Orchid-fungus fidelity: a marriage meant to last?

The characteristics of plant-mycorrhizae associations are known to vary in both time and space, but the ecological consequences of variation in the dynamics of plant-fungus interactions are poorly understood. For example, do plants associate with single fungi or multiple fungi simultaneously, and do the associations persist through a plant's lifetime or do plants support a succession of different fungi? We investigated these and other questions related to plant-fungus interactions in Goodyera pubescens, an evergreen terrestrial orchid of the eastern United States, that interacts with closely related fungi in the genus Tulasnella. Unlike the mycorrhizal associations of other plants, orchid-mycorrhizal associations only benefit the orchid, based on current evidence. Many terrestrial orchids have been found to associate with specific groups of fungi. This characteristic could potentially limit orchids to relatively narrow ranges of environmental conditions and may be a contributing factor in the decline of many orchids in the face of changing environmental conditions. We found that G. pubescens protocorms (developing embryos prior to leaf production) and adults associated with only one fungal individual at a time. The orchid-fungus association persists for years, but during a drought period that was associated with the death of many plants, surviving plants were able to switch to new fungal individuals. These results suggest that G. pubescens interacts with the same fungal partner during periods of modest environmental variation but is able to switch to a different fungal partner. We hypothesize that the ability to switch fungi allows G. pubescens to survive more extreme environmental perturbations. However, laboratory experiments suggest that switching fungi has potential costs, as it increases the risk of mortality, especially for smaller individuals. Our findings indicate that it is unlikely that switching fungi is a common way to improve tolerance of less severe environmental fluctuations and disturbances. These findings may have important implications for plant responses to severe climatic events or to more gradual environmental changes such as global warming.

Effects of age and race on skin condition and bacterial counts on hands of neonatal ICU nurses.

OBJECTIVE: The purpose of this study was to assess the relationship between demographic factors such as age and race and skin condition and bacterial counts on hands of nurses. METHODS: Nurses (n = 111) working in 1 of 2 neonatal ICUs in New York City were surveyed regarding reported hand care practices and demographics, the condition of their hands was assessed by a trained observer and by themselves using validated instruments, and a hand culture was obtained. RESULTS: There were no significant differences in any skin care practices by race, but nurses who wore powder-free gloves were significantly younger than those who did not (P =.004). There were no significant differences in bacterial counts on hands of black or white nurses (mean log colony-forming units 3.49 and 3.61 respectively, P =.63) and no significant correlation between age and microbial counts (r = 0.04, P =.72). In a logistic regression analysis, race, but not age, was a significant predictor of skin health. By both observer (P =.02) and self-assessment (P =.004) black nurses had healthier skin. CONCLUSION: Physiochemical differences in skin associated with demographic factors such as age and race may be exacerbated among those in disciplines such as nursing, for whom the skin of the hands is continually stressed by occupational practices such as frequent hand hygiene. Such demographic factors need be considered when assessing skin condition and when advocating for appropriate strategies to maximize skin health. The recommendations of the new CDC Hand Hygiene Guideline for Healthcare Settings(23) regarding maintaining skin health and providing moisturizers and products that are milder to the skin are timely and should be followed.