The development of microbiology has brought many discoveries in recent decades. And one of them is the features of the movement of flagellar bacteria. The arrangement of the engines of these ancient organisms turned out to be very complicated and, by the principle of their work, very different from the flagella of our closest eukaryotic relatives of protozoa. The hottest arguments between creationists and evolutionists flared up around the engine of the flagellar bacterium. About bacteria, their flagellar motors and much more - this article.
General biology
To begin with, we recall what kind of organisms these are and what place they occupy in the system of the organic world on our planet. The Bacteria domain unites a huge number of unicellular prokaryotic (without a decorated nucleus) organisms.
These living cells appeared in the arena of life almost 4 billion years ago and were the first settlers of the planet. They can be of very different shapes (cocci, rods, vibrios, spirochetes), but most of them are flagellates.
Where do bacteria live? Everywhere. More than 5 × 10 30 of them live on the planet. There are about 40 million of them in 1 gram of soil; up to 39 trillion live in our body. They can be found at the bottom of the Mariana Trench, in hot "black smokers" at the bottom of the oceans, in the ice of Antarctica, and at your moment there are up to 10 million bacteria.
The value is undeniable
Despite the microscopic dimensions (0.5-5 microns), their total biomass on Earth is greater than the biomass of animals and plants combined. Their role in the cycle of substances is irreplaceable, and their properties of consumers (organic destroyers) do not allow the planet to be covered with mountains of corpses.
Well, do not forget about pathogens: the causative agents of plague, smallpox, syphilis, tuberculosis and many other infectious diseases are also bacteria.
Bacteria are also used in human activities. Starting from the food industry (fermented milk products, cheeses, pickled vegetables, alcoholic beverages), the “green” economy (biofuels and biogas) to the methods of cell engineering and the production of medicines (vaccines, serums, hormones, vitamins).
General morphology
As already mentioned, these unicellular representatives of life do not have a nucleus, their hereditary material (DNA molecules in the form of a ring) are located in a specific area of the cytoplasm (nucleoid). Their cell has a plasma membrane and a dense capsule formed by peptidoglycan murein. Of the cellular organelles, bacteria have mitochondria; there may be chloroplasts and other structures with different functions.
Most bacteria are flagella. A dense capsule on the surface of the cell does not allow them to move by changing the cell itself, as amoeba do. Their flagella are dense protein formations of various lengths and diameters of about 20 nm. Some bacteria have a single flagellum (monotrich), while others have two (amphitrich). Sometimes flagella are located in bunches (lofotrichi) or cover the entire surface of the cell (peritrichi).
Many of them live in the form of single cells, but some form clusters (pairs, chains, filaments, hyphae).
Movement features
Flagellated bacteria can move in different ways. Some move only forward, and change direction by somersaults. Some are capable of twitching, others move by sliding.
The flagella of bacteria perform the functions of not only a cellular “paddle,” but they can also be a “boarding” tool.
Until recently, it was believed that the flagellum of the bacteria wags like the tail of a snake. Recent studies have shown that the flagellum of bacteria is much more complex. It works like a turbine. Attached to the drive, it rotates in one direction. The drive, or flagellar motor of a bacterium, is a complex molecular structure that works like muscle. With the difference that the muscle after performing compression should relax, and the bacterial motor works constantly.
Flagellum nanomechanism
Without delving into the biochemistry of motion, we note that in the creation of the drive the flagellum participates in up to 240 proteins, which are divided into 50 molecular components with a specific function in the system.
In this motor system of the bacterium, there is a rotor that moves, and a stator that provides this movement. There is a drive shaft, bushing, clutch, brakes and accelerators
This miniature engine allows bacteria to travel 35 times larger than its own size in just 1 second. At the same time, the body spends only 0.1% of all the energy that the cell spends on the flagellum itself, which makes 60 thousand revolutions per minute.
It is also surprising that the bacterium can replace and repair all the parts of its motor mechanism on the go. Just imagine that you are flying in an airplane. And technicians change the blades of a running motor.
Flagellum bacterium against Darwin
An engine capable of running at speeds of up to 60,000 rpm, self-stopping and using only carbohydrates (sugar) as a fuel, having a device akin to an electric motor - could such a device arise in the process of evolution?
It was this question that Michael Bihe, MD, asked himself in 1988. He introduced into biology the concept of an irreducible system - a system in which all its parts are simultaneously necessary to ensure its operation, and the removal of at least one part leads to a complete disruption of its functioning.
From the perspective of Darwin's evolution, all structural changes in the body occur gradually and only successful ones are selected by natural selection.
Conclusions of M. Biha presented in the book “Darwin's Black Box” (1996): the engine of the flagellar bacteria is an indivisible system of more than 40 parts, and the absence of at least one will lead to the complete non-functionality of the system, which means that this system could not occur by natural selection .
Creationist Balm
Creation theory presented by a scientist and professor of biology, dean of the Faculty of Biological Sciences at Lichai University of Bethlehem (USA) M. Behee immediately attracted the attention of church ministers and supporters of the theory of the divine origin of life.
In 2005, a lawsuit was even held in the United States, where Behe was a witness from the supporters of the theory of "reasonable design", which considered the introduction of Dover schools to study creationism in the course "On Pandas and People." The process was lost, the teaching of such a subject was recognized as contrary to the current constitution.
But the debate between creationists and evolutionists continues today.