scholarly journals Emergent myxobacterial behaviors arise from reversal suppression induced by kin contacts

2021 ◽  
Author(s):  
Rajesh Balagam ◽  
Pengbo Cao ◽  
Govind P Sah ◽  
Zhaoyang A Zhang ◽  
Daniel Wall ◽  
...  

A wide range of biological systems - from microbial swarms to bird flocks, display emergent behaviors driven by coordinated movement of individuals. To this end, individual organisms interact by recognizing their kin and adjusting their motility based on others around them. However, even in the best-studied systems, the mechanistic basis of the interplay between kin recognition and motility coordination is not understood. Here, using a combination of experiments and mathematical modeling, we uncover the mechanism of an emergent social behavior in Myxococcus xanthus. By overexpressing the cell surface kin recognition receptors, TraA and TraB, large numbers of cells adhere to one another and form organized macroscopic circular aggregates that spin clockwise or counterclockwise. Mechanistically, TraAB adhesion results in sustained cell-cell contacts that signal the Frz chemosensory pathway. In turn, cell reversals are suppressed and circular aggregates form as the result of cells' ability to follow cellular slime trails. Furthermore, our in-silico simulations demonstrate a remarkable ability to predict self-organization patterns when phenotypically distinct strains are mixed. Therefore, this work provides key mechanistic insights into M. xanthus social interactions and demonstrates how social recognition transforms physical interactions into emergent collective behaviors.

1957 ◽  
Vol s3-98 (44) ◽  
pp. 393-406
Author(s):  
B. M. SHAFFER

1. A description is given of the development of certain structures--centre, stream, and ring--formed by the amoebae of four species of Dictyostelium and Polysphondyliumduring aggregation, and of the outcome of experimentally cutting a stream, recombining lengths of stream in simple geometrical relationships, and excising a centre. 2. In all cases there is a high degree of intraspecific variation in behaviour, and it is not possible to predict, except in terms of rough probability, what the future course of development will be. 3. An amoeba at this stage of the life cycle can exist in one of four main states. In the first, it is unaggregated and cannot react chemotactically; in the second, it is unaggregated but can react; in the third, it is in a stream moving towards a centre or has properties similar to those of a stream cell; and in the fourth, it is in a centre and nearly stationary. Though an enormous variety of patterns may be produced by large numbers of interacting amoebae, their behavioural repertory may be considered, without too much simplification, to be restricted to approaching these four states in various sequences and at various rates. 4. Most of these sequences can be observed over a wide range of environmental conditions. Changes in humidity produce the greatest effect: the drier the culture, the stronger the drift from the first state to the fourth. 5. It is suggested that variability is occasioned by the simplicity of the mechanisms controlling development.


1970 ◽  
Vol 19 (1-2) ◽  
pp. 264-267 ◽  
Author(s):  
F.H. Reuling ◽  
J.T. Schwartz

In the late 1950's and early 1960's, it became evident that some glaucoma patients developed elevations of intraocular pressure, which were difficult to control, following prolonged use of systemic or ocular medications containing corticosteroids (Chandler, 1955, Alfano, 1963; Armaly, 1963). In addition, some patients without glaucoma, when treated with steroids for long periods of time, developed clinical signs of chronic simple glaucoma (McLean, 1950; François, 1954; Covell, 1958; Linner, 1959; Goldman, 1962). Fortunately, the elevation of intraocular pressure was reversible if the drug was discontinued.Over the past decade, extensive investigation of the “steroid response” has been undertaken. For this presentation, the steroid response may be considered as a gradual elevation of intraocular pressure, occurring over several weeks, in an eye being medicated with corticosteroid drops several times a day. The elevation in pressure is usually accompanied by a reduction in the facility of aqueous outflow. When relatively large numbers of subjects were tested with topical steroids, so that a wide range of responsiveness could be observed, a variation in individual sensitivity was demonstrated. Frequency distributions of intraocular pressure or change in pressure following steroids showed a skew toward the high side. On the basis of trimodal characteristics which they observed in such frequency distributions, Becker and Hahn (1964), Becker (1965) and Armaly (1965, 1966) considered the possible existence of several genetically determined subpopulations. These investigators distinguished three subpopulations on the basis of low, intermediate, and high levels of pressure response. It was hypothesized that these levels of response characterized three phenotypes, corresponding to the three possible genotypes of an allele pair, wherein one member of the pair determined a low level of response, and the other member determined a high level of response (Armaly, 1967).


Parasitology ◽  
1915 ◽  
Vol 8 (1) ◽  
pp. 11-16 ◽  
Author(s):  
L. E. Robinson

Variability in the size and, in a lesser degree, the taxonomic features of male ticks, has arrested the attention of all who have had occasion to examine moderately large numbers of examples of the same species. In the case of the female tick, this variability, though doubtless coextensive with that of the male, is more or less obscured by the wide range of variation in size, depending upon the degree of engorgement; and, also, by the fact that in the female tick the taxonomic characters are, as a rule, less pronounced. The present note is only concerned with variability in the size of the male.


1913 ◽  
Vol 17 (2) ◽  
pp. 117-131
Author(s):  
Hans Zinsser

The experiments recorded in this paper confirm the observations of Friedberger that acutely toxic bodies can be produced from typhoid bacilli by the action of sensitizer and complement and that, when small quantities of bacteria are used, an excess of sensitization either interferes with the formation of the poisons or leads to a cleavage of the bacterial proteid beyond the poisonous intermediate products spoken of as anaphylatoxins. Unlike the experience of other workers with poisons of this nature, however, our experiments have shown that the action of complement upon typhoid bacilli strongly sensitized or not at all sensitized may be carried on, at body temperature, for considerably longer than twelve hours without leading to a destruction of the poisons, and that this is true when the quantities of the bacteria used vary within the wide range of from one to twelve agar slants. It has been found, in fact, that in the case of this microorganism prolonged exposure at the higher temperature of considerable quantities of bacteria constitutes an unfailing method of regularly obtaining powerful poisons. The results obtained by the use of smaller quantities and the less vigorous complement action at low temperatures are far less regular or satisfactory. It would appear from this that complement action of considerable vigor is required to obtain from this bacillus any appreciable yield of anaphylatoxin, and that the poison, once formed, is not as unstable as that found in other microorganisms by Neufeld and Dold and others. In fact, although we have never observed complete lysis in vitro of the typhoid bacilli treated with antibody and complement, the sensitized bacteria exposed to the action of complement for as long as fifteen hours at 37.5° C. showed, in our experiments, much disintegration, and yet powerful poisons were present. Were the influence of lysis or of the too vigorous action of the serum bodies as rapidly poison-destroying in the case of this bacillus as it has been shown to be in the case of some other bacteria, it would be hard to understand how anaphylatoxins could play any part in the toxemia of typhoid fever. This phase of our experiments, however, seems to indicate that the conditions prevailing in the infected body at the height of this disease would furnish ideal criteria for anaphylatoxin production, since, in such cases, vigorously sensitized bacilli, in large numbers, are under the prolonged influence of considerable quantities of complement, conditions exactly comparable to those prevailing in our experiments. Granted that this state of affairs is actually the case, then the subsidence of the disease might depend merely upon limitation of the supply of antigen, as the increasing bactericidal action of the blood constituents come into play, and upon the consequent diminution of the anaphylatoxin. For as the bacteria diminish and the sensitizer increases, a changed proportion between them is established which, finally, as experiment has shown, results in a failure of anaphylatoxin production. For although our experiments have shown that, within a wide latitude of relative proportions of bacteria and antibody, anaphylatoxin can be formed, beyond this range an excess of one or the other element eventually will prevent their formation. It is not, however, the purpose of this paper to discuss the mechanism of the subsidence of the disease since this phase of the work will necessitate further experimental study. In regard to the experiments with kaolin, we were unable to confirm the contention of Keysser and Wassermann, though it is more than likely that toxic bodies could be formed by the action of complement upon any foreign proteid rendered amenable to its action. We are not inclined to attribute too much importance to these negative results, recording them merely as they occurred. However, should it be found subsequently that anaphylatoxins can be formed in this way, it seems unlikely that they are formed from the sensitizer or amboceptor as matrix, since this was not specifically adsorbed out of concentrated serum by the kaolin in our experiments. On the basis of experiments with so called endotoxins, ,we feel that the existence of such preformed intracellular poisons as an element in typhoid toxemia has not been proved, and is not absolutely necessary for the explanation of the phenomena occurring in this disease. However, the diarrhea, the hemorrhagic lesions, and the protracted symptoms following the injection of extracts and filtrates of the bacillus, differing so strikingly from the acute illness with rapid death or equally rapid recovery resulting from anaphylatoxin poisoning, would justify the assumption that poisons of this nature may still play a part in the disease, adding an additional specific characteristic to the clinical picture. As stated before, however, it is not improbable that all these characteristics may represent merely a more protracted or subacute state of anaphylatoxin toxemia. The experiments with autolysates, although none of them were fatal in their results upon guinea pigs, have sufficiently indicated that poisons comparable to anaphylatoxins can be formed in this way. This would indicate that a reaction of proteolysis, which may take place slowly by autolysis, is hastened by the action of complement, and its velocity is still further augmented by the increase, within certain limits, of the sensitization,—a conception which would attribute to the combined action of complement and sensitizer a function not incomparable to that of the bodies spoken of as catalytic agents.


2017 ◽  
Vol 119 (14) ◽  
pp. 1-7 ◽  
Author(s):  
Gary Natriello ◽  
Karen Zumwalt

The need for large numbers of individuals who can serve as effective teachers for the nation's young people has generated continuing interest in the recruitment, preparation, and retention of talented teachers for the past half-century, particularly since the civil rights and women's rights revolutions opened a wide range of career opportunities to many for whom teaching was historically one of the few fields available. Among the policy options under development in recent decades have been alternative routes into teaching, typically preparation experiences that differ in form and/or format from the established college-based certification programs. In this Teachers College Record Yearbook, we present the results of a longitudinal examination of one early alternative route program developed by the state of New Jersey. The New Jersey Provisional Teacher Program (or Alternate Route) is of particular interest both because it was the first of a generation of such programs created by various states in the final years of the 20th century and because its creation surfaced a range of issues and tensions that all the programs following in its wake have experienced.


2018 ◽  
Vol 17 (1) ◽  
pp. 160940691878345 ◽  
Author(s):  
Benjamin L. Read

Many qualitative social scientists conduct single-session interviews with large numbers of individuals so as to maximize the sample size and obtain a wide range of study participants. Yet in some circumstances, one-shot interviews cannot produce information of adequate quality, quantity, and validity. This article explains the several conditions that call for an alternative approach, serial interviewing, that entails interviewing participants on multiple occasions. This method is appropriate when studying complex or ill-defined issues, when interviews are subject to time constraints, when exploring change or variation over time, when participants are reluctant to share valid information, and when working with critical informants. A further benefit is the opportunity it provides for verifying and cross-checking information. This article delineates the general features of this technique. Through a series of encounters, the researcher builds familiarity and trust, probes a range of key topics from multiple angles, explores different facets of participants’ experiences, and learns from events that happen to take place during the interviews. This helps overcome biases associated with one-off interviews, including a tendency toward safe, simple answers in which participants flatten complexity, downplay sociopolitical conflict, and put themselves in a flattering light. This article illustrates the utility of this approach through examples drawn from published work and through a running illustration based on the author’s research on elected neighborhood leaders in Taipei. Serial interviewing helped produce relatively accurate and nuanced data concerning the power these leaders wield and their multiple roles as intermediaries between state and society.


2020 ◽  
Vol 240 ◽  
pp. 07011
Author(s):  
Kushagra Shrivastava ◽  
Keith Wen Kai Chia ◽  
Kang Jun Wong ◽  
Alfred Yong Liang Tan ◽  
Hwee Tiang Ning

Solar activity research provides insight into the Sun’s past, future (Science Daily, 2018). The solar activity includes observations of large numbers of intense sunspots, flares, and other phenomena; and demands a wide range of techniques and measurements on the observations. This research needs long term data collection before critical analyses can occur, to generate meaningful learning and knowledge. In this project, we will use solar imaging to make observations of solar activity, and take our baby steps to make contributions in citizen science. Observations will be made in 3 wavelengths to gain a more thorough analysis by looking at different perspectives of the Sun, namely H-Alpha, Calcium-K, and white light.


Author(s):  
Alastair H. C. Sommerville

SynopsisThe ecological role of native willows is described in terms of the diverse structure of the species involved, the wide range of plant communities they form and the large numbers of invertebrates associated with them. The conservation importance of the genusSalixis discussed along with comments on the necessary management to retain willow habitats.


2021 ◽  
Author(s):  
Julissa Rojas-Sandoval ◽  
Pedro Acevedo-Rodríguez ◽  
A. I. Popay

Abstract S. oleraceus is a common seed crop contaminant and has been carried either deliberately or accidentally by humans to almost every corner of the earth, where it invades mainly open and disturbed areas. It grows in a wide variety of environments on a wide range of substrates - roadsides, cultivated land, gardens, construction sites, sand dunes, logged or burned areas, on walls, mountain slopes, and near water. Once introduced to a new area the plants spread quickly because they grow and flower quickly and produce copious wind- and bird-dispersed seeds that germinate quickly in large numbers. They invade many cropped areas, especially among vegetable and winter crops. They are almost perfect 'designer weeds'. Additionally, this species has small light seeds which are easily dispersed by wind and water.


2022 ◽  
pp. 5-5
Author(s):  
Richard A. I. Drew ◽  
Meredith C. Romig

Abstract Large numbers of dacine specimens were collected throughout Papua New Guinea by trapping and host fruit sampling. Steinertype fruit fly traps, baited with cue lure, methyl eugenol or vanillylacetone (zingerone), were set in many localities over a wide range of ecosystems. In most cases, the traps were serviced on 2-week cycles for at least 1 year. Samples of rainforest and cultivated fruits were collected in some provinces. All specimens collected were preserved in a dry state and sent to R.A.I. Drew at Griffith University, Brisbane, Australia, for microscopic identification and curation. Data and photographs of Bactrocera longicornis were received from the Museum Nationale d'Histoire Naturelle, Paris, France. The subgeneric classification used herein follows Drew and Hancock (2016) and Hancock and Drew (2006, 2015, 2016, 2017a,b,c,d,e, 2018a,b,c, 2019).


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