Modeling endosymbioses: Insights and hypotheses from theoretical approaches.

Endosymbiotic relationships are pervasive across diverse taxa of life, offering key avenues for eco-evolutionary dynamics. Although a variety of experimental and empirical frameworks have shed light on critical aspects of endosymbiosis, theoretical frameworks (mathematical models) are especially well-suited for certain tasks. Mathematical models can integrate multiple factors to determine the net outcome of endosymbiotic relationships, identify broad patterns that connect endosymbioses with other systems, simplify biological complexity, generate hypotheses for underlying mechanisms, evaluate different hypotheses, identify constraints that limit certain biological interactions, and open new lines of inquiry. This Essay highlights the utility of mathematical models in endosymbiosis research, particularly in generating relevant hypotheses. Despite their limitations, mathematical models can be used to address known unknowns and discover unknown unknowns.

Black Queen Hypothesis, partial privatization, and quorum sensing evolution.

Microorganisms produce costly cooperative goods whose benefit is partially shared with nonproducers, called 'mixed' goods. The Black Queen Hypothesis predicts that partial privatization has two major evolutionary implications. First, to favor strains producing several types of mixed goods over nonproducing strains. Second, to favor the maintenance of cooperative traits through different strains instead of having all cooperative traits present in a single strain (metabolic specialization). Despite the importance of quorum sensing regulation of mixed goods, it is unclear how partial privatization affects quorum sensing evolution. Here, we studied the influence of partial privatization on the evolution of quorum sensing. We developed a mathematical population genetics model of an unstructured microbial population considering four strains that differ in their ability to produce an autoinducer (quorum sensing signaling molecule) and a mixed good. Our model assumes that the production of the autoinducers and the mixed goods is constitutive and/or depends on quorum sensing. Our results suggest that, unless autoinducers are costless, partial privatization cannot favor quorum sensing. This result occurs because with costly autoinducers: (1) a strain that produces both autoinducer and goods (fully producing strain) cannot persist in the population; (2) the strain only producing the autoinducer and the strain producing mixed goods in response to the autoinducers cannot coexist, i.e., metabolic specialization cannot be favored. Together, partial privatization might have been crucial to favor a primordial form of quorum sensing-where autoinducers were thought to be a metabolic byproduct (costless)-but not the transition to nowadays costly autoinducers.

O Uso de Internet e Redes Sociais e a Relação com Indícios de Ansiedade e Depressão em Estudantes de Medicina / The Use of the Internet and Social Networks and the Relationship with Symptoms of Anxiety and Depression among Medical Students

RESUMO Introdução: A internet é uma ferramenta imprescindível na atualidade, pois possibilita acesso fácil e rápido às informações e a manutenção de laços afetivos por meio das redes sociais. Entretanto, quando se percebe um uso descontrolado e desadaptativo, ocorre a chamada adicção por internet (AI). Estudos prévios investigaram diversas comorbidades associadas a esse transtorno, gerando um importante conhecimento importante para a conduta clínica. Objetivo: Investigar a correlação entre indicadores do uso de internet e redes sociais e a presença de sintomas ansiosos e depressivos. Métodos: Estudo descritivo, transversal, quantitativo, com amostragem por conveniência, realizado com estudantes de Medicina no ano de 2015. Os sintomas ansiosos e depressivos foram analisados por meio do Inventário de Ansiedade de Beck (BAI) e do Inventário de Depressão de Beck (BDI), respectivamente. Além disso, utilizou-se um questionário confeccionado pelos pesquisadores com base no Internet Addiction Test (IAT). Resultados: Dos 169 estudantes que participaram da pesquisa, 98,8% (167) fazem uso diário de internet e/ou redes sociais. Foi avaliada a prevalência de diversos indícios do uso prejudicial da internet, bem como a concepção dos participantes sobre seu uso. Não foi encontrada associação estatística entre o tempo gasto na internet e a presença de sintomas ansiosos e depressivos com os escores BAI e BDI. Contudo, foram percebidas algumas associações estatisticamente significativas com os resultados dos escores BAI e BDI tanto com indicadores da necessidade de verificação da internet quanto com indicativos do uso desadaptativo da internet. Conclusão: O presente estudo ratifica achados prévios na literatura que apontam que a AI não está necessariamente relacionada com o tempo gasto na internet, mas com o padrão desadaptativo do uso. Os resultados aqui encontrados podem servir de base para futuras intervenções em instituições de ensino que busquem minimizar o prejuízo desse transtorno cada vez mais presente.

ABSTRACT Introduction: The internet is now an essential tool, through which people enjoy easy and rapid access to information and can maintain personal relationships through social networks. However, when its use becomes uncontrolled and maladaptive, what can entail is known as Internet Addiction (IA). In previous studies, several comorbidities associated with this disorder have been investigated, generating knowledge that is important for clinical management. Objective: To investigate the correlation between indicators of internet use and social networks with the presence of symptoms of anxiety and depression. Methods: A descriptive, cross-sectional, quantitative study with convenience sampling, carried out with medical students in 2015. The anxiety and depression symptoms were analyzed through the Beck Anxiety Inventory (BAI) and the Beck Depression Inventory (BDI), respectively. In addition, a questionnaire made by the researchers based on the internet Addiction Test (IAT) was used. Results: Out of the 169 students who participated in the research, 98.8% (167) use the internet and/or social networks on a daily basis. The prevalence of various indications of the harmful use of the internet was evaluated, as well as the participants' conception of its use. No statistical association was found between the time spent on the internet and the presence of symptoms of anxiety and depression, according to the BAI and BDI scores. However, some statistically significant associations were observed between the results obtained from the BAI and BDI and indicators of the need for internet verification as well as signs of maladaptive use of the internet. Conclusion: The present study ratifies the previous findings in the literature by pointing out that IA is not necessarily related to the time spent on the internet, but rather to a maladaptive pattern of use. The results found here may serve as basis for future interventions in educational institutions that seek to minimize the damage of this disorder, which has become increasingly present.