Microbial biofilms in nature: unlocking their potential for agricultural applications

Soil environments are dynamic and the plant rhizosphere harbours a phenomenal diversity of micro-organisms which exchange signals and beneficial nutrients. Bipartite beneficial or symbiotic interactions with host roots, such as mycorrhizae and various bacteria, are relatively well characterized. In addition, a tripartite interaction also exists between plant roots, arbuscular mycorrhizal fungi (AMF) and associated bacteria. Bacterial biofilms exist as a sheet of bacterial cells in association with AMF structures, embedded within a self-produced exopolysaccharide matrix. Such biofilms may play important functional roles within these tripartite interactions. However, the details about such interactions in the rhizosphere and their relevant functional relationships have not been elucidated. This review explores the current understanding of naturally occurring microbial biofilms, and their interaction with biotic surfaces, especially AMF. The possible roles played by bacterial biofilms and the potential for their application for a more productive and sustainable agriculture is discussed in this review.

FUNGAL SYMBIONTS. Global assessment of arbuscular mycorrhizal fungus diversity reveals very low endemism

The global biogeography of microorganisms remains largely unknown, in contrast to the well-studied diversity patterns of macroorganisms. We used arbuscular mycorrhizal (AM) fungus DNA from 1014 plant-root samples collected worldwide to determine the global distribution of these plant symbionts. We found that AM fungal communities reflected local environmental conditions and the spatial distance between sites. However, despite AM fungi apparently possessing limited dispersal ability, we found 93% of taxa on multiple continents and 34% on all six continents surveyed. This contrasts with the high spatial turnover of other fungal taxa and with the endemism displayed by plants at the global scale. We suggest that the biogeography of AM fungi is driven by unexpectedly efficient dispersal, probably via both abiotic and biotic vectors, including humans.

Matrix study of irbesartan with hydrochlorothiazide in mild-to-moderate hypertension

The purpose of this study was to assess the safety and antihypertensive dose-response effects of irbesartan and hydrochlorothiazide (HCTZ) in patients with mild-to-moderate hypertension. After a 4- to 5-week single-blind placebo lead-in period, 683 patients with seated diastolic blood pressure (SeDBP) between 95 and 110 mm Hg were randomized to receive once-daily dosing with one of 16 different double-blind, fixed combinations of irbesartan (0, 37.5, 100, and 300 mg irbesartan) and HCTZ (0, 6.25, 12.5, and 25 mg HCTZ) for 8 weeks. The primary efficacy variable was the change from baseline in trough SeDBP after 8 weeks of therapy. Data were analyzed by response surface modeling. At Week 8, mean changes from baseline in trough SeDBP (mm Hg) ranged from -3.5 for placebo, -7.1 to -10.2 for the irbesartan monotherapy groups, -5.1 to -8.3 for the HCTZ monotherapy groups, and -8.1 to -15.0 for the combination groups. Irbesartan plus HCTZ produced additive reductions in both SeDBP and seated systolic BP, with at least one combination producing greater BP reduction than either drug alone (P < .001). All treatments were well tolerated; there were no treatment-related serious adverse events. Irbesartan tended to ameliorate the dose-related biochemical abnormalities associated with HCTZ alone. In conclusion, the combination of HCTZ in doses up to 25 mg with irbesartan, in doses up to 300 mg, is safe and produces dose-dependent reductions in BP.

Lack of interaction between sulindac or naproxen and propranolol in hypertensive patients

Seventeen patients with hypertension and osteoarthritis participated in a single-blind crossover study comparing the effects of sulindac 200 mg twice daily, naproxen 500 mg twice daily, and placebo on blood pressure. All patients were treated for hypertension with propranolol monotherapy. Blood pressures were back-titrated to achieve a baseline diastolic blood pressure of 90 to 100 mm Hg while taking naproxen. There were no significant differences in mean sitting or standing blood pressures among the patients receiving naproxen, sulindac, or placebo treatments. There was no change in pulse, weight, or any of the laboratory measurements at the end of each treatment phase. These results suggest that neither sulindac nor naproxen interferes with propranolol therapy for uncomplicated hypertension.

Etiology of pelvic infections treated by the gynecologic service of the Kasturba Hospital, Delhi, India

Selected etiologic and clinical characteristics of pelvic infections associated with gynecologic surgical procedures and other conditions were studied. During a 5 year period, 1,800 patients were admitted to Kasturba Hospital. Infections following sterilization by vaginal tubectomy were common while septic-induced abortion was the leading cause of maternal morbidity. Medical management was successful in most of the patients.