Impact of target site distribution for Type I restriction enzymes on the evolution of methicillin-resistant Staphylococcus aureus (MRSA) populations.

A limited number of Methicillin-resistant Staphylococcus aureus (MRSA) clones are responsible for MRSA infections worldwide, and those of different lineages carry unique Type I restriction-modification (RM) variants. We have identified the specific DNA sequence targets for the dominant MRSA lineages CC1, CC5, CC8 and ST239. We experimentally demonstrate that this RM system is sufficient to block horizontal gene transfer between clinically important MRSA, confirming the bioinformatic evidence that each lineage is evolving independently. Target sites are distributed randomly in S. aureus genomes, except in a set of large conjugative plasmids encoding resistance genes that show evidence of spreading between two successful MRSA lineages. This analysis of the identification and distribution of target sites explains evolutionary patterns in a pathogenic bacterium. We show that a lack of specific target sites enables plasmids to evade the Type I RM system thereby contributing to the evolution of increasingly resistant community and hospital MRSA

Buzz pollination in the Epacridaceae

Conostephium (Epacridaceae) has flowers that conform with a buzz-pollination syndrome but, unlike most plants with this form of pollination, the anthers are hidden within the corolla tube. Vibrations generated by bees grasping the apices of the corolla tubes must be transferred via short broad filaments to the anthers. The anthers do not have pores but each dehisces from the apex by a slit that elongates over the time the flowers take to senesce (up to 10 days). This may limit self-fertilisation as the stigma is receptive as soon as it appears from between the very short corolla lobes, so little pollen is released at first but later this would increase as the slit elongates. Visitation by pollinators has rarely been seen but several observations of native bees (Leioproctus and Lasioglossum) working the flowers are presented. The bees visit the nectarless flowers of Conostephium only for pollen and must forage at other kinds of flowers to obtain nectar. Pollen tubes occurred in the stigmas of most older flowers of C. pendulum, so pollen delivery does not seem to limit seed set. Despite this, the species sets few fruit. From examination of the taxonomic positions of likely buzz-pollinated taxa in the family, it appears that pollination by sonication has arisen independently several times in the Epacridaceae, with primarily two different floral configurations

The role of metabolic syndrome, adiposity, and inflammation in physical performance in the Health ABC Study

Background: Metabolic syndrome (MetS) and functional limitation have been linked, but whether and how specific components of MetS and associated factors, such as inflammation, drive this relationship is unknown.Methods: Data are from 2,822 men and women, aged 70-79 years, participating in the Health, Aging, and Body Composition (Health ABC) study and followed for 5 years. Presence of MetS at baseline was defined according to the National Cholesterol Education Program Adult Treatment Panel III guidelines. Interleukin-6, C-reactive protein, and body fat mass were measured at baseline. Measures of physical performance, including 400-m walk time, 20-m walking speed, and the Health ABC physical performance battery (PPB) were obtained at baseline and examination years 2, 4, and 6.Results: A total of 1,036 (37%) individuals met criteria for MetS. MetS was associated with poorer physical performance at baseline. Effect estimates between MetS and gait speed, and components of the Health ABC PPB (standing balance and repeated sit-to-stand performance) were modestly attenuated after adjustment for inflammation. All associations were attenuated to nonsignificance after adding total body fat mass to the model. Longitudinal analyses yielded similar results. Individual MetS component analysis revealed that abdominal obesity explained the largest fraction of the variation in physical performance.Conclusions: Although inflammatory biomarkers partially accounted for the relationship between MetS and aspects of physical performance, overall findings implicate adiposity as the primary factor explaining poorer physical performance in older adults with MetS. © 2013 The Author