Microbiology Today November 2000

Just how small IS the smallest unit of life? What IS a microbe? In this issue we look at some areas of research on the fringes of microbiology.

Not long ago, the discovery of viruses revolutionised our thinking about the size range of living things. Now even small strands of RNA are found to be infectious in plants and we are asked to believe that a protein can pass the species barrier and cause brain disease. Well known popular science writer and distinguished microbiologist John Postgate peers into these twilight zones of microbiology and wonders if the curiosities of today will lead to dramatic scientific advances tomorrow.

The recent outbreak of Mad Cow Disease and its probable link with new variant CJD in humans has left us wondering if we are sitting on a time bomb. How many people will suffer the terrifying symptoms of this fatal disease in future years? Scientists are working hard to reveal the secrets of the infectious agent of BSE, scrapie and other TSEs. Chris Bostock, Director of the Institute of Animal Health, Compton, looks in depth at prion proteins, considered by most scientists to be the likely culprit.

Contrary to popular belief, viruses are not the smallest causative agents of infectious diseases in plants. Single stranded RNAs called viroids can bring about devastating losses of crops. Nicola Spence and Dez Barbara, scientists at Horticultural Research International, reveal the secrets of these pathogens which could well be the most rapidly evolving biological system known.

Some genes like to get about. Mobile segments of DNA are common in nature and are known as transposons. In microbes they play an important part in adaptive evolution. The emergence of antimicrobial resistance, a major public health problem, is a good example of the role of transposons in the spread of traits within bacterial populations. Many of the genes responsible for resistance are carried on transposable elements. Nicholas West and Christoph Tang of the John Radcliff Hospital in Oxford, look at the wide-ranging effects of prokaryotic transposons and their possible exploitation by microbiologists.

Bacteria suffer from viral infections, as do algae and other micro-organisms. Bacteriophages and other viruses are abundant in marine ecosystems as Gunnar Bratbak and Mikal Heldal, researchers in the Aquatic Microbial Ecology Group at the University of Bergen in Norway, describe. The effects of these tiny life forms on population dynamics, community structure, biogeochemical cycles and climate are only just beginning to be understood. It may turn out that viruses rule the waves.

Everyone wants to know if there is life in space. Based on present evidence, in the solar system, it is likely to be microbial. Some evidence from meteorites seems to indicate that bacteria may have existed on Mars. The UK Astrobiology Forum has been set up to explore all facets of extra-terrestrial life as Don Cowan (University College London) and Monica Grady (Head of Meteoritics at the London Natural History Museum) explain.

Microbiologists are revising their views of the minimal size for a bacterium. Tiny viable life forms known as nanobacteria are cropping up in all kinds of environments, from deep sea sediments to the inside of gallstones in the human body. At least scientists think they are - there is some controversy over whether nanobacteria really exist. Allan Hamilton (University of Aberdeen) is on the side of the miniature organisms and believes that their impact on our understanding of living systems is potentially huge.

The majority of bacteria are still to be discovered by scientists. Only a relatively few species can be cultured in the laboratory. Molecular techniques are now beginning to reveal the true extent of bacterial biodiversity. These bacteria are identified solely by their 16S rRNA sequences. John Fry , Professor of Microbial Ecology at Cardiff University, describes some of the major new groups found and speculates that many of them may not turn out to be as unculturable as first believed.

Hot off the Press [Acrobat PDF] highlights some new developments in microbiological research that have been published in the Society's journals - Microbiology, Journal of General Virology and International Journal of Systematic and Evolutionary Microbiology. Topics covered include:
  • Predicting the progress of AIDS - variability in the progress of SIV infection in macaques is related to the characteristics of a certain type of blood cell
  • An early test for cancer? - antibodies to the product of a particular gene may have potential as a diagnostic test for cancers induced by Epstein-Barr virus
  • Resistance to anti-cancer drug cisplatin - research into slime mould cells may lead to a breakthrough into the mechanisms of cisplatin resistance by cancerous cells
  • Any old iron? - do microbes compete for iron in the environment?
  • Waste not, want not - three new microbes are discovered in waste treatment and disposal sites
  • Full metal jacket - cleaning up uranium pollution with bacteria
Going Public [Acrobat PDF], which features science promotion activities, covers:

  • Bugs, microbes and micro-organisms - Reg England describes the recent microbiology summer school he ran for 11-16 year-olds in Preston
  • Round-up - covers some past and future science promotion events

Other items include:

Last updated 29 May 2003