I REFER in this case not to one of the opening chapters of the Fellowship of the Rings, but in fact to the September edition of Trends in Microbiology, in which a Dutch research team lead by Luis Lugones describe some interesting work with mushrooms.
Building upon an earlier patent by Lugones, the paper by Elsa Berends1, proposes for the first time the use of mushroom-forming fungi (the basidiomycetes) to produce N-glycosylated therapeutic proteins, an important class of protein-based therapeutic drug that represent a multi-billion dollar market.
‘Glycoproteins’ (proteins that have been processed by attaching a small string of sugars) are often prescribed to plug gaps in the metabolism of patients who for various reasons were born with, or have developed, errors of metabolism; these include insulin for treatment of diabetes, erythropoietin for treatment of anaemia, blood-clotting factors for haemophilia and a further 93 products (as of 2007).
Continue reading “A shortcut to mushrooms…”
I HAD barely started reading this week’s edition of Nature when in the Research Highlights1 section a study really piqued my interest.
Surgeons operating to remove malignant tumours often struggle to differentiate such tumours from surrounding healthy tissues. To ensure the complete removal of a tumour, surgeons also need to remove some of the surrounding healthy tissue, which of course isn’t desirable, especially in the brain.
A surgical electrode is a popular means to bisect (cut out) tissues. This makes use of a high-frequency electric current that is focussed into a highly localised ‘blade’ that effectively evaporates biological tissue as it comes into contact: water in the cells rapidly boils, proteins are precipitated and the membranes of the cells disintegrate forming a gaseous cloud of molecular ions of the major tissue components.
An innovative study published by team of researchers in Budapest, lead by Zoltán Takáts2, makes use of the fact that thermal evaporation of different tissues results in gaseous clouds with potentially different ion signatures. The team coupled a suction tube to a surgical electrode, and when cutting begins the tube draws the ions into an instrument called a mass spectrometer, something with which all CSI fans should be familiar. Using this process Takáts’ team found they could differentiate between healthy and malignant tissues, which provides a great basis for real-time tissue analysis under the knife, so to speak.
Continue reading “The cutting edge…”
BACTERIA can find themselves in the rather undesirable position of being addicted to parasites. The parasites in question are not of the blood-sucking sort however, but rather of the gene-sucking sort.
In nature there are numerous genetic entities, various forms of DNA, that parasitise bacteria:
- bacteriophages (viruses that infect only bacteria),
- plasmids (usually a circular strand of DNA that exists separately to the bacteria’s chromosome),
- transposons (a unit that consists of a collection of genes that inserts itself into the host’s chromosome, but can cut itself free and reinsert itself elsewhere on the chromosome) and conjugative transposons (also capable of transferring themselves from cell to cell between bacteria),
- genomic islands (again, a collection of genes that usually encode particular functions – disease-causing factors or antibiotic resistance – that have arrived from another organism and have become fixed in the chromosome).
We also have integrative conjugative elements (ICEs) that, like conjugative transposons, insert themselves into the host’s chromosome where they are replicated along with the host’s DNA, but then periodically (often under stress) cut themselves free and mail a copy off to another host cell.
Transfer of any of the above genetic entities can result in a bacterial cell acquiring new and desirable traits as such as the ability to consume new food sources, or resist antibiotics, or be more invasive. These traits have been picked up via the many occasions that these elements have jumped into and out of bacterial chromosomes, taking bits of those chromosomes with them.
The transfer of new traits by these genetic entities is referred to as Horizontal Gene Transfer (HGT), which is a term that is perhaps easier to understand if we consider that sexual reproduction, the process by which your parents produced you, is a form of vertical gene transfer; so too is the division of a single bacterial cell to produce a copy of itself and a ‘daughter’ cell. By comparison, horizontal gene transfer might be likened to you reaching out to touch your cousin and acquiring his or her ginger hair and freckles.
The thing that unites these genetic elements is that, being parasites, they need the host cell in order to produce more of themselves. Sometimes these elements don’t provide anything useful to the cell, sometimes they’re more of a burden, but some of these genetic parasites have evolved ways to ensure that the cell doesn’t toss them aside.
Continue reading “Addicted to DNA…”
IF you hadn’t guessed already, I’m busy trying to write a paper at the moment. This being the case, I have managed to successfully postpone this onerous task by spending time reading other people’s papers. I’m now going to spend a little more time explaining one of them you, my lovely readers.
Many years ago, when I was a grad student, I found myself at an otherwise rather dull conference on nucleic acid research; but fortunately it was not a complete wash-out, a chance conversation with a grad student who happened to be presenting a poster on the adjacent board to mine introduced me to the world of molecular mimicry.
So what is mimicry and why is it important in the natural world? Mimicry is the imitation of one species by another, with the most well known purpose being to avoid being eaten. Most people will have encountered hoverflies, and may in the first instance have mistaken them for a wasp or a bee; from an evolutionary perspective, predators such as birds have also learnt to associate these warning (aposematic) colours with a stinging or poisonous prey, and so the Hoverfly gets to fly another day.
Continue reading “Mimicry: survival or flattery?…”
THE recent issue of Trends in Biochemical Sciences contained an interesting perspective piece from Alexander Shneider, PhD and CEO of CureLab in Massachusetts. He describes a revision, or alternative focus, of Thomas Kuhn’s (1962) theory of scientific (r)evolution. In this Shneider identifies four-stages of evolution through which a scientific disciple must pass to maturity:
Stage 1. The introduction of new objects / phenomena, with an accompanying language to adequately describe such phenomena.
Stage 2. Development of a ‘tool box’ of methods / techniques to probe the objects / phenomena; with advancements in methodologies helping to identify and understand the degree to which other phenomena fall into the realm of this new science.
Stage 3. The stage at which most of the specific knowledge is generated, with the majority of research publications being published, often focussing on the application of new research methods to objects / phenomena. Scientists may re-describe their subject matter using refinements from stage 2, in the same way that with the advent of molecular biology, biologists might re-describe old subject matter from this new context; thus creating new insights, new answers and new questions.
Stage 4. A seeming steady-state for a discipline, where the knowledge gained from earlier stages is is maintained and passed on, often with practical application; often with new means generated to present the information. Whilst ground breaking new discoveries are not necessarily made, this does not preclude crucial revisions to the role of this discipline within scientific environment.
Continue reading “Evolution of a scientific discipline…”
TODAY’S edition of Nature (14 May 2009) features a landmark paper from researchers at the University of Manchester School of Chemistry that describes the synthesis of a pyrimidine ribonucleotide from simple chemicals, which may have existed on an early Earth. The research by Matthew Powner, in the laboratory of John Sutherland, represents a major stepping stone in support of the ‘RNA World’ theory, which describes the origins of life as passing through a stage in which RNA was the sole mediator of inheritance and catalysis, i.e. no DNA or proteins.
You can learn more about RNA World theory at the Exploring Origins website, or via resources on the website of Jack Szostak, one of the pre-eminent leaders in the field who also presents an accompanying perspective in this edition.
Whilst RNA is certainly a versatile molecule, with one form or another capable of breaking itself apart, joining itself to other RNA molecules, promoting formation of peptide linkages (the primary links of proteins) and templating its own self-replication, a major limiting point has existed regarding the origins of the necessary precursors for the RNA itself, i.e. ribonucleotides. Since the late 60’s, chemists studying prebiotic chemistry have focussed on trying to identify conditions in which these ribonucleotides would spontaneously assemble from their constituent parts: a nucleobase (which can be adenine, guanine, cytosine or uracil), a ribose sugar and phosphate. However, this approach was based on the assumption that these sub-units would assemble first, before combining to form the ribonucleotides. Unfortunately, no realistic conditions have been found in which a nucleobase would join to a ribose sugar.
Continue reading “On the origins of life…”
HUMANS, as we know, are the product of tens of thousands of genes, but hidden elsewhere in your DNA are genes that are no longer functional; these vestigial genes are known as pseudogenes, and they are ancestral remnants from an earlier point in our evolution. In many cases they are simply inactivated duplicates of a current functional gene. In other cases they are genes that have been cut out, reversed and stitched back in; in this position, some believe they may act to regulate the correctly oriented ‘functional’ version of the gene. Alternatively, they may be ancestral genes encoding functions that have become inactive beacuse they are ultimately not necessary for survival. Now, what if we could turn on one of these ancestral genes? One that could actually help protect us from a modern day infection?
In the recent edition of PLoS Biology is an interesting study that describes the re-activation of just such a dormant human pseudogene, retrocyclin, and its potential use as a defensive barrier against infection with HIV-1 (a strain of the Human Immunodeficiency Virus that causes AIDS). Retrocyclin is theta-defensin, which are naturally produced, circular chains of 18 amino acids (a peptide). I have previously research blogged about the application of other such antimicrobial peptides.
Active, functional theta-defensins have only so far been identified in the old world monkeys: the Rhesus Macaque and Olive Baboon; in Humans and other primates, they exist as pseudogenes. At some point in evolutionary history, our ancestors started inheriting a genetic mutation, all be it one that exists at 100%. The Human version of the gene, retrocyclin, is inactive in Humans because of a premature ‘stop’ signal, which makes the cell abandon the production of the peptide too early.
Retrocyclin can be synthesised chemically in a lab, and in this manner that the authors of this paper (from laboratories at the University of Central Florida and UCLA) have previously shown that it is capable of inactivating HIV-1, thereby preventing its entry into cells; in fact, they have also shown that it can similarly prevent entry of Herpes Simplex Virus type I (responsible for coldsores) and type II (responsible for genital warts).
Continue reading “Re-awakening ancestral genes…”
IMAGINE that you’re walking along a path in the middle of a prairie, minding your own business. As you’re walking, you find yourself getting out of breath; you find you’re unable to exert yourself as you can’t seem to breath fast enough. Pretty soon you start becoming slovenly, slow moving, dulled; there’s something wrong with the air, there’s not enough oxygen; you’re in the ‘dead zone‘. You try to move away from where you are, but you don’t know where the bad air started. Before long, it’s too late.
A similar experience may happen to deep ocean fish. They need oxygen too, they just manage to get it from the water, but there’s a problem. A report in the April 17th edition of Science, by Peter Brewer and Edward Peltzer (Monterey Bay Aquarium Research Institute, Moss Landing) describes how ‘Ocean “dead zones” [defined as regions where normal respiration is greatly limited and the expenditure of effort is physiologically constrained], devoid of aerobic life, are likely to grow as carbon dioxide concentrations rise.’ In order to understand what their report is about, we need a little background.
Continue reading “The dead zone…”
INHERITANCE, the process by which some of your parents DNA is repackaged in the agreeable form of you, can be described as ‘vertical gene transfer’, i.e. the passage of information down a lineage. However, this is not the only means by which DNA information can travel.
I once spent six years conducting research into the mechanisms by which resistance to antibiotics can be spread within, and between, bacterial species. Much of this focussed on horizontal gene transfer (HGT), specifically the transfer between bacteria of DNA packages called ‘plasmids’, which can contain a full set of instructions on how to resist an antibiotic. Unlike inheritance, HGT is more akin to you reaching out and placing your hand on your cousin and acquiring their ginger hair, or nose shape.
This is of course a very serious issue, in fact it has never been more serious. The subject of HGT is a key topic in many aspects of biological sciences, and I’ve blogged about some of the interesting aspects of such DNA information transfer before.
In the past 10 years or so, an oft’ discussed topic of conversation at the scientific conferences I’ve attended has been the development of targeted antimicrobials. This is a move towards being able to ‘take-out’ (in the mafia sense) those specific bacterial species that are causing a particular infection/disease, but without providing a selective pressure to develop resistance to the drug on this, and neighbouring, bacterial species.
Continue reading “Targeting antibiotics…”
The next time you’re down the pub, engaging your favourite Chimpanzee in an arm wrestle, I want you to reflect on a few things (besides the absurdity of wrestling an Ape).
As you take up the strain, know that the fine-tuned positioning and slow, steady building of muscle force you exert is due to the greater amount of grey matter that you posses in your spinal cord; motor neuron nerves cells that connect to muscle fibres and regulate muscle movement. The huge surplus of motor neurons you possess allows you to engage smaller portions of your muscles at any given time. A Chimpanzee, by comparison, has fewer motor neurons, thus each neuron triggers a greater number of muscle fibres, resulting in a greater proportion of muscle activation.
Reflect on how this finely tuned, incremental strength allows you to engage in tensing your muscle for a longer period. It is this fine motor control that allows you to do delicate tasks, like be victorious on the Nintendo Wii or replace the RAM in your laptop, and you know that if the RAM chip stubbornly refuses to slot back into place, you can gently exert greater and greater precise force until it does.
Finally, as the arm wrestle begins in earnest, reflect on two last things: one, your brain limits the degree of your muscle activation in an attempt to prevent damage to the fine motor control components of your muscles; and two, a Chimpanzee has no such limitation. So as the Chimpanzee tears off your arm easily and beats you over the head with it, think to yourself that rather than engaging in an arm wrestle with a Chimp, which has four times your strength, try sitting at home playing your Nintendo Wii instead, the precise motions for which it seems we are supremely evolved.
Inspired by Alan Walker’s (Professor of Anthropology at Penn State) research article ‘The strength of Great Apes and the speed of Humans’; free to read in the recent issue of the journal Current Anthropology.
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