RESUMO
Cooperative social systems are susceptible to cheating by individuals that reap the benefits of cooperation without incurring the costs. There are various theoretical mechanisms for the repression of cheating and many have been tested experimentally. One possibility that has not been tested rigorously is the evolution of mutations that confer resistance to cheating. Here we show that the presence of a cheater in a population of randomly mutated social amoebae can select for cheater-resistance. Furthermore, we show that this cheater-resistance can be a noble strategy because the resister strain does not necessarily exploit other strains. Thus, the evolution of resisters may be instrumental in preserving cooperative behaviour in the face of cheating.
Assuntos
Dictyostelium/fisiologia , Modelos Biológicos , Comportamento Social , Animais , Comportamento Cooperativo , Dictyostelium/genética , Evolução Molecular , Genes de Protozoários/genética , Mutação/genética , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Esporos de Protozoários/fisiologiaRESUMO
Cooperation is central to many major transitions in evolution, including the emergence of eukaryotic cells, multicellularity and eusociality. Cooperation can be destroyed by the spread of cheater mutants that do not cooperate but gain the benefits of cooperation from others. However, cooperation can be preserved if cheaters are facultative, cheating others but cooperating among themselves. Several cheater mutants have been studied before, but no study has attempted a genome-scale investigation of the genetic opportunities for cheating. Here we describe such a screen in a social amoeba and show that cheating is multifaceted by revealing cheater mutations in well over 100 genes of diverse types. Many of these mutants cheat facultatively, producing more than their fair share of spores in chimaeras, but cooperating normally when clonal. These findings indicate that phenotypically stable cooperative systems may nevertheless harbour genetic conflicts. The opportunities for evolutionary moves and countermoves in such conflicts may select for the involvement of multiple pathways and numerous genes.
Assuntos
Comportamento Cooperativo , Dictyostelium/genética , Dictyostelium/fisiologia , Mutação/genética , Comportamento Social , Amoeba/genética , Amoeba/fisiologia , Animais , Agregação Celular , Quimera/genética , Quimera/fisiologia , Dictyostelium/citologia , Genes de Protozoários/genética , Genoma/genética , Genômica , Myxococcus xanthus/genética , Myxococcus xanthus/fisiologia , Fenótipo , Esporos de Protozoários/genética , Esporos de Protozoários/fisiologiaRESUMO
BACKGROUND: Competitive social interactions are ubiquitous in nature, but their genetic basis is difficult to determine. Much can be learned from single gene knockouts in a eukaryote microbe. The mutants can be competed with the parent to discern the social impact of that specific gene. Dictyostelium discoideum is a social amoeba that exhibits cooperative behavior in the construction of a multicellular fruiting body. It is a good model organism to study the genetic basis of cooperation since it has a sequenced genome and it is amenable to genetic manipulation. When two strains of D. discoideum are mixed, a cheater strain can exploit its social partner by differentiating more spore than its fair share relative to stalk cells. Cheater strains can be generated in the lab or found in the wild and genetic analyses have shown that cheating behavior can be achieved through many pathways. RESULTS: We have characterized the knockout mutant chtB, which was isolated from a screen for cheater mutants that were also able to form normal fruiting bodies on their own. When mixed in equal proportions with parental strain cells, chtB mutants contributed almost 60% of the total number of spores. To do so, chtB cells inhibit wild type cells from becoming spores, as indicated by counts and by the wild type cells' reduced expression of the prespore gene, cotB. We found no obvious fitness costs (morphology, doubling time in liquid medium, spore production, and germination efficiency) associated with the cheating ability of the chtB knockout. CONCLUSIONS: In this study we describe a new gene in D. discoideum, chtB, which when knocked out inhibits the parental strain from producing spores. Moreover, under lab conditions, we did not detect any fitness costs associated with this behavior.
Assuntos
Dictyostelium/genética , Dictyostelium/fisiologia , Genes de Protozoários , Dictyostelium/citologia , Técnicas de Inativação de Genes , Aptidão Genética , Esporos de Protozoários/citologia , Esporos de Protozoários/genéticaRESUMO
BACKGROUND: Honeybees use plant material to manufacture their own food. These insect pollinators visit flowers repeatedly to collect nectar and pollen, which are shared with other hive bees to produce honey and beebread. While producing these products, beehives accumulate a considerable number of microbes, including bacteria that derive from plants and different parts of the honeybees' body. Whether bacteria form similar communities amongst beehives, even if located in close proximity, is an ecologically important question that has been addressed in this study. Specific ecological factors such as the surrounding environment and the beekeeping methods used can shape the microbiome of the beehive as a whole, and eventually influence the health of the honeybees and their ecosystem. RESULTS: We conducted 16S rRNA meta-taxonomic analysis on honey and beebread samples that were collected from 15 apiaries in the southeast of England to quantify the bacteria associated with different beehives. We observed that honeybee products carry a significant variety of bacterial groups that comprise bee commensals, environmental bacteria and symbionts and pathogens of plants and animals. Remarkably, this bacterial diversity differs not only amongst apiaries, but also between the beehives of the same apiary. In particular, the levels of the bee commensals varied significantly, and their fluctuations correlated with the presence of different environmental bacteria and various apiculture practices. CONCLUSIONS: Our results show that every hive possesses their own distinct microbiome and that this very defined fingerprint is affected by multiple factors such as the nectar and pollen gathered from local plants, the management of the apiaries and the bacterial communities living around the beehives. Based on our findings, we suggest that the microbiome of beehives could be used as a valuable biosensor informing of the health of the honeybees and their surrounding environment.
RESUMO
BACKGROUND: Human, animal, and environmental health are increasingly threatened by the emergence and spread of antibiotic resistance. Inappropriate use of antibiotic treatments commonly contributes to this threat, but it is also becoming apparent that multiple, interconnected environmental factors can play a significant role. Thus, a One Health approach is required for a comprehensive understanding of the environmental dimensions of antibiotic resistance and inform science-based decisions and actions. The broad and multidisciplinary nature of the problem poses several open questions drawing upon a wide heterogeneous range of studies. OBJECTIVE: This study seeks to collect and catalogue the evidence of the potential effects of environmental factors on the abundance or detection of antibiotic resistance determinants in the outdoor environment, i.e., antibiotic resistant bacteria and mobile genetic elements carrying antibiotic resistance genes, and the effect on those caused by local environmental conditions of either natural or anthropogenic origin. METHODS: Here, we describe the protocol for a systematic evidence map to address this, which will be performed in adherence to best practice guidelines. We will search the literature from 1990 to present, using the following electronic databases: MEDLINE, Embase, and the Web of Science Core Collection as well as the grey literature. We shall include full-text, scientific articles published in English. Reviewers will work in pairs to screen title, abstract and keywords first and then full-text documents. Data extraction will adhere to a code book purposely designed. Risk of bias assessment will not be conducted as part of this SEM. We will combine tables, graphs, and other suitable visualisation techniques to compile a database i) of studies investigating the factors associated with the prevalence of antibiotic resistance in the environment and ii) map the distribution, network, cross-disciplinarity, impact and trends in the literature.
Assuntos
Antibacterianos , Bactérias , Animais , Humanos , Prevalência , Resistência Microbiana a Medicamentos/genética , Bactérias/genética , Viés , Antibacterianos/farmacologiaRESUMO
Although social groups are characterized by cooperation, they are also often the scene of conflict. In non-clonal systems, the reproductive interests of group members will differ and individuals may benefit by exploiting the cooperative efforts of other group members. However, such selfish behaviour is thought to be rare in one of the classic examples of cooperation--social insect colonies--because the colony-level costs of individual selfishness select against cues that would allow workers to recognize their closest relatives. In accord with this, previous studies of wasps and ants have found little or no kin information in recognition cues. Here, we test the hypothesis that social insects do not have kin-informative recognition cues by investigating the recognition cues and relatedness of workers from four colonies of the ant Acromyrmex octospinosus. Contrary to the theoretical prediction, we show that the cuticular hydrocarbons of ant workers in all four colonies are informative enough to allow full-sisters to be distinguished from half-sisters with a high accuracy. These results contradict the hypothesis of non-heritable recognition cues and suggest that there is more potential for within-colony conflicts in genetically diverse societies than previously thought.
Assuntos
Formigas/fisiologia , Hidrocarbonetos/química , Animais , Formigas/química , Formigas/genética , Comportamento Animal , Sinais (Psicologia) , Feminino , Variação Genética , Panamá , Comportamento SocialRESUMO
The present case study illustrates the case of a 47-year-old female (Ms X) with primary progressive Multiple Sclerosis (MS) who presented with central post-stroke pain (CPSP) over her left shoulder and underwent acupuncture treatment (AT) since she appeared irresponsive to conventional treatment. The aim of this case study is to explore the effectiveness of acupuncture as a complimentary treatment in improving central neurogenic pain in MS patients affected by CPSP. AT lasted six weeks, some modification of the conventional AT points was required to ensure continuity and safety of the treatment plan. In fact, Ms X suffered from gingivitis that led to hypersensitivity of her left upper limb (UL) to acupuncture needling; moreover, she experienced sensation loss in her legs as a result of post-stroke complications. The outcome showed that the subject's shoulder range of motion (ROM), Disabilities of the Arm, Shoulder and Hand (DASH) score and pain improved remarkably, enabling Ms X to resume post-stroke rehabilitation and reduce her analgesic intake.
Assuntos
Terapia por Acupuntura , Esclerose Múltipla , Neuralgia , Terapia por Acupuntura/efeitos adversos , Feminino , Humanos , Pessoa de Meia-Idade , Esclerose Múltipla/complicações , Esclerose Múltipla/terapia , Ombro , Dor de Ombro/etiologia , Dor de Ombro/terapia , Resultado do TratamentoRESUMO
Pseudomonas aeruginosa, is an opportunistic, bacterial pathogen causing persistent and frequently fatal infections of the lung in patients with cystic fibrosis. Isolates from chronic infections differ from laboratory and environmental strains in a range of traits and this is widely interpreted as the result of adaptation to the lung environment. Typically, chronic strains carry mutations in global regulation factors that could effect reduced expression of social traits, raising the possibility that competitive dynamics between cooperative and selfish, cheating strains could also drive changes in P. aeruginosa infections. We compared the expression of cooperative traits - biofilm formation, secretion of exo-products and quorum sensing (QS) - in P. aeruginosa isolates that were estimated to have spent different lengths of time in the lung based on clinical information. All three exo-products involved in nutrient acquisition were produced in significantly smaller quantities with increased duration of infection, and patterns across four QS signal molecules were consistent with accumulation over time of mutations in lasR, which are known to disrupt the ability of cells to respond to QS signal. Pyocyanin production, and the proportion of cells in biofilm relative to motile, free-living cells in liquid culture, did not change. Overall, our results confirm that the loss of social behaviour is a consistent trend with time spent in the lung and suggest that social dynamics are potentially relevant to understanding the behaviour of P. aeruginosa in lung infections.