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Archive - Jan 11, 2014

Team Seeks Source of Body Louse Pathology for Humans

A new study seeks to determine how one parasitic species can give rise to two drastically different outcomes in its host: The human body louse (Pediculus humanus) can transmit dangerous bacterial infections to humans, while the human head louse (also Pediculus humanus) does not. A report of the new study as published online on January 9, 2014 in the journal Insect Molecular Biology. "Body louse-transmitted diseases include trench fever, relapsing fever, and epidemic typhus," said University of Illinois entomology professor Dr. Barry Pittendrigh, who led the research. In a previous study, Dr. Pittendrigh and his colleagues compared the sequences of all protein-coding genes in head and body lice and determined that the two belonged to the same species – despite the fact that body lice are bigger than head lice, cling to clothing instead of hair, and can transmit disease. Since the early 2000s, Dr. Pittendrigh has worked with Dr. John M. Clark, a professor of environmental toxicology and chemistry at the University of Massachusetts, on the molecular biology and genomics of lice. Dr. Clark was a collaborator on the 2012 study, and the two have had "a long-term goal of trying to solve this question of why body lice transmit bacterial diseases and head lice don't," Dr. Pittendrigh said. In the new study, Dr. Clark's group infected head and body lice with Bartonella quintana, the bacterium that causes trench fever. Dr. Pittendrigh's laboratory then looked at gene expression in each to see how the insects responded to the infection. "Our experiments suggest that the head louse immune system is fairly effective in fighting off the bacteria that cause trench fever," Dr. Pittendrigh said.

MIT Study Discovers Extracellular Vesicles Produced by Ocean Microbes

Marine cyanobacteria — tiny ocean plants that produce oxygen and make organic carbon using sunlight and carbon dioxide — are primary engines of the Earth’s biogeochemical and nutrient cycles. They nourish other organisms through the provision of oxygen and with their own body mass, which forms the base of the ocean food chain. Now scientists at MIT have discovered another dimension of the outsized role played by these tiny cells: The cyanobacteria continually produce and release vesicles, spherical packages containing carbon and other nutrients that can serve as food parcels for marine organisms. The vesicles also contain DNA, likely providing a means of gene transfer within and among communities of similar bacteria, and they may even act as decoys for deflecting viruses. In a paper published in the January 10, 2014 issue of Science, postdoc Dr. Steven Biller, Professor Sallie (Penny) Chisholm, and co-authors report the discovery of large numbers of extracellular vesicles associated with the two most abundant types of cyanobacteria, Prochlorococcus and Synechoccocus. The scientists found the vesicles (each about 100 nanometers in diameter) suspended in cultures of the cyanobacteria as well as in seawater samples taken from both the nutrient-rich coastal waters of New England and the nutrient-sparse waters of the Sargasso Sea. Although extracellular vesicles were discovered in 1967 and have been studied in human-related bacteria, this is the first evidence of their existence in the ocean. “The finding that vesicles are so abundant in the oceans really expands the context in which we need to understand these structures,” says Dr. Biller, first author on the Science paper.

Bacteriophage phiM12 Analyzed

Innovative work by two Florida State University (FSU) scientists and colleagues shows the structural and DNA breakdown of a bacteria-invading virus and is being featured on the cover of the February 2014 issue of the journal Virology. Dr. Kathryn Jones and Dr. Elizabeth Stroupe, both assistant professors in the FSU Department of Biological Science, have deconstructed a type of virus called a bacteriophage, which infects bacteria. Their work will help researchers gain a better understanding of how this type of virus invades and impacts bacteria, and could be particularly useful for the agriculture industry. "It turns out there are a lot of novel things about it," Dr. Jones said. Until now, there was little known about this particular bacteriophage, called phiM12, which infects a nitrogen-fixing bacterium called Sinorhizobium meliloti. Dr. Jones focused on sequencing the DNA of phiM12 and analyzing its evolutionary context, while Dr. Stroupe examined its overall physical structure. "The bacteriophage is really just a tool for studying the bacterium," Dr. Stroupe said. "No one thought to sequence it before." That tool, Dr. Stroupe said, will give scientists more insight into the basic functions of the phiM12 bacteriophage. phiM12 is the first reported bacteriophage to have its particular combination of DNA sequences and the particular shape of its protein shell determined. Understanding both the DNA and structure may provide an understanding of the proteins a bacteriophage produces and how it chooses the bacteria it invades. In the case of phiM12, this could be particularly useful in the future for the agriculture community and seed companies. Important crop plants depend on biological nitrogen fixation by the bacteria that is preyed upon by this phage.