Geochemical Characteristics Related to the Gregite-Producing Multicellular Magnetotactic Prokaryote Candidatus Magnetoglobus multicellularis in a Hypersaline Lagoon

We studied the geochemical properties of sediment layers where the gregite-producing multicellular magnetotactic prokaryote Candidatus Magnetoglobus multicellularis exists. The ratio of iron and bioavailable sulfur concentrations regulates the population density of this microorganism. The population density can reach 8.5 × 10² cells/cm³ at an iron to sulfur ratio of 0.5. In iron- and sulfur-rich environments, microorganisms concentrated in the upper region of the oxic-anoxic zone, following an increasing nitrogen gradient with a lower isotopic ¹⁵N/¹⁴N ratio. Candidatus Magnetoglobus multicellularis prefers environmental conditions that favor the biomineralization of greigite, but in situations where the nutrient availability is low, it moves to more suitable sites.     

Opioidergic Modulation of Ventilatory Response to Sustained Hypoxia in Obese Zucker Rats

Objective: To determine whether altered central and/or peripheral opioidergic mechanisms contribute to the altered ventilatory response to sustained hypoxia in obese Zucker rats. Research Methods and Procedures: Eight lean (176 ± 8 [SEM] g) and eight obese (225 ± 12 g) Zucker rats were studied at 6 weeks of age. Pulmonary ventilation (V?_E), tidal volume (V_T), and breathing frequency (f) at rest and in response to sustained (30 minutes) hypoxic (10% O₂) challenges were measured on three separate occasions by the barometric method after the randomized, blinded administration of equal volumes of saline (control), naloxone methiodide (N_M; 5 mg/kg, peripheral opioid antagonist), or naloxone hydrochloride (N_HCl; 5 mg/kg, peripheral and central opioid antagonist). Results: Administration of N_M and N_HCl in lean animals had no effect on V?_E either at rest or during 30 minutes of sustained exposure to hypoxia. Similarly, N_M failed to alter V?_E in obese rats. In contrast, N_HCl significantly (p < 0.05) increased V?_E and V_T both at rest and during 2 to 10 minutes of hypoxic exposure in obese rats. After 20 to 30 minutes of hypoxic exposure, V_T remained elevated with N_HCl, but the earlier elevation of V?_E seemed to be attenuated due to a decrease in f at 20 minutes of exposure to hypoxia. Discussion: Thus, endogenous opioids modulate both resting V?_E and the ventilatory response to sustained hypoxia in obese, but not in lean, Zucker rats by acting specifically on opioid receptors located within the central nervous system.     

What Do We Study in Evolutionary Ethnobiology? Defining the Theoretical Basis for a Research Program

Many scientific fields investigate the relationship between humans and nature from different perspectives and with a wide range of questions. These fields include, for example, human ecology, human behavioral ecology, and evolutionary psychology, and they are linked through the fact that they all adopt ecological and/or evolutionary hypotheses to understand this phenomenon. In this paper, we define for the first time the field of evolutionary ethnobiology, which seeks to understand these relationships in a broad perspective, considering an interdisciplinary program that integrates the advances, tools, and insights from different scientific fields. This theoretical and methodological integration is necessary for the formation of theoretical bases in ethnobiology and in other areas that investigate the relationship between humans and nature.     

Amorphous mineral phases in magnetotactic multicellular aggregates

Magnetotactic multicellular aggregates consist of several bacteria that produce iron sulfide magnetosomes through a complex and poorly understood process. We observed new amorphous mineral particles within the cytoplasm of magnetotactic multicellular aggregates. Elemental mapping and electron energy loss spectroscopy detected iron and oxygen, but not sulfur, in these particles. These amorphous particles were about the same size as mature magnetosomes, around 50-70 nm in diameter. No membranes were observed surrounding the amorphous minerals. Partially crystalline inclusions composed of a crystalline core and an amorphous region around them similar in texture to the amorphous particles were also present. The shape of these amorphous regions followed the shape of the crystalline cores they enveloped. These regions also contained oxygen and iron. The crystalline phase, as previously reported, contained sulfur and iron. The presence of independent amorphous particles has not been reported before in magnetotactic multicellular aggregates.