The role of flagella in Pseudomonas-Pedobacter social motility across a surface

Bacteria often reside in multi-species communities where many behaviors result from interspecies relationships. In a two-species community, we show that co-culture of Pseudomonas fluorescens and Pedobacter sp. permits motility across a hard agar surface where neither species moves alone. Pseudomonas species engage in surface motility, including swimming and swarming, but these require moist environments. We are exploring the role of the Pseudomonas flagella in social motility. We deleted genes related to flagellar structure and function to study the importance of flagellar elements on the social phenotype. Using microscopy and swimming assays, we evaluate the effects of gene deletions on the presence and function of flagella in the resulting mutants, and evaluate the effect on social motility by observing the phenotype on both hard (2% w/v) and soft agar (1% w/v). Removal of the flagellar filament abolishes social motility, indicating a requirement for flagella in social motility. Removal of the flagellar motor also abolishes social motility, demonstrating that flagella must be functional. However, removal of membrane-spanning structural components, or part of the type III secretion system, results in mutants that lack flagella, but participate in a similar motile behavior with Pedobacter. Here we describe a role for flagella in motility of a two-species consortium across a hard agar surface, an environment considered non-permissive for flagellar motility. The requirement for both bacterial species indicates we are observing motility as a social phenotype, with a contribution from Pedobacter that enables the Pseudomonas flagella to function under conditions relevant in the natural soil environment.

Geographical mobility and social motility in the Aegean before and after 6600 BC

Zusammenfassung Eine der folgenreichsten Veränderungen in der Menschheitsgeschichte betrifft die Überwindung der Abhängigkeit von ausschließlich lokalen Ressourcen durch die am Beginn des Holozäns im Vorderen Orient einsetzende Domestikation von zuerst Pflanzen und dann Tieren. Jede Generation von Archäologen hat diesen Wandel im Lichte neu gewonnen Wissens aufgrund neuer Ausgrabungen und neuer analytischer Methoden reflektiert. Die Ausbreitung der produzierenden Wirtschaftsweise aus dem Kerngebiet in Nachbarregionen wurde dabei vornehmlich als kultureller Wandel gedeutet, der durch Auswanderer oder Kolonisten vollzogen worden wäre. Dementsprechend beinhalten die vorgeschlagenen Neolithisierungsmodelle lineare Bewegungen von Ost nach West, die den scheinbar abrupten Kulturwandel erklärten. Dabei wurde der Konzeptualisierung von Begriffen wie Kolonisation oder Migration, wie sie von Soziologen vorgeschlagen wurde, wenig Aufmerksamkeit geschenkt. Unter Berücksichtigung soziologischer Studien wird der Schwerpunkt dieser Untersuchung weniger auf dem schnellen kulturellen als vielmehr auf dem langsamen, generationenübergreifenden sozialen Wandel und auf der aktiven sozialen Beweglichkeit (Motilität) liegen. Die Perspektive ist folglich nicht die von Neuankömmlingen aus dem neolithischen Anatolien, sondern die der mesolithischen ägäischen Gemeinschaften. Es mag nämlich nicht die Entscheidung mobiler Bauern gewesen sein, nahe oder ferne Regionen zu „kolonisieren“, sondern die der Jäger und Sammler, Innovationen aus den Ursprungsgebieten (selektiv) zu übernehmen und ihren eigenen Bedürfnissen anzupassen. Als aktive Entscheidungsträger setzten sie einen Prozess in Gange, der nicht nur zu ökonomischen, sondern auch, über mehrere Generationen hinweg, zu sozialen und kulturellen Veränderungen führte.

A mobilidade e a expansão territorial na cidade de São Luís, MA: um novo paradigma social na ocupação do espaço urbano

Resumo O presente trabalho tem como objetivo refletir sobre transformações no campo social e urbano que influenciaram uma mudança de paradigma na ocupação da cidade de São Luís, MA. Relacionam-se fatores históricos ocorridos no espaço urbano com teorias das ciências sociais, considerando que a mobilidade interfere no crescimento da cidade e nas suas relações entre os indivíduos. Procura-se estabelecer um elo entre as infraestruturas viárias urbanas, oriundas de ações do poder público e transformações do comportamento da sociedade contemporânea, considerando a construção social motility, utilizada por Weert, Kauffmann e Kesselring (2008). Por fim, a pesquisa busca contribuir para a compreensão das transformações urbanísticas e sociais, a partir da segunda metade do século XX, na cidade de São Luís.

Cyclic AMP Regulates Social Behavior in African Trypanosomes

ABSTRACT The protozoan parasite Trypanosoma brucei engages in surface-induced social behavior, termed social motility, characterized by single cells assembling into multicellular groups that coordinate their movements in response to extracellular signals. Social motility requires sensing and responding to extracellular signals, but the underlying mechanisms are unknown. Here we report that T. brucei social motility depends on cyclic AMP (cAMP) signaling systems in the parasite's flagellum (synonymous with cilium). Pharmacological inhibition of cAMP-specific phosphodiesterase (PDE) completely blocks social motility without impacting the viability or motility of individual cells. Using a fluorescence resonance energy transfer (FRET)-based sensor to monitor cAMP dynamics in live cells, we demonstrate that this block in social motility correlates with an increase in intracellular cAMP levels. RNA interference (RNAi) knockdown of the flagellar PDEB1 phenocopies pharmacological PDE inhibition, demonstrating that PDEB1 is required for social motility. Using parasites expressing distinct fluorescent proteins to monitor individuals in a genetically heterogeneous community, we found that the social motility defect of PDEB1 knockdowns is complemented by wild-type parasites in trans. Therefore, PDEB1 knockdown cells are competent for social motility but appear to lack a necessary factor that can be provided by wild-type cells. The combined data demonstrate that the role of cyclic nucleotides in regulating microbial social behavior extends to African trypanosomes and provide an example of transcomplementation in parasitic protozoa. IMPORTANCE In bacteria, studies of cell-cell communication and social behavior have profoundly influenced our understanding of microbial physiology, signaling, and pathogenesis. In contrast, mechanisms underlying social behavior in protozoan parasites are mostly unknown. Here we show that social behavior in the protozoan parasite Trypanosoma brucei is governed by cyclic-AMP signaling systems in the flagellum, with intriguing parallels to signaling systems that control bacterial social behavior. We also generated a T. brucei social behavior mutant and found that the mutant phenotype is complemented by wild-type cells grown in the same culture. Our findings open new avenues for dissecting social behavior and signaling in protozoan parasites and illustrate the capacity of these organisms to influence each other's behavior in mixed communities.

A Glycosylation Mutant of Trypanosoma brucei Links Social Motility Defects In Vitro to Impaired Colonization of Tsetse Flies In Vivo

ABSTRACT Transmission of African trypanosomes by tsetse flies requires that the parasites migrate out of the midgut lumen and colonize the ectoperitrophic space. Early procyclic culture forms correspond to trypanosomes in the lumen; on agarose plates they exhibit social motility, migrating en masse as radial projections from an inoculation site. We show that an Rft1 −/− mutant needs to reach a greater threshold number before migration begins, and that it forms fewer projections than its wild-type parent. The mutant is also up to 4 times less efficient at establishing midgut infections. Ectopic expression of Rft1 rescues social motility defects and restores the ability to colonize the fly. These results are consistent with social motility reflecting movement to the ectoperitrophic space, implicate N-glycans in the signaling cascades for migration in vivo and in vitro , and provide the first evidence that parasite-parasite interactions determine the success of transmission by the insect host.

Insect Stage-Specific Adenylate Cyclases Regulate Social Motility in African Trypanosomes

ABSTRACTSophisticated systems for cell-cell communication enable unicellular microbes to act as multicellular entities capable of group-level behaviors that are not evident in individuals. These group behaviors influence microbe physiology, and the underlying signaling pathways are considered potential drug targets in microbial pathogens.Trypanosoma bruceiis a protozoan parasite that causes substantial human suffering and economic hardship in some of the most impoverished regions of the world.T. bruceilives on host tissue surfaces during transmission through its tsetse fly vector, and cultivation on surfaces causes the parasites to assemble into multicellular communities in which individual cells coordinate their movements in response to external signals. This behavior is termed “social motility,” based on its similarities with surface-induced social motility in bacteria, and it demonstrates that trypanosomes are capable of group-level behavior. Mechanisms governingT. bruceisocial motility are unknown. Here we report that a subset of receptor-type adenylate cyclases (ACs) in the trypanosome flagellum regulate social motility. RNA interference-mediated knockdown of adenylate cyclase 6 (AC6), or dual knockdown of AC1 and AC2, causes a hypersocial phenotype but has no discernible effect on individual cells in suspension culture. Mutation of the AC6 catalytic domain phenocopies AC6 knockdown, demonstrating that loss of adenylate cyclase activity is responsible for the phenotype. Notably, knockdown of other ACs did not affect social motility, indicating segregation of AC functions. These studies reveal interesting parallels in systems that control social behavior in trypanosomes and bacteria and provide insight into a feature of parasite biology that may be exploited for novel intervention strategies.