Three-dimensional printing of bacterial ecosystems
3D printing of bacteria within gelatin containers.
Bacteria in the human body often thrive within structured 3D communities that comprise multiple species. Mounting evidence suggests that relationships between structure and function in these microbial ecosystems mediate community attributes that influence human health, such as the virulence of infections within the cystic fibrosis lung and chronic wounds. Jodi Connell et al. (pp. 18380–18385) devised an approach that uses 3D microscopic printing to organize populations of mixed bacterial species within any structural arrangement. Based on a laser lithography system, the technique helps trap selected bacteria in sealed cavities of a highly porous gelatin that allows the enclosed cellular populations to rapidly grow and transmit biologically active molecules, including polypeptides, antibiotics, and chemical signals that trigger gene expression at certain population density thresholds. The authors also demonstrated that the 3D relationship between two bacterial species allows one pathogen’s resistance to an antibiotic to enhance the survival of a second species. The findings represent a tool that can help clarify mechanisms of cellular communication and the onset of social behaviors between microbes within aggregates, according to the authors. — T.J.
Childhood poverty may compromise emotion control during adulthood
The amygdala and prefrontal cortex play key roles in the brain’s emotional response to stress, with the amygdala detecting and responding to threats under the control of the prefrontal cortex. Aberrant activity in these regions can contribute to depression, anxiety, impulsive aggression, and substance abuse. Pilyoung Kim et al. (pp. 18442–18447) performed a longitudinal fMRI study to examine the effects of childhood family income on adult brain activity. The authors studied 54 young adults, half from low-income backgrounds and half from families with incomes of two to four times that of the poverty line at age 9. After controlling for adult income, the authors found that childhood poverty can exert a long-lasting effect on brain regions that control emotion. When participants were shown negative images and asked to lessen the intensity of their emotional reactions, the authors observed higher amygdala activity and decreased prefrontal cortex activity in adults who had lived in poverty as children compared with other participants. Additionally, the authors found that the neurological changes in response to childhood poverty at age 9 were further driven by exposure to chronic physical and social stress from ages 9 to 17. According to the authors, the findings might help design interventions aimed at reducing health disparities. — A.G.
Mass spectrometry reveals blood meal in Middle Eocene mosquito
Culiseta species, a blood-engorged female from the Middle Eocene Kishenehn Formation of northwestern Montana.
Blood-feeding, or hematophagy, occurs in roughly 14,000 species of extant insects, such as fleas, ticks, and mosquitos. Although this feeding strategy evolved independently numerous times, researchers rely on the morphology of mouthparts and taxonomic affiliation to identify blood-feeding animals because fossils that contain direct evidence of the behavior are extremely rare. Dale Greenwalt et al. (pp. 18496–18500) describe a fossilized blood-engorged mosquito from northwestern Montana that traces the existence of blood-feeding behavior in this family of insects to 46 million years ago. After finding high levels of iron in the specimen’s abdomen, the authors used nondestructive mass spectrometry to identify the source as heme, the functional group of hemoglobin that facilitates oxygen transport. Although large and fragile molecules such as DNA cannot survive fossilization, the authors report, this mosquito from the Middle Eocene confirms that certain complex organic molecules such as heme can be preserved under the right conditions across time. The findings support previous studies that report the existence of heme-derived compounds in terrestrial fossils and extend the fossil record of blood-feeding in this family of insects by 46 million years, according to the authors. — T.J.
Compound protects rodents against lethal doses of radiation
Diindolylmethane (DIM) is a putative cancer preventive agent derived from cruciferous vegetables such as cabbage and broccoli. Saijun Fan et al. (pp. 18650–18655) report that DIM protects mice against lethal doses of total body irradiation with gamma rays. The authors exposed rats to 13 Gy of radiation, and 10 minutes later began treating the animals with once-daily injections of DIM for 2 weeks. Up to 60% of the DIM-treated animals remained alive for 30 days after radiation exposure, whereas all of the untreated animals died within 10 days. Furthermore, DIM also provided protection when the first injection was administered 24 hours before or after radiation exposure. The authors found that physiologically relevant doses of DIM protected human breast cells from radiation exposure in vitro by activating proteins that mediate the cellular responses to DNA damage and oxidative stress. By contrast, DIM did not protect human breast cancer cell–derived tumors in mice against radiation exposure. According to the authors, the findings suggest that DIM, which has been used safely in humans in previous studies, may be useful for preventing or mitigating radiation sickness due to whole body irradiation, or for protecting normal tissues during radiation therapy for cancer treatment. — N.Z.
Human genome points to drugs that ease aversive memories
Genome-guided drug discovery.
Over the last decade, the Human Genome Project has led to increased knowledge about the genetic basis of human traits. Although this research has identified numerous connections between genes and human disease, the degree to which these discoveries will yield drug targets and therapeutic options remains unclear, particularly for complex illnesses such as neuropsychiatric disorders. Andreas Papassotiropoulos et al. (pp. E4369–E4374) performed a multi-national study on the genetic basis of aversive memory, a hallmark of posttraumatic stress disorder, and identified 20 potential drug target genes in two gene sets linked to the trait. With a double-blind, placebo-controlled study in healthy volunteers, the authors then tested a strategy aimed at using genomic information to identify a single drug capable of modulating aversive memory. The authors found that pharmacological intervention with one dose of the anti-histamine diphenhydramine, chosen specifically to target neural signaling associated with a neuroactive ligand-receptor interaction gene set, significantly reduced aversive memory recall without diminishing general mnemonic function. The findings demonstrate that genomic information, combined with appropriate data mining methods, can serve as a starting point for the identification of memory-modulating compounds, according to the authors. — T.J.