[ { "id": "authors:8krq9-1px22", "collection": "authors", "collection_id": "8krq9-1px22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MURmm08", "type": "article", "title": "Novel ultrastructures of Treponema primitia and their implications for motility", "author": [ { "family_name": "Murphy", "given_name": "Gavin E.", "clpid": "Murphy-G-E" }, { "family_name": "Matson", "given_name": "Eric G.", "clpid": "Matson-E-G" }, { "family_name": "Leadbetter", "given_name": "Jared R.", "orcid": "0000-0002-7033-0844", "clpid": "Leadbetter-J-R" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" }, { "family_name": "Jensen", "given_name": "Grant J.", "orcid": "0000-0003-1556-4864", "clpid": "Jensen-G-J" } ], "abstract": "Members of the bacterial phylum Spirochaetes are generally helical cells propelled by periplasmic flagella. The spirochete Treponema primitia is interesting because of its mutualistic role in the termite gut, where it is believed to cooperate with protozoa that break down cellulose and produce H2 as a by-product. Here we report the ultrastructure of T. primitia as obtained by electron cryotomography of intact, frozen-hydrated cells. Several previously unrecognized external structures were revealed, including bowl-like objects decorating the outer membrane, arcades of hook-shaped proteins winding along the exterior and tufts of fibrils extending from the cell tips. Inside the periplasm, cone-like structures were found at each pole. Instead of the single peptidoglycan layer typical of other Gram-negative bacteria, two distinct periplasmic layers were observed. These layers formed a central open space that contained two flagella situated adjacent to each other. In some areas, the inner membrane formed flattened invaginations that protruded into the cytoplasm. High-speed light microscopic images of swimming T. primitia cells showed that cell bodies remained rigid and moved in a helical rather than planar motion. Together, these findings support the 'rolling cylinder' model for T. primitia motility that posits rotation of the protoplasmic cylinder within the outer sheath.", "doi": "10.1111/j.1365-2958.2008.06120.x", "pmcid": "PMC3082362", "issn": "0950-382X", "publisher": "Blackwell", "publication": "Molecular Microbiology", "publication_date": "2008-03", "series_number": "6", "volume": "67", "issue": "6", "pages": "1184-1195" }, { "id": "authors:vq29t-gfh54", "collection": "authors", "collection_id": "vq29t-gfh54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120622-120016118", "type": "article", "title": "Reconstitution of Signaling in Bacterial Chemotaxis", "author": [ { "family_name": "Wolfe", "given_name": "Alan J.", "clpid": "Wolfe-A-J" }, { "family_name": "Conley", "given_name": "M. Patricia", "clpid": "Conley-M-P" }, { "family_name": "Kramer", "given_name": "Tina J.", "clpid": "Kramer-T-J" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Strains missing several genes required for chemotaxis toward amino acids, peptides, and certain sugars were\ntethered and their rotational behavior was analyzed. Null strains (called gutted) were deleted for genes that\ncode for the transducers Tsr, Tar, Tap, and Trg and for the cytoplasmic proteins CheA, CheW, CheR, CheB,\nCheY, and CheZ. Motor switch components were wild type, flaAII(cheC), or flaBll(cheV). Gutted cells with\nwild-type motors spun exclusively counterclockwise, while those with mutant motors changed their directions\nof rotation. CheY reduced the bias (the fraction of time that cells spun counterclockwise) in either case. CheZ\noffset the effect of CheY to an extent that varied with switch allele but did not change the bias when tested alone.\nTransducers also increased the bias in the presence of CheY but not when tested alone. However, cells\ncontaining transducers and CheY failed to respond to attractants or repellents normally detected in the\nperiplasm. This sensitivity was restored by addition of CheA and CheW. Thus, CheY both enhances clockwise\nrotation and couples the transducers to the flagella. CheZ acts, at the level of the motor, as a CheY antagonist.\nCheA or CheW or both are required to complete the signal pathway. A model is presented that explains these\nresults and is consistent with other data found in the literature.", "pmcid": "PMC212038", "issn": "0021-9193", "publisher": "American Society for Microbiology", "publication": "Journal of Bacteriology", "publication_date": "1987-05", "series_number": "5", "volume": "169", "issue": "5", "pages": "1878-1885" }, { "id": "authors:t4ns7-k1z63", "collection": "authors", "collection_id": "t4ns7-k1z63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140826-104818365", "type": "article", "title": "Geology of Annette, Gravina, and Duke islands, southeastern Alaska", "author": [ { "family_name": "Gehrels", "given_name": "George E.", "clpid": "Gehrels-G-E" }, { "family_name": "Saleeby", "given_name": "Jason", "clpid": "Saleeby-J-B" }, { "family_name": "Berg", "given_name": "Henry C.", "clpid": "Berg-H-C" } ], "abstract": "Geologic mapping, U\u2013Pb (zircon) geochronometry, and conodont studies indicate that the major pre-Jurassic assemblages on Annette, Gravina, Duke, and adjacent smaller islands include pre-Middle Ordovician metavolcanic and metasedimentary rocks (Wales metamorphic suite); Cambrian metaplutonic rocks; Ordovician \u2013 Early Silurian volcanic (Descon Formation), dioritic, and gabbroic rocks; Silurian trondhjemitic plutons; Early Devonian sedimentary (Karheen Formation) and volcanic rocks; Late Triassic sedimentary and volcanic rocks (Hyd Group); and a large body of Late Triassic pyroxene gabbro.Stratigraphic, structural, and intrusive relations record episodes of regional deformation, metamorphism, and uplift during Middle Cambrian \u2013 Early Ordovician time (Wales orogeny) and during middle Silurian \u2013 earliest Devonian time (Klakas orogeny). Upper Triassic strata were apparently deposited during a latest Paleozoic(?) \u2013 Triassic rifting event.Comparison with the geology of Prince of Wales Island indicates that the Annette and Craig subterranes of the Alexander terrane belong to the same tectonic fragment and that the Clarence Strait fault has ~15\u2002km of right-lateral displacement at this latitude. Our geochronologic data indicate that the pyroxene gabbro on Duke Island is Triassic in age and therefore probably unrelated to nearby Cretaceous(?) zoned ultramafic bodies.", "doi": "10.1139/e87-086", "issn": "1480-3313", "publisher": "NRC Research Press", "publication": "Canadian Journal of Earth Sciences", "publication_date": "1987-05", "series_number": "5", "volume": "24", "issue": "5", "pages": "866-881" }, { "id": "authors:y21nj-ner67", "collection": "authors", "collection_id": "y21nj-ner67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:SEGpnas86", "type": "article", "title": "Temporal comparisons in bacterial chemotaxis", "author": [ { "family_name": "Segall", "given_name": "Jeffrey E.", "clpid": "Segall-J-E" }, { "family_name": "Block", "given_name": "Steven M.", "clpid": "Block-S-M" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Responses of tethered cells of Escherichia coli to impulse, step, exponential-ramp or exponentiated sine-wave stimuli are internally consistent, provided that allowance is made for the nonlinear effect of thresholds. This result confirms that wild-type cells exposed to stimuli in the physiological range make short-term temporal comparisons extending 4 sec into the past: the past second is given a positive weighting, the previous 3 sec are given a negative weighting, and the cells respond to the difference. cheRcheB mutants (defective in methylation and demethylation) weight the past second in a manner similar to the wild type, but they do not make short-term temporal comparisons. When exposed to small steps delivered iontophoretically, they fail to adapt over periods of up to 12 sec; when exposed to longer steps in a flow cell, they partially adapt, but with a decay time of >30 sec. cheZ mutants use a weighting that extends at least 40 sec into the past. The gain of the chemotactic system is large: the change in occupancy of the receptor molecule produces a significant response.", "doi": "10.1073/pnas.83.23.8987", "pmcid": "PMC387059", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1986-12-01", "series_number": "23", "volume": "83", "issue": "23", "pages": "8987-8991" }, { "id": "authors:09h3t-mra32", "collection": "authors", "collection_id": "09h3t-mra32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KRIpnas85", "type": "article", "title": "Chimeric chemosensory transducers of Escherichia coli", "author": [ { "family_name": "Krikos", "given_name": "Alexandra", "clpid": "Krikos-A" }, { "family_name": "Conley", "given_name": "M. Patricia", "clpid": "Conley-M-P" }, { "family_name": "Boyd", "given_name": "Alan", "clpid": "Boyd-Alan" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" }, { "family_name": "Simon", "given_name": "Melvin I.", "clpid": "Simon-M-I" } ], "abstract": "The tar and tsr genes of Escherichia coli encode homologous transducer proteins that mediate distinct chemotactic responses. We report here the construction of two tasr chimeric genes in which the 5' coding region of the tar gene is fused to the 3' coding region of the tsr gene at either of two conserved restriction sites. Both chimeric genes code for chemotactically functional proteins. Results of analyses of behavior and methylation in cells carrying the chimeric genes support existing models for the disposition of transducer domains across the cell membrane and reveal that the receptors for internal pH map in a specific region of the COOH-terminal (cytoplasmic) domain.", "doi": "10.1073/pnas.82.5.1326", "pmcid": "PMC397253", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1985-03-01", "series_number": "5", "volume": "82", "issue": "5", "pages": "1326-1330" }, { "id": "authors:3kdhw-84345", "collection": "authors", "collection_id": "3kdhw-84345", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:SEGjbact85", "type": "article", "title": "Chemotactic signaling in filamentous cells of Escherichia coli", "author": [ { "family_name": "Segall", "given_name": "Jeffrey E.", "clpid": "Segall-J-E" }, { "family_name": "Ishihara", "given_name": "Akira", "clpid": "Ishihara-A" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Video techniques were used to record chemotactic responses of filamentous cells of Escherichia coli stimulated iontophoretically with aspartate. Long, nonseptate cells were produced from polyhook strains either by introducing a cell division mutation or by growth in the presence of cephalexin. Markers indicating rotation of flagellar motors were attached with anti-hook antibodies. Aspartate was applied by iontophoretic ejection from a micropipette, and the effects on the direction of rotation of the markers were measured. Motors near the pipette responded, whereas those sufficiently far away did not, even when the pipette was near the cell surface. The response of a given motor decreased as the pipette was moved away, but it did so less steeply when the pipette remained near the cell surface than when it was moved out into the external medium. This shows that there is an internal signal, but its range is short, only a few micrometers. These experiments rule out signaling by changes in membrane potential, by simple release or binding of a small molecule, or by diffusion of the receptor-attractant complex. A likely candidate for the signal is a protein or ligand that is activated by the receptor and inactivated as it diffuses through the cytoplasm. The range of the signal was found to be substantially longer in a cheZ mutant, suggesting that the product of the cheZ gene contributes to this inactivation.", "issn": "0021-9193", "publisher": "Journal of Bacteriology", "publication": "Journal of Bacteriology", "publication_date": "1985-01-01", "series_number": "1", "volume": "161", "issue": "1", "pages": "51-59" }, { "id": "authors:488fx-a0423", "collection": "authors", "collection_id": "488fx-a0423", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CONjbact84", "type": "article", "title": "Chemical modification of Streptococcus flagellar motors", "author": [ { "family_name": "Conley", "given_name": "M. Patricia", "clpid": "Conley-M-P" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Video techniques were used to record changes in motility of cells of Streptococcus sp. strain V4051 exposed to a variety of protein modification reagents. Starved cells were tethered to glass by a single flagellum, energized metabolically with glucose, or treated with valinomycin and energized artificially via shifts to media containing low concentrations of potassium ion. Experiments were devised that distinguished reagents that lowered the proton motive force from those that blocked the generation of torque (damaged the flagellar motors). Imidazole reagents blocked the generation of torque. Amino, sulfhydryl, dithiol, and disulfide reagents did not. Some of the imidazole, amino, and sulfhydryl reagents had long-term effects on the direction of flagellar rotation.", "pmcid": "PMC215517", "issn": "0021-9193", "publisher": "American Society for Microbiology", "publication": "Journal of Bacteriology", "publication_date": "1984-06", "series_number": "3", "volume": "158", "issue": "3", "pages": "832-843" }, { "id": "authors:613w9-e4455", "collection": "authors", "collection_id": "613w9-e4455", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ISHjbact83", "type": "article", "title": "Coordination of flagella on filamentous cells of Escherichia coli", "author": [ { "family_name": "Ishihara", "given_name": "Akira", "clpid": "Ishihara-A" }, { "family_name": "Segall", "given_name": "Jeffrey E.", "clpid": "Segall-J-E" }, { "family_name": "Block", "given_name": "Steven M.", "clpid": "Block-S-M" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Video techniques were used to study the coordination of different flagella on single filamentous cells of Escherichia coli. Filamentous, nonseptate cells were produced by introducing a cell division mutation into a strain that was polyhook but otherwise wild type for chemotaxis. Markers for its flagellar motors (ordinary polyhook cells that had been fixed with glutaraldehyde) were attached with antihook antibodies. The markers were driven alternately clockwise and counterclockwise, at angular velocities comparable to those observed when wild-type cells are tethered to glass. The directions of rotation of different markers on the same cell were not correlated; reversals of the flagellar motors occurred asynchronously. The bias of the motors (the fraction of time spent spinning counterclockwise) changed with time. Variations in bias were correlated, provided that the motors were within a few micrometers of one another. Thus, although the directions of rotation of flagellar motors are not controlled by a common intracellular signal, their biases are. This signal appears to have a limited range.", "issn": "0021-9193", "publisher": "Journal of Bacteriology", "publication": "Journal of Bacteriology", "publication_date": "1983-07-01", "series_number": "1", "volume": "155", "issue": "1", "pages": "228-237" }, { "id": "authors:e3j64-54t80", "collection": "authors", "collection_id": "e3j64-54t80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BLOjbact83", "type": "article", "title": "Adaptation kinetics in bacterial chemotaxis", "author": [ { "family_name": "Block", "given_name": "Steven M.", "clpid": "Block-S-M" }, { "family_name": "Segall", "given_name": "Jeffrey E.", "clpid": "Segall-J-E" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Cells of Escherichia coli, tethered to glass by a single flagellum, were subjected to constant flow of a medium containing the attractant alpha-methyl-DL-aspartate. The concentration of this chemical was varied with a programmable mixing apparatus over a range spanning the dissociation constant of the chemoreceptor at rates comparable to those experienced by cells swimming in spatial gradients. When an exponentially increasing ramp was turned on (a ramp that increases the chemoreceptor occupancy linearly), the rotational bias of the cells (the fraction of time spent spinning counterclockwise) changed rapidly to a higher stable level, which persisted for the duration of the ramp. The change in bias increased with ramp rate, i.e., with the time rate of change of chemoreceptor occupancy. This behavior can be accounted for by a model for adaptation involving proportional control, in which the flagellar motors respond to an error signal proportional to the difference between the current occupancy and the occupancy averaged over the recent past. Distributions of clockwise and counterclockwise rotation intervals were found to be exponential. This result cannot be explained by a response regular model in which transitions between rotational states are generated by threshold crossings of a regular subject to statistical fluctuation; this mechanism generates distributions with far too many long events. However, the data can be fit by a model in which transitions between rotational states are governed by first-order rate constants. The error signal acts as a bias regulator, controlling the values of these constants.", "issn": "0021-9193", "publisher": "Journal of Bacteriology", "publication": "Journal of Bacteriology", "publication_date": "1983-04-01", "series_number": "1", "volume": "154", "issue": "1", "pages": "312-323" }, { "id": "authors:06j29-xxf04", "collection": "authors", "collection_id": "06j29-xxf04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LAPjbact82", "type": "article", "title": "Gliding motility of Cytophaga sp. strain U67", "author": [ { "family_name": "Lapidus", "given_name": "I. Richard", "clpid": "Lapidus-I-R" }, { "family_name": "Berg", "given_name": "Howard C.", "clpid": "Berg-H-C" } ], "abstract": "Video techniques were used to analyze the motion of the gliding bacterium Cytophaga sp. strain U67. Cells moved singly on glass along the long axis at a speed of about 2 micrometers/s, advancing, retreating, stopping, pivoting about a pole, or flipping over. They did not flex or roll. Cells of different lengths moved at about the same speed. Cells sometimes spun continuously about a pole at a frequency of about 2 HZ, the body moving in a plane parallel to that of the glass or on the surface of a cone having either a large or a small solid angle. Polystyrene latex spheres moved to and fro on the surfaces of cells, also at a speed of about 2 micrometers/s. They moved in the same fashion whether a cell was in suspension, gliding, or at rest on the glass. Two spheres on the same cell often moved in opposite directions, passing by one another in close proximity. Small and large spheres and aggregates of spheres all moved at about the same speed. An aggregate moved down the side of a cell with a fixed orientation, even when only one sphere was in contact with the cell. Spheres occasionally left one cell and were picked up by another. Cell pretreated with small spheres did not adhere to glass. When the cells were deprived of oxygen, they stopped gliding, and the spheres stopped moving on their surfaces. The spheres became completely immobilized; they no longer moved from cell to cell or exhibited Brownian movement. Cytophaga spp. are known to have a typical gram-negative cell envelope: an inner (cytoplasmic) membrane, a thin peptidoglycan layer, and an outer (lipopolysaccharide) membrane. Our data are consistent with a model for gliding in which sites to which glass and polystyrene strongly adsorb move within the fluid outer membrane along tracks fixed to the rigid peptidoglycan framework.", "issn": "0021-9193", "publisher": "Journal of Bacteriology", "publication": "Journal of Bacteriology", "publication_date": "1982-07-01", "series_number": "1", "volume": "151", "issue": "1", "pages": "384-398" } ]