Type VII secretion--mycobacteria show the way

Recent evidence shows that mycobacteria have developed novel and specialized secretion systems for the transport of extracellular proteins across their hydrophobic, and highly impermeable, cell wall. Strikingly, mycobacterial genomes encode up to five of these transport systems. Two of these systems, ESX-1 and ESX-5, are involved in virulence - they both affect the cell-to-cell migration of pathogenic mycobacteria. Here, we discuss this novel secretion pathway and consider variants that are present in various Gram-positive bacteria. Given the unique composition of this secretion system, and its general importance, we propose that, in line with the accepted nomenclature, it should be called type VII secretion.     

Leukemic stem cells show the way

The blood-related cancer leukemia was the first disease where human cancer stem cells (CSCs), or leukemic stem cells (LSCs), were isolated. The hematopoietic system is one of the best tissues for investigating cancer stem cells, since the developmental hierarchy of normal blood formation is well defined. Leukemia can now be viewed as aberrant hematopoietic processes initiated by rare leukemic stem cells (LSC) that have maintained or reacquired the capacity for indefinite proliferation through accumulated mutations and/or epigenetic changes. Yet, despite their critical importance, much remains to be learned about the developmental origin of LSC and the mechanisms responsible for their emergence in the course of the disease. This report will review our current knowledge on leukemic stem cell development and finally demonstrate how these discoveries provide a paradigm for identification of Cancer Stem Cell (CSC) from solid tumors.     

Paving the way to the future of Amazonia

The fate of the Brazilian Amazon is threatened by a new wave of frontier expansion following new infrastructure commitments worth US$40 bn from the federal Government. In a recent paper, alarming rates of deforestation and forest degradation have been predicted, which could be either pessimistic or optimistic depending on the scale of forest disturbance being considered. A more decisive preventative approach is needed to prevent further impoverishment of both the biota and rural population of Amazonia.     

Axon guidance: morphogens show the way

Hedgehog and Wnt family proteins can act as classic developmental morphogens to pattern a field of nai;ve cells. Surprising new studies show that members of these same protein families also act as guidance cues for growing axons in the developing nervous system.     

Which way the future?

Just as the principle of uniformitarianism is a fundamental tenet of science, the past experiences of the Field Studies Council provide an insight, and possibly a signpost, to the future. During the last thirty years, there have been significant changes in the numbers and categories of visitor attending the residential Centres. Expansion between 1956 and 1976 was almost entirely due to A-level courses in biology and geography but in the last ten years there has been considerable diversification. Adult amateur naturalists and younger, pre-A-level, school pupils are the obvious growth categories now. In the GCSE examination syllabuses, more than ever before, there is a commitment to ecology and to fieldwork (with the latter compulsory in all Geography syllabuses). Against such a background one might expect an optimistic prediction for the FSC's future. Unfortunately, and for a variety of reasons, many educationalists promote the view that ecology can be taught in the classroom and that first-hand observations of animals and plants in an aquarium provide sufficient practical work. There is a growing need for those who believe in the necessity for genuine field observation of the environment, in the environment, to voice their concern at the acceptance of any such alternatives/substitutes. Although environmental awareness has been heightened in recent years one might question whether there has been a concommitant raising of environmental understanding. It is increasingly important that, as the scale and scope of decisions about the environment expand, the level of understanding of those who make decisions (and of those who elect them) should also be raised. It is no longer politic nor wise to accept Montaigne's assertion, “that men are most apt to believe what they least understand”. I suggest that our target for the future be “Breadth with Excellence”. If the FSC can move toward that goal it can face the daunting task of trying to achieve “Environmental Understanding for AH”.     

A fungal sexual revolution: Aspergillus and Penicillium show the way

Fungi have some of the most diverse sex lives in nature, ranging from self-fertility to obligate outcrossing systems with several thousand different sexes, although at least 20% of fungal species have no known sexual stage. However, recent evidence suggests that many supposed 'asexual' species do indeed have the potential to undergo sexual reproduction. Using experimental and genomic findings from Aspergillus and Penicillium species as examples, it is argued that evidence such as the presence and expression of apparently functional sex-related genes, the distribution of mating-type genes, detection of recombination from population genetic analyses, and the discovery of extant sexual cycles reveal an on-going revolution in the understanding of fungal asexuality.     

Spatial guidance of cell asymmetry: septin GTPases show the way

Eukaryotic cells develop asymmetric shapes suited for specific physiological functions. Morphogenesis of polarized domains and structures requires the amplification of molecular asymmetries by scaffold proteins and regulatory feedback loops. Small monomeric GTPases signal polarity, but how their downstream effectors and targets are spatially co-ordinated to break cell symmetry is poorly understood. Septins comprise a novel family of GTPases that polymerize into non-polar filamentous structures which scaffold and restrict protein localization. Recent studies show that septins demarcate distinct plasma membrane domains and cytoskeletal tracks, enabling the formation of intracellular asymmetries. Here, we review these findings and discuss emerging mechanisms by which septins promote cell asymmetry in fungi and animals.     

Past and future approaches to ischemia-reperfusion lesion associated with liver transplantation

Ischemia-reperfusion (I/R) injury associated with liver transplantation remains a serious complication in clinical practice, in spite of several attempts to solve the problem. The present review focuses on the complexity of I/R injury, summarizing conflicting results obtained from the literature about the mechanisms responsible for it. We also review the therapeutic strategies designed in past years to reduce I/R injury, attempting to explain why most of them have not been applied clinically. These strategies include improvements in pharmacological treatments, modifications of University of Wisconsin (UW) preservation solution based on a variety of additives, and gene therapy. Finally, we will consider new potential protective strategies using trimetazidine, 5-amino-4-imidazole carboxamide riboside (AICAR), melatonin, modulators of the renin-angiotensin system (RAS) and the phosphatidylinositol-3-OH kinase (PI3K)-Akt and the p42/p44 extracellular signal-regulated kinases (Erk 1/2) pathway. These strategies have shown promising results for I/R injury but have not been tested in experimental liver transplantation to date. Moreover, we will review ischemic preconditioning, taking into account the recent clinical studies that suggest that this surgical strategy could be appropriate for liver transplantation.     

Ecology of the North Sea: Problems,successes, failures,future needs

After defining ‘ecology’, outlining the basic categories of ecological research and listing examples of modern ecological investigations, this introductory paper focusses on basic considerations; it is, in essence, a programmatic contribution. Research details on the ecology of the North Sea are the subject of the following papers. Theproblems of ecological North Sea research are formidable. Hydrological and biological fluctuations and variabilities are pronounced. Exchange patterns with the Atlantic are complex, and the inputs of rivers and rain defy exact measurement and prediction. Season, weather, climate—and as yet insufficiently known and controlled human-caused impacts—further complicate the situation. All this results in an unusually high degree of uncertainty. New questions and problems arise before the old ones can be answered or solved. Nevertheless, ecological North Sea research has achieved manysuccesses. The North Sea is the most intensively investigated sea area on our planet. Generations of zoologists, botanists and hydrographers — and more recently microbiologists, meteorologists, climatologists, chemists, pathologists and toxicologists — have produced an impressive body of knowledge. Slowly we are beginning to understand the forces that govern energy budgets and balances, material fluxes, and the factors that control and direct ecosystem dynamics. Essential driving forces of ecosystem dynamics result from microbial, especially bacterial, activities. Ecological modelling has paved the way for new theories and insights, and holds promise for progress towards a predictive ecology.Failures and shortcomings include insufficient long-term research, inadequately designed experiments, and misconceptions in environmental protection. Net changes in ecological processes of an heterogeneous and intensely varying environment such as the North Sea can only be comprehended adequately against the background of sustained measurements over decades.Future needs include: more long-term research; and new patterns of management, institutional organization and financial support. Essential breakthroughs in field-work demand more teamwork, in-situ experimentation and surveys from space. Studies on the health status of organisms and ecosystems should receive more attention. Finally, there is need for changes in human behaviour: we must use our insight and willpower to meet the deadly consequences of our self-made scientific-technological evolution by an equally self-made ethical evolution aimed at achieving a re-harmonization with nature.     

A review of mangrove rehabilitation in the Philippines: successes,failures and future prospects

From half a million hectares at the turn of the century, Philippine mangroves have declined to only 120,000 ha while fish/shrimp culture ponds have increased to 232,000 ha. Mangrove replanting programs have thus been popular, from community initiatives (1930s–1950s) to government-sponsored projects (1970s) to large-scale international development assistance programs (1980s to present). Planting costs escalated from less than US$100 to over $500/ha, with half of the latter amount allocated to administration, supervision and project management. Despite heavy funds for massive rehabilitation of mangrove forests over the last two decades, the long-term survival rates of mangroves are generally low at 10–20%. Poor survival can be mainly traced to two factors: inappropriate species and site selection. The favored but unsuitable Rhizophora are planted in sandy substrates of exposed coastlines instead of the natural colonizers Avicennia and Sonneratia. More significantly, planting sites are generally in the lower intertidal to subtidal zones where mangroves do not thrive rather than the optimal middle to upper intertidal levels, for a simple reason. Such ideal sites have long been converted to brackishwater fishponds whereas the former are open access areas with no ownership problems. The issue of pond ownership may be complex and difficult, but such should not outweigh ecological requirements: mangroves should be planted where fishponds are, not on seagrass beds and tidal flats where they never existed. This paper reviews eight mangrove initiatives in the Philippines and evaluates the biophysical and institutional factors behind success or failure. The authors recommend specific protocols (among them pushing for a 4:1 mangrove to pond ratio recommended for a healthy ecosystem) and wider policy directions to make mangrove rehabilitation in the country more effective.     

Past, present and future directions in human genetic susceptibility to tuberculosis

The historical impression that tuberculosis was an inherited disorder has come full circle and substantial evidence now exists of the human genetic contribution to susceptibility to tuberculosis. This evidence has come from several whole-genome linkage scans, and numerous case-control association studies where the candidate genes were derived from the genome screens, animal models and hypotheses pertaining to the disease pathways. Although many of the associated genes have not been validated in all studies, the list of those that have been is growing, and includes NRAMP1, IFNG, NOS2A, MBL, VDR and some TLR . Certain of these genes have consistently been associated with tuberculosis in diverse populations. The future investigation of susceptibility to tuberculosis is almost certain to include genome-wide association studies, admixture mapping and the search for rare variants and epigenetic mechanisms. The genetic identification of more vulnerable individuals is expected to inform personalized treatment and perhaps vaccination strategies.     

Life on the edge: Past and future of mangroves

Wetlands Ecology and Management -     

Plant breeding: Past achievements and expectations for the future

Plant breeding improvements have been responsible for 50 percent or more of the gains in yield per unit area of major crop plants in the United States over the past 50 yr. Rates of gain attributable to genetic improvements have averaged 1% per year, have generally been linear, and show no sign of slackening. Extrapolations indicate that varieties and hybrids of the year 2000 will yield, on average, 15% more than those of 1985 Improvements in tolerance to environmental stress, in grain-to-straw ratios, and in standability, as well as maintenance of required levels of resistance to disease, insect and nematode pests, have been the major genetic causes of higher achieved yields and will continue to be the foundation for further gains in productivity and stability. Broadened genetic diversity is also an increasingly important goal to promote stability and increase productivity potentials. Proportionately large research inputs are now needed to maintain desired rates of improvement, compared to earlier years. It seems likely that contributions from biotechnology will become increasingly important in years to come if improvement rates are to be maintained.     

Back to the future: natural history and the way forward in modern fungal ecology

The growing power and increasing availability of molecular tools for identifying fungi in environmental samples has revolutionized the way that fungal ecologists work. As a result, more people from around the globe have jumped into the fungal community sequencing endeavor. Paradoxically, as these extensive datasets accumulate we are often at a loss for interpretation due to the lack of basic autecology and natural history information for most fungi. As a result we are in danger of learning less and about more and more. I suggest that one way forward in fungal ecology is through a modern version of fungal natural history, with a focus on holistic understanding of individual species and ecosystems, but driven by modern genomic and molecular tools. By combining the extensive data generated through environmental sequencing with an intensive, molecular-based natural history we can create a synergy that will propel fungal ecology forward.