Dr PAUl HUMPHREYS, senior lecturer in microbiology at Huddersfield University’s School of Applied Sciences, says it’s a microbial world, if we could only notice it!
‘It’s a shame that the microbes’ good work goes unnoticed until something goes wrong’
WE are surrounded by microbes, or bugs as they are often called in the media.
All the surfaces we touch, the air we breathe, our pets and the people we come into contact with are all carrying microbes.
A gram of garden soil for example can have over a billion bacteria in it.
Much of the media coverage of microbes focuses on negative aspects, such as their ability to cause disease.
Advertisers spend a lot of air time telling us we need to be cleaning and sterilising our homes, particularly the surfaces in our kitchens and bathrooms.
I am the first person to stress the need for good hygiene.
But it is important to remember that most microbes are completely harmless. Most are far more helpful than they are harmful.
Microbes in the environment play important roles essential for all life on the planet. One group of bacteria “fix” nitrogen gas in the atmosphere and turn it into fertiliser that plants can use.
Any gardener who grows lupins may have noticed they have what appear to be deformed roots. These are actually root nodules that house nitrogen-fixing bacteria.
This allows lupins to grow where the soil is short of nitrogen; along railway embankments for example.
The relationship with the plants is so close that the bacteria involved change the way they grow quite dramatically because the plants provide such an ideal home for them.
Some species of plants have their own species of bacteria. The plant and the bacteria recognise each other in the soil through chemical communication.
Fungi also have very close relationships with plants. Some trees and orchids can only grow in the presence of specific fungi.
Microbes also play a big part in the food we eat. Most people will know that bread, beer and wine are all produced using yeasts, as are less obvious foods such as traditional vinegar, sauerkraut, soy sauce and chocolate.
There is also a vast array of fermented milk products, which usually employ bacteria. The most common of these are the cheeses and yogurts we see in our supermarkets.
Worldwide, there is a much greater variety of fermented milk products and it does not have to be cows’ milk that is used as a starting point.
There are products made from goats’ milk, mares’ milk (kumis) and camels’ milk (shubat).
There is even a drink called kefir that includes both bacteria and yeast in the fermentation, so you get alcohol in your yogurt; it definitely tastes a lot better than it sounds!
It is thought that alcohol fermentations and fermented milks were discovered by accident and developed into technologies because they make water and milk safer to drink.
This is because these fermentations kill any harmful bacteria present in the water or milk and provide a product with a longer shelf life.
It is not only the microbes in our food which may help us. The microbes that live in and on our bodies also have positive effects.
Their role generally goes unnoticed until something goes wrong. This can occur when our natural body flora is disrupted in some way. One example is the condition known as “antibiotic sore tongue” that occurs when the bacteria which live in the mouth are disrupted by antibiotics.
Occasionally this can allow a yeast called candida to take over, because it is resistant to antibiotics.
A similar, but much more serious condition, can occur when our gut flora are disrupted by antibiotics.
In healthy individuals the large numbers of bacteria living in our guts provide what is known as colonisation resistance.
This means they prevent other bacteria taking up residence in our guts.
Disease-causing bacteria such as aalmonella and campylobacter have had to evolve specialised mechanisms to overcome this natural resistance.
This colonisation resistance can be lost if antibiotics disrupt the natural population of bacteria present in the gut, which can allow disease-causing bacteria to become established. Disruption by antibiotics is a contributing factor to Clostridium difficile (C. diff) infections in hospitals.
These C. diff infections often occur in the elderly and this may be because populations of beneficial gut bacteria are known to reduce as we get older.
“Digestive health” is a phrase we hear quite a lot in the media, often associated with yogurt drinks and other dairy products.
These so-called “probiotics” contain bacteria that are known to be members of our gut flora and which contribute to our colonisation resistance. Many probiotics contain large number of bacteria but whether or not they are able to survive the digestive system and take up residence where we need them has been questioned.
Research paid for by the Food Standards Agency used a simulated human gut to show that some organisms from Probiotic products did survive the stomach and digestive system. But it was more difficult to show that Probiotic bacteria became established in a gut or changed the overall numbers of bacteria.
Probiotics have been investigated to treat C. diff infection as a way of re-establishing the gut microbial communities but the effectiveness of this treatment has not been proven.
There is no doubt that the microbes that we live with, in and on our bodies, can contribute to our general health. It’s a shame that their good work generally goes unnoticed until something goes wrong.
One of the positive impacts of the probiotic movement is a greater awareness of the positive contribution of “friendly bacteria”.