Unlike viruses, bacteria are capable of independent reproduction, and boast their own metabolism. From this it follows that certain poisons (antibiotics) will have an effect on them. Antibiotics either destroy them or stop them from proliferating. The former are bactericidal, or bacterium killers; the latter are bacteriostatics.
Bacteria reproduce, or rather multiply, by fission. They do this very quickly: in the right circumstances, an ordinary coli intestinal bacterium starts to divide almost immediately, doubling its numbers every quarter of an hour(!). For example, if a single cell starts proliferating at midnight, by midnight the following day the number of its daughter cells will, in theory, be 2 to the power of 96, an extraordinary sum.
It is impossible even to imagine such a number – let us consider this in slightly greater detail! If the size of a bacterium is a thousandth of a millimetre, then a colony of around a billion bacteria represents a mass the size of a pinhead. Let’s conduct an imaginary experiment. We take a coli bacterium, place it in a culture medium at 37 degrees Celsius for it to proliferate. As the coli bacterium is capable of splitting, that is doubling, every quarter of an hour, in half an hour one bacterium will be four, and in an hour will be sixteen. In two hours we will have 256 specimens. If they continue to proliferate at the same rate, in the thirtieth quarter of an hour, that is seven and a half hours later, there will be about a billion bacteria, about as many as fit in a space the size of a pinhead.
After this – at least according to the laws of mathematics – all hell breaks loose. After the fiftieth round of splitting, the culture would be a litre in volume; fifteen hours from the outset, it would fill a cubic metre! And if this fantastic pace continues, the mass of bacteria by the end of the twenty-fourth hour would be eighty billion cubic metres, roughly the size of Mount Everest. All of this in the space of a single day, from a single bacterium! These numbers are only theoretical, of course, but adequate to give us a feeling of how dangerous an enemy superior creatures have to battle with day by day.
Fortunately, there are a number of defence mechanisms which stop this furious multiplication at a much earlier stage. The body protects itself, takes up the struggle with the intruders, destroys them and weakens them – if its immune system is in order, of course. The orgy of the bacteria is also limited by other factors. As their numbers increase, so their nutrition becomes less and less sufficient. The amount of their own metabolic by-products grows, which has a toxic “backfire” effect on them after a certain concentration is reached. (Humans do the same – we call it industrial pollution.) As a matter of interest, we note that laboratory experiments have shown that if the best conditions are provided for the bacteria – if there is an unlimited supply of nutrition and poisonous metabolic by-products are removed on a continuous basis – the speed of proliferation declines once a certain density is reached, then soon stops altogether. We do not know the real explanation for this phenomenon: it seems that after a while, bacteria, like other creatures, have simply had enough of each other. In any case, it is the fantastic self-regulatory power of nature that is behind this.
We can use various chemical compounds (poisons) to defend against pathogenic bacteria once they have entered the body and their excessive proliferation is threatening its well-being. This includes the group of antibiotics, which is growing in size as it decreases in effectiveness. We do have other chemicals, like copper sulphate or potassium permanganate, but they are slowly becoming forgotten. We can use plant extracts like the alkaloids of garlic. These substances affect bacteria directly just as antibiotics do, killing them or preventing their proliferation. But we should never forget that in the end it is the body’s immune system that defeats the pathogen – substances (medicines) introduced from outside are just a help in this.