successful and reminds us how little we
actually know about what goes on in
our intestines.How do we get bacteria
to work for us?
We tend to think of bacteria as mostly
causing disease. Tuberculosis, leprosy,
cholera, typhoid fever, syphilis, and
streptococci and staphylococci infections
are all caused by bacteria. But bacteria
work for us all the time, often in unseen
ways, both in our bodies and in the wider
world. Some bacteria produce, without
any artificial stimulus, metabolites that
help cells function. Penicillin is made
by moulds, of course, but another
early antibiotic, streptomycin, came
from the soil bacterium that gives the
spring earth its pleasant, musty smell.
Escherichia coli, or E. coli, is an
important tool in the laboratory. It is
relatively easy to grow, reproduces quickly
and has long been a favourite for scientists
studying many fundamental biological
issues, including natural selection and
the characteristics of the even-smaller
infective particles, the viruses (called
‘phages’ when they infect bacteria).
Studying phages and aspects of bacterial
genetics helped create modern molecular
biology, and bacteria are still at its heart.
Since recombinant DNA technology
was developed (the ‘recombinant’ simply
refers to the fact that strands of DNA
from one organism are recombined into
another one), bacteria have acquired
many new pharmaceutical and industrial
uses. They are used to make proteins, by
recombining the relevant portion of the
DNA into the bacterium’s own DNA.
In this way, human insulin, interferon,
human growth hormone and other
medicines are produced by bacteria in
the laboratory. Even vaccines can be
manufactured by bacteria.
As long as the appropriate segments
of DNA coding a protein can be
identified, the potential of bacterial
production is vast. Bacteria are so
ubiquitous and so versatile that the limits
depend only on scientific ingenuity.keeping other species at bay.
When we take antibiotics, they can
alter the composition of the gut’s flora,
killing them as they pass through our
intestines and sometimes allowing
less desirable bacteria to flourish. Of
increasing importance is Clostridium
difficile, a bacterium usually acquired
in hospital by patients who have been
taking antibiotics for other conditions.
C. difficile causes diarrhoea and
other complaints, and can even be
fatal. Although it can be treated with
antibiotics, it sometimes returns when
they are stopped. One recent alternative
treatment has been transplanting faeces
from a healthy person into the patient,
to help restore normal bacterial flora.
The faecal transplant is done either
through a long tube down the nose or
into the rectum via an enema. Although
it seems rather crude, it has proved veryMRSA bacteria pictured here
are responsible for several
types of infection that are
notoriously difficult to treatWilliam Bynum was at University College London
for 30 years. His book A Little History of Science is
now available in paperback.