Are we prepared for animal cell technology in the 21st century?

Large scale animal cell culture for the production of complex therapeutic proteins has been a major success of the biotechnology industry. Today, approximately half of the $ 5 billion annual turnover of the biotechnology industry is based upon this technology, in many cases with reactors of more than 10 m³. As we look towards the 21 st century, however, we can see novel approaches to the production of therapeutic proteins, by means of gene and cellular therapies. These technologies present new engineering challenges to the animal cell technologist. Are we prepared to meet these challenges? The needs include: small-scale reactors for the preparation of autologous cell lines, methods for the production of viruses to be used as vectors in gene therapy, artificial organ and the processing of xenogenic cell lines and tissues for cellular implants in humans. More attention should be given to three-dimensional cell cultures. Mass transfer considerations need to be extended beyond just oxygen transfer, to include cellular communication in small systems; this is becoming increasingly important for the control and optimise growth and product formation. Apart from improvements of large-scale systems, substantial advantages could be gained by studying new methods for the production and delivery of therapeutic proteins, using small-scale cell culture systems. We should adapt teaching, regulatory, patent and clinical infrastructure to meet this challenge in a harmonious way.     

ISCR elements: novel gene-capturing systems of the 21st century?

"Common regions" (CRs), such as Orf513, are being increasingly linked to mega-antibiotic-resistant regions. While their overall nucleotide sequences show little identity to other mobile elements, amino acid alignments indicate that they possess the key motifs of IS91-like elements, which have been linked to the mobility ent plasmids in pathogenic Escherichia coli. Further inspection reveals that they possess an IS91-like origin of replication and termination sites (terIS), and therefore CRs probably transpose via a rolling-circle replication mechanism. Accordingly, in this review we have renamed CRs as ISCRs to give a more accurate reflection of their functional properties. The genetic context surrounding ISCRs indicates that they can procure 5' sequences via misreading of the cognate terIS, i.e., "unchecked transposition." Clinically, the most worrying aspect of ISCRs is that they are increasingly being linked with more potent examples of resistance, i.e., metallo-beta-lactamases in Pseudomonas aeruginosa and co-trimoxazole resistance in Stenotrophomonas maltophilia. Furthermore, if ISCR elements do move via "unchecked RC transposition," as has been speculated for ISCR1, then this mechanism provides antibiotic resistance genes with a highly mobile genetic vehicle that could greatly exceed the effects of previously reported mobile genetic mechanisms. It has been hypothesized that bacteria will surprise us by extending their "genetic construction kit" to procure and evince additional DNA and, therefore, antibiotic resistance genes. It appears that ISCR elements have now firmly established themselves within that regimen.     

Regulating genomics in the 21st century: from logos to pathos?

There is currently an important change in the governance of genomics. In the past, much of the regulatory discussion about genomics has focused on issues of risk. Today, a new discussion is evolving that emphasizes the uncertainties involved in the development and diffusion of genomics into society. The increasing importance of emotional language and the focus on trust in the discussion about genomics reflects the attempt to substitute for the shortcomings of logos with ethos and pathos.     

Agricultural biotechnology for crop improvement in a variable climate: hope or hype?

Developing crops that are better adapted to abiotic stresses is important for food production in many parts of the world today. Anticipated changes in climate and its variability, particularly extreme temperatures and changes in rainfall, are expected to make crop improvement even more crucial for food production. Here, we review two key biotechnology approaches, molecular breeding and genetic engineering, and their integration with conventional breeding to develop crops that are more tolerant of abiotic stresses. In addition to a multidisciplinary approach, we also examine some constraints that need to be overcome to realize the full potential of agricultural biotechnology for sustainable crop production to meet the demands of a projected world population of nine billion in 2050.     

Unnatural history: is a paradigm shift of natural history in 21st century ornithology needed?

Natural history, across disciplines, is essential for the continuation of science, especially as we attempt to identify the myriad of threats that biodiversity faces in this rapidly changing world. Recording the natural history of birds is perhaps the most prominent, widespread and long‐standing pursuit of this activity. Yet, there is a distinct decrease in publishing of natural history in the ornithological sciences. Concomitantly, the natural history information being published is often in small and regional journals, less accessible by the global ornithological community. We argue that historical natural history needs a modern reinvigoration, and should focus on placing natural history observations in the context of an anthropogenically altered world – ‘unnatural history’. This includes, but is not limited to, behavioural adaptations, novel diet choices, hybridization and novel adaptations to urbanization. Here, we elaborate on natural history's place in modern ornithology, how this relates to citizen science and the potential cost of ignoring it. Ultimately, increased accessibility of natural history observations, encouragement of amateur ornithologists' participation in professional societies (and vice versa) and targeted citizen science projects are potential mechanisms by which to reinvigorate natural history in 21st century ornithology.     

Biotechnological detoxification: an unchanging source–sink balance strategy for crop improvement

The wide occurrence of natural phytotoxins renders many crops unfit for human consumption. To overcome this problem and produce detoxified crop varieties, we propose the use of biotechnological strategies that can enhance the harvest index without the need to increase crop biomass or alter whole plant architecture.     

Living matter—nexus of physics and biology in the 21st century

Cells are made up of complex assemblies of cytoskeletal proteins that facilitate force transmission from the molecular to cellular scale to regulate cell shape and force generation. The “living matter” formed by the cytoskeleton facilitates versatile and robust behaviors of cells, including their migration, adhesion, division, and morphology, that ultimately determine tissue architecture and mechanics. Elucidating the underlying physical principles of such living matter provides great opportunities in both biology and physics. For physicists, the cytoskeleton provides an exceptional toolbox to study materials far from equilibrium. For biologists, these studies will provide new understanding of how molecular-scale processes determine cell morphological changes.The distinction between being “alive” or “not alive” has been a long-standing question for those interested in our natural world. In many ancient cultures, the difference between living organisms and inorganic matter was thought to be due to innate differences arising from a “vital force,” such that biology operated with different fundamental properties than the physical world. The ability to disprove such theories came about over the course of the 17th to the 19th centuries, as scientists developed theories of atoms and were able to synthesize organic matter from inorganic constituents. Over the past 100 years, developments in molecular biology and biochemistry have provided a wealth of information on the structure and function of biological molecules, much of which was acquired in collaborations between physical and biological scientists. Application of X-ray–scattering techniques first developed to study metals enabled discovery of the structure of complicated biological molecules ranging from DNA to ion channels. Use of laser trapping techniques first developed to trap and cool atoms enabled precise force spectroscopy measurements of single molecular motors. We now know that biological molecules, while more complicated than their inorganic counterparts, must obey the rules of physics and chemistry.This wealth of molecular-scale information does not directly inform the behaviors of living cells. The organelles within cells are made up of complex and dynamic assemblies of proteins, lipids, and nucleic acids, all immersed within an aqueous environment. These assemblies are somehow able to build materials that can robustly facilitate the plethora of morphological and physical behaviors of cells at the subcellular (intracellular transport), cellular (division, adhesion, migration), and multicellular (tissue morphogenesis, wound healing) length scales. The dynamic cytoskeleton transmits information and forces from the molecular to the cellular length scales. But what is it about the behaviors of biological molecules that endow cells with the ability to respirate, move, and replicate themselves robustly—all qualities we consider essential to “life”? For these questions, understanding of the physics and chemistry of systems of biological molecules is needed. Interactions that occur within ensembles of molecules lead to emergent properties and behaviors that cannot be predicted at the single-molecule level. These emergent chemical and physical properties of living matter are likely fundamentally different from inorganic or “dead” materials. Discovering the underlying principles of living matter provides fantastic opportunities to learn new physics and biology.The fields of condensed matter physics and materials science study the physical properties that emerge when objects (e.g., atoms, molecules, grains of sand, or soap bubbles) are placed in sufficiently close proximity, such that interactions between them cannot be ignored. Interatomic or intermolecular interactions give rise to emergent properties that are not seen in isolated species. Familiar examples involve electron transport across a material or a material''s response to externally applied magnetic fields or mechanical forces. These emergent properties, such as conductivity, elasticity, and viscosity, enable us to predict the behavior of a collection of objects in these condensed phases. In this paper, I will focus on my perspective of how approaches to understanding the mechanical properties of physical materials can inform understanding of the mechanical properties of living matter found within cells.In a crystal of metal, precisely organized atoms are located nanometers apart, and the energies of their interactions are on the scale of an electron volt (40-fold larger than thermal energy or twice the energy released on the hydrolysis of a single ATP molecule). These give rise to an energy density, or elastic modulus, on the order of gigapascals, which underlies the rigidity of metals. For small deformations, the restoring force between atoms means that this metal behaves like an elastic spring: after a force is applied, the metal returns to its original shape. Understanding force transmission through crystalline metals was facilitated by the development of elasticity theory in the 16th and 17th centuries. Fluids, such as water, lack crystalline order, but predictive understanding of fluid flows and forces was captured through development of theories of fluid dynamics. Now think of another material, Silly Putty, which behaves elastically at short timescales (it bounces like a rubber ball) but then oozes and flows at long timescales, acting like a viscous fluid. Silly Putty is made of long polymers that are trapped by one another at short timescales, but thermal energy is sufficient to allow them to diffuse and translocate at long timescales. Silly Putty is also a “soft material,” in that the polymer''s interaction energies are at the thermal energy level, and its length scale is at the micrometer level. Materials like Silly Putty were thought to be too complicated for analytical theory. It was only in the middle of the 20th century that the theoretical framework to understand these “messy” and “disorganized” polymer-based materials was developed.The most powerful theories for understanding these vastly different forms of physical matter were developed in the absence of even the simplest of computers. The theories relied on developing physical properties or parameters to describe the material with a “mean field,” a type of coarse-graining that identifies the essential properties of individual constituents and interactions but ignores many other details. These mean fields give us new intuitions concerning the origin of material properties and give rise to definitions of physical parameters, such as elasticity and viscosity. However, these theories also require materials that do not jostle around a lot and remain close to equilibrium. In fact, understanding materials “far from equilibrium” has been identified as a major challenge in physics for the next century (National Research Council, 2007) .Materials formed by dynamic protein assemblies in the cytoskeleton are disorganized, heterogeneous, and driven far from equilibrium. Motor proteins generate local stresses, and their activity is spatially modulated. The polymerization and depolymerization of cytoskeletal polymers is controlled by a myriad of regulatory proteins. All these dynamic molecular processes endow the cytoskeletal assemblies with unique behaviors that enable them to support complex physiological tasks. It is likely these dynamics also provide underlying robustness of the cells in response to fluctuating and changing environments. These properties make living cells exquisite materials that cannot be captured by existing frameworks of physical matter. I suspect that we have not yet identified the important parameters needed to characterize their properties. The rich dynamics created by active biological matter present a formidable challenge in the area of materials science.How do we hope to understand the properties of these complex cytoskeletal assemblies and materials? It may seem as though understanding cytoskeletal machinery is an insurmountable feat, the approaches that have been successful for physical materials will not work, and we must rely on complex simulations that require modeling of all individual components. This may be true. However, I think that this is a pessimistic view. Just consider how complicated physical materials would be if we did not have the appropriate parameters to describe the macroscopic responses and had instead became obsessed about knowing the details of all the interactions between underlying atoms and molecules? In the same vein, I believe that predictive insights into biological matter will emerge through development of new physical theories that use mean-field approaches to understanding materials that contain active components and are driven far from equilibrium. The burgeoning field of active-matter physics is currently considering these questions (Ramaswamy, 2010) . However, these theoretical approaches require physical measurements of cells and cellular proteins that may not be clearly linked to a physiological process or have a clear biological context. Materials built from cytoskeletal proteins in vitro should also provide an excellent source of experimental measurements, but closer collaboration with theorists working in this field and collaboration between biochemists and experimental physical scientists is needed to develop control over such materials. Developing predictive physical theories of the cytoskeleton will elucidate principles of why “the whole is more than the sum of its parts” that will provide greater control and design over living matter, in the same way that engineering has provided great advances in applications of materials from the physical world.What do biologists gain from theories of living matter? These theories will provide a crucial link between molecular and cellular length scale behaviors and will provide insight into the mechanisms of why specific molecular perturbations alter cell behavior. Moreover, they should provide us with general design principles of living matter. What are the basic aspects of a machine needed to separate chromosomes, establish polarity, or generate contractile forces that is utilized across different cell types? Can knowing these aspects provide insight into the evolution of cellular machines and the robustness of cell behavior? Thus, study of cellular materials both provides new opportunities for physicists and will provide crucial predictive understanding of cell physiology.Open in a separate windowMargaret L. Gardel     

African trypanosomes in the 21st century: what is their future in science and in health?

The African trypanosomes remain well recognised for their role as an interesting model eukaryote for basic science, but are loosing ground in their ability to contribute to understanding common cellular mechanisms. At the same time, the diseases they cause remain as prevalent as ever, but appear increasingly irrelevant in their wider medical, social, economic and political context. What can be done to keep trypanosome biology relevant and vigorous in the 21st century?     

Riparian Ecosystems in the 21st Century: Hotspots for Climate Change Adaptation?

Riparian ecosystems in the 21st century are likely to play a critical role in determining the vulnerability of natural and human systems to climate change, and in influencing the capacity of these systems to adapt. Some authors have suggested that riparian ecosystems are particularly vulnerable to climate change impacts due to their high levels of exposure and sensitivity to climatic stimuli, and their history of degradation. Others have highlighted the probable resilience of riparian ecosystems to climate change as a result of their evolution under high levels of climatic and environmental variability. We synthesize current knowledge of the vulnerability of riparian ecosystems to climate change by assessing the potential exposure, sensitivity, and adaptive capacity of their key components and processes, as well as ecosystem functions, goods and services, to projected global climatic changes. We review key pathways for ecological and human adaptation for the maintenance, restoration and enhancement of riparian ecosystem functions, goods and services and present emerging principles for planned adaptation. Our synthesis suggests that, in the absence of adaptation, riparian ecosystems are likely to be highly vulnerable to climate change impacts. However, given the critical role of riparian ecosystem functions in landscapes, as well as the strong links between riparian ecosystems and human well-being, considerable means, motives and opportunities for strategically planned adaptation to climate change also exist. The need for planned adaptation of and for riparian ecosystems is likely to be strengthened as the importance of many riparian ecosystem functions, goods and services will grow under a changing climate. Consequently, riparian ecosystems are likely to become adaptation ‘hotspots’ as the century unfolds.