The
gut of humans and animals is verily a microbial
ecosystem
Until about 150 years ago,
we did not realize that there are over a million
life forms on earth, which we could not see
with our naked eyes. Thanks to Louis Pasteur,
Robert Koch and others, and the use of microscopes
as standard equipment in science laboratories,
these organisms came to be visualized, identified
and classified as (what else) microorganisms
or microbes.
First
impression
From the very start, they were considered a
nuisance-disease-causers and even death-dealers.
The eponymous term, Pasteurization, destroys
these microbes and makes food and milk safe
from their ill effects. Even before Pasteur,
Edward Jenner found a way to prevent small pox,
through not quite knowing that the villain was
a virus, a microbe. And it was Joseph Lister,
another Englishman, who showed that the simple
act of doctors washing and scrubbing their hands
could prevent thousands of deaths in hospitals;
this simple act offers antiseptic protection.
Are all microbes a disease spreading nuisance?
That there are some which actually help us came
to be known by about 1910 or so. The Russian
Nobelwinner biologist Ilya Mechnikov was researching
on why many Bulgarian peasants live longer and
healthier than others, and suggested the secret
to be the yoghurt that they consume.
Yoghurt beneficial
Yoghurt contains the bacterial family called
Bifido bacterium (earlier called lactobacillus
bifidus), which colonize our gut and lower
intestines. They not only help us in digesting
milk and related food, but also reduce stomach
disorders, allergies and even some tumours.
These gut bacteria live in a mutual give and
take relationship with us. Such symbiosis has
earned the title probiotic agents. Indeed, the
stomach upset that we experience when we take
antibiotics like erythromycin or penicillin
is because these drugs not only target the disease-causing
germs, but on the probiotic ones in our body
as well. Yoghurt and cheese are given to repopulate
our bellies with the bifidus and in severe cases
a dose of lactobacillus itself.
It is not just us, Ruminants such as cattle
depend for their digestion on the bacteria,
fungi and protests that colonize their second
stomach for digestion. These help to digest
cellulose and several other materials that the
cattle have eaten.
Indeed, the gut of animals and humans is verily
a microbial ecosystem-akin to a tropical rainforest.
Latest estimates reveal that there are hundreds
of 200 such microbes colonizing our body.
And we seem to need them just as much for our
lives, as they do us. This has led some scientists
to suggest that we humans have actually coevolved
with many of these essential in-house bacteria.
When the human genome was read out, letter by
letter, in its3 billion long vocabulary, it
was found that several hundred genes in us came
actually from bacteria, and hundreds more from
viruses.
Not only have we had microbes colonizing our
bodies all these years, helping our physiological
machinery works smoothly, but we have even snatched
off some of their genes and incorporated them
into our genome as part of our heritage. How,
then, are we different from plants which depend
on bacteria (called rhizobium) that offer them
nitrogen in an assimilable form? The rhizobium
in turn gets its oxygen in assimilable form
from the plant.
Such a given and take scenario lets us ask
the question: Is bad microbes that causes us
trouble always bad, or does it have any redeeming
quality at all?
Colonizing
A few years ago, Drs Barry Marashall and Robin
Warren showed that stomach and duodenal ulcers
are caused not just by stress or by eating hot
food alone, but actually because of a bacterium
colonizing our gastric system, called Helicobacter
pylori.
Now comes a twist to the story. Dr Martin Blaser
of the NYU School of Medicine finds that H.pylori
could even be helpful to us. It has been living
in mammalian stomachs since 150 million years
ago, as a symbiont. other materials that the
cattle have eaten.
Its actual role, he claims, is to regulate
the acidity levels in the stomach, in a way
that is helpful both to its host and to itself.
It is when one of its genes (called cag) that
is activated then toxicity occurs, provoking
ulcers.
In a sense then, H.pylori, acts as
a regulator or switch. In addition, it appears
or switch. In addition, it appears to boost
up our immune system to fight other bugs.
Blaser's analysis
Blaser's analysis shows that children infected
with H.pylori are far less likely to
have asthma and hay fever than those who have
been given routine antibiotic treatment for
such things as ear infections.
Thus H.pylori is not all bad: it has
some saving grace too. The trick is not to annihilate
it with antibiotics but control its level. Come
to think of it – this is no different
from our NRI cousins, whose children fall sick
the moment they come here. Their bodies are
not as well immune-primed with the microbes
abundant in the Indian air and water as ours
are.
Given a couple of months here, they can become
as resistant as we.
SOURCE
: The Hindu, September 18, 2008.
