Editor's Note: Some of the articles described below are not yet available at the PNAS site, but they are scheduled to be posted some time this week.
Stanford University's Justin Sonnenburg and colleagues used 16S ribosomal RNA sequencing as part of their effort to look at ways in which the gut microbial community composition and glycan content in host intestinal mucus shift in relation to diet. Through a series of humanized mouse experiments, the team found that mutant animals missing a mucus-related gene had different gut microbes and intestinal mucus composition when fed diets high in glucose and lacking plant polysaccharides than when fed a typical diet with plenty of polysaccharides. "Together, these data demonstrate the differences in host genotype that affect the carbohydrate landscape of the distal gut interact with diet to alter the composition and function of resident microbes in a diet-dependent manner," they write.
Populations of the aquatic crustacean species Hyalella azteca vary dramatically in their sensitivity to an insecticide called pyrethroid, with at least some forms of resistance arising as a result of point mutations in sequences coding for components of the voltage-gated sodium channels targeted by pyrethroids, another PNAS study says. An Indiana University-led team turned to targeted gene sequencing, array-based gene expression patterns, and other types of profiling to explore the nature of pyrethroid sensitivity or resistance in H. azteca from 10 populations — seven from the wild and three from the lab — that varied by 550-fold in their susceptibility to the insecticide. "Our results have far-reaching implications for biomonitoring programs in general," the study's authors write, "and especially those relying on H. azteca."
French researchers report on findings from their analysis of viral genome packaging and interactions between the eight RNA fragments that make up the influenza A virus. Results of their sequence deletion and other experiments using an avian H5N2 influenza A strain suggest at least two RNA segments of the influenza A genome interact with one another in infected host cells in ways that bolster viral replication and other infectious processes. "We identified a direct interaction between two viral genomic RNA segments of an influenza A virus," they note, "and demonstrated that this interaction takes place in infected cells, is required for optimal viral replication, and favors co-packaging of the interacting RNA segments."