Behavior of <i>Rhizobium meliloti</i> in oxygen gradients

Zhulin, Igor B.; Lois, Augusto F.; Taylor, Barry

doi:10.1016/0014-5793(95)00561-m

Cited by 14 publications

(12 citation statements)

References 19 publications

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“…Even more interesting was the observation that the motility response observed for the different Shewanella strains correlated not only with the redox potential of the electron acceptors used in the different experiments, but also with the current-generating ability of the strains, again suggesting that this unique response could have a kinetic basis. We do note that the electrokinetic response is similar to the chemokinetic response observed by Zhulin et al (22), during studies on behavioral responses to oxygen in Rhizobium meliloti. These authors showed that R. meliloti responds to oxygen by increasing the swimming speed of cells and correlated this response with changes in proton motive force.…”

Section: Discussionsupporting

confidence: 56%

Electrokinesis is a microbial behavior that requires extracellular electron transport

Harris

El‐Naggar²,

Bretschger³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

133

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We report a previously undescribed bacterial behavior termed electrokinesis . This behavior was initially observed as a dramatic increase in cell swimming speed during reduction of solid MnO 2 particles by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. The same behavioral response was observed when cells were exposed to small positive applied potentials at the working electrode of a microelectrochemical cell and could be tuned by adjusting the potential on the working electrode. Electrokinesis was found to be different from both chemotaxis and galvanotaxis but was absent in mutants defective in electron transport to solid metal oxides. Using in situ video microscopy and cell tracking algorithms, we have quantified the response for different strains of Shewanella and shown that the response correlates with current-generating capacity in microbial fuel cells. The electrokinetic response was only exhibited by a subpopulation of cells closest to the MnO 2 particles or electrodes. In contrast, the addition of 1 mM 9,10-anthraquinone-2,6-disulfonic acid, a soluble electron shuttle, led to increases in motility in the entire population. Electrokinesis is defined as a behavioral response that requires functional extracellular electron transport and that is observed as an increase in cell swimming speeds and lengthened paths of motion that occur in the proximity of a redox active mineral surface or the working electrode of an electrochemical cell.

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Section: Discussionsupporting

confidence: 56%

Electrokinesis is a microbial behavior that requires extracellular electron transport

Harris

El‐Naggar²,

Bretschger³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

133

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“…Our results show that highly motile bacteria can congregate at a preferred concentration gradient. This has been reported for aerotactic bacteria [10,14,32,33], but to the best of our knowledge has not been previously shown for amino acids. The formation of the motile bands by the marine bacteria could be a strategy evolved for life in a turbulent environment.…”

Section: Implications In the Open Oceansupporting

confidence: 44%

Marine bacterial organisation around point-like sources of amino acids

Barbara¹,

Mitchell²

2003

FEMS Microbiology Ecology

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To better understand the trigger for and use of motility in marine bacterial chemotaxis, specific (amino acids) chemical stimuli were used to test the effect on bacterial speed and reorientation. An assay system was developed to analyse bacterial behavioural responses to point-like nutrient sources (beads 10-40 mum). The marine bacteria Pseudoalteromonas haloplanktis, Shewanella putrefaciens, Deleya marina, the enteric bacterium Escherichia coli and an enriched assemblage of marine bacteria were used in the assay. E. coli responded to the amino acids (e.g. serine, leucine) in this assay in a manner similar to the classical capillary plating method, and accumulated near the attractants using biased random walks and maximum speeds of less than 30 mum s(-1). The marine bacteria travelled more than 100 mum s(-1) and reversed direction instead of randomly tumbling to reorientate. Marine bacteria also showed different chemotactic responses. The enriched marine community and P. haloplanktis were repelled by serine while leucine was an attractant for all three marine isolates. More importantly marine bacteria formed band specific distances (>20 mum) away from individual beads. The bands were composed of free-swimming bacteria rather than bacteria attached to the beads or chamber surfaces. The bands' formation time (25-180 s) and width (5-20 mum) varied depending on the bacterial strains and attractant. This variation in chemotactic responses by the marine isolates may reflect adaptations to specific ecological niches of bacterioplankton in the ocean. However, band forming ability by marine bacteria has still only been reported in experimental studies, nutrient coupling between nutrient sources and bands of chemotactic marine bacteria have yet to be detected in the natural environment. The fragility of the bands, a clear association between free-swimming bacteria and nutrient, indicates the difficulty and potentially sets limits for finding microzones of bacteria around particles in the open ocean.

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“…It is evident that the two cytoplasmic receptors are important for the chemokinesis response of S. meliloti ( (78). In addition, deleting either of the two PAS domain-encoding DNA regions had no effect on the chemotactic behavior of the resulting mutant strains on swarm plates (data not shown).…”

Section: Discussionmentioning

confidence: 95%

Functional Analysis of Nine Putative Chemoreceptor Proteins inSinorhizobium meliloti

2007

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The process of chemotaxis enables many motile bacterial species to sense their environment and move in a beneficial direction. The underlying signaling pathway for responding to changes in the concentrations of chemical attractants or repellents has been most intensely studied for Escherichia coli and Salmonella enterica serovar Typhimurium (for reviews, see references 24 and 69). In the absence of a chemical stimulus, E. coli shows a random swimming pattern consisting of alternating runs and tumbles. The addition of an attractant or the removal of a repellent promotes counterclockwise flagellar rotation and therefore straight runs. Ergo, the cell is directed to a more advantageous environment. The signal transduction pathway to the flagellar motor consists of chemoreceptor proteins and a two-component signaling system. E. coli uses four membrane-bound methyl-accepting chemotaxis proteins (MCPs)-Tar for aspartate and maltose, Tsr for serine, Trg for ribose and galactose, and Tap for dipeptides-as well as the membrane-bound Aer as an oxygen sensor (16,24). MCP molecules typically consist of a periplasmic ligand-binding domain, two transmembrane helices, and a highly conserved cytoplasmic signaling domain (24, 67). To enable high sensitivity over a range of attractant concentrations, adaptational modifications are introduced at specific glutamate residues in two methylation helices, MH1 and MH2 (38). Methyl groups are transferred from S-adenosylmethionine by the methyltransferase CheR (72), while their removal is accomplished by the methylesterase CheB (33, 68). The highly abundant major receptors in E. coli, Tsr and Tar, have an NWETF pentapeptide sequence at the C terminus, which serves as a docking site for CheR and CheB (12,25,77).Recent studies suggest that chemotaxis in other bacteria departs from the E. coli model by involving more che genes and chemoreceptors (4,7,17,59,70). The nitrogen-fixing plant symbiont Sinorhizobium meliloti, a member of the alpha subgroup of proteobacteria (52), differs from the enterobacterial (gamma-subgroup) behavioral scheme in its modes of flagellar rotation, signal processing, and gene regulation (59). The rigid complex flagellar filaments consist of four related flagellin subunits, and interflagellin bonds lock the filaments into righthandedness (21,29,60). Hence, S. meliloti cells are propelled by flagella that rotate exclusively clockwise, and swimming cells respond to tactic stimuli by modulating their rotary speed (8,58). In E. coli, tactic signals are processed by a single response regulator, CheY, and a phosphatase, CheZ. In contrast, signal processing in S. meliloti involves a retrophosphorylation loop with two response regulators, CheY1 and CheY2, but no phosphatase (64, 65). CheY2 is the main regulator of motor function, causing a decrease in the rotary speed of the unidirectional clockwise-rotating flagellar motor (59). It has been reported previously that S. meliloti exhibits positive chemotactic responses toward a wide range of substances such as amino acids, sug...

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Behavior of Rhizobium meliloti in oxygen gradients

Cited by 14 publications

References 19 publications

Electrokinesis is a microbial behavior that requires extracellular electron transport

Electrokinesis is a microbial behavior that requires extracellular electron transport

Marine bacterial organisation around point-like sources of amino acids

Functional Analysis of Nine Putative Chemoreceptor Proteins inSinorhizobium meliloti

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