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Archive - Apr 28, 2017

Plague Bacilli Hide Out in Amoebae

Yersinia pestis, the bacterium that causes bubonic plague, can survive within the ubiquitous soil protozoan, the amoeba, by producing proteins that protect against the latter microbe's digestion. The research was published online on April 28, 2017 in Applied and Environmental Microbiology, a journal of the American Society for Microbiology. The article is titled “Yersinia pestis Resists Predation by Acanthamoeba castellanii and Exhibits Prolonged Intracellular Survival.” The research is important because plague is a re-emerging disease, according to the Centers for Disease Control and Prevention (CDC), with 95 percent of cases occurring in sub-Saharan Africa and Madagascar. Modern antibiotics are effective, but without prompt treatment, plague can cause serious illness, or death. Y. pestis spreads from rodent to rodent, and sometimes to human, often via fleas. It uses the protective niche of the amoeba to abide in when conditions are unfavorable to its spread, that is, when rodents are scarce, said Viveka Vadyvaloo, PhD, Assistant Professor, Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington. Amoebae are similar to certain human immune cells, the macrophages, in their ability to engulf bacteria, or other nourishing items of similar size. These are taken up within special compartments called vacuoles, which in both amoebae and humans are capable of digestion. "With this in mind, graduate student Javier Benavides-Montaño separately cultured three distinct Y. pestis strains that have been associated with human epidemics, with a common laboratory strain of the free-living soil amoeba, Acanthamoeba castellanii, in a medium that supports the latter's growth," said Dr. Vadyvaloo. Benavides-Montaño then tested Y.

Bacterial Symbionts Transition Between Insect Defensive Mutualism & Plant Pathogenicity; May Be Treasure Trove of New Antibiotics

An international team of researchers has discovered a remarkable microbe with a Jekyll and Hyde character. The bacterium Burkholderia gladioli lives in specific organs of a plant-feeding beetle and defends the insect's eggs from detrimental fungi by producing antibiotics. However, when transferred to a plant, the bacterium can spread throughout the tissues and negatively affect the plant. Microbes are not always hostile players when interacting with animals and plants, they can also be powerful allies. In fact, transitions between antagonistic and cooperative lifestyles in microbes are likely not an exception, although such shifts have rarely been observed directly. In a new study published online on April 28, 2017 in Nature Communications, researchers from Johannes Gutenberg University Mainz (JGU), the Max Planck Institute for Chemical Ecology and the Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI) - in Jena, and the Universidad Estadual Paulista in Rio Claro, Brazil, gathered evidence for such a transition. The open-access article is titled “Antibiotic-Producing Symbionts Dynamically Transition Between Plant Pathogenicity and Insect-Defensive Mutualism.” Like many other insects, a group of herbivorous beetles, the Lagriinae, is in great need of an efficient defense. They lay their eggs on humid soil under leaf litter, where encounters with mold fungi are guaranteed. Researchers lead by Professor Martin Kaltenpoth from Mainz University have now discovered that the presence of a special bacterium, Burkholderia gladioli, on the eggs of the beetle Lagria villosa strongly reduces the risk of fungal infection and helps them survive.