Conservation of xcp genes, involved in the two-step protein secretion process, in different Pseudomonas species and other gram-negative bacteria

Summary The two-step protein secretion pathway in Pseudomonas aeruginosa is dependent on the xcp genes. We investigated whether a similar secretion mechanism is present in non-pathogenic Pseudomonas spp. and in other gram-negative bacteria. The plant growth stimulating Pseudomonas strains P. putida WCS358, P. fuorescens WCS374 and Pseudomonas 1310 appeared to secrete proteins into the extracellular medium. Southern hybridization experiments showed the presence of xcp genes in these strains and also in other gram-negative bacteria, including Xanthomonas campestris. Complementation experiments showed that the xcp gene cluster of P. aeruginosa restored protein secretion in an X. campestris secretion mutant. The secretion gene cluster of X. campestris however, restored secretion capacity in P. aeruginosa mutants only to a low degree. Two heterologous proteins were not secreted by P. fuorescens and P. aeruginosa. The results suggest the presence of a similar two-step protein secretion mechanism in different gram-negative bacteria, which however, is not always functional for heterologous proteins.     

Expression of a chimaeric granule-bound starch synthase-GUS gene in transgenic potato plants

Granule-bound starch synthase is the key enzyme in amylose synthesis. The regulation of this gene was investigated using a chimaeric gene consisting of a 0.8 kb 5 upstream sequence of the granule-bound starch synthase gene from potato and the -glucuronidase gene which was introduced into potato using an Agrobacterium tumefaciens binary vector system. The chimaeric gene was highly expressed in stolons and tubers, whereas the expression in leaves, stems or roots from greenhouse-grown plants was relatively low. However, leaves from in vitro grown plantlets exhibited an elevated GUS expression. The expression of the chimaeric gene was inducible in leaves by growth on relatively high concentrations of sucrose, fructose and glucose and was about 30- to 50-fold higher than in leaves from greenhouse-grown plants. The granule-bound starch synthase gene is expressed organ-specifically since stolons and tubers showed GUS activities 125- to 3350-fold higher than in leaves. The activities in these two organs are 3- to 25-fold higher than the expression of the CaMV-GUS gene. Histochemical analysis of different tissues showed that only certain regions of leaves and roots express high GUS activities. Stolons and tubers show high expression.     

Colonization of the rhizosphere of crop plants by plant-beneficial pseudomonads

Abstract: Efficient colonization of the plant root is thought to be crucial for the plant-beneficial effect of particular Pseudomonas strains. Since root colonization is often the limiting step for successful plant growth stimulation, this process needs improvement. It is therefore important to acquire more information as regards (i) the conditions in the rhizosphere, and (ii) the bacterial traits that are involved in colonization. This review discusses some recent studies that focus on these two issues.     

Death and cannibalism in a seasonal environment facilitate bacterial coexistence

Bacterial populations can evolve and adapt to become diverse niche specialists, even in seemingly homogeneous environments. One source of this diversity arises from newly 'constructed' niches that result from the activities of the bacteria themselves. Ecotypes specialized to exploit these distinct niches can subsequently coexist via frequency-dependent interactions. Here, we describe a novel form of niche construction that is based upon differential death and cannibalism, and which evolved during 20 000 generations of experimental evolution in Escherichia coli in a seasonal environment with alternating growth and starvation. In one of 12 populations, two monophyletic ecotypes, S and L, evolved that stably coexist with one another. When grown and then starved in monoculture, the death rate of S exceeds that of L, whereas the reverse is observed in mixed cultures. As shown by experiments and numerical simulations, the competitive advantage of S cells is increased by extending the period of starvation, and this advantage results from their cannibalization of the debris of lysed L cells, which allows the S cells to increase both their growth rate and total cell density. At the molecular level, the polymorphism is associated with divergence in the activity of the alternative sigma factor RpoS, with S cells displaying no detectable activity, while L cells show increased activity relative to the ancestral genotype. Our results extend the repertoire of known cross-feeding mechanisms in microbes to include cannibalism during starvation, and confirm the central roles for niche construction and seasonality in the maintenance of microbial polymorphisms.     

Preventing fatal diseases increases healthcare costs: cause elimination life table approach.

OBJECTIVES: To examine whether elimination of fatal diseases will increase healthcare costs. DESIGN: Mortality data from vital statistics combined with healthcare spending in a cause elimination life table. Costs were allocated to specific diseases through the various healthcare registers. SETTING AND SUBJECTS: The population of the Netherlands, 1988. MAIN OUTCOME MEASURES: Healthcare costs of a synthetic life table cohort, expressed as life time expected costs. RESULTS: The life time expected healthcare costs for 1988 in the Netherlands were 56,600 Pounds for men and 80,900 Pounds for women. Elimination of fatal diseases--such as coronary heart disease, cancer, or chronic obstructive lung disease--increases healthcare costs. Major savings will be achieved only by elimination of non-fatal disease--such as musculoskeletal diseases and mental disorders. CONCLUSION: The aim of prevention is to spare people from avoidable misery and death not to save money on the healthcare system. In countries with low mortality, elimination of fatal diseases by successful prevention increases healthcare spending because of the medical expenses during added life years.     

Improved Methods in the Diagnosis of Ureteral Duplication and Ectopia

Ureteral duplication with ectopia is of clinical importance because it is attended by a high incidence of persistent urinary disease. Its diagnosis is frequently made difficult by the obscure position of the extravesical ureteral orifice, and often by its obstruction, which may block the passage of radiopaque medium. But it is in precisely such cases that early diagnosis and treatment are most essential to the preservation of renal function. The chances of diagnosis have been increased within recent years by the development of new or modified radiographic and nonradiographic techniques.     

Regression analysis of recent changes in cardiovascular morbidity and mortality in The Netherlands.

OBJECTIVES: To test whether recent declines in mortality from coronary heart disease were associated with increased mortality from other cardiovascular diseases. DESIGN: Poisson regression analysis of national data on causes of death and hospital discharges. SETTING AND SUBJECTS: Population of the Netherlands, 1969-93. MAIN OUTCOME MEASURES: Annual changes in mortality from coronary heart disease, stroke, and other cardiovascular diseases and annual changes in hospital discharge rates for acute coronary events, stroke, and congestive heart failures. RESULTS: Patterns of cardiovascular mortality changed abruptly in 1987-93. Annual decline in mortality from coronary heart disease increased sharply for women and men: from -1.9% (95% confidence interval -2.2% to -1.6%) and -1.7% (-1.9% to -1.4%) respectively in 1979-86 to -3.1% (-3.5% to -2.6%) and -4.2% (-4.6% to -3.9%) in 1987-93. The longstanding decline in mortality from stroke levelled off: from annual change of -3.3% (-3.7% to -2.8%) and -3.2% (-3.7% to -2.8%) in 1979-86 to -0.1% (-0.7% to 0.4%) and -1.1% (-1.7% to -0.5%) in 1987-93. Mortality from other cardiovascular diseases, however, started to increase: from -2.0% (-2.4% to -1.6%) and -0.2% (-0.5% to 0.2%) in 1979-86 to 1.5% (1.0% to 2.0%) and 1.9% (1.5% to 2.3%) in 1987-93. Hospital discharge rates for acute coronary heart disease, congestive heart failure, and stroke increased during 1980-6. During 1987-93 discharge rates for stroke and coronary heart disease stabilised but rates for congestive heart failure increased. CONCLUSION: Improved management of coronary heart disease seems to have reduced mortality, but some of the gains are lost to deaths from stroke and other cardiovascular diseases. The increasing numbers of patients with coronary heart disease who survive will increase demands on health services for long term care.     

Live longer through PHAsting

Dietary restriction provides considerable health benefits and may even increase life span in humans. Panowski et al. (2007) have now identified PHA-4/FoxA as an essential and specific component of DR-induced life-span extension in C. elegans.