The biodiversity of beneficial microbe-host mutualism: the case of rhizobia

Symbiotic nitrogen fixation is the main route for sustainable input of nitrogen into ecosystems. Nitrogen fixation in agriculture can be improved by inoculation of legume crops with suitable rhizobia. Knowledge of the biodiversity of rhizobia and of local populations is important for the design of successful inoculation strategies. Soybeans are major nitrogen-fixing crops in many parts of the world. Bradyrhizobial inoculants for soybean are very diverse, yet classification and characterization of strains have long been difficult. Recent genetic characterization methods permit more reliable identification and will improve our knowledge of local populations. Forage legumes form another group of agronomically important legumes. Research and extension policies valorizing rhizobial germplasm diversity and preservation, farmer training for proper inoculant use and legal enforcement of commercial inoculant quality have proved a successful approach to promoting the use of forage legumes while enhancing biological N₂ fixation. It is worth noting that taxonomically important strains may not necessarily be important reference strains for other uses such as legume inoculation and genomics due to specialization of the different fields. This article points out both current knowledge and gaps remaining to be filled for further interaction and improvement of a rhizobial commons.     

The Role of Urologists in the Management of Hormone-Refractory Prostate Cancer

In 2001, approximately 80,000 European men will die from hormone-refractory prostate cancer (HRPC), making it one of the leading causes of death among males. Androgen withdrawal is the most effective form of systemic therapy for men with advanced prostate cancer, producing response rates in approximately 80% of patients. The majority of men, however, become refractory to hormonal manipulations and die within a few years. Because HRPC is associated with a median survival that rarely exceeds 12 months, and because there is fear of adding further treatment-related toxicity, many urologists are reluctant to offer chemotherapy to their patients. Even though chemotherapy is not curative for men with HRPC, it may prolong survival and provide palliative effects for some patients. Recent research with newer drugs suggests that prostate cancer may not be as resistant to chemotherapy as previously believed. Therefore, enrollment into clinical trials evaluating chemotherapy in advanced prostate cancer is appropriate. Proper patient selection for chemotherapy is a key role of the urologist because continual care is provided by the urologist, best equipping him or her to direct patients toward appropriate treatment options during the various stages of disease. Caring for a patient with HRPC requires the coordinated efforts of a multidisciplinary team, which should be led by the urologist.     

Impact of salinity-tolerant MCM6 transgenic tobacco on soil enzymatic activities and the functional diversity of rhizosphere microbial communities

The development of genetically modified plants for agriculture has provided numerous economic benefits, but has also raised concern over the potential impact of transgenic plants upon the environment. The rhizosphere is the soil compartment that is directly under the influence of living roots; it constitutes a complex niche likely to be exploited by a wide variety of bacteria potentially influenced by the introduction of transgenes in genetically modified plants. In the present study, the impact of overexpression of the salinity stress-tolerant minichromosome maintenance complex subunit 6 (MCM6) gene upon functional diversity and soil enzymatic activity in the rhizosphere of transgenic tobacco in the presence and absence of salt stress was examined. The diversity of culturable bacterial communities and soil enzymes, namely, dehydrogenases and acid phosphatases, was assessed and revealed no significant (or only minor) alterations due to transgenes in the rhizosphere soil of tobacco plants. Patterns in principal components analysis showed clustering of transgenic and non-transgenic tobacco plants according to the fingerprint of their associated bacterial communities. However, the presence of MCM6 tobacco did not cause changes in microbial populations, soil enzymatic activities or the functional diversity of the rhizosphere soil microbial community.     

The response of breadfruit nutrition to local climate and soil: A review

Breadfruit (Artocarpus altilis) has been promoted as an underutilized crop with tremendous potential to address global hunger and transform agricultural practices in the tropics. While traditionally confined to Oceania, breadfruit has been spread throughout the global tropics in the 250 years, with a significant increase in distribution and production over the last 20–30 years, bringing the crop into a vast array of growing conditions. We apply a systematic protocol to 33 previous studies representing 41 locations to explore the effect of abiotic environmental factors on nutritive aspects of breadfruit in three categories: proximate analyses, micro- and macro-nutrients, and vitamins. In applying linear and multi-variate regressions, data suggests that the abiotic factors play a strong role in the nutritive value of the crop and that each category of nutrition responds differently to the environment. In general, proximate analyses were most responsive to average annual precipitation, while vitamin concentrations respond to both climate and soil parameters; micro- and macro-nutrients show little correlation to climate or soils. We present findings in the context of previous research on abiotic influence of food nutrition.