Flagellate Motility, Behavioral Responses and Active Transport in Purple Non-Sulfur Bacteria

Armitage, Judith P.; Kelly, David J.; Sockett, R. Elizabeth

doi:10.1007/0-306-47954-0_47

Cited by 3 publications

(2 citation statements)

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“…There has been interest and controversy for many years about whether free-swimming phototrophic bacteria can sense the direction of light as well as its intensity, i.e., whether they show true phototaxis (3,4,12,14). It is well-known that phototrophic bacteria, including Chromatium, Rhodospirillum, and Thiospirillum spp., reverse direction when swimming through a light/dark boundary, causing them to be trapped on the light side of the boundary (reviewed in reference 6).…”

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Photoresponses of the purple nonsulfur bacteria Rhodospirillum centenum and Rhodobacter sphaeroides

et al. 1997

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We have measured the photoresponse of two purple nonsulfur bacteria, Rhodobacter sphaeroides and Rhodospirillum centenum, under defined conditions in a light beam propagating at 90°to the optical axis of the microscope. This beam presented cells with a steep gradient of intensity perpendicular to the direction of propagation and a shallow gradient in the direction of light propagation. R. centenum, a species that reverses to change direction, accumulated in the light beam, as expected for a "scotophobic" response, while R. sphaeroides, which stops rather than reverses, accumulated outside the light beam. We also compared the behavior of liquid-grown R. centenum, which swims by using a single polar flagellum, to that of surface-grown R. centenum, which swarms over agar by using many lateral flagella and has been shown to move as colonies toward specific wavelengths of light. When suspended in liquid medium, both liquid-and surface-grown R. centenum showed similar responses to the light gradient. In all cases, free-swimming cells responded to the steep gradient of intensity but not to the shallow gradient, indicating they cannot sense the direction of light propagation but only its intensity. In a control experiment, the known phototactic alga Chlamydamonas reinhardtii was shown to swim in the direction of light propagation.

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Photoresponses of the purple nonsulfur bacteria Rhodospirillum centenum and Rhodobacter sphaeroides

et al. 1997

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“…The motility, chemotaxis, and flagellar structure of R. sphaeroides have been the subject of previous studies (4)(5)(6)53). We are interested in extending the molecular characterization of flagellar proteins and in studying the mechanisms of flagellar export, assembly, and genetic regulation in this organism.…”

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Structural and genetic analysis of a mutant of Rhodobacter sphaeroides WS8 deficient in hook length control

et al. 1997

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Motility in the photosynthetic bacterium Rhodobacter sphaeroides is achieved by the unidirectional rotation of a single subpolar flagellum. In this study, transposon mutagenesis was used to obtain nonmotile flagellar mutants from this bacterium. We report here the isolation and characterization of a mutant that shows a polyhook phenotype. Morphological characterization of the mutant was done by electron microscopy. Polyhooks were obtained by shearing and were used to purify the hook protein monomer (FlgE). The apparent molecular mass of the hook protein was 50 kDa. N-terminal amino acid sequencing and comparisons with the hook proteins of other flagellated bacteria indicated that the Rhodobacter hook protein has consensus sequences common to axial flagellar components. A 25-kb fragment from an R. sphaeroides WS8 cosmid library restored wild-type flagellation and motility to the mutant. Using DNA adjacent to the inserted transposon as a probe, we identified a 4.6-kb SalI restriction fragment that contained the gene responsible for the polyhook phenotype. Nucleotide sequence analysis of this region revealed an open reading frame with a deduced amino acid sequence that was 23.4% identical to that of FliK of Salmonella typhimurium, the polypeptide responsible for hook length control in that enteric bacterium. The relevance of a gene homologous to fliK in the uniflagellated bacterium R. sphaeroides is discussed.Many bacterial species have the ability to move, and they alter the direction of their movement in response to different external stimuli, which enables them to migrate to more favorable environments (33). Swimming motility (as opposed to gliding and other types of motility) involves the function of a complex structure called the flagellum. The flagellum is composed of three main parts, the basal body, the hook, and the filament (for recent reviews, see references 9, 33, and 46). Much of the information generated to date regarding flagellar structure, assembly, function, and genetics has been obtained from the gram-negative organisms Escherichia coli and Salmonella typhimurium (reviewed in references 20 and 32). These enteric bacteria possess between 5 and 10 peritrichous flagella per cell. The flagellum can rotate either counterclockwise, causing the filaments to form a bundle that produces translational motion, or clockwise (CW), causing the cell to tumble and reorient (31, 49).The filament is connected to the basal body through the hook, which works as a flexible coupling that allows torque generated by the motor to be transmitted to the filament (10, 11). For this purpose, the hook of the bacterial flagellum requires a rather well-defined length (23). A shorter hook would not generate a sufficient bend angle (23), and presumably a long flexible coupling would not permit effectively directed transmission of torque (57). The mean length that has been established for different bacterial species varies from 55 Ϯ 6 nm for the wild-type hook of S. typhimurium (15) to 69 Ϯ 8 nm for Treponema phagedenis (29) and u...

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Behavioral Responses of Rhodobacter sphaeroides to Linear Gradients of the Nutrients Succinate and Acetate

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Armitage

2000

Appl Environ Microbiol

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Rhodobacter sphaeroides cells were tethered by their flagella and subjected to increasing and decreasing nutrient gradients. Using motion analysis, changes in flagellar motor rotation were measured and the responses of the cells to the chemotactic gradients were determined. The steepness and concentration ranges of increasing and decreasing gradients were varied, and the bacterial responses were measured. This allowed the limits of gradients that would invoke changes in flagellar behavior to be determined and thus predicts the nature of gradients that would evoke chemotaxis in the environment. The sensory threshold was measured at 30 nM, and the response showed saturation at 150 M. The study determined that cells detected and responded to changing concentration rates as low as 1 nM/s for acetate and 5 nM/s for succinate. The complex sensory system of R. sphaeroides responded to both increasing and decreasing concentration gradients of attractant with different sensitivities. In addition, transition phases involving changes in the motor speed and the smoothness of motor rotation were found.The bacterial environment is subject to constant change. Environmental factors such as nutrient concentrations, light levels, oxygen concentration, pH, and the presence of toxins all vary over time. These changes are sensed by motile bacteria, which respond by moving along concentration gradients towards optimum conditions for growth, a process known as taxis. The means of locomotion used by motile bacteria does vary, but most species use flagellum-driven motility. The bacterial flagellum is a semirigid helical filament driven at its base by a rotary motor (reviewed recently in reference 2). Unstimulated bacteria (a condition unlikely to exist outside the laboratory) swim randomly around their environment, periodically changing direction. Bacteria sense changes in their environment with time (temporal sensing), as they are too small to sense spatial difference. This means that they must compare the current environmental status with previous measurements. When a gradient of attractant is sensed, their direction-changing frequency alters to bias swimming up the gradient. The mechanism of direction changing varies between species and is controlled by the bacterial chemotaxis signal transduction (Che) pathway.Chemotaxis has been extensively studied in Escherichia coli. In this organism counterclockwise rotation causes smooth swimming, and switching to clockwise rotation causes a tumble and a change in the subsequent direction of smooth swimming. The Che pathway controlling this switching in E. coli is well understood (1, 14). Membrane-spanning methyl-accepting chemotaxis proteins (MCPs) sense a decrease in the concentration of attractant in the periplasm (15). The MCPs transmit a signal via CheW, which interacts with the cytoplasmic domain of the MCP, to activate CheA, a histidine protein kinase. CheA autophosphorylates, and the phosphate group is then transferred to the response regulator, CheY, which interacts with the flagellar ...

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Flagellate Motility, Behavioral Responses and Active Transport in Purple Non-Sulfur Bacteria

Cited by 3 publications

References 103 publications

Photoresponses of the purple nonsulfur bacteria Rhodospirillum centenum and Rhodobacter sphaeroides

Photoresponses of the purple nonsulfur bacteria Rhodospirillum centenum and Rhodobacter sphaeroides

Structural and genetic analysis of a mutant of Rhodobacter sphaeroides WS8 deficient in hook length control

Behavioral Responses of Rhodobacter sphaeroides to Linear Gradients of the Nutrients Succinate and Acetate

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