liquid flow was applied in a flow chamber, cells reoriented and moved upstream with reduced speeds. Forces generated by cells at various gliding speeds were calculated by multiplying their estimated frictional drag coefficients with their velocities relative to the liquid. The gliding speed decreased linearly with force. At zero speed, the force measurements extrapolated to 26 pN at 22.5 and 27.5 degrees C. At zero force, the speed extrapolated to 2.3 and 3.3 microm/s at 22.5 and 27.5 degrees C, respectively--the same speeds as those observed for free gliding cells. Cells attached to beads were also trapped by an optical tweezer, and the stall force was measured to be 26 to 28 pN (17.5 to 27.5 degrees C). The gliding speed depended on temperature, but the maximum force did not, suggesting that the mechanism is composed of at least two steps, one that generates force and another that allows displacement. Other implications of these results are discussed.     

Chemotactic response of monocytes to thrombin

Human alpha-thrombin, the procoagulant activation product of prothrombin, elicits chemotaxis in human peripheral blood monocytes and several macrophagelike continuous cell lines, most notably J-774.2, but not in human peripheral blood granulocytes. alpha-Thrombin is effective in stimulating cell movement at concentrations ranging from 10(-10) to 10(-6) M but is optimally active at 10(-8) M. At the latter concentration, the degree of response is equivalent, on a molar basis, to that observed with the peptide formylmethionylleucylphenylalanine, (FMP). In contrast to thrombin, prothrombin produces a minimal chemotactic response in monocytes and J-774.2. Blockade of alpha- thrombin's active center with diisopropylfluorophosphate (DIP-F) or tryptic proteolysis of the procoagulant exosite (i.e., gamma-thrombin) fails to alter chemotactic activity. On the other hand, addition of equimolar amounts of antithrombin III (AT3) to alpha-thrombin reduces thrombin-mediated chemotaxis by 60%, and increased ratios of AT3 to enzyme completely suppress chemotaxis. We conclude that thrombin is a potent monocyte chemotaxin and that the domains in thrombin involved in stimulating cell movement are distinct from the catalytic site and the fibrin recognition exosite. These chemotactic domains appear to be sequestered in prothrombin and in the thrombin-AT3 complex and, as such, are unavailable to the chemotactic receptor on the monocyte cell membrane.     

Chemotactic response of a marine bacterium to breakdown products of an insoluble substrate

Abstract The basis for this work was to investigate whether bacteria immobilized on or in a solid substrate resulted in the release of low molecular weight products that act as chemoattractants for other bacteria In the surrounding aqueous phase. Chemotaxis of a marine vibrio was observed microscopically along the gradient of breakdown products generated by a Flavobacterium sp. immobilized in an alginate-agar bead. The chemotactic phenomenon was confirmed by a viable counting technique. The chemoattractant was derived from neither the alginate nor the agar but probably was amino acids produced from protein present as a contaminant in the alginate.     

Chemotactic response of frozen-thawed bovine spermatozoa towards follicular fluid

The aim of this study was to verify whether cattle spermatozoa respond by chemotaxis to follicular fluid (FF). The experimental conditions were defined to maintain a frozen-thawed sperm population with great motility and capacitation, and lesser sperm agglutination. Several sperm preparation conditions were studied: sperm separation from the seminal plasma by Sephadex column or migration-sedimentation, incubation under capacitating conditions in the presence or absence of a superficial layer of mineral oil, and different pH of the culture medium. The percentage of motile and agglutinated spermatozoa was determined in plate dishes under inverted phase contrast microscope. The percentage of capacitated spermatozoa was calculated as the difference between the percentages of acrosome reacted spermatozoa with and without lysophosphatidylcholine stimulation. The most ideal experimental conditions to evaluate chemotaxis in frozen-thawed cattle spermatozoa were: to separate the cells from the seminal plasma by migration-sedimentation and to incubate them under oil, in culture medium at pH 7.2, for less than 2h. The chemotaxis assays were conducted with spermatozoa treated as mentioned above which were confronted to several dilutions of FF (1:10(3), 1:10(4), 1:10(5), 1:10(6)) in a chemotaxis chamber by videomicroscopy and computer image analysis. A subpopulation of capacitated spermatozoa ( approximately 10%) that responded chemotactically to a concentration gradient generated by FF (1:10(4) to 1:10(5)) was observed. Since cryopreserved spermatozoa are regularly used to artificially inseminate the cows, the sperm chemotactic response towards FF would be potentially used to diagnose the bull sperm sample or to select the spermatozoa in the most functional state.     

Chemotactic response of marine micro-organisms to micro-scale nutrient layers

The degree to which planktonic microbes can exploit microscale resource patches will have considerable implications for oceanic trophodynamics and biogeochemical flux. However, to take advantage of nutrient patches in the ocean, swimming microbes must overcome the influences of physical forces including molecular diffusion and turbulent shear, which will limit the availability of patches and the ability of bacteria to locate them. Until recently, methodological limitations have precluded direct examinations of microbial behaviour within patchy habitats and realistic small-scale flow conditions. Hence, much of our current knowledge regarding microbial behaviour in the ocean has been procured from theoretical predictions. To obtain new information on microbial foraging behaviour in the ocean we have applied soft lithographic fabrication techniques to develop 2 microfluidic devices, which we have used to create (i) microscale nutrient patches with dimensions and diffusive characteristics relevant to oceanic processes and (ii) microscale vortices, with shear rates corresponding to those expected in the ocean. These microfluidic devices have permitted a first direct examination of microbial swimming and chemotactic behaviour within a heterogeneous and dynamic seascape. The combined use of epifluorescence and phase contrast microscopy allow direct examinations of the physical dimensions and diffusive characteristics of nutrient patches, while observing the population-level aggregative response, in addition to the swimming behaviour of individual microbes. These experiments have revealed that some species of phytoplankton, heterotrophic bacteria and phagotrophic protists are adept at locating and exploiting diffusing microscale resource patches within very short time frames. We have also shown that up to moderate shear rates, marine bacteria are able to fight the flow and swim through their environment at their own accord. However, beyond a threshold high shear level, bacteria are aligned in the shear flow and are less capable of swimming without disturbance from the flow. Microfluidics represents a novel and inexpensive approach for studying aquatic microbial ecology, and due to its suitability for accurately creating realistic flow fields and substrate gradients at the microscale, is ideally applicable to examinations of microbial behaviour at the smallest scales of interaction. We therefore suggest that microfluidics represents a valuable tool for obtaining a better understanding of the ecology of microorganisms in the ocean.     

Chemotactic response of wild-type and aggregation-defective mutants of Polysphondylium violaceum

Abstract. The aggregation-specific chemoattractant for Polysphondylium violaceum is N-propionyl-γ-L-glutamyl-L-ornithine-δ-lactam ethyl ester, or glorin. Wild-type amoebae allowed to develop in liquid culture acquire increased ability to respond to glorin shortly after starvation, i.e., just prior to the time they become aggregation competent. Similarly, as development proceeds, the amoebae show decreased sensitivity to folic acid, but they show almost no response to cyclic AMP at any time during their development in liquid culture. The optimum concentrations for the chemotactic response are 10^-8 M for glorin and 10^-5–10^-6 M for folic acid. A class of aggregation-defective mutants, aggA , will not aggregate in the absence of an excreted pheromone, D factor. During development in liquid culture in the presence or absence of D factor, these aggA mutants show a chemotactic response similar to that of wild-type amoebae to folic acid and glorin. However, D factor does enhance the chemotactic response of aggA mutants to glorin. In the absence of D factor, mutant amoebae will form fruiting bodies if exposed to a chemotactic gradient of either folic acid or glorin. Under these conditions, the mutant amoebae circumvent the requirement for D factor in order to develop.     

Chemotactic response of human neutrophils to N-acetyl chitohexaose in vitro

N-Acetyl chitohexaose (NACOS-6) was able to display chemotactic response of human neutrophils in vitro. In order to analyze the mechanism, a series of chemotaxis studies by means of neutrophils treated with inhibitors of phospholipase A2, cyclooxygenase, or lipoxygenase to NACOS-6 was conducted. The treatment of neutrophils with inhibitors of phospholipase A2 or cyclooxygenase resulted in decrease of number of migrated cells. However, the lipoxygenase inhibitors did not exhibit the same effect. On the other hand, the treatment of neutrophils with inhibitors of phospholipase A2 or lipoxygenase resulted in decrease of chemotactic response to Formyl-Met-Leu-Phe (FMLP), although the cyclooxygenase inhibitors did not inhibit chemotaxis of neutrophils. Neutrophils added to exogenous prostaglandin E2 (PGE2) caused an enhanced chemotactic response to NACOS-6. These results indicate that the mechanism of chemotactic response to NACOS-6 was different from that of FMLP, and that the response was enhanced by PGE2 released from the neutrophils with stimulation of NACOS-6.     

Chemotactic response of Ginseng bacterial soft-rot to Ginseng root exudates

Our purpose was to evaluate chemotactic response of Ginseng bacterial soft-rot to ginseng root exudates. The exudates of plant roots has a significant influence on the population changes of rhizosphere microorganisms and chemotaxis is an important way in which many pathogens sense the signals of host plants and invade the host plants. In this study, with the capillary method, we tested the chemotactic responses of Ginseng bacterial soft-rot for three ginseng roots exudates under four chemotactic parameters (concentration, temperature, pH and time). The results showed that the chemotatic response of the Ginseng bacterial soft-rot for the ginseng roots exudates at the water layer where pH = 7 and the concentration was 0.0125 mg/L reached its peak value under the circumstance that the exudates was cultivated for 60 min at 25 °C. The chemotatic ratios were respectively 124.89% and 89.44%. For the butanol extract layer and the petroleum ether faction at the concentration of 0.125 mg/L and the pH value at 7, the ginseng roots exudatess reached peak values at 25 °C and 30 °C and 60 min and 75 min respectively, and the chemotatic ratios were respectively 139.64% and101.87%, and 115.29% and 81.36%. The three ginseng roots exudates had positive effects for the chemotaxis of the Ginseng soft-rot bacteria, but the effect declined as the concentration increased.     

Chemotactic response of Escherichia coli to chemically synthesized amino acids.

In Escherichia coli, seven of the commonly occurring amino acids are strong attractants: L-aspartate, L-serine, L-glutamate, L-alanine, L-asparagine, glycine, and L-cysteine, in order of decreasing effectiveness. The chemotactic response to each amino acid attractant is mediated by either methyl-accepting chemotaxis protein I or II, but not by both. Seven of the commonly occurring amino acids are repellents. This work was carried out with chemically synthesized amino acids.     

Chemotactic response of rat mammary adenocarcinoma cell clones to tumor-derived cytokines

A cytokine with an apparent molecular weight of 53,000 daltons was isolated from serum-free medium conditioned by MTLn3 cells or from homogenates of MTLn3 cells, a highly metastatic variant of the rat 13762NF mammary adenocarcinoma. The chemotactic responses of MTLn3 and the low metastatic variant MTLn2 cells to this cytokine were tested in vitro using modified Boyden chambers. Both the chemotactic and chemokinetic movements of MTLn3 cells were stimulated by the MTLn3-derived cytokine. In addition, the MTLn3-derived cytokine stimulated a relatively small, but significant chemotactic migration of MTLn2 tumor cells, while these cells did not respond to medium conditioned by MTLn2 cells. MTLn3 cells themselves did not respond chemotactically to type I collagen or medium conditioned by MTLn2 cells. These results suggest that the chemotactic response may be a function of metastatic potential of the invading tumor cells. The production of tumor cytokines that enhance tumor cell motility may thus represent a phenotypic difference between 13762NF tumor cell subpopulations of high and low metastatic potential.     

Chemotactic response of splenic mononuclear cells to angiotensin II in murine schistosomiasis

Murine Schistosomiasis mansoni is a parasitic infection associated with a delayed-type hypersensitivity granulomatous reaction to the schistosome eggs. This reaction is characterized by the accumulation of mononuclear cells and other inflammatory cell types around the eggs. Granuloma macrophages produce angiotensin II (AII), which appears to have immunoregulatory function. By using an in vitro chemotaxis assay, this study demonstrated that AII is a chemotactic factor for splenic mononuclear cells derived from infected mice. The response was bimodal, with peak activities occurring at 10(-10) and 10(-6) M. AII was chemotactic for T lymphocytes, B lymphocytes, and a large population of unidentified mononuclear cells at the optimal chemotactic concentrations of the peptide. At high concentrations, AII was also chemotactic for phagocytic mononuclear cells. Sar1, ala8-AII, an analog of AII with antagonist activity, completely blocked AII-induced chemotaxis. A [3H]-AII binding assay revealed high-affinity specific binding on spleen cells. The binding was rapid, was dependent on radioligand concentration, and was reversible. These latter observations suggest that the chemotactic activity of AII for subpopulations of splenic mononuclear cells is mediated via AII receptors.     

Biosynthesis of a sulfonolipid in gliding bacteria

Gliding bacteria of the genus Cytophaga synthesize sulfonolipids (1,2) that contain capnine (1-deoxy-15-methylhexadecasphinganine-1-sulfonic acid). Studies of the incorporation of radiolabeled compounds by C. johnsonae show that cysteate is utilized preferentially to both cystine and inorganic sulfate as a precursor of capnine sulfur and to both cystine and serine as a precursor of carbons 1 and 2 of capnine. The results are consistent with a pathway in which capnine is formed by condensation of cysteate with a fatty acyl CoA. Cystine, added as the sole sulfur source in the presence of glucose, provides the sulfur but not the carbon for capnine. Hence, these cells form cysteate not by direct oxidation of cystine (or cysteine), but by transfer of its sulfur to a different carbon compound.     

Physiological ecology of a gliding bacterium containing bacteriochlorophyll a

[This corrects the article on p. 577 in vol. 47.].